JP7460527B2 - Controlled Energy Storage Balance Technology - Google Patents

Description

[0001] Photovoltaic (PV) power plants generate electricity by converting solar energy into electricity. The generated electricity is then provided to a power grid. The solar energy source (i.e., the sun's light) is characterized as having an intensity that varies over time. Thus, the PV generators in such PV power plants incorporate power generation optimization devices (also called "optimizers"). One type of optimizer is named a "maximum power point tracker (MPPT)" (or "MPPT device"), which tracks an instantaneous maximum power production point (MPPP) voltage that the MPPT device uses to control the operation of the PV power plant. This practice is referred to herein as "blind MPPT verification." The MPPT device is typically software or firmware that tracks a time-varying voltage that results in maximum power production from a time-varying solar energy source.

[0002] The subject matter claimed herein is not limited to embodiments that solve any disadvantages or operate only within environments such as those described above. Rather, this "background" is provided only to indicate one exemplary technology area in which some embodiments described herein may be implemented.

[0003] The embodiments described herein are directed to an energy storage system that includes an energy reservoir and a system controller. The energy reservoir is charged with DC energy from a DC energy source while discharging the DC energy to a DC/AC converter. The system controller regulates the DC energy discharged from the energy reservoir to the DC/AC converter to approximately balance the amount of DC energy charged to the energy reservoir. Because this charging and discharging is approximately balanced, the size of the energy reservoir can be made very small in relation to the amount of charging and discharging. This is advantageous when the charging and discharging flows are large, as is the case when the energy reservoir receives charge from all or a significant portion of a power plant, such as a solar power plant. With such a controller, the use of the energy reservoir is technically feasible, even with such large current flows.

[0004] The system controller includes a detection component, a determination component, and a delivery component, where the detection component is configured to measure a stored energy level in the energy reservoir. The determination component is configured to evaluate whether an adjustment should be made using the measured stored energy level. The delivery component is configured to encode instructions to perform the adjustment into a coded message when the determination component determines that an adjustment should be made, and is configured to deliver the coded message to the DC/AC converter.

[0005] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0006] To explain the manner in which the above-described advantages and other advantages and features can be obtained, a more particular description of the various embodiments will be made with reference to the accompanying drawings. With the understanding that these drawings depict only sample embodiments and therefore should not be considered as limiting the scope of the invention, the embodiments will be described and explained with additional particularity and detail through the use of the accompanying drawings.

[0007] FIG. 1 is a block diagram of various power plants in which decoupling devices are used with energy reservoirs. [0007] FIG. 2 is a block diagram of various power plants in which decoupling devices are used with energy reservoirs. [0007] FIG. 1 is a block diagram of various power plants in which decoupling devices are used with energy reservoirs. FIG. 1 is a block diagram of a power plant set up in an experiment, with two AC power producing units set up in a conventional manner, with a wattmeter and an energy meter measuring the output of each power producing unit. FIG. 2B is a block diagram of the power plant of FIG. 2A used to verify improved energy output to the grid after modification to include a decoupling device and an energy reservoir. [0010] FIG. 1 is a block diagram of a power plant with two channels of power delivery, one channel calling for the use of an energy reservoir and one that does not call for users of the energy reservoir. [0011] FIG. 4 is a block diagram of a power plant representing the broader embodiment of FIG. 3; [0012] FIG. 1 is a block diagram of a power plant in which power is delivered through the use of an energy reservoir. [0013] FIG. 6 is a block diagram of a power plant representing a broader embodiment of FIG. [0014] FIG. 1 is a block diagram of a power plant. [0015] FIG. 2 is a block diagram of a maximum energy utilization point tracking (MEUPT) controller in accordance with the principles described herein. FIG. 9 is a block diagram of the MEUPT controller of FIG. 8 in the context of a power plant.

[0017] Patent publications US2016/0036232 and US2017/0149250 A1, the contents of which are incorporated herein by reference, provide a blind MPPT verification practice for grids that achieves suboptimal amounts of electricity. A PV energy system is disclosed. These patent publications state that in order to efficiently extract electricity for energy use, the characteristics of the energy extraction device should be matched to effectively and efficiently extract the electrical energy produced. Teach. Moreover, these patent applications teach that related devices should also deliver the extracted electricity for tailored and/or efficient energy utilization.

[0018] These patent publications further emphasize that energy utilization efficiency is closely dependent on power demand in addition to power production. Moreover, these publications teach that in any energy system, the general power consumption does not necessarily equal the power production, even when the laws of energy conservation and charge conservation are obeyed.

[0019] Instead of using an MPPT device as the optimizer for a solar power plant, the referenced patent publication proposed using a "maximum energy utilization point tracker," or "MEUPT device," as the PV power plant optimizer. Such an optimizer is referred to herein as a "MEUPT optimizer." According to the referenced patent publication, the MEUPT optimizer is designed to capture what it calls "excess energy," which it defines as electrical energy that is produced but not extracted and/or delivered to the power grid for utilization. That definition of "excess energy" is also used herein.

[0020] The MEUPT optimizer is also designed to temporarily store the captured excess energy in an energy reservoir and then prepare and deliver this electrical energy to the power grid for utilization. Thus, the electricity sales revenue of a PV power plant can be enhanced when incorporating a MEUPT optimizer.

[0021] Section 1: Function of the MEUPT Optimizer
[0022] According to the principles described in US 2016/0036232 and US 2017/0149250 A1 ("Referenced Patent Publications"), the MEUPT optimizer of one embodiment disclosed herein comprises an excess energy extractor, an energy reservoir, and a MEUPT controller. The MEUPT controller works in cooperation with the energy extractor and the DC/AC converter. The terms "power" and "energy" are used interchangeably in the art (although not strictly the same). Thus, unless otherwise specified, each term has the same meaning.

[0023] The energy extractor extracts an initial oscillating power train from the generated DC power source. The extracted initial power chain complies with the AC power grid requirements of the power grid. In other words, the extracted initial power chain has a time-varying sinusoidal voltage with a peak voltage that fits the power grid voltage range. Moreover, the power (proportional to the square of the voltage) is in the form of ( ^sin2 (ωt) or ^cos2 (ωt)) and is synchronized (with the same phase and frequency) with the power grid.

[0024] The surplus energy extractor, on the other hand, extracts the remaining oscillating power train remaining from subtracting the initial oscillating power train from the produced DC power. In other words, this residual vibration powertrain is the residual vibration powertrain that remains after providing the initial vibration powertrain to the power grid. The remaining oscillating powertrain has a 90° phase shift compared to the initial oscillating powertrain provided to the power grid. Due to the 90° phase shift, this remaining oscillating powertrain cannot be immediately converted to AC power for provision on the same power grid. The energy reservoir is therefore used to temporarily store excess energy of the remaining vibrating powertrain. The stored energy is then supplied to the DC/AC converter. Therefore, the stored surplus energy can be converted into AC power that is synchronized (with the same phase and frequency) with the same power grid.

[0025] The MEUPT controller measures the energy level of the reservoir, estimates the amount of energy in the reservoir that is extractable, and delivers this information to the associated DC/AC converter so that this amount of energy is extractable by the DC/AC converter. The DC/AC converter then extracts the stored energy from the reservoir for conversion to AC power in the form of a suitable pulsating power train and provides the AC power to the power grid. Thus, when a PV power plant incorporates a MEUPT optimizer, it can provide almost all of its produced electrical energy to the power grid. In contrast, without the MEUPT optimizer, the PV power plant according to the referenced patent publication can provide less than half of its produced power/energy to the power grid.

[0026] Section 2: Improving conventional PV power plants with MEUPT
[0027] Solar power plants are often rated by the number of megawatts (MW). Traditionally, when a solar power plant is advertised as rated at x MW (where x is some positive number), this is the DC power production rating of all solar strings. This means that the total is x MW. Such conventional solar power plants also have a three-phase DC/AC converter with a total manufacturer declared DC/AC conversion capacity of no more than x MW. This principle summarizes the operation of conventional power plants with conventional MPPT implementations.

[0028] In other words, a conventional PV power plant rated at x MW consists of a string of x MW PV photovoltaic panels, which convert solar energy into DC electricity. The generated DC electricity is then extracted by a three-phase DC/AC converter, converted into suitable AC power that meets all the AC power requirements of the power grid, and then provided to the power grid. This AC power provided to the power grid is also referred to herein as the "initial oscillatory powertrain." Recall that the total manufacturer-declared DC/AC conversion capacity of the DC/AC converter is no greater than x MW, which is the total amount of DC generation capacity of the installed photovoltaic panels declared by the photovoltaic panel industry.

[0029] According to the description in referenced patent publications US2016/0036232 and US2017/0149250 A1, an initial oscillating power train (extracted by an energy extractor) is subtracted from the total DC power produced by a photovoltaic panel string. Rest vibrations that occur when the powertrain is present. In other words, this powertrain is a residual oscillating powertrain that has about a 90° phase difference from the initial oscillating powertrain extracted by the energy extractor and provided to the power grid.

[0030] Since the remaining oscillating powertrain is approximately 90° out of phase from the power grid, this remaining oscillating powertrain is directly conditioned, converted to AC power, and provided to the same power grid. It is possible to According to the principles disclosed in the referenced patent publications, an energy reservoir temporarily stores the energy contained within this 90° out-of-phase residual oscillating powertrain (represented surplus energy stored time). After this surplus energy is stored in an energy reservoir, it can serve as DC energy that can be supplied to a DC/AC converter. This surplus energy can then be converted to AC power that meets all power grid requirements (including synchronization with the power grid), and thus the resulting AC power may be applied to the same grid. .

[0031] Section 3: Preventing Energy Leakage from the Energy Reservoir
[0032] Before elaborating on the energy reservoir design considerations for the MEUPT optimizer, a key issue is first addressed herein. Specifically, a photovoltaic panel string may have very high resistance at nightfall, but when the sun is strong at noon, the photovoltaic panel string may conduct significant current in either direction. Thus, electrical energy stored in the reservoir may leak through and heat the photovoltaic panel during the day. Thus, decoupling diodes may be added to each of the photovoltaic panel strings such that electrical energy can flow from each photovoltaic panel string to charge the reservoir, but the energy in the reservoir cannot flow back from the reservoir to the photovoltaic panel string. Next, various energy reservoir systems that achieve this decoupling are described with reference to Figures 1A, 1B, and 1C.

[0033] Section 4: Design Considerations for Energy Reservoirs
[0034] Figure 1A shows a block diagram illustrating an energy reservoir 1300A designed to temporarily store excess power resulting from the power stream produced from a set of solar cell strings 1100A that subtracts from the power extracted by the DC/AC converter 1200A when it converts that power to AC power. The AC power is provided to an AC power grid 1600A through a transformer 1500A. The reservoir 1300A receives the remaining oscillating power train through a set of decoupling diodes 1400A. In one example, this energy reservoir 1300A is designed to temporarily store the excess energy of a 1 MW PV power plant for 2 minutes.

[0035] As an example only, assume that the main energy source can be kept at constant intensity for 2 minutes (and that the PV string 1100A power production is kept to allow constant 1 MW generator power production). do. In the analysis below, both the initial vibration powertrain and the remaining vibration powertrain have the same iteration shape, but with a 90 degree phase difference. First, we examine how energy reservoirs can be designed using brute force. Note that the purpose of the energy reservoir is to temporarily store excess energy so that the DC/AC converter can later convert this stored energy.

[0036] As discussed in the referenced patent publications, the estimated ratio of surplus energy to produced DC electrical energy is greater than 0.5 for typical conventional PV power plants. For analysis, the PV power plant has a 1 MW PV photovoltaic panel string, and the DC power is converted to AC power to provide VAC 3-phase AC power to a grid and line voltage of 380 Hz, which is 50 Hertz. Assume that In this case, the duration of one power cycle is equal to approximately 0.01 seconds, and the total phase current is up to 1,000,000/(380/1.732), where 1.732 is the square root of 3. is the value of This ratio is the ratio of peak voltage to line voltage (line-to-phase voltage or "phase voltage" in three-phase AC power). Storing the charge associated with excess energy within the power cycle for this power plant is approximately 8V Faraday (0.5*0.01*1,000,000/(380/1.732)) would require equivalent charge capacity. Here, “V” is the designed voltage difference before and after charging the reservoir.

[0037] To maximize the energy utilization of this PV station, in some embodiments, the operating voltage of the MEUPT optimizer should be within 75% of the PV maximum power production voltage. In other words, a voltage range of 75% maximum power production should be observed in those embodiments of the MEUPT optimizer. Measured IV data typically indicates that this range is about 80 volts. When this voltage range is selected as the charge/discharge voltage range for the energy reservoir (i.e., V = 80 volts), the charge capacity of the energy reservoir is approximately 0.1 Faraday/MW/power cycle (where and the power cycle lasts 0.01 seconds).

[0038] If the design consideration is to store this maximum amount of excess energy accumulating over two minutes, then the equivalent charge capacity required is equal to 1200 Faradays (100*120*0.1) for a 1 MW PV plant. In this specification, this equivalent charge capacity required is referred to as the "full maximum charge capacity" and the amount of energy stored in the associated reservoir is referred to as the "full maximum energy reservoir capacity" or "full maximum excess energy."

[0039] If thin film capacitors were to be used to meet this required charge capacity, the set of thin film capacitors required to achieve that charge capacity would be extremely large in volume and cost prohibitive in terms of capital. expensive. Therefore, it is impractical to design such an energy reservoir consisting only of thin film capacitors.

[0040] As a twist to this brute force design, Faraday devices (such as batteries) could be incorporated into the design to reduce volume and size. Our careful analysis revealed that the required charge capacity is in fact technically manageable for energy reservoirs with thin film capacitors and Faraday devices. However, the cost of such reservoirs remains too high to be beneficial unless the price of the battery can be reduced by at least a third while maintaining the same performance.

[0041] By using electrolytic capacitors, the required capital cost can be substantially reduced. However, such would increase operating costs due to the relatively short lifetime of such capacitors. Therefore, the use of electrolytic capacitors is also currently impractical. Therefore, the brute force approach does not achieve an economically advantageous design with the full required maximum energy reservoir capacity.

[0042] The principles described herein solve this problem using the following observations by the inventors.
(1) Most existing DC/AC converters can easily step up or down by 3% in 1 second. Furthermore, an existing 500kW DC/AC converter can easily step up or down by more than 10kW in one second during operation.
(2) As a rough observation, a typical 1 MW PV power plant starts producing electricity from zero power every morning and, in its normal daily operation, rarely ramps up its electricity production faster than 10 kW/s. .
(3) MW-level PV power plants (supposedly rated greater than 1 MW) can sometimes experience ramp rates greater than 10 kW per second during short power surges. However, the energy contained in this short surge (or even in the larger 100 kW per second surge) is small when compared to the total daily energy produced in a MW level power plant.

[0043] Given these three factors, the inventors have determined that (1) power generation in each of the photovoltaic panel strings starts at zero each morning, and (2) the PV generators do not instantly generate full power. Thus, the remaining oscillating power train does not instantly ramp up to its maximum value. In other words, the remaining oscillating power train generally ramps up much more gracefully than the ramp rate of a DC/AC converter. Moreover, the amount of energy in any short ramp-up spike is not a significant issue in energy collection for PV stations rated at 1 MW or greater.

[0044] Thus, instead of designing an energy reservoir that is capable of storing the full maximum amount of excess energy, the principles described herein propose to design the reservoir to store a net amount of energy (e.g., over two minutes) equal to the difference between the excess energy input to the reservoir and the energy that the DC/AC converter extracts from the reservoir. This amount of energy is referred to herein as the "maximum differential excess energy." This amount of maximum differential excess energy is much smaller than the maximum full excess energy. It is therefore easier to design such a smaller energy reservoir. This is both manageable in technology and cost-effective.

[0045] FIG. 1B shows a block diagram symbolically illustrating an energy reservoir 1300B that stores excess power resulting from a power stream produced from a set of solar cell strings 1100B that reduces the power extracted by a DC/AC converter 1201B. At the same time, another DC/AC converter 1202B is supported by MEUPT controller 1310B to receive approximately the same amount of DC energy from energy reservoir 1300B (including surplus power). Both DC/AC converters 1201B and 1202B simultaneously convert the received DC energy to AC power and provide the AC power to the same grid 1600B through the same transformer 1500B. In doing so, the net energy storage load on reservoir 1300B can be reduced to a much smaller capacity when compared to the capacity of reservoir 1300A shown in FIG. 1A.

[0046] FIG. 1C shows a configuration modified from that shown in FIG. 1B, but with approximately the same performance of the configuration shown in FIG. 1B. As shown in FIG. 1C, the energy reservoir 1300C stores the DC power stream produced by the PV solar cell string 1100C through the diode set 1400C. The two DC/AC converters 1201C and 1202C are instructed by the MEUPT controller 1310C to receive approximately the same total DC power (as a whole) from the energy reservoir 1300C in an amount approximately equal to the DC energy input produced by the PV string. Thus, there is a very small net power input balance at the input and output of the reservoir 1300C. Both 1201C and 1202C simultaneously convert the received DC power to AC power provided to the same grid 1600B through the same transformer 1500C.

[0047] In summary, as shown in FIG. 1B, the energy reservoir (when properly decoupled) allows the produced DC power to be integrated into the energy extractor (which can be incorporated as a module in the DC/AC converter 1201B). Excess energy can be extracted and stored in the form of the residual vibrating powertrain that remains after being extracted by the The other DC/AC converter 1201B is designed to extract approximately an equal amount of energy from the energy reservoir 1300B to reduce the net amount of excess energy stored in the reservoir. Therefore, relatively small reservoirs are appropriate.

[0048] As also shown in FIG. 1C, the energy reservoir 1300C (when properly decoupled) can receive all the produced DC power from the PV string 1100C. The oscillating power train is then extracted by the DC/AC converters 1201C and 1202C, but the excess energy (leftover power) is also implicitly stored in the energy reservoir 1300C in the form of the remaining oscillating power train, which is 90° out of phase. As can be seen, this excess energy is also implicitly automatically extracted and stored in the reservoir 1300C.

[0049] Applying either of the designs shown in FIG. 1B (or FIG. 1C), the designed energy reservoir can serve as an energy reservoir for the purpose of the MEUPT optimizer. This temporarily stores a small amount of net excess energy that is 90° out of phase. The demanding task of energy reservoir design is then shifted to the task of designing a suitable MEUPT controller.

[0050] Section 5: Required functions of MEUPT controller
[0051] The controller should be able to direct the associated DC/AC converter to consistently extract an appropriate amount of energy from the reservoir that is substantially equal to the amount in surplus power charging the reservoir. It is. In doing so, the net amount of energy storage into the reservoir can be minimized and an appropriately balanced energy storage within the reservoir can be maintained to stabilize system operation. In doing so, the energy reservoir only needs to store (or provide) the energy difference between the surplus power to be charged and the power extracted by the short time duration DC/AC converter.

[0052] With a capable controller, the energy difference can be designed to be manageably small. The time duration is long enough to step up or down to the DC/AC converter in matching excess energy, and long enough to significantly reduce the capacity of the reservoir while still keeping system operation stable. It can be designed to be as short as possible. Therefore, the estimated reservoir capacity can be reduced to less than 0.001 times the maximum full surplus energy capacity. This capacity is less than 2 Faradays per 1 MW PV power plant, a manageable charge capacity even when using thin film capacitors. An example of a suitable MEUPT controller is described below with respect to Sections 12-14 below.

[0053] Section 6: Combined Capacitor/Battery Energy Reservoir
[0054] Another problem is that a good thin film capacitor can last 10-15 years while still retaining more than 80 percent of its original capacity, whereas a good battery can last less than 5 years and have nearly 70 percent of its charge capacity after that time. Therefore, a careful design balance is suggested to optimize the economic cost. Moreover, the amount of energy in the reservoir should be large enough to stabilize the operation at all times. Design simulations show that with the current prices of thin film capacitors and batteries, a typical 20-year optimal energy reservoir design for a 1 MW PV station is one with a 0.1-1 Faraday thin film capacitor combined with an approximately 50 amp-hour automatic battery string with an appropriate operating voltage.

[0055] Section 7: Preventing Mutual Power Dissipation within PV Strings
[0056] As explained above, the decoupling technique applied in FIGS. 1B and 1C allows the string of photovoltaic panels to charge the energy reservoir, while power is transferred from the reservoir to the PV solar panels. Prevents backflow into the battery string. When properly applying a set of decoupling diodes, this technique can not only prevent energy leakage from the reservoir through the PV photovoltaic panel string, but also the phenomenon discovered by the inventors. can. This phenomenon is referred to herein as a "mutual power dissipation phenomenon between PV strings,""mutual power dissipation phenomenon," or "power dissipation phenomenon."

[0057] This phenomenon occurs when several parallel-connected PV strings collect the produced power. This phenomenon is especially noticeable when the parallel-connected PV strings have very different I-V characteristics, photovoltaic conversion efficiencies, and/or maximum power production voltages.

[0058] For example, when less than all photovoltaic panels in less than all strings are cast with a shadow, the strings that are in the shadow will have lower photovoltaic conversion efficiencies than those outside the shadow. has. In other words, these solar cell strings will have very different IV characteristics even at the same time of day due to the different casting of the shadow. When these solar strings are connected in parallel, the high efficiency strings transfer a portion of the produced power to the lower efficiency solar strings in order to interrupt the power production within the PV solar strings. can be discharged to. The inventors experimentally confirmed this phenomenon. Experiments also show that this phenomenon is preventable when PV solar cell strings are properly decoupled.

[0059] Moreover, the power dissipation phenomenon can also occur when the parallel-connected PV strings have very different maximum power production voltages. For example, assume there are two parallel-connected photovoltaic panel strings, one with 15 stringed photovoltaic panels and the other with 19 stringed photovoltaic panels. The power generated in the string with 19 panels flows deterministically through the string with 15 panels, and the power dissipation phenomenon occurs. Experiments show that the power received from the two parallel-connected strings can be reduced to less than half of the power produced by the string with 19 panels alone. When properly decoupled, the power received from the two parallel-connected strings can be restored to about 1.53 times the power produced by the string with 19 panels alone. The experiments described above show that (a) the mutual power dissipation phenomenon exists, and (b) proper decoupling techniques can prevent this phenomenon.

[0060] In another experiment, a PV plant was arranged to have two power producing units. Each unit consisted of 85 photovoltaic panels of the same make and model. Each of the two power producing units was configured with five parallel connected PV strings to collect the produced DC energy. The two PV strings were configured with 15 panels connected in series, two strings with 17 panels connected in series, and another string with 21 panels connected in series. When the maximum power production voltages of these 10 strings were measured separately at noon under clear skies, the maximum power production voltages ranged from a minimum of 420 volts to a maximum of 610 volts. Thus, these parallel connected PV solar cell strings have very different maximum power production voltages under the same clear sky.

[0061] Each of the power production units converts the collected DC power to AC power via a different DC/AC converter. To measure the energy and power produced within each production unit, a kilowatt clock and wattmeter were connected to the AC output of each of the DC/AC converters of each production unit. These units were then connected to a transformer to provide AC power to the grid. If there are 72 identical readings of two wattmeters over a period of 36 days, and at the end of this 36 day period there are identical readings of two kilowatt clocks, then the It is confirmed that all elements (including the two sets of instruments) were substantially identical.

[0062] One power producing unit was then modified to be configured with four strings of 21 panels (and one unused panel), while the other power producing unit remained unchanged from the five strings described above. The measured power production of the modified power producing unit was typically 4.1 times greater than the power production of the other power producing unit at noon when the sky was clear. The accumulated energy provided was then measured for 60 days. This energy was obtained from the readings of the two kilowatt clocks. The modified power producing unit provided 3.38 times more energy to the grid than the unmodified power producing unit. The above experiments clearly and conclusively prove that the mutual power dissipation phenomenon does indeed exist within parallel connected PV strings, especially with strings having very different I-V characteristics or very different maximum power voltages.

[0063] In conclusion, appropriate decoupling techniques according to the principles described herein can prevent energy leakage from the energy reservoir through the solar cell strings and also prevent the discovered mutual power dissipation phenomenon between PV strings.

[0064] Section 8: Experiments to prove the existence of surplus energy
[0065] Before describing the design of the MEUPT optimizer, this section describes an experiment that conclusively proves the existence of excess energy in such a PV power plant. This is predicted by the referenced patent publications US 2016/0036232 and US 2017/0149250 A1. Again, the referenced patent publications define excess energy as electrical energy that is produced but not extracted and/or utilized before being converted to heat. Specifically, in a PV power plant, "excess energy" includes the remaining electrical energy that exists after the produced DC energy is extracted and converted to AC power by a three-phase DC/AC converter. The MEUPT optimizer can be designed to capture/utilize this remaining electrical energy, i.e., excess energy. In the following, the experimental setup and step-by-step execution of the experiment are described.

[0066] FIG. 2A shows a starting setup of a PV power plant 2000A with two AC power production units 2100A and 2200A. Each of AC power production units 2100A and 2200A performs blind MPPT verification and provides three-phase AC power to power grid 2600A. AC power production unit 2100A consists of a DC generator 2110A and a three-phase DC/AC (15kW) converter 2130A. AC power production unit 2200A consists of a DC generator 2220A and a 3-phase DC/AC (15kW) converter 2230A. Generator 2110A uses two parallel connected PV strings 2111A and 2112A to generate DC electricity. Power generation 2220A uses two other parallel connected solar cell strings 2221A and 2222A to generate DC electricity. Each of the four PV strings consists of 25 series connected photovoltaic panels. Each panel is capable of producing 250W of power at noon on a clear day.

[0067] The DC generator 2110A supplies DC power to the three-phase DC/AC converter 2130A. The DC generator 2220A supplies DC power to the three-phase DC/AC converter 2230A. These two converters 2130A and 2230A then convert the supplied DC power to three-phase AC power. In the experiment, the AC output power of the power producing units 2100A and 2200A was measured by two three-phase AC wattmeters (in kW) 2351A and 2352A, respectively. The AC energy production (in kW*hours) of these two power producing units 2100A and 2200A was also measured by two kW clocks 2361A and 2362A, respectively. The produced three-phase AC power was then provided to the grid 2600A via the transformer 2500A. The PV power plant was operated and the energy production of the two AC power producing units 2100A and 2200A was measured for a period of seven days.

[0068] The readings of the two kW clocks were equal every day during this time period. This provides a high degree of confidence that all elements of the two power producing units 2100A and 2200A (including the two sets of measuring equipment) are substantially identical. After this step, one of the two AC power producing units 2200A was kept unchanged, while the other AC power producing unit 2100A was modified to have a different configuration 2100B, shown on the left side of FIG. 2B.

[0069] Power production unit 2200B of FIG. 2B is unmodified power production unit 2200A of FIG. 2A. Further, elements 2351B, 2361B, 2352B, 2362B, 2500B, and 2600B in FIG. 2B are the same as elements 2351A, 2361A, 2352A, 2362A, 2500A, and 2600A in FIG. 2A, respectively. Moreover, although the configuration of power production unit 2100B is different in FIG. 2B than power production unit 2100A of FIG. 2A, some of the elements of power production unit 2100B of FIG. 2B are included within power production unit 2100A of FIG. 2A. It is the same as the element shown in For example, PV strings 2111B and 2112B of FIG. 2 are the same as PV strings 2111A and 2112A of FIG. 2A, respectively. Similarly, DC/AC converter 2130B in FIG. 2B is the same as DC/AC converter 2130A in FIG. 2A.

[0070] The following six steps describe how power production unit 2100A was modified to the configuration of 2100B and are described with reference to the left side of FIG. 2B. Step 1 is to add a set of decoupling diodes 2311B between the solar cell strings 2111B and 2112B and the 3-phase DC/AC converter 2130B, which implements blind MPPT verification. Step 2 was to add energy reservoir 2410B to the configuration. Step 3 was to connect energy reservoir 2410B to the DC terminal of DC/AC converter 2130B through another set of decoupling diodes 2312B and through the SW1 switch. Step 4 was to add another 3-phase DC/AC converter 2130S (20kW) to the configuration. Converter 2130S was operated according to the designed direction of MEUPT controller 2420B. Step 5 was to connect the DC/AC converter 2130S to the energy reservoir 2410B through another set of decoupling diodes 2313B and through switch SW2. Step 6 was to connect the output terminal of converter 2130S to power and energy measurement equipment sets 2351B and 2361B through switch SW3. Note that the referenced "decoupling diode set" may be diodes called "blocking diodes" in the art. Switches SW1, SW2, and SW3 are added as shown in FIG. 1B, so that the associated devices can be introduced into (or removed from) the experiment at appropriate times in the designed experiment execution steps described below. It should also be noted that

[0071] The first evening after the above modifications were made. SW1 was turned on, but switches SW2 and SW3 were turned off. Converters 2130B and 2230B began operating early the next morning. Power meters 2351B and 2352B measuring the two outputs of power production units 2100B and 2200B gave the same reading. Reservoir 2410B also begins to charge, as indicated by the measurement of a high terminal voltage on reservoir 2410B. The system operated as described throughout the first day. The measured energy provided by the two power production units 2100B and 2200B were equal, as shown in the readings of kW clocks 2361B and 2362B. This experimental step showed that the added decoupling diode set 2311B and reservoir 2410B did not change the power and energy production of power production unit 2100B.

[0072] Switches SW1, SW2, and SW3 were turned on the night after the first operating day (second night). Converters 2130B and 2230B began operating early in the morning (second day), and converter 2130S began operating at a lower power conversion level approximately 15 minutes after converters 2130B and 2230B began operating. Thereafter, converter 2130 increased its conversion power level approximately every two minutes. This is consistent with controller design and reservoir energy level increments. The reading on wattmeter 2351B (for unit 2100B) reached approximately twice the reading on wattmeter 2352B (for unit 2200B) throughout the day and until approximately sunset. The energy provided by the two power production units 2100B and 2200B until the end of the second day was obtained from the readings of the two kW clocks. The results showed that the energy provided from the modified power production unit 2100B was more than twice the energy provided from the unmodified power production unit 2200B. For the next six consecutive days, switches SW1, SW2, and SW3 remain on, and the energy provided by the modified power production unit 2100B is consistently greater than twice the energy of the power production unit 2200B each day. Ta.

[0073] The following evening, switches SW2 and SW3 were turned off. The measured energy provided from power producing units 2100B and 2200B returned to the same level for the next five consecutive days with switches SW2 and SW3 remaining turned off. The next evening, switches SW2 and SW3 were turned on again. The measured energy production of power producing unit 2100B was again greater than twice the energy production of power producing unit 2200B for each of the next five consecutive days with switches SW2 and SW3 remaining on.

[0074] As explained above, the step-by-step implementation of this experiment will reduce the Conclusively prove the existence of energy. Specifically, in a PV power plant, when the produced DC energy is extracted by a three-phase DC/AC converter, residual energy still exists. The MEUPT optimizer can capture and utilize this excess energy to increase the electricity provided to the power grid.

[0075] Section 9: Designed MEUPT Optimizer Configuration
[0076] The modified power generation unit 2100B (described above and shown in FIG. 2B) can serve as an example of a PV power generation unit that incorporates a MEUPT optimizer. In this case, the MEUPT optimizer includes three decoupling diode sets 2311B, 2312B, and 2313B, a reservoir 2140B, and a MEUPT controller 2320B. Note that in the following the decoupling diode set is referred to as "decoupling device".

[0077] The connections of the MEUPT optimizer module are shown in FIG. 2B and described above. Note that the excess energy is passively extracted by the energy reservoir 2410B in this embodiment. Another power extractor is included as a module in the three-phase DC/AC inverter 2130S, which extracts the excess energy stored in the reservoir 2410B. The AC power conversion level of the converter 2130S is regulated by the MEUPT controller 2320B so that the power charge to the energy reservoir 2410B is approximately balanced with the power discharged from the energy reservoir 2410B. Thus, the "net" power charged to the reservoir in a period of time can be as small as you like. A smaller power charge has the benefit of allowing a smaller energy reservoir 2410B, at the expense of tighter control by the MEUPT controller 2320B.

[0078] Another embodiment is shown in FIG. 3. This embodiment shows a PV power plant 3000 configuration incorporating a MEUPT optimizer with only one AC power production unit 3100 that converts solar power to DC power using a 500 kW photovoltaic panel 3110. In other words, the AC power production unit 3100 consists of a DC generator 3110 and a three-phase DC/AC (500 kW) converter 3130. The generator 3110 generates DC electricity using 80 parallel connected solar cell strings. Each of the 80 solar cell strings consists of 25 parallel connected solar cell panels. Each panel is advertised to have a DC power production capacity of 250 W at noon with clear skies. Note that this DC generator 3110 is called a 500 kW electric generator (80*25*250W=500kW) and this PV plant is called a 500 kW PV plant.

[0079] As shown in FIG. 3, a generator 3110 provides DC power to a three-phase DC/AC converter 3130 (with an advertised 500 kW) through a decoupling device 3311. The generator 3110 is a server as a DC energy source that also supplies DC power to the energy reservoir 3410 through the decoupling device 3312 to charge the energy reservoir 3410. Therefore, excess energy is passively extracted by the reservoir 3410. The reservoir 3410 then supplies (or discharges) DC power to another three-phase DC/AC converter 3130S (with an advertised 500 kW) through a decoupling device 3313. Converter 3130 operates as an MPPT optimizer and converter 3130S operates as a MEUPT controller. Converters 3130 and 3130S convert separately supplied DC power to three-phase AC power and deliver it to power grid 3600 via the same transformer 3500.

[0080] The DC/AC converters used in the above description are of two types: one type that receives its DC power directly from a PV solar cell string and another type that receives its DC power from an energy reservoir. Note that it can be classified into two types. When a distinction between types of converters is necessary in this disclosure and the detailed description below, herein the type that receives DC power from a PV solar cell string is also referred to as a "PS DC/AC converter" and is referred to as a "PS DC/AC converter" The other type, which receives DC power from a reservoir, is also referred to as an "ER DC/AC converter." When that distinction is necessary when using three-phase DC/AC converters in this disclosure, the converters are classified herein as "PS three-phase DC/AC converters" and "ER three-phase DC/AC converters," respectively. called a converter.

[0081] To reiterate on a broader level, as the configuration shown in FIG. Provides optimization services for PV power plants. The produced DC power is extracted by the manufacturer's MW "PS 3-phase DC/AC converter" 4130 through a decoupling device 4311. The remaining power is charged into an energy reservoir 4410 through another decoupling device 4312, thus extracting and storing excess energy. The stored surplus energy is then converted by another manufacturer's publication z MW "ER 3-phase DC/AC Converter" 4130S through another decoupling device. One of the converters 4130 is regulated by the MPPT optimizer and the other converter 4130S is regulated by the MEUPT controller. Both converters convert the appropriate amount of DC power to three-phase AC power and provide the three-phase AC power to the power grid 4600 via the same transformer 4500. Note that in this configuration, x=y=z=0.5.

[0082] FIG. 5 illustrated another embodiment incorporating a MEUPT optimizer within a large-scale PV power plant. The power plant is equipped with a photovoltaic panel string 5110 rated at 0.5 MW and two announced 500 kW three-phase DC/AC converters 5130 and 5130S. This embodiment shows another configuration for the MEUPT optimizer. PV power plant 5000 may be considered to include one AC power production unit (hereinafter also referred to as "AC power production unit 5100"). The AC power production unit 5100 consists of a DC generator 5110 consisting of a photovoltaic panel rated at 500 kW and two 3-phase DC/AC (each rated at 500 kW) converters 5130 and 5130S. Generator 5110 uses 80 parallel connected solar cell strings to generate DC electricity. Each of the 80 solar cell strings consists of 25 parallel-connected photovoltaic panels. Each photovoltaic panel is rated to have a DC power production capacity of 250W. Energy reservoir 5410 receives DC power from generator 5110 through decoupling device 5311. The two three-phase DC/AC converters 5130 and 5130S extract DC power from the reservoir 5410 through two separate decoupling devices, including a decoupling device 5312 for converter 5130 and a decoupling device 5313 for converter 5130S. receive. Converters 5130 and 5130S are regulated by the MEUPT controller to extract the appropriate amount of power from reservoir 5410 and convert DC power to three-phase AC power for provision to power grid 5600 via transformer 5500.

[0083] To elaborate more broadly on the configuration shown in FIG. 5, the MEUPT optimizer provides optimization services for an x MW PV power plant. The PV power plant has one AC power production unit with a string of photovoltaic panels having a total rated DC power generation capacity x MW. The DC generator charges the energy reservoir through the decoupling device. The energy reservoir supplies DC electricity to two three-phase DC/AC converters through two separate sets of decoupling devices. The total manufacturer declared conversion capacity of the two "ER 3-phase DC/AC converters" is z ₁ +z ₂ =z MW. The two converters are regulated by the MEUPT controller to convert the appropriate amount of DC power to three-phase AC power. The electricity produced by the two converters is provided to the power grid via the same transformer. The configuration described above is a modification and is shown in FIG. Note that in this configuration, x=0.5, y=0, z=1.

[0084] This specification will now compare the two configurations shown in FIGS. 4 and 6. In the configuration shown in FIG. 4, the DC generator supplies DC power to a "PS 3-phase DC/AC converter" with a manufacturer's declared capacity of y MW, and charges the energy reservoir with the remaining power. In FIG. 4, the energy reservoir supplies DC power to an "ER 3-phase DC/AC converter" with a manufacturer's declared capacity of z MW. Without the PS 3-phase DC/AC converter in the configuration shown in Figure 6 (i.e., y=0), the generated DC power charges the energy reservoir through the decoupling device, and the energy reservoir Supply DC electricity to two ER 3-phase DC/AC converters through two separate sets of devices. Therefore, in the configuration of FIG. 3, x=y=z=0.5, and in the configuration of FIG. 6, x=0.5, y=0, z=1. In a further embodiment of FIG. 6, there is no energy reservoir 6410. Instead, solar cell string 6110 provides DC power to converter 6130 via decoupling device 6311.

[0085] The only remaining design problem for the MEUPT optimizer is then to identify the optimal power match relationship between the parameters representing the rated capacity of the solar cell string and the parameters of the converter. Specifically, the task is to identify the relationship between x, y, and z values in the optimal situation. As a note, the value of the sum y+z is not greater than the value x in a conventional PV power plant, as explained in Section 2.

[0086] The value x is specified for the MW value of the rated DC power production capacity of the PV string, and the value y is specified by the manufacturer of the "PS 3-phase DC/AC converter" that converts the DC energy provided by the PV string. The value z is specified for the total MW value of the declared capacity, and the value z is specified for the total MW value of the manufacturer declared capacity of the "ER 3-phase DC/AC converter" converting the DC energy supplied by the energy reservoir. Please also note that.

[0087] For example, in FIG. 6, x is equal to 0.5, i.e., 0.5 MW manufacturer's declared total PV capacity. y is equal to 0, meaning that no "PS 3 Phase DC/AC Converter" is installed. z is equal to 1, meaning that 1 MW total manufacturer's declared capacity of two "ER 3 Phase DC/AC Converters" is installed to receive DC power from the energy reservoir and convert the DC energy to three-phase AC power. Note that the value of y+z is not less than twice the value of the x value in both of the configurations described above. The term "capability" is also referred to as the "power rating" of the device and is interchangeable unless otherwise indicated.

[0088] Section 10: Optimal Power Match Relationship.
[0089] Due to different disciplines (industries), the definition of power ratings for photovoltaic panels is different from that of DC/AC converters. The power rating of a photovoltaic panel is defined as the maximum DC power that the photovoltaic panel can produce at noon with clear skies. The photovoltaic panel manufacturing industry uses certain types of lighting lamps (referred to herein as "standard lamps") to simulate clear skies. Noon is simulated by vertically illuminating the luminous flux through the solar penal surface. Therefore, the manufacturer's published power production capacity may be very close to the actual DC generator capacity. Experiments carried out by the inventors also confirm the above statement. Therefore, the total DC power generation capacity of the PV solar cell string is determined to be reliable. The title "Manufacturer Published Capability" is omitted herein when discussing the power rating of a solar cell string. On the other hand, the DC/AC converter manufacturing industry defines power ratings for DC/AC converters according to power grid industry conventions, referred to herein as "power grid conventions." This convention and definition of DC/AC converter capability is detailed below.

[0090] The AC power grid industry enforces conventions (referred to as power grid conventions) to ensure that constructed three-phase AC power grids can meet declared power delivery capabilities. A three-phase AC power grid consists of three or four power lines that can deliver a time-varying sinusoidal function of voltage and current as one phase in each pair of power lines. Power grid conventions define voltages that are published in standards as the "standard" maximum voltage that power lines can withstand (referred to as "line voltage"). Similarly, the specified maximum current published in the standard is the maximum current that the power line will carry (referred to as the "maximum phase current"). When a device is manufactured to follow power grid conventions, the voltage published in the device's standard is the maximum voltage that all relevant components must withstand. Similarly, the maximum current published in a standard is the maximum current carrying capacity for all relevant components of one phase connected to one pair of power lines. The time-varying functions of device voltage and current must also follow a sinusoidal function for each phase in the AC power grid.

[0091] To reiterate, the specified voltage of a three-phase DC/AC converter is defined as the line voltage of the three-phase power. The specified maximum current is defined as the maximum current carrying capability of the pair of power lines for each phase. The specified maximum power is defined as the sum of the maximum power capabilities that the three phases can withstand. In other words, when following power grid conventions, the power lines of each phase and the connected power devices should be capable of delivering one third (1/3) of the specified maximum power, or, in other words, the "manufacturer's declared power rating" of a three-phase DC/AC converter is 3*U*I, where U is the phase voltage and I is the phase current. Each pair of power lines is capable of delivering U*I power, or 1/3 of the "manufacturer's declared power rating." Each module that connects to a pair of power lines is also required to carry or deliver 1/3 of its published specified power rating when following power grid conventions.

[0092] For example, consider a three-phase DC/AC converter that specifies "AC voltage = 315 VAC, maximum current = 916 Amps, and maximum power output = 500 kW." The designation "AC voltage = 315 VAC" should be read as "The output line voltage of this converter is 315 volts." Or, when the three phases are balanced, the phase voltage U of any phase is U = 315/1.732 = 181.9 volts (where 1.732 is the line voltage to phase voltage ratio, the square root of 3). The specified "maximum current = 916 amps" should be read as the power lines and all components in each phase are designed to guarantee I = 916 amps of current carrying capability. The specified "maximum power output = 500kW" is the maximum power conversion and delivery capability of all components of each DC/AC conversion phase = U * 1 = 181.9 * 916 = 500 / 3KW, and 3 conversions The total maximum power conversion and delivery capacity of the associated modules in a phase is the sum of each phase or 3*U*I=3*181.9*916=500kW, which is based on the power grid conventions mentioned in the previous paragraph. When following, it should be understood that the defined "Manufacturer Published Power Rating" = 3*U*I.

[0093] The three phases in a three-phase DC/AC converter are closely correlated to have a 120° phase difference. In other words, one pair (phase) of power lines delivers a time-varying power of U*I sin ² (ωt). The second phase delivers a time-varying power of U*I sin ² (ωt+120°), and the third phase delivers a time-varying power of U*I sin ² (ωt-120°). to be delivered. Each pair of three phase power lines delivers three closely correlated oscillating AC power trains. Note that the power conversion capacity P(t) is not equal to the defined "manufacturer published power rating". The power conversion capacity P(t) is expressed as a function of time and is obtained according to a defined three-phase AC power limit.

[0094] In other words, the DC/AC power conversion capacity P(t) has a strictly correlated phase difference of 120° and a power waveform that follows a squared sinusoidal oscillation of sin ² (ωt) or cos ² (ωt). is obtained from the sum of the time-varying power outputs of three phases, with ω, synchronized with a power grid (same phase and frequency) that forces a constant angular frequency ω.

[0095] Next, the time-varying power conversion capacity P(t) of the three-phase DC/AC converter is obtained. The power conversion capacity of a three-phase DC/AC converter as a function of time is P(t)=U*I*(sin ² (ωt)+sin ² (ωt+120°)+sin ² (ωt−120°)). As defined above, U is the phase voltage, I is the phase current, and ω is the constant angular frequency of the power grid. It can also be shown that sin ² (ωt+120°)+sin ² (ωt−120°)=cos ² (ωt)+1/2. Therefore, the power conversion capacity P(t) of a three-phase DC/AC converter as a function of time is: P(t)=U*I*(sin ² (ωt)+sin ² (ωt+120°)+sin ² (ωt−120 ))=U*I*(sin ² (ωt)+cos ² (ωt)+1/2)=U*I*(1+1/2)=3/2(U*I).

[0096] In other words, the sum of these three strictly correlated pulsating powertrains in three phases is constant. In other words, the total power delivery of these three pairs of power lines is constant. That is, the sum of the three modules associated with the three phases is constant. However, this constant is only equal to one-half (1/2) of the "declared power capability." This is the relationship between power conversion capacity and the defined "published power capability" of a three-phase DC/AC converter when following power grid conventions.

[0097] Recall that, as explained earlier, the "manufacturer's declared power rating" or the referenced "manufacturer's declared power capability" of a three-phase DC/AC converter is 3*U*I when following power grid convention. Comparing this with the power conversion capacity obtained above, P(t)=3/2(U*I). It is clear that the DC/AC power conversion capacity of the obtained three-phase DC/AC converter is only half of the "manufacturer's declared power capability".

[0098] As an example, take again the three-phase DC/AC converter described above. This three-phase DC/AC converter specifies "AC voltage = 315 VAC, maximum phase current = 916 amps, and maximum power output = 500 kW". In reality, the DC/AC power conversion capacity of this three-phase DC/AC converter is only 250 kW. To arrive at the above conclusion, first confirm that the advertised maximum power i.e. 500 kW is actually equal to 3*U*I, where U is the phase voltage obtained from the specified line voltage, I is the advertised maximum current, and the power conversion capacity of this converter is equal to 3/2*U*I = 250 kW.

[0099] The optimal power matching relationship (as defined) for parameters x, y, and z is such that the value of (y+z) is not less than the value of 2x. where the associated PV power plant consists of x MW PV solar cell strings, the PS 3-phase DC/AC converter has a total manufacturer declared power capacity of y MW, and the ER 3-phase DC/AC Converter has a total Manufacturer Declared Power Capability of z MW. The "PS 3-phase DC/AC converter" and the "ER 3-phase DC/AC converter" can be operated either by one or more MPPT controllers or by one or more MEUPT controllers. In order to implement MEUPT optimization, it is preferable to operate all DC/AC converters by a MEUPT controller.

[00100] Section 11: Summary
[00101] Figure 7 illustrates abstractly the configuration of a PV solar power plant 7000. The plant comprises x MW total solar photovoltaic panels arranged in solar cell strings 7100. DC power generated in solar cell strings 7100 provides DC power input to a group of three-phase DC/AC converters 7301 through decoupling device 7201 and charges excess power to a reservoir 7400 through decoupling device 7202. The energy reservoir 7400 provides DC power input to a group of three-phase DC/AC converters 7302 through decoupling device 7203. Both three-phase DC/AC converters 7301 and 7302 provide converted three-phase AC power to a power grid 7600 through a transformer 7500. The total "manufacturer declared capacity" of converter 7301 is y MW. The total "manufacturer declared capacity" of converter 7302 is z MW. The value of the sum (y+z) is not less than the value of 2x. Recall that when describing the conventional PV power plant described in Section 2 using a similar configuration, the value of (y+z) is not greater than the value of x. Therefore, when a design with a value of (y+z) is greater than x, or even better than 1.1 times x, it means that some of the excess energy can be captured to augment the electrical energy provided to the power grid.

[00102] Converters 7301 and 7302 are all operable by the MEUPT controller described above. In some embodiments, some or one of the converters are operated by the MEUPT controller, or none of the converters are operated by the MEUPT controller. Moreover, in some embodiments, one or some of decoupling devices 7201, 7202, and 7203 are optional in the configuration. PV solar cell string 7100 provides DC power input to converter 7301. Accordingly, PV solar cell string 7100 is referred to herein as a "PS converter." Energy reservoir 7400 provides DC power input to converter 7302. Accordingly, PV solar cell string 7100 is referred to herein as an "ER converter." The terms total "manufacturer published power rating" and total "manufacturer published power capability" shall be abbreviated herein as "published power."

[00103] Reiterating the description of the configuration shown in FIG. 7, the PV power plant 7000 comprises an x MW solar cell string 7100 as a DC generator. The DC generator 7100 provides input to a "PS converter" 7301 with a "declared power" of y MW through a decoupling device 7201, which charges the remaining power in a reservoir 7400 through another decoupling device 7202. The reservoir 7400 provides input to an "ER converter" 7302 with a "declared power" of z MW through a decoupling device 7203. All three-phase DC/AC converters 7301 and 7302 provide converted three-phase AC power to the power grid 7600 through a transformer 7500. In an embodiment, the value of (y+z) is not less than the value of 2x. However, when the value of (y+z) is greater than the value of x, the design can receive partial benefits to enhance the electrical energy sales to the power grid.

[00104] A MEUPT optimizer according to the principles described herein can be useful for small-scale PV power plants or large-scale PV power plants with one or more AC power production units. Moreover, with appropriately designed decoupling devices, energy leakage from the energy reservoir through the PV solar cell string can be prevented. Moreover, with properly designed decoupling devices, the discovered "mutual power dissipation" phenomenon can be prevented. It can also be used to receive only the surplus energy after the energy extraction of the "PS converter" or to receive all the DC energy produced before the extraction. Finally, the MEUPT optimizer can also serve PV power plants equipped with single-phase DC/AC converters.

[00105] Section 12: Design constraints for the MEUPT controller
[00106] Figure 8 illustrates a MEUPT controller 8000 (also referred to as a "system controller") that represents an example of the MEUPT controller 2320B of Figure 2B. The MEUPT controller 8000 consists of three executable components: a detection component 8100, a decision component 8200, and a delivery component 8300.

[00107] Detection component 8100 measures the energy level stored within reservoir 8400. Examples of reservoirs are reservoir 2410B of FIG. 2B, energy reservoir 3410 of FIG. 3, energy reservoir 4410 of FIG. 4, energy reservoir 5410 of FIG. 5, energy reservoir 6410 of FIG. 6, and energy reservoir 7410 of FIG.

[00108] The determination component 8200 determines the appropriate power draw level to approximately balance the charge provided to and discharged from the energy reservoir 8400.

[00109] The delivery component 8300 delivers a coded message of the appropriate power draw level determined above to the redundant DC/AC converter 8500. The converter interprets and follows the coded message so that the converter can operate continuously at the commanded power level to approximately balance the in-charging energy. Examples of converters 8500 that draw from the reservoir 8400 are converter 2130S of FIG. 2B, converter 3130S of FIG. 3, converter 4130S of FIG. 4, converter 5130S of FIG. 5, converter 6130S of FIG. 6, and converter 7302 of FIG. 3.

[00110] To obtain an economically beneficial MEUPT optimizer, the design of the MEUPT controller depends on the following parameters and variables: (1) the capacity of the energy reservoir 8400; (2) the step-up/step-down of the DC/AC converter 8500; (3) the IV characteristics of the solar cell string, (4) the weather at the location of the PV power plant, and (5) the amount of charge that the MEUPT controller, working with the surplus DC/AC converter, provides to the energy reservoir. taking into account that the difference (or balance) between the amount of charge and the amount of charge drawn from the energy reservoir can be minimized. A simple design can only be derived when applying a custom designed controller for any PV power plant that takes these parameters and variables into account.

[00111] Section 13: MEUPT Controller Design
[00112] It is not practical to custom design a MEUPT controller for every single PV power plant that can use the MEUPT controller. On the other hand, it is very difficult to pursue a simple design for the required MEUPT controller, especially when a custom design controller is not possible. However, the terminal voltage of the energy reservoir can be considered as a measure influenced by each of the five parameters and variables. Therefore, the above five design constraints can be made into two parts when the terminal voltage of the MEUPT energy reservoir is chosen as the decision parameter.

[00113] When comparing the measured terminal voltages to a set of site-specific "standard voltage intervals," it became apparent to the inventors that the power extraction and conversion levels currently being performed by the system were quantifiable as power extraction levels that were (1) too low, (2) too high, or (3) not adequate. Thus, the MEUPT controller design task can be separated into 1) a normal industrial controller and 2) a custom-built site-specific "standard voltage interval" table (referred to herein as the "voltage interval table").

[00114] Once a site-specific voltage interval table is constructed for the PV plant, it can work in concert with the industrial controller to achieve the required MEUPT controller function. The industrial controller then consists of a detection component, a determination component, and a delivery component, as also shown in FIG. 8. However, in this case, the detection component 8100 measures the terminal voltage of the energy reservoir 8400. The determination component 8200 compares the measured voltage with the voltage interval table and determines the appropriate power draw to approximately balance the charging energy. The delivery component 8300 again delivers a coded message of the appropriate power draw level determined above to the redundant DC/AC converter 8500, so that the converter can operate continuously at the commanded power level to approximately balance the incoming and outgoing charges of the energy reservoir 8400.

[00115] In one embodiment, the detection component 8100 of the MEUPT controller 8000 measures the terminal voltage of the excess energy reservoir 8400 in real time. Even so, the determination component 8200 may still perform a comparison (of the measured voltage to the voltage interface table) every specified time interval comparison. This comparison may result in one of three situations:

(1) If the comparison of the measured voltage and the voltage interval table indicates that the power level is too low, the controller 8000 causes the three-phase DC/AC converter 8500 to One level increment of extraction and transformation can be requested (through delivery component 8300).

(2) If the comparison of the measured voltage and the voltage interval table indicates that the power level is too high, the controller 8000 causes the three-phase DC/AC converter 8500 to One level reduction of extraction and transformation may be requested (through delivery component 8300).

(3) If the comparison of the measured voltage to the voltage interval table indicates that the power level is appropriate, the controller 8000 may request that the three-phase DC/AC converter 8500 remain at the same power extraction level for the next specified time interval, at least until the next occurrence of the comparison.

[00116] When the power extraction/conversion regulation level of the DC/AC converter is small enough, the above design will reduce the step-up/down rate of all types of DC/AC converters for all types of energy reservoir capacities. In contrast, it can function for all types of solar cell string IV characteristics and for all weather conditions at a PV site. Therefore, it is important that the controller be able to direct small adjustment steps to the three-phase DC/AC converter that draws power from the energy reservoir.

[00117] A typical conventional centralized three-phase DC/AC converter can operate with very small regulation steps when commanded. However, the communication channel equipped with what is called in the art (and is also called herein) a "dry junction box" typically has only a 6-bit communication channel via optical messages. To command more than six power extraction levels through the dry junction box, a coding-decoding technique is used. This technique allows passing up to 2 ⁶ =64 messages to command the power extraction levels. With up to 64 regulated power extraction levels, the required near-zero net balance in the reservoir's incoming and outgoing energy is technically achievable.

[00118] Section 14: PV Power Plant Incorporating MEUPT Optimizer
[00119] As shown in FIG. 9, a PV power plant 9000 incorporating a MEUPT optimizer 9200 including a MEUPT controller 9210. The MEUPT controller 9200 has three executable components: a sensing component 9211 that measures the terminal voltage of the surplus energy reservoir 9400, a determining component 9212 that compares the measured voltage with the voltage interval table of the PV station. , a distribution component 9213 that notifies the three-phase DC/AC converter 4502 via the distribution component 4213 to start up, step down, or stay the same. Components 9211, 9212, and 9213 in FIG. 9 are examples of components 8100, 8200, and 8300 in FIG. 8, respectively. Energy reservoir 9400 in FIG. 9 is an example of energy reservoir 8400 in FIG. 8. Converter 9502 is an example of converter 8500 in FIG.

[00120] The PV power plant 9000 also consists of a PV solar cell string 9100. The solar cell string 9100 converts solar energy into electricity and delivers the generated DC power to the excess energy reservoir 9400 through the decoupling device 9320. The three-phase DC/AC converter 9502 receives the input DC power from the excess energy reservoir 9400 through the decoupling device 9330. Collectively, the solar cell string 9100 of FIG. 9 is a DC energy source for charging the energy reservoir and is an example of the solar cell strings 2111A and 2111B of FIG. 2B, the solar cell string 3110 of FIG. 3, the solar cell string 4110 of FIG. 4, the solar cell string 5110 of FIG. 5, the solar cell string 6110 of FIG. 6, and the solar cell string 7110 of FIG. 7. The decoupling device 9320 in FIG. 9 is an example of the decoupling device 2312B in FIG. 2B, the decoupling device 3312 in FIG. 3, the decoupling device 4312 in FIG. 4, the decoupling device 5311 in FIG. 5, the decoupling device 6311 in FIG. 6, and the decoupling device 7202 in FIG. 7. The decoupling device 9330 in FIG. 9 is an example of the decoupling device 2313B in FIG. 2B, the decoupling device 3313 in FIG. 3, the decoupling device 4313 in FIG. 4, the decoupling device 5313 in FIG. 5, the decoupling device 6313 in FIG. 6, and the decoupling device 7203 in FIG. 7.

[00121] As mentioned above, the MEUPT controller 9210 instructs the three-phase DC/AC converter 9502 to extract an appropriate amount of energy from the energy reservoir 9400 to balance the input energy charge from the solar cell string 9100. This results in near-zero energy being charged or extracted from the reservoir 9400. Thus, a small energy reservoir 9400 is suitable for the PV station. The converted AC power from the DC/AC converter is provided to the connected power grid 9700 through the transformer 9600.

[00122] As used herein, the term "executable component" is used with reference to FIGS. 8 and 9. The term "executable component" is a designation for a structure that is well understood by those skilled in the art of computing to be a structure that may be software, hardware, firmware, or a combination thereof. . For example, when implemented in software, one skilled in the art will appreciate that the structure of an executable component is computer-readable, regardless of whether such executable component resides within a heap of a computing system. It will be appreciated that the software may include software objects, routines, and methods that may be executed on a computing system regardless of whether they reside on a storage medium.

[00123] In such cases, those skilled in the art will understand that when interpreted by one or more processors of a computing system (e.g., by a processor thread), the executable It will be appreciated that the structure of the components resides on a computer-readable medium. Such structures may be directly computer readable by a processor (as if the executable components were binary). Alternatively, the structure is interpretable and/or compiled (whether in a single step or in multiple steps) to produce such a binary that is directly interpretable by a processor. It may be structured as follows. Such an understanding of exemplary structures of executable components is well within the understanding of those skilled in the art of computing when using the term "executable component."

[00124] The term "executable component" also refers to firmware or hardware, such as within a field programmable gate array (FPGA), application specific integrated circuit (ASIC), or any other specialized circuit. It will be well understood by those skilled in the art to include structures that are implemented exclusively or almost exclusively within. Thus, the term "executable component" refers to structures that are well understood by those skilled in the art of computing, whether implemented in software, hardware, or in combination. This is the term.

[00125] The invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects as illustrative only and not as restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalence of the claims are to be embraced within the scope of the invention.

Claims (15)

1. An energy storage system configured to provide power to a power grid, comprising:
an energy reservoir configured to receive DC energy from a DC energy source at an input of the energy reservoir and to transmit the received DC energy to another device at an input of the other device;
a system controller configured to adjust the amount of DC energy delivered to the other device such that the amount of DC energy delivered to the other device is approximately equal to the amount of DC energy received by the energy reservoir from the DC energy source , thereby providing an energy storage capacity of the energy reservoir with an energy storage capacity of less than 2 Faradays per megawatt of the DC energy source;
23. An energy storage system comprising: 2. The energy storage system of claim 1, wherein the DC energy source is a power plant and the energy reservoir of DC includes a capacitor. 3. The energy storage system of claim 2, wherein the energy reservoir of DC includes only a capacitor. 3. The energy storage system of claim 2, wherein the energy reservoir of DC includes only a thin film capacitor. 2. The energy storage system of claim 1, wherein the DC energy source is a power plant and the energy reservoir of DC includes a thin film capacitor. The energy storage system of claim 1, wherein the system controller comprises:
a sensing component configured to measure the energy level stored within the energy reservoir;
a decision component configured to use the measured stored energy level of the energy reservoir to evaluate whether an adjustment should be made;
the determining component, when determining that the adjustment should be made, is configured to encode an instruction to perform the adjustment into a coded message, the coded message comprising: a delivery component configured to deliver DC energy to said further device to be discharged and also configured to properly adjust the discharge power. 7. The energy storage system of claim 6 , wherein the sensing component measures the stored energy level by measuring a terminal voltage of the energy reservoir. 8. The energy storage system of claim 7 , wherein the measurement of the terminal voltage of the energy reservoir is performed in real time. 9. The energy storage system of claim 8 , wherein the determining component is configured to perform the evaluation of whether adjustments should be made periodically at specified time intervals. 7. The energy storage system of claim 6 , wherein the determining component is configured to perform the evaluation of whether an adjustment should be made periodically at specified time intervals. 7. The energy storage system of claim 6 , wherein the DC energy is discharged into the other device, at least one DC/AC converter. 12. The energy storage system of claim 11 , wherein the delivery component is configured to deliver the coded message to the DC/AC converter through an equipped communication channel. 12. The energy storage system of claim 11 , wherein the delivery component is configured to deliver a respective coded message to each of a plurality of DC/AC converters including the DC/AC converter. , energy storage system. 14. The energy storage system of claim 13 , wherein the distribution component is configured to distribute the respective coded message to at least one of the plurality of DC/AC converters via an equipped communication channel. 12. The energy storage system of claim 11 , wherein the energy reservoir is capable of retaining the amount of DC energy received from the DC energy source for a period of no more than 3 AC cycles of the power grid. .

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