JP5384155B2 - Power generation system - Google Patents

Description

  The present invention relates to a power generation system including a power supply device using natural energy.

  In recent years, there is an increasing number of cases where a power supply device (for example, a solar power supply device) using natural energy is provided in each consumer (for example, a house or a factory) that receives supply of AC power from a substation. The power supply device is connected to a power distribution system provided under the substation, and the power output by the power supply device is output not only to the power consuming device provided in the consumer, but also to the power distribution system. As described above, the flow of power from the consumer to the distribution system is called “reverse power flow”, and the power output from the customer to the power distribution system is called “reverse power flow”.

  By the way, the output of the power supply device using natural energy can fluctuate according to the weather or the like. Therefore, when a reverse power flow is made from the power supply device to the power distribution system, the reverse power flow varies with the output variation of the power supply device. As a result, the system frequency of the power distribution system may fluctuate. Such fluctuations in the system frequency become more prominent as the number of customers with power supply devices using natural energy increases.

  Here, a power generation system that includes a power supply device and a power storage device using natural energy and charges and discharges the power storage device according to output fluctuations of the power supply device has been proposed (see Patent Document 1). According to such a power generation system, rapid fluctuations in reverse power flow can be suppressed.

Japanese Patent Laid-Open No. 2001-5543

  However, the method described in Patent Document 1 has a problem that the life of the power storage device is shortened because the power storage device is frequently charged and discharged every predetermined unit time.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a power generation system capable of extending the life of a power storage device.

  A power generation system according to a feature of the present invention is a power generation system connected to a distribution system to which AC power is distributed, a power supply device that generates output power by using natural energy, a power storage device that is charged and discharged, and When the output power detection unit and the output power increase trend or decrease trend continue for a predetermined period, reverse power flow from the power supply device and the power storage device to the distribution system based on the value of the output power in the predetermined period A target value setting unit for setting a target value of the generated power, and charge / discharge control for controlling charging from the power supply device to the power storage device and discharging from the power storage device to the distribution system based on the target value The gist is to include a control unit.

  In the power generation system according to the features of the present invention, the predetermined period is greater than ¼ of the load fluctuation period to be governed by the governor-free operation in the distribution system, and the load fluctuation period to be subject to load frequency control in the distribution system. It may be smaller than 1/4.

  In the power generation system according to the features of the present invention, the target value setting unit sets a new target value based on the storage capacity of the power storage device after a predetermined time has elapsed from the start of charge / discharge control, and the charge / discharge control unit The charge / discharge control may be executed based on the set new target value.

  In the power generation system according to the features of the present invention, the charge / discharge control unit may adjust the storage capacity of the power storage device to a predetermined initial capacity after the end of the charge / discharge control.

  According to the present invention, it is possible to provide a power generation system capable of extending the life of a power storage device.

It is the schematic which shows the structure of the power distribution system 1 which concerns on embodiment. 1 is a block diagram illustrating a configuration of a power generation system 100 according to an embodiment. It is a block diagram which shows the structure of the grid connection apparatus 200 which concerns on embodiment. It is a graph which shows an example of transition of output electric power P. It is a graph which shows typically change of reverse tidal current electric power _PREV . It is a flowchart which shows the fluctuation | variation detection process of the grid connection apparatus 200 which concerns on embodiment. It is a flowchart which shows the smoothing process of the grid connection apparatus 200 which concerns on embodiment. It is a flowchart which shows the initialization process of the grid connection apparatus 200 which concerns on embodiment. It is a graph which shows transition of the output electric power P of a certain solar cell power generation system. 6 is a graph showing a simulation result according to Example 1. 10 is a graph showing a simulation result according to Example 2. 10 is a graph showing a simulation result according to Example 3.

  Below, the grid connection system which concerns on embodiment of this invention is demonstrated, referring drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

  However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Therefore, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  In the following description, the flow of power from the distribution system to the consumer is referred to as “tidal current”, and the power flowing from the distribution system to the consumer is referred to as “tidal power”. In addition, the flow of power from the consumer to the power distribution system is called “reverse power flow”, and the power flowing from the customer to the power distribution system is called “reverse power flow”.

(Configuration of power distribution system)
Hereinafter, the configuration of the power distribution system according to the embodiment will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating a configuration of a power distribution system 1 according to the embodiment.

  As shown in FIG. 1, the power distribution system 1 includes a plurality of high-voltage power supply sources 10 (high-voltage power supply source 10A, high-voltage power supply source 10B), a substation 20, and a plurality of customers 30 (customers 30A to 30I). ).

  The high voltage power supply source 10 transmits high voltage power to the substation 20 via the high voltage power transmission line 40. The high-voltage power supply source 10 is, for example, a power plant.

  The substation 20 distributes AC power generated by stepping down high-voltage power to each customer 30 via the distribution system 50. The distribution system 50 is a unit in which the substation 20 manages each customer 30. Although not shown, the substation 20 may have a plurality of distribution systems 50 under its control.

  Each consumer 30 includes a power generation system 100. The power generation system 100 is electrically connected to the substation 20 via the power distribution system 50. The power generation system 100 inputs and outputs power (tidal current and reverse power flow) with the power distribution system 50.

(Configuration of power generation system)
Below, the structure of the electric power generation system which concerns on embodiment is demonstrated, referring drawings. FIG. 2 is a block diagram illustrating a configuration of the power generation system 100 according to the embodiment.

  As illustrated in FIG. 2, the power generation system 100 includes a plurality of power consuming devices 102 (power consuming devices 102 </ b> A to 102 </ b> C), a power supply device 104, a power storage device 106, and a grid interconnection device 200.

  The power consuming device 102 consumes the tidal power distributed from the distribution system 50 and the output power P output from the power supply device 104. The power consuming apparatus 102 is, for example, a home appliance.

  The power supply device 104 generates the output power P by using natural energy. The power supply device 104 is, for example, a solar power supply device or a wind power supply device. It should be noted that the output power P generated by the power supply device 104 varies depending on the weather and weather. In the present embodiment, the output power P generated by the power supply device 104 can be reversely flowed to the distribution system 50 via the grid interconnection device 200.

The power storage device 106 has a predetermined rated capacity _CCAP and is a chargeable / dischargeable device. Specifically, power storage device 106 stores output power P generated by power supply device 104. In addition, the power storage device 106 flows the stored power back to the power distribution system 50. The power storage device 106 is, for example, a secondary battery such as a lithium ion battery or a nickel metal hydride battery, or an electric double layer capacitor.

In the present embodiment, the initial capacity C _START of the power storage device 106 is determined and is, for example, 50% of the rated capacity C _CAP , but is not limited to this.

The grid interconnection device 200 controls the interconnection of the power distribution system 50, the plurality of power consuming devices 102, the power supply device 104, and the power storage device 106. Specifically, the grid interconnection device 200 controls, for example, discharging from the power storage device 106 to the power distribution system 50 and charging from the power supply device 104 to the power storage device 106. In the following description, it should be noted that the reverse power flow power _PREV includes the output power P of the power supply device 104 and the discharge power Q discharged from the power storage device 106.

(Configuration of grid interconnection device)
Below, the structure of the grid connection apparatus which concerns on embodiment is demonstrated, referring drawings. FIG. 3 is a block diagram illustrating a configuration of the grid interconnection device 200 according to the embodiment.

  As shown in FIG. 3, the grid interconnection device 200 includes a detection unit 201, a determination unit 202, a target value setting unit 203, a charge / discharge control unit 204, a DC / DC conversion unit 205, and a power conditioner 206.

(Detection unit)
The detection unit 201 detects the output power P of the power supply device 104 every detection cycle T _D (for example, 1 minute). FIG. 4 is a graph showing an example of the transition of the output power P. Detection period T _D in the graph of FIG. 4 is 1 minute. Note that the detection unit 201 may detect the output power P when the output power P is equal to or greater than a predetermined ratio (for example, 10%) of the rated output _PCAP of the power supply device 104.

(Judgment part)
The determination unit 202 determines whether or not the increasing tendency or decreasing tendency of the output power P has continued for a predetermined period T _T.

Specifically, first, the determination unit 202 detects a power fluctuation range ΔP that is a difference between the output power P _LAST detected at the previous detection timing and the output power P _THIS detected at the current detection timing. calculated for each period _{T D.} Determination unit 202 determines whether or not power fluctuation width ΔP is 30% or more of rated output _PCAP . Determination unit 202 repeats calculation of power fluctuation range ΔP until it is determined that power fluctuation range ΔP is 30% or more of rated output _PCAP . Thus, in this embodiment, although the power variation width ΔP regarded as the output power P with a not less than 30% of the rated output P _CAP is increasing or decreasing, but is not limited thereto. If the power fluctuation range ΔP is larger than 0% of the rated output _PCAP , it can be considered that the output power P tends to increase or decrease.

Next, when the determination unit 202 determines that the power fluctuation width ΔP is 30% or more of the rated output _PCAP , that is, when it is determined that the output power P tends to increase or decrease, It is determined whether or not the increasing tendency or decreasing tendency of the power P continues for a predetermined period T _T. Specifically, the determination unit 202 continues to change the output power P outside the range of the output power P _LAST ± 10% from the time when the output power P _LAST is detected to the time after a predetermined period T _T. It is determined whether or not to do.

Next, the determination unit 202 determines that when the output power P continues to change outside the range of the output power P _LAST ± 10%, that is, the output power P continues to increase or decrease over a predetermined period T _T. In such a case, the fact is notified to the target value setting unit 203.

Here, the predetermined period T _T is larger than ¼ of a load fluctuation period to be a target of governor-free (GF) operation in the distribution system 50, and is a load frequency control (LFC: Load Frequency) in the distribution system 50. It should be noted that it is less than ¼ of the load fluctuation period to be controlled. The governor-free operation is an operation for eliminating minute cycle fluctuations of up to several minutes (for example, 2 minutes) among the load fluctuations in the distribution system 50. The governor-free operation is performed by power generation output control by releasing the restriction of the governor provided in the high-voltage power supply source 10. LFC is control for eliminating short-cycle fluctuations of a load fluctuation in the distribution system 50 whose period is about several minutes to several tens of minutes (for example, about 2 to 20 minutes). The LFC is provided separately from the high-voltage power supply source 10 and is performed by output control in a power plant for frequency control that can cope with short-cycle fluctuations. It should be noted that long-period fluctuations with a period exceeding ten minutes among the load fluctuations in the distribution system 50 can be eliminated by economic load distribution control (EDC). For GF operation, LFC, and EDC, see “Ryuichi Yokoyama,“ Power Liberalization and Technology Development-Aiming to Improve Management Efficiency and Supply Reliability of Electricity Business in the 21st Century ”—Chapter 5”, and “ Detailed report, No. 869 ”.

  By the way, in the case where a reverse power flow is made from a large number of power supply devices 104 to the power distribution system 50, the output power of each of the large number of power supply devices 104 may fluctuate due to weather fluctuations near the power distribution system 50. In this case, in the power distribution system 50, any one of minute period fluctuation, short period fluctuation, or long period fluctuation occurs. As described above, micro cycle fluctuations and long cycle fluctuations can be handled by GF operation and EDC. Therefore, it is not necessary to eliminate the fluctuation of the output power that causes the minute period fluctuation and the long period fluctuation in the power generation system 100. On the other hand, in order to eliminate short-cycle fluctuations, it is necessary to add a power plant for frequency control according to the scale of the distribution system 50. For this reason, it is desirable that fluctuations in output power that cause short-period fluctuations be eliminated within the power generation system 100. It should be noted that the cycle of the short cycle variation varies depending on the scale of the power distribution system 50 and the like.

In the present embodiment, the predetermined time period T _T is larger than 1/4 the period of the load fluctuation to be GF operation, 1/4 smaller than the period of the load fluctuation to be LFC eligible. For this reason, the determination unit 202 has a tendency to increase or decrease the output power P with respect to fluctuations in the output power P that cause short-period fluctuations, not fluctuations in the output power P that cause minute fluctuations. It is determined that it continues.

(Target value setting section)
The target value setting unit 203 sets a target value for the reverse flow power _PREV in response to the notification from the determination unit 202. In the present invention, the reverse power flow _PREV is a power that flows backward from the customer 30 to the power distribution system 50, and is a combined power of the output power P of the power supply device 104 and the discharge power of the power storage device 106. It should be noted.

Specifically, the target value setting unit 203, based on the value of the output power P in a predetermined time period _{T T,} sets the first target value _{P SET1} is a target value of the backward flow power _{P REV.} The target value setting section 203 sets a first arrival time _{T 1} of the up backward flow power _{P REV} reaches the first target value _{P SET1.}

Specifically, the target value setting section 203, an output power _{P LAST,} the value between the output power _{P T} in the output power _{P LAST} the time after a predetermined period of time _{T T} from the detected time (e.g., output The intermediate value between the power P _LAST and the output power _PT is set to the first target value P _SET1 . The target value setting section 203, the period of the short period fluctuation 1/4 (e.g., 30 seconds to 5 minutes) to set the _{T 1} first arrival time or more. However, the first target value P _SET1 may be a value between the output power P _LAST and the output power _PT, and the first arrival time T ₁ is a time that can smooth the fluctuation of the output power P. Good.

Further, the target value setting unit 203 sets a second target value P _SET2 that is a new target value of the reverse flow power _PREV based on the power storage capacity C _T1 of the power storage device 106 after the first arrival time T _{1 has} elapsed. To do. The target value setting section 203 sets a second arrival time _{T 2} of the up backward flow power _{P REV} reaches the second target value _{P SET2.}

Specifically, when the storage capacity C _T1 is equal to or greater than the initial capacity C _START , the target value setting unit 203 sets a value larger than half of the rated output _PCAP (for example, 75% of the rated output _PCAP ) to the second target. Set to the value P _SET2 . On the other hand, when the storage capacity C _T1 is less than the initial capacity C _START , the target value setting unit 203 sets a value smaller than half of the rated output P _CAP (for example, 25% of the rated output P _CAP ) as the second target value. Set to P _SET2 . The target value setting section 203, the period of the short period fluctuation 1/4 (e.g., 30 seconds to 5 minutes) to set the second arrival time _{T 2} above. However, the second target value P _SET2 only needs to be a value between the output power P _LAST and the output power _PT, and the second arrival time T ₂ is a time that can smooth the fluctuation of the output power P. Good.

Further, the target value setting section 203, during a period from time _{t 1} to time _{t 2, the} second target value _{P SET2} is a case which is set to more than half the value of the rated output _{P CAP,} power storage device 106 When the storage capacity C of the power storage device 106 is less than the initial capacity C _START or when the second target value P _SET2 is set to a value smaller than half of the rated output P _CAP. when C is equal to or higher than the initial capacity _{C START,} it sets the third target value _{P SET3} as the new target value of the backward flow power _{P REV.} Third target value _{P SET3} is, for example, a half of the rated output _{P CAP.}

(Charge / Discharge Control Unit)
The charge / discharge control unit 204 is charged from the power supply device 104 to the power storage device 106 and discharged from the power storage device 106 to the power distribution system 50 based on the target value of the reverse power flow _PREV set by the target value setting unit 203. The charge / discharge control which is the control of is executed. Thereby, the charge / discharge control unit 204 smoothes the fluctuation of the output power P of the power supply device 104.

FIG. 5 is a graph schematically showing the transition of the reverse power flow _PREV from the power generation system 100 to the distribution system 50. In Figure 5, the output power _{P LAST} the time _{t T} after the predetermined time period _{T T} from the time _{t LAST} detected power supply 104, the charge and discharge control is started by the charge-discharge control unit 204.

Discharge control unit 204, so that the backward flow power _{P REV} is a first target value _{P SET1} from time _{t T} to the time _{t 1} of _{T 1} after the first arrival time, executes the charge and discharge control. As shown in FIG. 5, if the downward trend of the output power P has continued for a predetermined period of time T _T is the charge-discharge control unit 204, in addition to discharging power Q outputted to the output power P. On the other hand, although not shown, when the increasing tendency of the output power P continues for a predetermined period T _T , the charge / discharge control unit 204 sets a part of the output power P as the charging power R to the power storage device 106. .

Specifically, charge / discharge control unit 204 calculates discharge power Q from power storage device 106 based on the following equation (1) from time t _T to time t ₁ .
[Equation 1]
Discharge power Q1 = Reverse power flow power P _REV −Output power P (i) (1)
= (Output power P _T + first target value P _SET1 × i / T ₁ ) _−output power P (i)
However, in the formula (1), i is the elapsed time from the time t _T, the output power P (i) is the output power P at the time i has passed since the time t _T. It should be noted that when the discharge power Q1 calculated based on the formula (1) is a negative value, the calculated value represents the charge power R. Charging / discharging control unit 204 controls charging / discharging of power storage device 106 in accordance with calculated discharging power Q1.

Then, the charge and discharge control unit 204, so that the backward flow power _{P REV} is the second target value _{P SET2} from time _{t 1} to time _{t 2} of the second arrival time _{T 2} after a lapse executes discharge control . Specifically, the charge and discharge control unit 204, during the period from time t ₁ to time t ₂ calculates discharge power Q2 from the power storage device 106 based on the following equation (2).
[Equation 2]
Discharge power Q2 = Reverse power flow power P _REV −Output power P (j) (2)
= (First target value P _SET1 + second target value P _SET2 × j / T ₂ ) _−output power P (j)
However, in the formula (2), j is the time elapsed from the time _{t 1,} the output power P (j) is the output power P from time _{t 1} when j elapsed. It should be noted that, similarly to the equation (1), when the discharge power Q2 calculated based on the equation (2) is a negative value, the calculated value represents the charging power R. Charging / discharging control unit 204 controls charging / discharging of power storage device 106 in accordance with calculated discharging power Q2.

Further, the charge and discharge control unit 204, during a period from time _{t 1} to time _{t 2, the} case where the third target value _{P SET3} by the target value setting section 203 is set, the power storage device based on the following equation (3) The discharge power Q3 from 106 is calculated.
[Equation 3]
Discharge power Q3 = reverse power flow power P _REV (k) _−output power P (k) (3)
= Reverse flow power P _REV (k) + (third target value P _{SET3 −reverse} flow power P _REV (k)) × l / k)
However, in Formula (3), k is the time elapsed from the time t ₁ to the third target value P _SET3 setting, and the reverse power flow power P _REV (k) and the output power P (k) are the time t _{1 Are the} reverse power flow power _PREV and the output power power P after the elapse of k. l is an elapsed time after the third target value P _{SET3 is} set. Charging / discharging control unit 204 controls charging / discharging of power storage device 106 in accordance with calculated discharging power Q3.

Next, charge / discharge control unit 204 adjusts the storage capacity C of power storage device 106 to initial capacity C _START after time t _{2 has} elapsed, that is, after the end of charge / discharge control. Discharge control unit 204 in order to initialize the storage capacity C, and sets the target value P _SETS initialization of backward flow power P _REV.

Specifically, when the storage capacity C is equal to or greater than the initial capacity C _START , the charge / discharge control unit 204 sets a value that is more than half of the rated output P _CAP (for example, 75% of the rated output P _CAP ) as an initialization target value. Set to P _SETS . On the other hand, when the storage capacity C is less than the initial capacity C _START , the charge / discharge control unit 204 sets a value less than half of the rated output _PCAP (for example, 25% of the rated output _PCAP ) to the initialization target value P. Set to _SETS . Charging / discharging control unit 204 calculates discharge power Q4 from power storage device 106 based on the following equation (4).
[Equation 4]
Discharge power Q4 = initialization target value P _SETS −output power P (m) (4)
However, in the formula (4), m is the time elapsed from time _{t 2, the} output power P (m) is the output power P when m elapses from the time _{t 2.} Charging / discharging control unit 204 controls charging / discharging of power storage device 106 in accordance with calculated discharging power Q4. Specifically, the charge and discharge control unit 204, by discharging when power storage capacitance C is equal to or greater than the initial capacity C _START, also by charging when battery capacity C is less than the initial capacity C _START The power storage capacity C is initialized.

(DC / DC converter and power conditioner)
The DC / DC conversion unit 205 performs voltage step-up / step-down for appropriate input / output between the power supply device 104 or the distribution system 50 and the power storage device 106.

As shown in FIG. 3, the power conditioner 206 includes a maximization control unit 206a, a power adjustment unit 206b, and a DC / AC conversion unit 206c. The maximization control unit 206a maximizes the output power of the power supply device 104. Power adjustment unit 206b adjusts the backward flow power _{P REV} in cooperation with the charging and discharging control unit 204. The DC / AC converter 206c converts the output power P and the discharge power Q into AC power.

(Fluctuation detection)
Hereinafter, detection of fluctuations by the grid interconnection device according to the embodiment will be described with reference to the drawings. The variation detection is detection of a variation that needs to be smoothed (a variation that causes a short period variation). FIG. 6 is a flowchart showing the fluctuation detection process of the grid interconnection device 200 according to the embodiment.

As shown in FIG. 6, in step S10, the grid interconnection device 200 includes an output power _{P LAST} power supply 104 at the previous detection timing, detects the output power _{P THIS} at the current detection timing.

In step S11, the grid interconnection device 200 calculates a power fluctuation range ΔP between the output power P _LAST and the output power P _THIS .

In step S12, the grid interconnection device 200 determines whether or not the power fluctuation width ΔP is 30% or more of the rated output _PCAP . When the power fluctuation width ΔP is 30% or more of the rated output _PCAP , the process proceeds to step S13. If the power fluctuation width ΔP is not 30% or more of the rated output _PCAP , the process returns to step S10.

In step S13, the grid interconnection device 200 may increase or decrease the output power P is determined whether to continue for a predetermined period of time T _T. When the increasing tendency or decreasing tendency of the output power P continues for a predetermined period T _T , the process shifts to a smoothing process described later, assuming that the fluctuation of the output power P is detected. On the other hand, when the increasing tendency or decreasing tendency of the output power P does not continue over the predetermined period T _T , the process returns to step S10.

(Smoothing of reverse power flow)
Hereinafter, smoothing by the grid interconnection device according to the embodiment will be described with reference to the drawings. FIG. 7 is a flowchart showing the smoothing process of the grid interconnection device 200 according to the embodiment.

As shown in FIG. 7, in step S20, the grid interconnection device 200 includes a first target value _{P SET1} is a target value of the backward flow power _{P REV,} reverse power flow _{P REV} reaches the first target value _{P SET1} setting the first arrival time T ₁ of the till.

In step S21, the grid interconnection device 200, such that the backward flow power _{P REV} is a first target value _{P SET1} from time _{t T} to the time _{t 1} of _{T 1} after the first arrival time, perform a charge and discharge control To do. Specifically, charging / discharging control unit 204 controls charging / discharging of power storage device 106 based on discharging power Q1 calculated from the above equation (1).

In step S22, the grid interconnection device 200, based on the storage capacity _{C T1} of the power storage device 106 at time _{t 1,} the second target value _{P SET2} of backward flow power _{P REV,} reverse power flow _{P REV} is a second target setting the second arrival time _{T 2} of the to reach a value _{P SET2.}

In step S23, the grid interconnection device 200, such that the backward flow power _{P REV} is the second target value _{P SET2} from time _{t 1} to time _{t 2} of the second arrival time _{T 2} after the execution of the charging and discharging control To do. Specifically, charging / discharging control unit 204 controls charging / discharging of power storage device 106 based on discharging power Q2 calculated from the above equation (2).

In step S24, the grid interconnection device 200, the second target value _{P SET2} is set to more than half the value of the rated output _{P CAP,} and storage capacity C of the power storage device 106 is less than the initial capacitance _{C START} Whether or not the second target value P _SET2 is set to a value smaller than half of the rated output P _CAP and the storage capacity C of the power storage device 106 is equal to or greater than the initial capacity C _START. judge. If either condition is met, the process proceeds to step S25. On the other hand, if neither condition is met, the process proceeds to step S27.

In step S25, the grid interconnection device 200 discards the second target value P _SET2 and newly sets a third target value P _SET3 .

In step S26, the grid interconnection device 200, such that the backward flow power _{P REV} is the third target value _{P SET3} to time _{t 2, the} performing the charge and discharge control. Specifically, charging / discharging control unit 204 controls charging / discharging of power storage device 106 based on discharging power Q3 calculated from equation (3) above.

In step S27, the grid interconnection device 200 determines whether the host vehicle has reached the time _{t 2.} When it reaches the time t _2, the charge and discharge control ends. On the other hand, when it has not reached the time t _2, the process returns to step S24.

(Initialization of power storage device)
Hereinafter, initialization of the power storage device by the grid interconnection device according to the embodiment will be described with reference to the drawings. FIG. 8 is a flowchart showing the initialization process of the grid interconnection device 200 according to the embodiment.

As shown in FIG. 8, in step S30, the grid interconnection device 200 determines whether or not the storage capacity C is _{equal to} or greater than the initial capacity C _START . If the storage capacity C is greater than or equal to the initial capacity C _START , the process proceeds to step S31. If the storage capacity C is not equal to or greater than the initial capacity C _START , the process proceeds to step S33.

In step S31, the grid interconnection device 200 sets a value equal to or greater than half of the rated output _PCAP to the initialization target value _PSETS . The grid interconnection device 200 discharges the power storage device 106 based on the discharge power Q4 (positive value) calculated from the above equation (4).

In step S32, the grid interconnection device 200 determines whether or not the storage capacity C has reached the initial capacity C _START . When the storage capacity C reaches the initial capacity C _START , the process ends. If the storage capacity C is not the initial capacity C _START , the process returns to step S31.

In step S33, the grid interconnection device 200 sets a value less than half of the rated output _PCAP as the initialization target value _PSETS . The grid interconnection device 200 charges the power storage device 106 based on the discharge power Q4 (negative value) calculated from the above equation (4).

In step S34, the grid interconnection device 200 determines whether or not the storage capacity C has reached the initial capacity C _START . When the storage capacity C reaches the initial capacity C _START , the process ends. If the storage capacity C is not the initial capacity C _START , the process returns to step S33.

(Function and effect)
In the power generation system 100 according to the embodiment, the target value setting unit 203 outputs the output power P in the predetermined period T _T when the increasing tendency or decreasing tendency of the output power P of the power supply device 104 continues over the predetermined period T _T. based on the value, we set the first target value _{P SET1} of backward flow power _{P REV.} The charge / discharge control unit 204 performs charge / discharge control of the power storage device 106 based on the first target value P _SET1 .

Thus, the charge and discharge control of the power storage device 106, increase or decrease of the output power P of the power supply device 104 is performed only if continued for a predetermined period of time T _T. Therefore, compared with the case where charge / discharge control is performed intermittently at predetermined intervals, the number of times of charge / discharge of power storage device 106 can be reduced. Therefore, the life of the power storage device 106 can be extended.

Here, FIG. 9 is a graph showing the transition of the output power P of the solar cell power generation system on April 29, 2008. If you set the predetermined time period T _T in 2 minutes, according to the power generation system 100 according to the embodiment, the period A shown in FIG. 9, B, only charging and discharging control for three variations of C is performed. On the other hand, in the case where charge / discharge control is performed with a value calculated by the moving average method every 2 minutes, 24 times of charge / discharge control is performed between 10:47 and 11:35. Thus, according to the power generation system 100 according to the embodiment, it is obvious that the number of times of charging / discharging the power storage device 106 can be reduced.

Further, in the embodiment, the predetermined period T _T is larger than ¼ of the load fluctuation period to be subjected to GF operation and smaller than ¼ of the load fluctuation period to be subjected to LFC. Therefore, the charge / discharge control is executed not with respect to fluctuations in the output power P that cause minute cycle fluctuations but with fluctuations in the output power P that cause short-period fluctuations. Therefore, in order to reduce the amount of charge / discharge that is performed to eliminate the fluctuations in the output power P that can be eliminated by the GF operation, and to eliminate fluctuations in the output power P that cause short-cycle fluctuations that are subject to LFC. It is possible to ensure the charge / discharge performed at the same time. As a result, it is possible to reduce the necessity of adding a power plant for frequency control to the distribution system 50 due to the output fluctuation of the power supply device 104 provided in each customer 30.

Further, in the embodiment, the target value setting unit 203, based on the start of the charge and discharge control to the storage capacitance C of the power storage device 106 in the first arrival time T ₁ after sets a new second target value P _SET2 . Therefore, since the target value can be set in accordance with the output fluctuation of the power supply device 104 caused by the solar radiation fluctuation after the first target value P _{SET1 is} set, the fluctuation can be smoothed efficiently.

The charge / discharge control unit 204 adjusts the storage capacity C of the power storage device 106 to the initial capacity C _START after the end of the charge / discharge control. Therefore, the charge / discharge control to be executed next time can be quickly handled, and the charge / discharge control can be executed under the same conditions each time without causing excess or deficiency of the storage capacity of the power storage device 106.

[Other Embodiments]
Although the present invention has been described with reference to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, it should be noted that the numerical values exemplified in the above-described embodiments are examples. Numerical values used for various thresholds can be appropriately set according to the configurations of the power distribution system 1 and the power generation system 100.

  Moreover, in embodiment mentioned above, although the structure of the electric power generation system 100 was demonstrated using FIG.2 and FIG.3, it is not restricted to this. In particular, it should be noted that at least one of the configurations included in the grid interconnection device 200 may be included in the power supply device 104, the power storage device 106, and the like.

  Note that the hardware configuration of the grid interconnection device 200 described above can be realized as a program module. Therefore, the processing executed in the grid interconnection device 200 described above may be executed by a general-purpose computer or the like having the function of the grid interconnection device 200.

  Hereinafter, examples of the solar cell module according to the present invention will be specifically described. However, the present invention is not limited to those shown in the following examples, and may be appropriately changed within the scope not changing the gist thereof. Can be implemented.

Example 1
A simulation was performed on changes in the output power P of the photovoltaic power generation device, the discharge power Q of the power storage device, the reverse power flow _PREV (P + Q), and the storage capacity C of the power storage device when a predetermined weather fluctuation occurred. FIG. 10 is a graph illustrating a simulation result according to the first embodiment.

In Example 1, it was assumed that weather fluctuations occurred in the order of clear (-3 minutes to -2 minutes), cloudy (-2 minutes to 3 minutes), and clear (3 minutes to 13 minutes). Moreover, it was set a predetermined time period T _T is a condition that charging and discharging control is executed in two minutes. Further, the capacity of the entire power generation system was set to 4000 W, the output power P in clear weather was set to 3500 W, the output power P in cloudy weather was set to 700 W, the storage capacity C was set to 1000 Wh, and the initial capacity C _START of the power storage device was set to 500 Wh.

  Under such conditions, a change in the output power P was detected at 0 minutes, and charge / discharge control was started. Thereafter, the charge / discharge control of the power storage device was completed in 10 minutes, and the initialization of the storage capacity C was started.

As shown in FIG. 10A, it was confirmed that the reverse power flow _PREV was smoothed although the output power P fluctuated rapidly. In addition, as shown in FIG. 10 (b), the storage capacity C has changed within a range of 478 to 614 Wh (47.8 to 61.4%), so it has been confirmed that the storage apparatus is unlikely to deteriorate. .

(Example 2)
In Example 2, weather changes occur in the order of clear (-3 minutes to -2 minutes), cloudy (-2 minutes to 0 minutes), clear (0 minutes to 10 minutes), and cloudy (10 minutes to 17 minutes). It was assumed. Other conditions were set the same as in Example 1.

FIG. 11 is a graph illustrating a simulation result according to the second embodiment. As shown in FIG. 11B, the storage capacity C increases to 754 Wh (75.4%), and increases by 254 Wh from the initial capacity C _START . Therefore, the type and capacity of the power storage device can be determined based on the characteristics, lifespan, and the like of the power storage device so that 254 Wh can be supported.

(Example 3)
In Example 3, weather fluctuations occurred in the order of cloudy (-3 minutes to -2 minutes), clear (-2 minutes to 0 minutes), cloudy (0 minutes to 10 minutes), and sunny (10 minutes to 16 minutes). It was assumed. Other conditions were set the same as in Example 1.

FIG. 12 is a graph illustrating a simulation result according to the third embodiment. As shown in FIG. 12B, the storage capacity C decreases to 254 Wh (25.4%), and decreases from the initial capacity C _START by 246 Wh. Therefore, the type and capacity of the power storage device can be determined based on the characteristics, lifespan, and the like of the power storage device so that 254 Wh can be supported.

ΔP: power fluctuation range C: storage capacity C _CAP ... rated capacity C _START ... initial capacity P ... output power P _CAP ... rated output P _REV ... reverse power flow P _SETS ... target value for initialization Q ... discharge power R ... charge power T ₁ ... First arrival time T ₂ ... Second arrival time T _D ... Detection period T _T ... Predetermined period 1 ... Distribution system 10 ... High-voltage power supply source 20 ... Substation 30 ... Consumer 40 ... High-voltage power transmission line 50 ... Power distribution system 100 ... Power generation system 102 ... Power consumption device 104 ... Power supply device 106 ... Power storage device 200 ... System interconnection device 201 ... Detection unit 202 ... Determining unit 203 ... Target value setting unit 204 ... Charge / discharge control unit 205 ... DC / DC Conversion unit 206 ... Power conditioner 206a ... Maximization control unit 206b ... Power adjustment unit 206c ... DC / AC conversion unit

Claims (4)

A power generation system connected to a distribution system to which AC power is distributed,
A power supply device that generates output power by utilizing natural energy;
A power storage device for charging and discharging;
A detection unit for detecting the output power;
When the increasing or decreasing tendency of the output power continues over a predetermined period, based on the value of the output power in the predetermined period, the power that is reversely flowed from the power supply device and the power storage device to the distribution system A target value setting unit for setting a target value;
And a charge / discharge control unit that performs charge / discharge control, which is control of charging from the power supply device to the power storage device and discharging from the power storage device to the power distribution system, based on the target value. Power generation system. The predetermined period is greater than ¼ of the load fluctuation period subject to governor-free operation in the distribution system and less than ¼ of the load fluctuation period subject to load frequency control in the distribution system. The power generation system according to claim 1. The target value setting unit sets a new target value based on the storage capacity of the power storage device after a predetermined time has elapsed since the start of the charge / discharge control.
The power generation system according to claim 1, wherein the charge / discharge control unit executes the charge / discharge control based on the set new target value. The power generation system according to claim 1, wherein the charge / discharge control unit adjusts the storage capacity of the power storage device to a predetermined initial capacity after the end of the charge / discharge control.

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