JP5709779B2 - Power storage type power generation system - Google Patents

Description

  The present invention typically connects a solar cell to a grid, supplies the generated power of the solar cell or power from the grid to the load, and can store the generated power of the solar cell or power from the grid. The present invention relates to a power storage type power generation system.

In recent years, houses and other buildings equipped with a solar power generation system are increasing, and there is a fixed price purchase system for surplus power. In the future, a system for purchasing all of the generated power is scheduled to be created, and further spread of the solar power generation system is expected.
On the other hand, when a large number of photovoltaic power generation systems are introduced, the reverse power flow to the grid of generated power increases, and power generation in the photovoltaic power generation system is expected to suppress the reverse power flow due to a rise in system voltage in the future. Control is a challenge. In order to cope with this problem, it is expected to introduce a system that charges the storage battery with generated power, suppresses reverse power flow, and promotes local production and consumption of power, and demonstration tests are being conducted in various places. In addition, the introduction of storage batteries is expected to be used as an emergency power source in the event of a system power outage during disasters, etc., and in recent years, the in-vehicle storage batteries of electric vehicles have been used as storage batteries for houses and other buildings due to the mass production of electric vehicles. The development momentum of the system is also increasing.

As these specific examples, an AC connection system and a DC connection system are known. The AC connection system is a system that interconnects the photovoltaic power generation system and the storage battery system with an AC system, and the DC connection system connects the solar battery and the storage battery with a DC system, and mixes the generated power and the discharge power from the storage battery. This is a system that converts to AC and connects to the grid.
In the AC connection system, when the generated power is charged into the storage battery, the DC power is once converted into AC, then converted into DC again and charged, so that conversion loss occurs and there is a problem in efficiency. In addition, when the system is out of power, the photovoltaic power generation system and the storage battery system are disconnected, so that the generated power cannot be charged, and there is a problem that the storage battery cannot be used if the remaining storage amount of the storage battery is completely discharged. Furthermore, each grid connection protection function (active method of islanding detection function) of the power conditioner of the photovoltaic power generation system and the storage battery system may interfere with each other. A multi-unit interconnection test is required to confirm that the protective function of the inverter does not interfere, and the procedure for introduction is complicated.

  On the other hand, since the DC connection system does not need to be converted to AC when charging the generated power to the storage battery, it is excellent in terms of efficiency, and since the generated power of the solar battery can be charged to the storage battery as a single system in an emergency, An independent power source that can be repeatedly charged and discharged can be configured. Moreover, since it is a single system, if there is no other system interconnection system, a multi-unit interconnection test is also unnecessary. However, in the case of a DC connection system, there is a problem that the electric power converted into AC cannot be classified into electric power derived from solar cells and electric power derived from storage batteries. In particular, it is necessary to clarify that the power is derived from solar cells when utilizing the purchase system by making the power flow backward. This power classification is also necessary to prevent the sale of electric power by using a purchase system that charges inexpensive nighttime power to a storage battery and makes an expensive unit price of power.

JP 2009-33797 A JP 2009-33802 A JP 2002-171694 A

  In order to cope with the problem of the power classification of the DC connection system, Patent Documents 1 to 3 describe that storage batteries that can charge the system power at night when the power generated by the solar battery is reversely flowed through the system. Is stopped, or the storage battery is disconnected from the system. In the systems of Patent Documents 1 to 3, since the storage battery always stops at the time of reverse power flow, the surplus power cannot be reverse power flow while charging the power generated by the solar battery to the storage battery capable of charging and discharging the system power. .

  The present invention has been made on the basis of such a technical problem. Typically, a power storage type power generation system capable of causing a surplus power to flow backward while charging power generated by a solar battery to a storage battery. The purpose is to provide.

In the DC connection system of the solar cell and the power storage unit, if for reverse power flow surplus power of electric power generated by the solar cell to the grid, the backward flow power to only the power generated by the solar cell origin, when power storage unit is discharged state It is sufficient to prevent reverse flow.
The present invention made there is a power generation unit that is connected to an external system and receives natural energy to generate power,
A power conditioner comprising a DC / DC converter connected to the power generation unit, an AC / DC converter and a charger / discharger each connected in series to the DC / DC converter, and power generated by the power generation unit and the system A power storage unit that stores and discharges the electric power via a charger / discharger and is DC-connected to the power generation unit, and a control unit that controls power generation of the power generation unit and charge / discharge of the power storage unit. The control unit includes a received power detection unit for controlling the power generation unit and the power storage unit so as to obtain predetermined received power at the power receiving end, and a reverse power flow when the power storage unit is in a discharged state. It has a discharge detection unit that detects discharge and a reverse flow detection unit that detects the occurrence of reverse power flow toward the system, and the reverse power flow detection unit detects reverse power flow while the discharge detection unit detects discharge. When detecting, stop the power conditioner, the control function of disconnecting the power conditioner from the grid, characterized in that it comprises a.
According to the power generation system of the present invention, only when the reverse flow occurs when the power storage unit is discharged, the power conditioner is stopped, the power conditioner is disconnected from the system, the power storage unit is in the charging It becomes possible to reversely flow, and it is possible to operate the power storage unit and the solar cell in consideration of efficient and economical efficiency.
In addition, according to the present invention, the reverse power flow is always limited to the generated power, for example, the power generated by the solar battery, so that the power storage unit is charged with cheap nighttime power and the purchase system is used to make the power unit price expensive. Thus, it is possible to prevent power from being sold.

In the power generation system of the present invention, the operation of stopping the power conditioner after detecting the reverse power flow at the time of discharge and the disconnecting operation from the power conditioner system are the same as in the general-purpose power generation system having no power storage unit. The system is stopped by the gate block of the converter (inverse conversion device), and disconnection from the system is performed by opening the disconnection relay. In addition to the disconnection operation similar to a general-purpose power generation system, the disconnection relay is not opened and only the charger / discharger is gate-blocked to stop only the discharge of the power storage unit and prevent reverse power flow of the discharge power. It is also possible to do.

The reverse power relay is well known as a reliable device in a power storage type power generation system using solar cells, and the reverse power relay can be used as a reverse power flow detection unit in the present invention.
The reverse power relay according to the present invention is in an operating state while the discharge detection unit detects discharge, outputs a reverse power detection signal when detecting a reverse power flow , stops the power conditioner, and turns off the power conditioner. While the system is disconnected from the system and the discharge detection unit does not detect the discharge, the reverse power relay is in an inoperative state and reverse power flow can be permitted.

The power generation system according to the present invention can be operated by at least two operations. The first operation prioritizes power supply to the load, and the second operation prioritizes charging of the power storage unit.
The first operation is to supply the generated power to the load when the power generated by the power generation unit is larger than the power required for the load connected between the power generation system and the grid, and the remainder to the power storage unit. Charge. In that case, it controls so that the receiving end electric power of a received electric power detection part becomes zero so that charging electric power may be only generated electric power. However, when the surplus power exceeds the maximum charging power, the surplus power is reversely flowed through the system while charging the power storage unit is continued.
On the other hand, when the power generated by the power generation unit is less than or equal to the power necessary for the load connected between the power generation system and the system, the power stored in the power storage unit is discharged toward the load for the insufficient power. That's it. At that time, control is performed so that the receiving end power of the received power detection unit becomes zero so that the discharge power does not flow backward to the system. However, when the load exceeds the sum of the generated power and the maximum discharge power, the excess power shortage is supplied from the grid power to the load.
The power receiving end power is set to zero in order to prevent reverse power flow during charging and discharging of generated power only, but the power receiving end power is in a forward power flow (purchasing direction of system power). Control may be performed with predetermined received power.

The second operation is that if the power generated by the power generation unit is larger than the reference charging power in the power generation system, the generated power is charged into the power storage unit, and the remainder is transferred between the power storage type power generation system and the system. Supply the connected load. If there is more residue after supplying the load, the remaining power is reversely flowed to the system as surplus power while charging the power storage unit is continued.
On the other hand, when the power generated by the power generation unit is less than or equal to the reference charging power in the power generation system, and further when the power generated by the power generation unit is larger than the power required for the load connected to the power generation system, The generated power is supplied to the load without discharging from the battery or charging the power storage unit, and the remaining power flows back to the grid as surplus power. In addition, when the power generated by the power generation unit is less than the power required for the load connected to the power generation system, as in the first operation, the received power detection unit prevents the discharge power from flowing back into the system. While controlling the receiving end power to be zero, the power stored in the power storage unit is discharged toward the load for the insufficient power.

According to the power generation system of the present invention, since the system is disconnected from the system only when a reverse power flow occurs when the power storage unit is discharged, it is possible to reverse the power flow while the storage battery is being charged. The battery can be operated efficiently and economically. In particular, in the case of a system in which the storage battery is stopped or disconnected when a reverse power flow occurs during conventional charging, there is a problem that the power generated by the solar battery cannot be sufficiently charged to the storage battery in the daytime. In the case of a system that suppresses and controls the generated power so as not to generate a reverse power flow, there is a problem that the generated power cannot be efficiently extracted. However, according to the power generation system of the present invention, the generated power of the solar cell is not suppressed. In addition, the maximum power point tracking control (MPPT control) used for the power generation control of the solar battery can be continued, and it is possible to simultaneously ensure the amount of charge to the storage battery by the generated power and maximize the generated power. In addition, since the power that flows backward to the grid is generated from solar cells, the unit price of the surplus power fixed price purchase system can be applied, and the economy is improved.
In addition, according to the present invention, the reverse power flow is always limited to the power generated by the solar battery, so the battery is charged with cheap nighttime power, and the power is sold by utilizing a purchase system that makes the power unit price expensive. This can be prevented.

It is a block diagram which shows the structure of the power storage type solar power generation system in 1st Embodiment. In the power storage solar power generation system according to the first embodiment, (a) shows a state in which a reverse power flow occurs while charging the storage battery, and (b) detects a reverse power flow while discharging from the storage battery. It is a block diagram which shows the state which disconnected the power conditioner of an electric power storage type solar power generation system, and prevented the discharge electric power of a storage battery from flowing backward into a system | strain. It is a flowchart which shows the procedure of the 1st operation example of the power storage type solar power generation in 1st Embodiment. It is a flowchart which shows the procedure of the 2nd operation example of the power storage type solar power generation in 1st Embodiment. It is a block diagram which shows the structure of the power storage type solar power generation system in 2nd Embodiment.

[First Embodiment]
Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
In the solar power generation system 1 in the first embodiment shown in FIG. 1, the solar cell 10 is connected to the system 40 by the power conditioner 19, and the generated power of the solar cell 10 or the power from the system 40 is supplied to the AC load 50 in the daytime. And a power storage type power generation system that stores power from the grid 40 in the storage battery 60 at night. The solar power generation system 1 corresponds to a direct current connection system that stores power generated by the solar battery 10 in the storage battery 60 as direct current power without converting it into alternating current.

The power conditioner 19 includes a DC / DC converter 21 connected to the solar cell 10, an AC / DC converter 22 and a charger / discharger 23 connected in series to the DC / DC converter 21, and an AC / DC converter. 22 and a disconnecting relay 24 provided on an electric wire connecting the system 40.
The electric power generated by the solar cell 10 is converted into a predetermined voltage by the DC / DC converter 21 and supplied to one or both of the AC / DC converter 22 and the charger / discharger 23.
The AC / DC converter 22 performs both an inverter operation that converts DC power (generated power) from the solar cell 10 that has passed through the DC / DC converter 21 into AC power and a converter operation that converts AC power from the system 40 into DC power. It has a function.
The charger / discharger 23 controls charging of power to the storage battery 60 and discharging of power from the storage battery 60.
The disconnection relay 24 performs connection and disconnection between the power conditioner 19 and the system 40.
Moreover, the photovoltaic power generation system 1 includes a current detector 28 installed between the power conditioner 19 and the system 40, and a received power detection configured by a control unit 26 that acquires a current signal detected by the current detector 28. A circuit 29 is provided. The control unit 26 performs power generation and charge / discharge control of the power converter 20 in accordance with the AC load 50 so that the received power becomes zero or a predetermined received power value, and adjusts the output of the power conditioner 19.

The solar power generation system 1 includes a storage battery discharge detection circuit 30.
The storage battery discharge detection circuit 30 includes a current detection unit 31 and a storage battery discharge detection signal generation unit 32.
The current detector 31 detects a current flowing between the charger / discharger 23 and the storage battery 60. The detected current signal is sent to the storage battery discharge detection signal generation unit 32.
The storage battery discharge detection signal generation unit 32 transmits the storage battery discharge detection signal Id to the reverse power relay (RPR) 25 when the current signal I detected by the current detection unit 31 indicates the current in the discharge direction from the storage battery 60. Then, the reverse power relay 25 is set in the operating state.
The system 40 supplies AC power from an electric power company, and is connected to a distribution board (not shown).
The AC load 50 includes an electric device that operates with an AC power source used in a building, and is connected to a distribution board. The AC load 50 varies depending on the type and number of electrical devices actually used.
In the present embodiment, the storage battery 60 is mounted on an automobile, but power storage devices that can store electric power and can be discharged as needed can be widely applied.

The photovoltaic power generation system 1 includes a reverse power relay 25 that detects that a reverse power flow has occurred toward the system 40 between the disconnection relay 24 and the system 40.
When the reverse power relay 25 detects that a reverse power flow has occurred while the storage battery 60 is being discharged, a reverse power detection signal Ib is transmitted to the power converter 20. When the AC / DC converter 22 receives the reverse power detection signal Ib, the AC / DC converter 22 blocks the gate, stops the output of power in the system direction (reverse conversion operation), and also blocks the DC / DC converter 21 and the charger / discharger 23, Stop. The reverse power detection signal Ib is also transmitted to the disconnecting relay 24. The disconnection relay 24 is opened when the reverse power detection signal Ib is received. Thus, the power conditioner 19 is stopped and disconnected from the system.
The reverse power relay 25 in the present embodiment receives the storage battery discharge detection signal Id, and is set to be in an operating state only when the storage battery 60 is discharged. Therefore, the stop of the power converter 20 based on the reverse power detection signal Ib and the disconnection of the disconnect relay 24 based on the reverse power detection signal Ib are performed when the reverse power relay 25 receives the storage battery discharge detection signal Id. As long as executed.
Here, similarly to the general-purpose power generation system having no power storage unit, the power converter 20 mainly including the gate block of the AC / DC converter 22 based on the reverse power detection signal Ib, and the disconnecting relay 24 The reverse power flow is more reliably prevented by stopping the power conditioner 19 and disconnecting from the system 40 by performing both of the opening of the battery, but by only blocking the charger / discharger 23, the discharge power of the storage battery And the disconnection relay 24 is not opened and the operation of the power conditioner 19 is continued.

The basic operation of the photovoltaic power generation system 1 having the above configuration is as follows.
The DC power generated by the solar cell 10 (hereinafter sometimes referred to as “PV power”) is set to a predetermined voltage by the DC / DC converter 21. This direct current is supplied to the AC / DC converter 22 or the charger / discharger 23.
The generated DC power is supplied to the AC / DC converter 22 so that the received power is zero or a predetermined received power value in the received power detection circuit 29 in accordance with the AC load 50, and is converted into AC power. Consumed at load 50.

On the other hand, the generated power that has not been converted to AC power is charged into the storage battery 60 while the charging power is controlled by the charger / discharger 23. At this time, if the generated power that has not been converted into AC power exceeds the maximum charging power, the excess is supplied to the AC / DC converter 22, converted into AC power, and backflowed into the grid 40 as surplus power. .
Of course, the grid power from the grid 40 can be used for charging the storage battery 60. In this case, AC system power supplied from the system 40 is converted into direct current by the AC / DC converter 22 and then charged to the storage battery 60 while charging power is controlled by the charger / discharger 23. It is advantageous to use nighttime power with a low charge for charging system power. In addition, system power and generated power can be used together for charging the storage battery 60. In this case, the DC / DC converter 21 converts the generated power into a predetermined voltage, and the AC / DC converter 22 converts the system power into direct current. Then, after the both powers are merged, the storage battery 60 is charged through the charger / discharger 23.

The photovoltaic power generation system 1 can discharge PV power or grid power stored in the storage battery 60 and use it for consumption of the AC load 50. In this case, the stored PV power or system power is AC / DC so that the received power is zero or a predetermined received power value in the received power detection circuit 29 in accordance with the AC load 50 so as not to flow backward to the system. It is supplied to the converter 22, converted into AC power, and consumed by the AC load 50. On the other hand, when the AC load 50 exceeds the maximum discharge power, the excess is supplemented by the system power and consumed by the AC load 50. Further, PV power directly supplied from the solar battery 10 without passing through the storage battery 60 can be used in combination with the discharge power from the storage battery 60. In this case, the generated power set to a predetermined voltage by the DC / DC converter 21 and the discharge power set to a predetermined voltage by the charger / discharger 23 are merged, and then converted into AC power by the AC / DC converter 22 to obtain an AC load. 50 can be consumed.
The stored PV power or system power discharged from the storage battery 60 is controlled by the received power detection circuit 29 so that the received power becomes zero or a predetermined received power value, so that a reverse power flow to the system 40 does not occur. However, there is a risk that a reverse power flow may occur due to poor control. However, in the present embodiment, while discharging from the storage battery 60, the reverse power relay 25 is operated to monitor the reverse power flow so that the reverse power flow does not occur.

As described above, according to the power storage solar power generation system 1 of the first embodiment, the power converter 20 is stopped only when a reverse power flow occurs when the storage battery 60 is discharged, and the power condition is Since the na 19 is configured to be disconnected from the system 40, the reverse flow can be caused even when the storage battery 60 is being charged. Specific cases in which reverse power flow can occur are, for example, as follows. According to the photovoltaic power generation system 1, reverse power flow, that is, power sale can be performed while charging PV power even in the following cases. Therefore, efficient and economical operation of the storage battery or solar battery is possible.
(1) When the storage battery 60 limits the charging power near the full charge, the remaining power after the generated power is consumed by the AC load 50 becomes larger than the charging power and surplus power is generated. (2) Among the PV power When the storage battery 60 is operated while charging a certain amount and the remaining power is supplied to the AC load 50, but the AC load 50 is smaller than the remaining power and the surplus power is generated even after the supply (3) Solar cell 10 or solar cell In the case of a system in which the capacity of the charger / discharger 23 is smaller than the capacity of the DC / DC converter 21 to which the power is connected, the generated power in the normal time exceeds the maximum charging power. Since the power to be generated can always be limited to the power generated by the solar cell 10, it is possible to sell power at a unit price at the time of power generation of the solar cell 10 by the fixed price purchase system. .

[Operation example]
Next, with reference to FIGS. 2 to 4, two operation examples of the solar power generation system 1 will be described. In the first operation example (FIG. 3), priority is given to the supply of generated power to the AC load 50, and in the second operation example (FIG. 4), power storage to the storage battery 60 is prioritized.
[First operation example]
The first operation example is divided into a night power time zone and a daytime power time zone. In the daytime power time zone, charging / discharging of the storage battery 60 is performed depending on whether or not the PV power by the solar cell 10 exceeds the AC load 50. It is divided. In addition, the presence or absence of reverse power flow to the system is classified according to whether the difference between the PV power and the AC load exceeds the maximum charge power, and the power from the system is determined depending on whether the difference between the AC load and the PV power exceeds the maximum discharge power. The presence or absence of supply is classified.
(1) Nighttime power time zone The nighttime power from the system 40 is charged in the storage battery 60 (step S101 Yes in FIG. 3).
Further, all AC loads 50 in the building are covered with power from the system 40, and the storage battery 60 is not discharged. The state of charge at the end of the night charge is not a full charge so that surplus power of the PV power of the solar cell 10 can be charged to the storage battery 60 in the daytime. of charge: SOC) is set as a target value (step S103 in FIG. 3). The target value is predicted from a daytime weather forecast, predicted solar radiation amount, predicted power demand amount of the AC load 50, etc., in addition to a fixed value determined by the balance between the power generation capacity of the solar cell 10 and the capacity of the storage battery 60 and the AC load 50. It may be a variable that changes from day to day based on the surplus power.

(2) When the PV power exceeds the power required for the AC load 50 in the daytime power time zone The PV power of the solar cell 10 is required for the AC load 50 in the daytime power (No in step S101 in FIG. 3) time zone. When the electric power (hereinafter simply referred to as AC load 50) is exceeded (step S105 Yes in FIG. 3), surplus power after the PV power of the solar cell 10 is supplied to the AC load 50 in the building is charged in the storage battery 60. In this case, processing differs depending on whether or not the difference between the PV power and the AC load 50 exceeds the maximum charging power (step S107 in FIG. 3). Here, the maximum charging power is determined by the specifications of the charger / discharger 23 and the storage battery 60, and is the maximum power that can charge the storage battery 60. When the difference between the PV power and the AC load 50 exceeds the maximum charge power (step S107 Yes in FIG. 3), the surplus power corresponding to the excess of the maximum charge power is charged to the grid 40 while charging the storage battery 60 with the maximum charge power. Reverse current. (FIG. 3 Steps S109 and S119).
For example, when the storage battery 60 is near full charge, the maximum charge power is suppressed, and surplus power is generated even after charging, the storage battery 60 reversely flows (sells power) the surplus power to the system 40 in the charged state. . At this time, since the storage battery 60 is being charged, the reverse power relay 25 is in a non-operating state, and therefore a reverse power flow is possible. This state is shown in FIG. 2 (a), and the electric wires indicated by the thick lines between the devices indicate that power flows in the direction of the attached arrows (FIG. 2 (b) also). The same). In addition, since reverse power flow electric power is surplus electric power originating in the solar cell 10, the unit price of the fixed price purchase system is applied as the unit price for power sale.
On the other hand, when the difference between the PV power and the AC load 50 is equal to or less than the maximum charging power (No in Step S107 in FIG. 3), the storage battery 60 is charged with the difference power between the PV power and the AC load 50 (Step S111 in FIG. 3).

(3) When PV power is less than 50 AC load during daytime power hours (morning, evening, etc.)
On the other hand, when the PV power of the solar cell 10 is less than or equal to the AC load 50 (No in step S105 in FIG. 3), the AC load 50 in the building is discharged by discharging the power from the storage battery 60 to the AC load 50 for the insufficient power. To supply power.
By doing so, the local production and local consumption of the electric power by the solar cell 10 and the storage battery 60, the peak cut of received electric power, and the peak shift of the electric power demand by night electric power are promoted. Note that the electric power to be discharged is based on the electric power from the grid 40 stored in the night electric power time zone and the surplus electric power stored as an excess of the PV electric power of the solar cell 10.
In the above case, the process differs depending on whether or not the difference between the PV power and the AC load 50 exceeds the maximum discharge power (step S113 in FIG. 3). Here, the maximum discharge power is determined by the specifications of the charger / discharger 23 and the storage battery 60, and is the maximum power that the storage battery 60 can discharge. When the difference between the PV power and the AC load 50 exceeds the maximum discharge power (FIG. 3, Step S113 Yes), the power is discharged and supplied to the AC load 50 with the maximum discharge power, and the excess of the maximum discharge power is insufficient. Electric power is supplied from the system 40 (steps S115 and S121 in FIG. 3). On the other hand, when the difference between the PV power and the AC load 50 is equal to or less than the maximum discharge power (No in step S113 in FIG. 3), the power is discharged and supplied to the AC load 50 with the power difference between the PV power and the AC load 50 (FIG. 3 Step S117).
In this process, since the storage battery discharge detection circuit 30 detects the discharge of the storage battery 60, the reverse power relay 25 enters an operating state. Should a reverse power flow to the grid 40 occur due to a malfunction of the storage battery 60 or the like, the reverse power detection signal Ib is transmitted from the reverse power relay 25, and the power conditioner 19 is stopped and disconnected from the grid 40. The discharge power of the storage battery 60 is prevented from flowing back into the system 40. This state is shown in FIG. In this case, system power is supplied from the system 40 to the AC load 50.

[Second example]
In the first operation example, priority is given to supplying PV power to the AC load 50 in the building, but priority is given to charging the PV power to the storage battery 60 as in the second operation example described below, and the storage battery The surplus power after charging 60 can be supplied to the AC load 50 in the building. The second operation example considers the following.
In photovoltaic power generation, PV power fluctuates depending on the amount of solar radiation, and the load in the building also fluctuates. Therefore, when power is preferentially supplied to the load 50 in the building, the surplus power fluctuates greatly and the storage battery 60 is charged. Electric power may become unstable. In particular, the charger / discharger 23 has high efficiency in the vicinity of the rated capacity. However, when the surplus power is insufficient and the charging power is reduced, charging is performed at a low load, and thus the efficiency is reduced. Therefore, in the second operation example, reference charging power that can be efficiently charged is set based on the charger / discharger 23. In addition, when the in-vehicle storage battery 60 is applied, it may be used as mobile power. Therefore, if the surplus power is insufficient, the travel distance is limited due to the shortage of charge power, or the system 40 Therefore, it is necessary to supplement the amount of charging power with the expensive daytime power.

(1) Nighttime power time zone The nighttime power from the system 40 is charged in the storage battery 60 (step S201 Yes in FIG. 4).
The AC load 50 in the building is all covered with power from the grid 40, the battery 60 is not discharged, and the charging is up to the target value (step S203 in FIG. 3), as in the first operation example. .

(2) When the PV power exceeds the reference charging power in the daytime power time zone When the PV power of the solar cell 10 exceeds the predetermined reference charging power in the daytime power (step S201 No in FIG. 4) time zone (FIG. 4, step S205 Yes), after the PV power is charged in the storage battery 60, it is supplied to the AC load 50 in the building. In this case, the process differs depending on whether the PV power exceeds the maximum charging power (step S207 in FIG. 4). When the PV power exceeds the maximum charging power (step S207 in FIG. 4), the storage battery 60 is charged with the maximum charging power (step S209 in FIG. 4). Further, if the value obtained by subtracting the maximum charging power from the PV power is larger than the AC load 50, the surplus power is caused to flow backward to the grid 40 (steps S223 and S225 in FIG. 4). Otherwise, the insufficient power is supplied to the AC load 50 by system power (steps S223 and S227 in FIG. 4).
On the other hand, when the PV power is equal to or lower than the maximum charge power (No in step S207 in FIG. 4), the storage battery 60 is charged with the PV power (step S211 in FIG. 4). In this case, system power is supplied to the AC load 50 (step S229 in FIG. 4). Note that the charging power to the storage battery 60 does not necessarily need to be fully charged with PV power when the charging power exceeds the reference charging power, and is surplus as constant power charging with the reference charging power that is a range in which the efficiency characteristics during charging are not significantly reduced. Electric power may be supplied to the AC load 50.

  The surplus power after being used for the charging power is supplied to the AC load 50, and when surplus power is generated, the surplus power is reversely flowed (power sold) to the grid 40. At this time, since the storage battery 60 is being charged, the reverse power relay 25 is in an inoperative state, and a reverse power flow is possible. In addition, since reverse power flow electric power is surplus electric power originating in the solar cell 10, the unit price of the fixed price purchase system is applied as the unit price for power sale.

(3) When PV power is below the standard charging power during the daytime power hours (morning, evening, etc.)
When it is a time zone of daytime power (No in step S201 in FIG. 4) and the PV power of the solar battery 10 is equal to or lower than a predetermined reference charging power (No in FIG. 4), charging is low. PV power is preferentially supplied to the AC load 50 in the building.

In this case, the process differs depending on whether the PV power exceeds the AC load 50 (step S213 in FIG. 4).
That is, when the PV power exceeds the AC load 50 (FIG. 4, step S213 Yes), the PV power is supplied to the AC load 50 without charging / discharging the storage battery 60 (FIG. 4, step S215) (FIG. 4, step S233). ), Surplus power (PV power-AC load) flows backward to the grid 40 (power sales, step S235 in FIG. 4). At this time, since the storage battery 60 is not charged / discharged, the reverse power relay 25 is in a non-operating state, and a reverse power flow is possible.

On the other hand, when the PV power is equal to or less than the AC load 50 in the building (No in Step S213 in FIG. 4), the power is supplied from the storage battery 60 to the AC load 50 in the building.
By doing so, the local production and local consumption of the electric power by the solar cell and the storage battery 60, the peak cut of the received electric power, and the peak shift of the electric power demand by night electric power are promoted. In addition, it is the same as that of the 1st operation example that the electric power discharged is based on the electric power from the system | strain 40 stored by the night electric power time slot | zone, and the electric power stored as a surplus of PV electric power.
In the above case, the process differs depending on whether or not the difference between the AC load 50 and the PV power exceeds the maximum discharge power (step S215 in FIG. 4). That is, when the difference between the AC load 50 and the PV power exceeds the maximum discharge power (step S217 in FIG. 4), power is discharged and supplied to the AC load 50 with the maximum discharge power. Is supplied from the grid 40 (steps S219 and S231 in FIG. 4). On the other hand, when the difference between the AC load 50 and the PV power is equal to or less than the maximum discharge power (No in step S217 in FIG. 4), power is discharged and supplied to the AC load 50 with the power difference between the AC load 50 and the PV power (FIG. 4). 3 Step S117).
In this process, since the storage battery discharge detection circuit 30 detects the discharge of the storage battery 60, the reverse power relay 25 enters an operating state. In the unlikely event that a reverse power flow to the grid 40 occurs due to poor control of the storage battery 60 or the like, a reverse power detection signal Ib is transmitted from the reverse power relay 25, and the power conditioner 19 is stopped and disconnected from the grid 40, The discharge power of the storage battery 60 is prevented from flowing back into the system 40.

  According to the second operation example, since the PV power is preferentially charged to the storage battery 60, the charging / discharging device 23 is operated near a low load by reducing the influence of the load fluctuation in the building and securing the charge amount. Therefore, a decrease in charging efficiency is suppressed. Moreover, since priority is given to the charge to the storage battery 60, when the vehicle-mounted storage battery 60 is used, the amount of charge is easily secured, and it becomes possible to suppress a state of insufficient charge when used as mobile power. .

[Second Embodiment]
Next, the photovoltaic power generation system 2 according to the second embodiment will be described with reference to FIG.
The solar power generation system 2 obtains the same effect as the solar power generation system 1 of the first embodiment without using the reverse power relay 25.
The photovoltaic power generation system 2 includes a received power detection circuit 29 and a storage battery discharge detection circuit 30 similar to those of the first embodiment, and receives the storage battery discharge detection signal Id transmitted by the storage battery discharge detection signal generation unit 32. Acquired by the control unit / reverse power relay 27 of the circuit 29.
When the controller / reverse power relay 27 receives the storage battery discharge detection signal Id and determines that a reverse power flow is occurring in the grid 40 based on the current signal acquired from the current detector 28, the reverse power The detection signal Ib is transmitted to the power converter 20. When the AC / DC converter 22 receives the reverse power detection signal Ib, the AC / DC converter 22 blocks the gate, stops the output of power in the system direction (reverse conversion operation), and also blocks the DC / DC converter 21 and the charger / discharger 23, Stop. The reverse power detection signal Ib is also transmitted to the disconnecting relay 24. The disconnection relay 24 is opened when the reverse power detection signal Ib is received. Thus, the power conditioner 19 is stopped and disconnected from the system. Thus, the control unit / reverse power relay 27 stops the power conditioner 19 and disconnects from the system 40 only when the storage battery 60 is discharged and a reverse power flow is detected.

As described above, since the photovoltaic power generation system 2 of the second embodiment can be made to reversely flow even when the storage battery 60 is being charged, as in the first embodiment, the storage battery 60 and the solar battery 10 are efficiently and economically efficient. Operation in consideration of sex becomes possible. In addition, since the power flowing in the reverse direction can always be limited to the power generated by the solar cell 10, it is possible to sell power at the unit price at the time of generating the solar cell 10 which is higher than the power purchased by the fixed price purchase system. .
Furthermore, the photovoltaic power generation system 2 of the second embodiment has a cost advantage since the controller / reverse power relay 27 can be configured by software and the reverse power relay 25 can be omitted.

,
In addition, although the solar power generation systems 1 and 2 demonstrated above are supposed to generate electric power with the solar cell 10, this invention replaces the power generation source (for example, wind power generation) derived from natural energy with the solar cell 10, or The solar cell 10 can be used.
Moreover, although the solar power generation system 1 and 2 demonstrated above showed the building in which the building was a house and the electrical storage part was an in-vehicle storage battery, the building is not limited to a house, for example, a building other than a house such as a factory or various facilities. The present invention can also be applied, and is not limited to an in-vehicle storage battery, but can also be applied to a stationary storage battery installed in a building.
Furthermore, the installation position of devices such as the reverse power relay 25 and the current detector 28 is not limited to the power receiving end, and can be installed at any place where it is desired to suppress reverse power flow.
In addition to this, as long as it does not depart from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

DESCRIPTION OF SYMBOLS 1, 2 Solar power generation system 10 Solar cell 19 Power conditioner 20 Power converter 21 DC / DC converter 22 AC / DC converter 23 Charger / discharger 24 Disconnect relay 25 Reverse power relay 26 Control part 27 Control part and reverse power relay 28 Current detector 29 Received power detection circuit 30 Storage battery discharge detection circuit 31 Current detection unit 32 Storage battery discharge detection signal generation unit 40 System 50 AC load 60 Storage battery I Current signal Ib Reverse power detection signal Id Storage battery discharge detection signal

Claims (4)

A power generation unit that is connected to an external system and generates natural energy.
A power conditioner comprising: a DC / DC converter connected to the power generation unit; and an AC / DC converter and a charger / discharger connected in series to the DC / DC converter,
A power storage unit that stores and discharges the power generated by the power generation unit and the power from the system via the charger / discharger and is DC-connected to the power generation unit,
A control unit that controls power generation of the power generation unit and charge / discharge of the power storage unit,
The controller is
A received power detection unit for controlling the power generation unit and the power storage unit to have a predetermined received power at a power receiving end;
In order to prevent a reverse power flow when the power storage unit is in a discharged state, a discharge detection unit that detects a discharge from the power storage unit,
A reverse power flow detection unit that detects that a reverse power flow has occurred toward the system,
If the reverse power flow detection unit detects the reverse power flow while the discharge detection unit is detecting the discharge, the power conditioner is stopped and the power conditioner is disconnected from the system. Control for preventing reverse power flow, and while the discharge detection unit does not detect the discharge, the reverse power flow detection unit does not detect the reverse power flow, and the power storage unit is charging Control that allows reverse power flow from the power generation unit,
A power storage type power generation system comprising: The reverse power flow detection unit comprises a reverse power relay,
The reverse power relays, together with an operating state while the discharge detection portion is detecting the discharge, and outputs a reverse power detection signal upon detecting the reverse power flow, and stops the power conditioner, the power While disconnecting the conditioner from the system, while the discharge detector is not detecting the discharge, the reverse power relay is in an inoperative state, allowing the reverse power flow,
The power storage type power generation system according to claim 1. When the power generated by the power generation unit is larger than the power required for the load connected to the power generation system,
Supplying the generated power to the load, and charging the remainder of the power storage unit;
When the power generated by the power generation unit is less than or equal to the power required for the load connected to the power generation system,
About the insufficient power, the power stored in the power storage unit is discharged toward the load,
In the power storage type power generation system that includes the received power detection unit and controls power generation of the power generation unit and charge / discharge of the power storage unit so as to be predetermined received power,
When the power generated by the power generation unit is larger than the power required for the load and the residual after supply to the load exceeds the maximum charging power of the power storage unit, the surplus power that is the excess is stored in the power storage It was possible to perform reverse power flow to the system while continuing to charge the part ,
The power storage type power generation system according to claim 1 or 2. When the power generated by the power generation unit is larger than the reference charging power in the power generation system,
Supplying the remaining power stored in the power storage unit to the load connected to the power generation system;
When the power generated by the power generation unit is less than or equal to the reference charging power in the power generation system,
further,
When the power generated by the power generation unit is larger than the power required for the load connected to the power generation system, the generated power is not discharged from the power storage unit or charged to the power storage unit. To the load, the surplus power is reversely flowed to the grid,
When the power generated by the power generation unit is less than or equal to the power required for the load connected to the power generation system,
About the insufficient power, the power stored in the power storage unit is discharged toward the load,
In the power storage type power generation system that includes the received power detection unit and controls power generation of the power generation unit and charge / discharge of the power storage unit so as to be predetermined received power,
When the power generated by the power generation unit is larger than the reference charging power, and the remaining power stored in the power storage unit exceeds the power consumption of the load, the surplus power that is the excess is converted to the power storage unit. It was possible to carry out reverse power flow to the system while continuing to charge
The power storage type power generation system according to claim 1 or 2.

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