JP5738212B2 - 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 to the introduction of storage batteries, it is expected to be used as an emergency power source in the event of a system power outage in the event of a disaster, etc. Development momentum is also increasing.

Specific examples of these systems include a system that connects a photovoltaic power generation system and a storage battery system via an AC system (AC connection system), and a solar battery and a storage battery that are connected by a DC system, generating power and discharge power from the storage battery. A system (DC connection system) that mixes and converts to AC and connects to the grid has been put to practical use.
In this way, the introduction of a system with a storage battery is advancing, but at present, it is more advantageous to sell the surplus power of the generated power than charging the storage battery when considering the economics by the surplus power purchase system. Therefore, the utilization method of the storage battery is mainly an operation method in which inexpensive nighttime electric power is charged and discharged in an expensive daytime period. In the case of such an operation method, since the surplus power of the generated power is not charged to the storage battery, there is a problem that it does not contribute to the stabilization of the system voltage originally expected for the storage battery.

In buildings where a solar power generation system is introduced, if the load in the building is smaller than the generated power, surplus power can be reversely flowed (sold) into the system. However, the grid voltage may increase if the power generated by the solar cell continues to flow backward when the load in the entire region is small and clear weather continues. For this reason, the photovoltaic power generation system is provided with a voltage rise suppression function in order to prevent the voltage on the grid side from exceeding the operating regulation value of the electric power company. When this function is activated, it is impossible to output the maximum generated power that can be output by the solar cell, and thus problems such as a reduction in the operating rate of the solar power generation facility and a decrease in energy saving and economic efficiency are regarded as problems. The voltage rise suppression function is a function that automatically adjusts the voltage of the power generation equipment when the system side voltage reaches the operating regulation value of the electric power company. A phase reactive power control function that suppresses the rise in system voltage by supplying phase reactive power whose current phase is ahead of the voltage, and an output control function that regulates the voltage by suppressing the output of the power generation equipment itself. is there. Any of these methods has a problem in that the generated power is lowered during operation because it is controlled to suppress the maximum generated power that can be output by the power generation facility.
In addition, general-purpose photovoltaic power generation systems that are becoming popular are controlled as a single power generation facility, and the voltage rise suppression function operates automatically. There is no coordination of voltage adjustment. In particular, the use of a storage battery is expected to suppress voltage rise, but in the above AC connection system, even if there is a power storage facility, unless a function for cooperative control of the power generation facility and the power storage facility against voltage increase is provided The voltage rise suppression function of the power generation facility operates automatically and has a problem of suppressing output.

  Therefore, Patent Document 1 describes history data such as system side voltage fluctuation status, date and time, outside temperature, and weather conditions when voltage rise suppression occurs, current system side voltage fluctuation situation, date and time, outside temperature, weather conditions, and the like. Based on the current data, the presence or absence of voltage rise suppression is predicted, and when it is predicted that the voltage rise suppression will occur, the power that stores the surplus generated power generated by the solar power generation device in the energy storage device A residential power system with control means has been proposed.

JP 2011-172334 A

However, as in Patent Document 1, the method of determining suppression of voltage increase by prediction cannot cope with a case where the system voltage has increased against prediction.
Therefore, in the present invention, without relying on uncertain factors as predicted, for example, the reverse power flow (sold power) to the system by photovoltaic power generation is limited by the increase in system voltage, and the power generation output is suppressed. It is an object of the present invention to provide a power storage type power generation system that can use the generated power without waste by charging a storage battery even under conditions.

The present invention made there is a power generation unit that is connected to an external system and generates power by receiving sunlight , a power storage unit that stores power generated by the power generation unit and power from the system, and is DC-connected to the power generation unit. A power conditioner including a DC / DC converter connected to the power generation unit, an AC / DC converter and a charger / discharger connected in series to each other in series with respect to the DC / DC converter via a DC bus, Or, a load supplied with AC power via the AC / DC converter and an instruction to the AC / DC converter are used to control the reverse flow of the generated power to the system and to give an instruction to the charger / discharger. And a control unit that controls power generation of the power generation unit and charge / discharge of the power storage unit. In addition, although this system has the voltage rise suppression function required for grid connection similarly to a general purpose photovoltaic power generation system, since it is a direct current connection system, it has the function as one system.
According to the present invention, the control unit stops the reverse flow of the generated power based on the comparison between the system voltage and a predetermined threshold voltage when the generated power is flowing backward toward the system, or In addition to reducing the generated power flowing in the reverse direction, the power storage unit is charged with the generated power and selectively includes two modes described below .
According to the power generation system of the present invention, when the system voltage rises, the generated power can be charged to the power storage unit so as to suppress the operation of the voltage increase suppression function possessed by the system, so without suppressing the generated power, Power generation can be continued. In particular, since the maximum power point tracking control (MPPT control) used for the power generation control of the solar cell can be continued, the operation with the maximum generated power that the system can output becomes possible. Moreover, since the power generation system of the present invention uses a DC connection system, and this system can always monitor the system voltage as a single system, it does not rely on prediction of the system voltage, and other equipment outside this system. Therefore, it is possible to appropriately determine switching from reverse power flow to charging.

The power generation system of the present invention includes two control modes of reverse power flow and charging by the control unit.
In the first form, when the system voltage becomes equal to or higher than a predetermined threshold voltage, the control unit stops the reverse power flow of surplus power that is the remaining power supplied to the load and stores all surplus power. Charge the part. Then, after continuing the charging operation for a predetermined time, the control unit can stop the charging of the power storage unit with the surplus power of the generated power and can resume the reverse flow of the surplus power of the generated power.
According to the first form, since the surplus power of the generated power is used to charge the entire power storage unit, the reverse power flow to the system is eliminated and the system voltage is within the appropriate voltage range of the power company as long as the system side is normal. Thus, the system voltage can be stabilized. Moreover, it is also possible to suppress the efficiency fall by the low load driving | running of a charger / discharger by using surplus electric power for whole charge.

In the first form, when the system voltage is lower than a predetermined threshold voltage, the power generated by the power generation unit is greater than the power required for the load connected to the power generation system, as in a general-purpose photovoltaic power generation system. Is larger, the generated electric power is supplied to the load via the DC / DC converter and the AC / DC converter, and the surplus electric power that is the remainder is reversely flowed to the system. Then, when the system voltage becomes equal to or higher than a predetermined threshold voltage while surplus power is flowing backward through the system, the charging operation and the reverse power flow are resumed according to the above procedure. Here, the threshold voltage is set lower than the operating voltage of the voltage increase suppressing function possessed by the system, whereby the operation of the voltage increase suppressing function is suppressed.

The second embodiment, corresponding to the difference between the bus voltage is the voltage on the DC bus, the surplus power detection voltage is a threshold voltage which is determined surplus power is generated in power generation, charging the charge reservoir section The surplus power of the generated power to be generated and the surplus power of the generated power to be reversed are distributed.
According to the second form, it is possible to charge the power storage unit while making reverse power flow, that is, selling power, so surplus power that can not be sold can be charged while continuing to sell surplus power as much as possible. Economic efficiency can be improved.

  In the second embodiment, the system voltage can also be detected via a DC voltage (DC bus voltage) in a DC bus provided between the power generation unit and the system. Then, since a control unit can be provided as software in a power converter (power conditioner) including a DC / DC converter, an AC / DC converter, etc., the configuration of the power generation system can be simplified and the cost can be reduced. .

  According to the power generation system of the present invention, even if the system voltage rises and the generated power cannot be reversely flowed into the system, the generated power can be charged to the power storage unit, so that the generated power can be used without wasting it. be able to. Moreover, since the charging of the power storage unit is determined based on the system voltage, the generated power can be used more reliably.

It is a block diagram which shows the structure of the power storage type solar power generation system in 1st Embodiment. It is a flowchart which shows the control procedure of the electric power storage type solar power generation system in 1st Embodiment. In the power storage solar power generation system according to the first embodiment, (a) the surplus power of the generated power indicates a state in which a reverse power flow occurs in the system, and at this time, the storage battery is stopped. (B) is a block diagram showing a state in which the reverse power flow is stopped and charging is performed. It is a block diagram which shows the structure of the power storage type solar power generation system in 2nd Embodiment.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
[First Embodiment]
The solar power generation system 1 in the first embodiment shown in FIG. 1 connects the solar cell 10 to the system 40 by the power conditioner 19 and supplies the generated power of the solar cell 10 to the AC load 50 in the daytime. Is larger than the AC load 50, the surplus power is reversely flowed into the system, and when it is smaller than the AC load 50, the insufficient power is supplied by discharging the power stored in the storage battery 60 from the system 40 at night. System. In addition, when the generated power and the discharged power from the storage battery are insufficient with respect to the AC load 50, the system supplies power from the system 40 to the AC load 50.
Moreover, the solar power generation system 1 comprises the direct current | flow connection system which stores in the storage battery 60 as direct current power, without converting the electric power generated with the solar cell 10 into alternating current. Since a commercially available solar power generation system is generally used for the AC connection system, it is difficult for the storage battery system to recognize the operating status of the voltage rise suppression function and switch to charging operation. Since the system voltage is constantly monitored and the voltage rise suppression function is held, the system voltage rises due to reverse power flow and before switching to the operating voltage of the voltage rise suppression function, switch to charging control of the surplus power to the storage battery. Is easily possible.

The power conditioner 19 includes a DC / DC converter 21 connected to the solar cell 10, and an AC / DC converter 22 and a charger / discharger 23 connected in series to the DC / DC converter 21 by a DC bus 24. The power converter 20 is provided.
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 storage battery 60.
The AC / DC converter 22 performs both an inverter operation that converts DC power (PV 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 system 40 supplies AC power from an electric power company, and is connected to a distribution board (not shown).
The AC load 50 includes a plurality of electric devices that operate with AC power used in a house or other building, and is connected to a distribution board. The AC load 50 varies depending on the type and number of electrical devices actually used. The AC load 50 is supplied with AC power via the system 40 or the AC / DC converter 22. The AC power via the AC / DC converter 22 includes power generated by the solar battery 10 and power discharged from the storage battery 60.
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 power conditioner 19 of the solar power generation system 1 includes a control unit 30.
The control unit 30 controls the output voltage and current by giving an instruction to the AC / DC converter 22, and activates the voltage rise suppression function when the system voltage rises, thereby performing phase advance reactive power control and output power control. It has a function. Further, the control unit 30 has a function of controlling charging and discharging and stopping thereof by giving an instruction to the charger / discharger 23. When the system voltage increases, the control unit 30 uses surplus power prior to the operation of the voltage increase suppressing function. A function for switching to charge control is provided. For this reason, when the system voltage rises, first suppress the increase in the system voltage by charging control of surplus power, only when the storage battery is fully charged or the surplus power exceeds the maximum charging power, and the voltage increase cannot be suppressed only by charging control. Control is performed so that the voltage rise suppression function is activated.
Control unit 30 in order to perform the control described above, sequentially acquires the system voltage V _s which is measured by the voltage detector 31. In addition, the control unit 30 configures a current detector 28 and a received power detection circuit 29 installed at the power receiving end in order to perform control so that a reverse power flow does not occur when switching to surplus power charging control. The received power detection circuit 29 is also used to control the received power so that the discharged power does not flow backward to the grid when the generated power is insufficient for the AC load 50 and discharge control from the storage battery 60 is performed. Circuit. The control unit 30 holds the threshold voltage V _t , and the threshold voltage V _t prevents the system voltage from rising due to the reverse power flow of the surplus PV power and the voltage rise suppression function from operating. It is set in the range above the appropriate system voltage and below the voltage settling value when the voltage rise suppression function is activated. Thus, since the reverse power flow operation is switched to the charging operation before the voltage increase suppression function is activated, it is possible to suppress the output suppression of the generated power due to the operation of the voltage increase suppression function.

A control procedure by the control unit 30 will be described with reference to FIG. This control procedure is based on the premise that reverse power flow is performed.
Control unit 30 compares the system voltage _{V s} obtained from the threshold voltage _{V t} and the voltage detector 31 (FIG. 2, step S101).
When the system voltage V _s becomes _{equal to} or higher than the threshold voltage V _t (step S101 Yes in FIG. 2), the control unit 30 instructs the AC / DC converter 22 to stop the reverse flow (step S103 in FIG. 2). The discharger 23 is instructed to start charging the storage battery 60 (step S105 in FIG. 2). The photovoltaic power generation system 1 shifts from a reverse power flow operation of surplus power to a charging operation.
When the system voltage V _s is less than the threshold voltage V _t (No in step S101 in FIG. 2), the control unit 30 continues the comparison.
The control unit 30 continues the charging operation for a predetermined time from the instruction to stop the reverse power flow and start the charging, and stops charging the storage battery 60 in the charger / discharger 23 after the predetermined time has elapsed (step S107 in FIG. 2). An instruction is given (step S109 in FIG. 2), and the AC / DC converter 22 is instructed to return to the reverse power flow operation (step S111 in FIG. 2). The solar power generation system 1 returns to the reverse power flow operation from the surplus power charging operation.
When returning to the reverse power flow operation, the control unit 30 returns to the procedure of comparing the threshold voltage V _t with the system voltage V _s acquired from the voltage detector 31 (step S101 in FIG. 2), and the reverse power flow operation is performed. Meanwhile, the same procedure as above is repeated.

The operation of the photovoltaic power generation system 1 having the above configuration is as follows.
The DC PV power generated by the solar cell 10 is converted into a predetermined voltage by the DC / DC converter 21. This DC power is supplied to the AC / DC converter 22 or the charger / discharger 23.
The PV power passing through the AC / DC converter 22 is consumed by the AC load 50, and the surplus power is reversely flowed to the grid 40. In the present embodiment, as described above, when the reverse power flow is performed, when the system voltage V _s becomes _{equal to} or higher than the threshold voltage V _t , the reverse power flow is stopped and charging of the storage battery 60 with surplus power is started. To do.

  On the other hand, the PV power passing through the charger / discharger 23 is charged into the storage battery 60 while the charging power is controlled by the charger / discharger 23. At this time, the surplus can be charged to the storage battery 60 while the PV power passing through the AC / DC converter 22 is consumed by the AC load 50. In addition, when the full charge and surplus electric power exceed charge electric power, and the further surplus which cannot be charged with a storage battery generate | occur | produces, the surplus can also be made to flow backward to the system | strain 40. FIG. However, in this case, when the operating voltage of the voltage rise suppression function is reached by surplus power, the output of the generated power is suppressed by the voltage rise suppression function.

  The solar power generation system 1 can discharge the power stored in the storage battery 60 (derived from PV power or system power) and use it for consumption of the AC load 50. In this case, the discharge power is supplied to the AC / DC converter 22 while being controlled by the charger / discharger 23, converted into AC power here, and then supplied to the AC load 50. At this time, the charger / discharger 23 and the AC / DC converter 22 are controlled by the received power detection circuit 29 so that the discharge power does not flow backward at the power receiving end. At the time of discharge control, PV power supplied directly from the solar cell 10 without passing through the storage battery 60 and discharge power from the storage battery 60 can be used together and supplied to the AC load 50.

Next, a specific operation example of the solar power generation system 1 will be described.
This operation example shows an operation example of a nighttime power storage type solar power generation system giving priority to economy, and is divided into a nighttime power time zone and a daytime power time zone. Is divided depending on whether or not the PV power exceeds the power required for the AC load 50 (hereinafter simply referred to as AC load 50). Note that this operation example is merely an example.
(1) Nighttime power time zone Charges the storage battery 60 with nighttime power from the system 40.
Further, all the AC load 50 is covered with electric power from the system 40 and the storage battery 60 is not discharged. In addition, SOC (State Of Charge: SOC) at the end of the night charge is, for example, 90 so that the surplus power of the PV power of the solar battery 10 can be charged in the storage battery 60 to cope with the charging operation when the system voltage rises in the daytime. %.

(2) When the PV power exceeds the AC load 50 during the daytime power hours The surplus power after the PV power is supplied to the AC load 50 is caused to reversely flow (sell power) in the system. This state is shown in FIG. In FIG. 3A, a thick line indicates that power is flowing in the direction of the attached arrow (the same applies to FIG. 3B). When the system voltage V _s increases due to the reverse flow of surplus power and reaches a threshold voltage V _t (eg, 107 V), the operation is switched to the surplus power charging operation. Even during the surplus power charging operation, the PV power is supplied to the AC load 50 through the AC / DC converter 22. This state is shown in FIG.
After switching to the charging operation, the charging operation is continued for a predetermined time (eg, 30 minutes). When the PV power decreases while the charging operation continues and the AC load 50 becomes higher, the charging control is switched to the discharging control, and the electric power stored in the storage battery 60 is discharged and supplied to the AC load 50. . At this time, when the AC load 50 is larger than the power supplied by the PV power and the discharge power of the storage battery 60, the insufficient power is supplied from the system 40. In addition, after switching to a charge driving | operation, it does not switch to discharge control until predetermined time passes, but all the insufficient electric power by the supply by PV electric power may be supplied from the system | strain 40. FIG.
After the predetermined time has elapsed, the charging operation is stopped and the operation returns to the reverse power flow operation (surplus power). Thereafter, when the system voltage V _s to the threshold voltage V _t rises to charge operation again. If the storage battery 60 reaches full charge before the voltage rise is settled, the voltage rise cannot be suppressed by charge control. Is possible.

(3) When PV power is less than 50 AC load during daytime power hours (morning, evening, etc.)
When the PV power is equal to or less than the AC load 50, the power is supplied to the AC load 50 by discharging the system power stored in the night power hours in addition to the PV power. At this time, the charger / discharger 23 and the AC / DC converter 22 are controlled by the received power detection circuit 29 so that the discharge power does not flow backward at the power receiving end. Discharge low-cost nighttime stored power in the daytime to suppress the purchase of expensive daytime power from the grid 40 and improve economy, and also cuts the peak of received power and shifts the peak demand for power due to nighttime power Promote.

  As described above, the addition of the voltage increase suppression function utilizing the charging operation to the storage battery 60 according to the first embodiment suppresses the output suppression of the generated power by the conventional voltage increase suppression function, and the system voltage required for the storage battery 60 Efficient operation of solar power generation utilizing the charging function for stabilization becomes possible.

[Second Embodiment]
Next, the photovoltaic power generation system 2 according to the second embodiment will be described with reference to FIG.
When the system voltage V _s becomes _{equal to} or higher than the threshold voltage V _t , the first embodiment temporarily stops the power transmitted to the system 40, whereas the photovoltaic power generation system 2 corresponds to the system voltage V _s. Then, control is performed to distribute the charging power to the storage battery 60 and the power (power sale) to flow backward to the grid 40. Since the reverse power flow (power sale) can be continued as much as possible even when the system voltage rises, it is possible to improve the economy relative to the first embodiment. Note that the storage battery 60 of the photovoltaic power generation system 2 of the second embodiment does not charge up to 100% as in the first embodiment, and always leaves some room for charging.

The solar power generation system 2 includes a control unit 35 that performs the above control.
In the control unit 35, a direct current voltmeter (DCPT) 37 acquires a voltage (DC bus voltage V _b , measurement value) on the DC bus 24. Here, when the system voltage rises and the voltage rise suppression function is activated, power transmission to the system 40 side by the AC / DC converter 22 is suppressed, and when the PV power is larger than the power transmitted to the system 40, the DC bus voltage _Vb increases. In this way, the fluctuation of the system voltage can be known by detecting the fluctuation of the DC bus voltage _Vb .
Control unit 35 holds a surplus power detection voltage V _d. The surplus power detection voltage _Vd is a threshold voltage at which it is determined that surplus power is generated in the PV power when the voltage is higher than this.
The surplus power detection voltage _Vd is compared with the DC bus voltage _Vb . Specifically, the calculation of DC bus voltage V _b −surplus power detection voltage V _d (= V _b−d ) is performed. For example, when the surplus power detection voltage V _d is 302 V and the DC bus voltage V _b is 300 V, V _b−d = −2 V is output as the calculation result. Further, the surplus power detection voltage _{V d} is 302V, when the DC bus voltage _{V b} is _{304V, V b-d} = 2V is outputted as a result of calculation.

Computation result (V _b-d), after being converted into a current value corresponding to the calculation result is sent as the charge current command I _n to the rechargeable discharge device 23. However, the controller 35 limits the charging current command I _n are provided. The lower limit of this limit is 0A (zero amperes). _{Therefore, V b-d} is equal a negative number, the charging current command _{I n} is output as 0A. On the other hand, the upper limit of the charge current command I _n, the maximum charging current I _m corresponding is set to the charge state of the device capacity and the storage battery 60 of the charging and discharging unit 23.

More are as, the control unit 35, DC bus voltage V _b to output the charge current command I _n equal to or lower than the surplus power detection voltage V _d as 0A. At this time, it is determined that there is no surplus power, and the storage battery 60 is not charged. For example, if the PV power is 10 kW and the power consumption of the AC load 50 is 0 kW (load stop state), the power is all reversely flowed (sold) into the grid 40. In addition, it is the same as that of 1st Embodiment that the reverse power flow has arisen as a premise.
On the other hand, the control unit 35, when the DC bus voltage _{V b} is greater than or equal to the surplus power detection voltage _{V d,} and outputs a charge current command _{I n} as nA. At this time, it is determined that the surplus power corresponding to the charge current command I _n are generated, the electric power corresponding to it is charged to the battery 60. As much as the storage battery 60 is charged, the electric power flowing backward to the grid 40 is reduced. For example, _assuming that the PV power is 10 kW and the power consumption of the AC load 50 is 0 kW (load stop state), the reverse power (sold power) power to the system 40 is 5 kW and the charging power is 5 kW according to the charging current command In. The power sale power to the system 40 can be distributed to 3 kW, the charging power can be distributed to 7 kW, the power sale power to the system 40 can be distributed to 0 kW, and the charging power can be distributed to 10 kW. In other words, it is possible that the charge current command I _n the range of the maximum charging current I _{m (A)} from 0A, allocate PV power to the backward flow power and charging power.

Next, a specific operation example of the solar power generation system 2 will be described.
This operational example, the value of the system voltage V _s, is divided into three. Note that this operation example is merely an example.
(1) When the system voltage is the standard voltage (PV power: 10kW, AC load 50; 0kW → reverse power flow to the system; 10kW)
If the system voltage _{V s} is the standard voltage _{(V b-d} is a negative number), the transmission of all the PV power to the grid 40 side. For example, assuming that the PV power is 10 kW, the reverse power (sold power) power to the grid 40 is 10 kW.
At this time, since the DC bus voltage by AC / DC converter 21 is always controlled to a standard voltage, DC bus voltage falls below the surplus power detection voltage _{V d.} Therefore, the charging current command I _n the PV power output from the control unit 35 becomes excessive is always 0A.

(2) When the voltage rise suppression function is activated by the rise of the system voltage and the reverse power flow is restricted (PV power: 10kW, AC load 50; 0kW → Reverse power flow to the system: 5kW)
When only 5 kW of PV power 10 kW can be transmitted to the system 40, 5 kW is the surplus. In this case, since the power flowing into the DC bus 24 via the DC / DC converter 21 exceeds the power flowing out from the DC bus 24 via the AC / DC converter 22, the DC bus voltage rises.
When the DC bus voltage exceeds the surplus power detection voltage _{V d,} the control unit 35 operates to output a positive value the charging current command _{I n,} DC bus voltage _{V b} is surplus power detection voltage _V d _{(V b- d} = 0V).
As described above, the surplus PV power is charged in the storage battery 60.

(3) When the system voltage further rises and the reverse power flow cannot be reversed due to the voltage rise suppression function (PV power: 10kW, AC load 50; 0kW → Reverse power flow to the system; 0kW)
If no power can be transmitted to the grid 40 side, 10 kW is the surplus. In this case, the storage battery 60 is charged with the surplus 10 kW of PV power by the same operation as in (2).

  As described above, according to the second embodiment, in addition to the same effects as those of the first embodiment, reverse power flow, that is, the power storage unit can be charged while selling power. However, it can be used efficiently.

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.
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 AC / DC converter 22 DC / DC converter 23 Charger / discharger 24 DC bus 28 Current detector 29 Received power detection circuit 30 Control part 31 Voltage detection vessel 35 control unit 37 DC voltmeter 40 system 50 AC load 60 battery _{I m} maximum charging current _{I n} charge current command _{V b} bus voltage _{V d} surplus power detection voltage _{V s} system voltage _{V t} threshold voltage

Claims (3)

A power generation unit that is connected to an external system and generates power by receiving sunlight ,
A power storage unit that stores power generated by the power generation unit and power from the grid, and is connected to the power generation unit in a DC connection;
A DC / DC converter connected to the power generation unit, and a power conditioner including an AC / DC converter and a charger / discharger connected in series to each other in series via a DC bus with respect to the DC / DC converter,
A load supplied with AC power via the system or the AC / DC converter;
A control unit that controls reverse flow of the generated power to the system by giving an instruction to the AC / DC converter, and controls charge / discharge to the power storage unit by giving an instruction to the charger / discharger; With
The controller is
When the generated power is flowing backward toward the grid,
Based on the comparison of the predetermined threshold voltage and the system voltage, the reverse flow of the generated power is stopped, or, together with reducing the generated power for reverse power flow, to charge the generated electric power to said power storage unit ,And,
The controller is
When the threshold voltage is exceeded, the reverse power flow of the surplus power that is the residual that has supplied the generated power to the load is stopped, and
Let the power storage unit charge all of the surplus power of the generated power,
After continuing the charging for a predetermined time, the first form of stopping the charging to the power storage unit by surplus power of the generated power and restarting the reverse power flow ,
Or
Corresponding to the difference between the bus voltage, which is a voltage on the DC bus, and the surplus power detection voltage, which is a threshold voltage at which surplus power is determined to be generated in the generated power, surplus generated power to be charged in the power storage unit A second mode for distributing the power and the surplus power of the generated power to be reverse-flowed ,
A power storage type power generation system. In the first form,
Power generated by the power generating unit is greater than the power required to the load connected to the power generation system,
Supplying the generated power to the load via the DC / DC converter and the AC / DC converter, and surplus is directed to the reverse flow;
The power storage type power generation system according to claim 1 . In the second embodiment,
The system voltage is detected via a DC voltage in a DC bus between the power generation unit and the system.
The power storage type power generation system according to claim 1 .

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