Connection unit, battery unit, power generation system, and method for operating the power generation system

Abstract

To provide a connection unit, a battery unit, a power generation system, and a method of operating the power generation system, which can prevent waste of generated power and flexibly cope with changes in facilities after the start of operation.SOLUTION: A power generation system includes a battery unit 30 that stores surplus power not transmitted by a power conditioner 20 out of the power generated by a power generation unit 10, and a connection unit 40 that connects the power generation unit 10, the power conditioner 20, and the battery unit 30 to each other. A controller 33 of the battery unit 30 controls a bidirectional DC / DC converter 32 to charge a storage battery 31 with surplus power out of the generated power output from the MPPT control DC / DC converter 41 of the connection unit 40, or discharges electric power stored in the storage battery 31 to the power conditioner 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a connection unit, a battery unit, a power generation system, and a method for operating a power generation system. [Background technology]

[0002] As an example of a power generation system that transmits power generated from renewable energy to a grid, there is a photovoltaic power generation system equipped with a power conditioner for efficiently transmitting power generated by sunlight to the grid. The power conditioner of a photovoltaic power generation system usually has a maximum power point tracking (MPPT) control function, and performs control so that the generated power is drawn at the maximum point.

[0003] Some of such power generation systems are equipped with a storage battery (for example, Patent Documents 1 and 2). The power generation systems described in Patent Documents 1 and 2 charge the generated power to a storage battery, and transmit the power stored in the storage battery to a grid via a grid-connected power conditioner. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-177571 A [Patent Document 2] JP 2017-192191 A Summary of the Invention [Problem to be solved by the invention]

[0005] The power output of solar power generation, a type of renewable energy, is dependent on the weather. For this reason, solar power generation system operators who have signed power purchase contracts may install power generation equipment with a generating capacity greater than the contracted amount so that they can sell electricity close to the contracted amount even on cloudy days.

[0006] However, many of the existing solar power generation systems currently in operation do not have storage batteries, and electricity generated on sunny days in excess of the contracted amount becomes surplus electricity and is not used effectively.

[0007] However, adding a storage battery to a solar power generation system after it has started operating requires changes to the equipment specifications of the solar power generation system, an application for changes, and major modifications, making it difficult to implement.

[0008] Furthermore, in a power generation system equipped with a storage battery, when a battery unit is replaced due to a change in equipment specifications or deterioration in the performance of the storage battery, there is a problem that the entire equipment must be replaced or significantly modified.

[0009] The present invention has been made in consideration of the above-mentioned situation, and aims to provide a connection unit, a battery unit, a power generation system, and an operating method for a power generation system that prevent waste of generated power and can flexibly adapt to equipment after operation has begun. [Means for solving the problem]

[0010] In order to achieve the above object, a connection unit according to a first aspect of the present disclosure comprises: A connection unit that connects a power generation unit, a power conditioner that transmits power generated by the power generation unit to a grid, and a battery unit to each other, a first MPPT control DC (Direct Current) / DC converter that performs MPPT (Maximum Power Point Tracking) control of the power generated by the power generation unit; a main transmission line connecting the first MPPT control DC / DC converter and the power conditioner; a charge / discharge path connecting the main power transmission path and the battery unit; By controlling a bidirectional DC / DC converter inserted between the charge / discharge path and the storage battery of the battery unit, surplus power generated by the power generation unit that is not transmitted by the power conditioner is charged to the storage battery, or the power stored in the storage battery is discharged to the power conditioner.

[0011] A battery unit according to a second aspect of the present disclosure includes: A battery unit connected to a power generation unit via a connection unit and connected to a power conditioner via the connection unit, the power conditioner transmitting power generated by the power generation unit to a power grid, the connection unit has a first MPPT control DC / DC converter between the power generation unit and the battery unit, the first MPPT control DC / DC converter performing MPPT control of the electric power generated by the power generation unit, The battery unit includes: A storage battery that stores surplus power that is not transmitted by the power conditioner out of the power generated by the power generation unit; a bidirectional DC / DC converter inserted between the first MPPT control DC / DC converter and the storage battery; and a controller that controls the bidirectional DC / DC converter to charge the surplus power to the storage battery or discharge the power stored in the storage battery to the power conditioner.

[0012] A power generation system according to a third aspect of the present disclosure includes: A power generation system having a power generation unit and a power conditioner that transmits power generated by the power generation unit to a power grid, a battery unit including a storage battery that stores surplus power generated by the power generation unit and not transmitted by the power conditioner, a bidirectional DC / DC converter that switches between charging and discharging the storage battery, and a controller that controls the storage battery and the bidirectional DC / DC converter; a connection unit that connects the power generation unit, the power conditioner, and the battery unit to each other and has a first MPPT control DC / DC converter that performs MPPT control of the power generated by the power generation unit; The controller of the battery unit controls the bidirectional DC / DC converter to charge the surplus power to the storage battery or to discharge the power stored in the storage battery to the power conditioner.

[0013] A method for operating a power generation system according to a fourth aspect of the present disclosure includes: A method for operating a power generation system having a power generation unit and a power conditioner that transmits power generated by the power generation unit to a power grid, comprising: The power generation system includes: A battery unit including a storage battery that stores surplus power generated by the power generation unit and not transmitted by the power conditioner, and a bidirectional DC / DC converter that switches between charging and discharging the storage battery; a connection unit that connects the power generation unit, the power conditioner, and the battery unit to each other and has a first MPPT control DC / DC converter that performs MPPT control of the power generated by the power generation unit; a charging step of setting a high-voltage DC side voltage of the bidirectional DC / DC converter lower than a high-voltage DC side voltage of the first MPPT control DC / DC converter and charging the storage battery with the surplus power; a discharging step of discharging the power stored in the storage battery by setting a high-voltage DC side voltage of the bidirectional DC / DC converter higher than a high-voltage DC side voltage of the first MPPT control DC / DC converter; The present invention is characterized by having the following. Effect of the Invention

[0014] According to the present invention, charging and discharging are performed using the storage battery of the battery unit connected via the connection unit, which prevents waste of generated electricity and makes it possible to flexibly respond to equipment after it has started operating. [Brief description of the drawings]

[0015] [Figure 1] 1 is a block diagram showing a hardware configuration of a power generation system according to an embodiment; [Diagram 2] 11 is a graph showing a difference in output voltage depending on whether or not a voltage fluctuation absorption unit is present. [Diagram 3] 4 is a flowchart showing a process of a controller of the battery unit. [Figure 4] 4 is a flowchart showing the operation of the power generation system during the day. [Diagram 5] 4 is a flowchart showing the operation of the power generation system at night. [Figure 6] 4 is a graph showing changes over time in generated power and surplus power of the power generation system according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] (Embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are given the same reference numerals. A power generation system 1 according to this embodiment is a power generation system that stores power generated by a power generation unit 10 and transmits the power to a grid. In this embodiment, a case will be described in which the power generation unit 10 generates solar power using a solar panel.

[0017] Fig. 1 is a block diagram showing a hardware configuration of a power generation system 1 according to the present embodiment. As shown in Fig. 1, the power generation system 1 includes a power generation unit 10, a power conditioner (referred to as PCS in the figure) 20 that transmits power generated by the power generation unit 10 to a grid, a battery unit 30 that stores surplus power that is not transmitted by the power conditioner 20 among the power generated by the power generation unit 10, and a connection unit 40 that connects the power generation unit 10, the power conditioner 20, and the battery unit 30 to each other.

[0018] The power generation unit 10 is a unit that generates power by converting solar energy into electric power using a solar panel. The power conditioner 20 has a well-known configuration including a maximum power point tracking (MPPT) controlled direct current (DC) / DC converter and a DC / alternating current (AC) inverter, and transmits electric power to the grid while being interconnected with the grid.

[0019] The power generation unit 10 and the power conditioner 20 may be existing equipment having a conventional configuration, or may be included in a power generation system after operation has commenced. In other words, the power generation unit 10 and the power conditioner 20 may be directly connected to each other by old wiring indicated by the dashed arrow in Fig. 1. When the power generation unit 10 and the power conditioner 20 are existing equipment, the power generation system 1 is realized as a power generation system with a storage battery by retrofitting the battery unit 30 and the connection unit 40 by changing the wiring.

[0020] The connection unit 40 includes an MPPT control DC / DC converter 41, a main transmission line 42 connecting the MPPT control DC / DC converter 41 and the power conditioner 20, a charge / discharge line 43 connecting the main transmission line 42 and the battery unit 30, and a voltage fluctuation absorption unit 44 inserted into the main transmission line 42.

[0021] The MPPT control DC / DC converter 41 (first MPPT control DC / DC converter) performs MPPT control on the output of the power generation unit 10. The MPPT control DC / DC converter 41 has the same function as the MPPT control DC / DC converter (second MPPT control DC / DC converter) included in the power conditioner 20.

[0022] The voltage fluctuation absorbing unit 44 is a unit that absorbs voltage fluctuations that occur due to interference between the MPPT control DC / DC converter 41 and the MPPT control DC / DC converter of the power conditioner 20, and is configured by a filter, for example. By absorbing the voltage fluctuations due to this interference, the voltage fluctuation absorbing unit 44 can suppress adverse effects on the charging and discharging operations of the bidirectional DC / DC converter 32 included in the battery unit 30.

[0023] 2 is a graph showing the difference in output voltage with and without the voltage fluctuation absorption unit 44. It can be seen that the minute voltage fluctuations seen in the output voltage without the voltage fluctuation absorption unit 44 on the left are suppressed in the output voltage with the voltage fluctuation absorption unit 44 on the right.

[0024] The connection unit 40 further includes an input connection terminal for connecting the power generation unit 10 to the MPPT control DC / DC converter 41, and an output connection terminal for connecting the main power transmission line 42 to the power conditioner 20. The number of the output connection terminals corresponds to the number of circuits of the MPPT control DC / DC converter of the power conditioner 20, and the output connection terminals are arranged on a terminal block. The terminal block may be equipped with a reverse current prevention diode connected to each output connection terminal.

[0025] The connection unit 40 has the above-mentioned configuration, and transmits the power generated by the power generation unit 10 to the power conditioner 20 via the MPPT control DC / DC converter 41 and the voltage fluctuation absorbing unit 44.

[0026] The battery unit 30 comprises a storage battery 31, a bidirectional DC / DC converter 32 connected between the storage battery 31 and a charge / discharge path 43 of the connection unit 40, and a controller 33 that controls the storage battery 31 and the bidirectional DC / DC converter 32.

[0027] Here, the power conditioner 20, the battery unit 30, and the connection unit 40 can be operated independently of each other, and there is no need to transmit and receive control signals. Therefore, even when a battery unit 30 is additionally installed to the existing power generation unit 10 and power conditioner 20, or when the power conditioner 20 is replaced or the control contents related to the power conditioner 20 are changed, there is no need to transmit and receive signals between the power conditioner 20 and the battery unit 30 and the connection unit 40.

[0028] The storage battery 31 of the battery unit 30 is any battery capable of monitoring the amount of stored electricity, for example, a redox flow battery (hereinafter, referred to as RFB). RFBs are suitable for this power generation system 1 because they are easy to control, have excellent environmental resistance, and have a long life. In this embodiment, a case where the storage battery 31 is an RFB will be described.

[0029] 1, the storage battery 31 includes an RFB stack 311, a positive electrode electrolyte tank unit 312 and a pump 313, and a negative electrode electrolyte tank unit 314 and a pump 315, in which electrolyte piping is connected to the RFB stack 311. The electrolyte tank units 312 and 314 can increase or decrease the number of electrolyte tanks even when the power generation system 1 is newly installed or after it is in operation, and thus the power storage capacity can be easily increased or decreased.

[0030] Furthermore, the storage battery 31 includes a monitor cell 316 that measures the open circuit voltage (OCV) of the electrolyte. By measuring the OCV with the monitor cell 316, the amount of charge stored in the entire storage battery 31 can be obtained.

[0031] The bidirectional DC / DC converter 32 is a DC / DC converter that controls charging and discharging of the storage battery 31, and switches between charging and discharging operations by switching the voltage on the high-voltage direct current (hereinafter referred to as HVDC) side.

[0032] The controller 33 controls the storage battery 31 and the bidirectional DC / DC converter 32. The controller 33 has a function of supervising control of the entire battery unit 30, including issuing charge / discharge control commands and electrolyte flow rate control commands to the storage battery 31 and the bidirectional DC / DC converter 32.

[0033] The charge / discharge control of the battery unit 30 by the controller 33 will be described with reference to the flowchart of Fig. 3. Fig. 3 is a flowchart showing the process of the controller 33 of the battery unit 30.

[0034] When the power generation unit 10 generates power and the output voltage of the power generation unit 10 reaches the tracking voltage range of the MPPT control DC / DC converter 41, the HVDC side voltage V D maintains a preset voltage V1.

[0035] When the controller 33 starts the charge / discharge control, it first monitors the power generated by the power generating unit 10 and calculates the power generated by the power generating unit 10 P A is the rated power P of the power conditioner (PCS) 20 B It is determined whether or not it is equal to or less (step S101).

[0036] Power generation P of power generating unit 10 A is the rated power P of the power conditioner (PCS) 20 B If it exceeds the HVDC side voltage V E The HVDC side voltage V of the MPPT controlled DC / DC converter 41 is DThe power generation unit 10 sets the power supply voltage V2 to a lower value (step S102) and sets the battery unit 30 to a charging mode (step S103). A Of these, the rated power P of the power conditioner (PCS) 20 B Surplus power (P A -P B ) is charged into the storage battery 31 (charging step).

[0037] On the other hand, the generated power P of the generating unit 10 A is the rated power P of the power conditioner (PCS) 20 B If it is equal to or lower than the HVDC side voltage V E The HVDC side voltage V of the MPPT controlled DC / DC converter 41 is D (step S105), and the battery unit 30 is set to the charging mode (step S106). A is the rated power P of the power conditioner 20 B Since the power generation is P A All of this is transmitted to the grid by the power conditioner 20. The battery unit 30 is in the charging mode, but is not being charged.

[0038] Power generation P of power generating unit 10 A is the rated power P of the power conditioner (PCS) 20 B If it is nighttime (step S104: Yes), the controller 33 adjusts the HVDC side voltage V E is set to the value of V2 (step S107). In this case, since it is nighttime, the generated power P A is 0 kW, and the HVDC side voltage V D is 0V.

[0039] Next, the controller 33 monitors the OCV measured by the monitor cell 316, and if the OCV is equal to or lower than a predetermined threshold (step S108: Yes), the amount of charge stored in the storage battery 31 is insufficient, and so charging and discharging of the storage battery 31 is stopped (step S109). If the OCV is higher than the predetermined threshold (step S108: No), the controller 33 sets the battery unit 30 to a discharge mode (step S110), and the power stored in the storage battery 31 is discharged to the connection unit 40 via the bidirectional DC / DC converter 32 (discharge step). The discharged power is transmitted to the grid by the power conditioner 20.

[0040] Thereafter, if the manager of the power generation system 1 or the like performs an operation to end the charge / discharge control (step S111: Yes), the controller 33 ends the process. On the other hand, if the charge / discharge control is not to be ended (step S111: No), the process returns to step S101 and the monitoring of the generated power continues.

[0041] The operation of the power generation system 1 configured as above will be described with reference to the flowcharts of Figures 4 and 5. Figure 4 is a flowchart showing the operation of the power generation system 1 during the day, and Figure 5 is a flowchart showing the operation of the power generation system 1 at night.

[0042] When the solar panel of the power generation unit 10 receives sunlight in the morning, it automatically starts generating power (step S201). When the output voltage of the solar panel reaches the tracking voltage range of the MPPT control DC / DC converter 41, the HVDC side voltage V D maintains the preset voltage V1 (step S202).

[0043] The controller 33 controls the generated power P A The generated power P A is the rated output P of the power conditioner (PCS) 20 B It is determined whether the generated power P A is the rated output P of the power conditioner 20B If it is equal to or smaller than this (step S203: Yes), the power generation power P A is all transmitted to the grid via the power conditioner 20 (step S204).

[0044] At this time, the controller 33 sets the battery unit 30 to a charging mode, but the HVDC side voltage V E The HVDC side voltage V of the MPPT controlled DC / DC converter 41 is D Since V1 is set to the same voltage as V E ≧V D Therefore, charging is not performed (step S205).

[0045] Power generation P of power generating unit 10 A becomes larger, and the rated power P B If it exceeds (step S203: No), the generated power P A Of which, rated power P B is transmitted to the grid by the power conditioner 20 (step S206), and (P A -P B ) is surplus electricity.

[0046] At this time, the controller 33 continues the charging mode as the operation mode of the battery unit 30, and the HVDC side voltage V E The HVDC side voltage V of the MPPT controlled DC / DC converter 41 is D Set the lower voltage V2. This allows V E <V D The surplus power is charged into the storage battery 31 via the bidirectional DC / DC converter 32 (step S207).

[0047] Next, at night, the power generation of the power generation unit 10 is stopped (step S301) as shown in FIG. A At this time, the MPPT control DC / DC converter 41 is below the tracking voltage range, so it stops operating and the HVDC side voltage V Dbecomes 0V (step S302).

[0048] If nighttime power transmission is not performed because a setting is made not to perform nighttime power transmission, or because a time period for performing nighttime power transmission is set and the time is outside the time period (step S303: No), there is no power generation in the power generation unit 10 and no discharge from the storage battery 31, so power transmission is stopped (step S304). E By setting V to V1 and putting the battery unit 30 into charging mode, it is possible to prepare for the resumption of power generation. E ≧V D Therefore, charging is not performed (step S305).

[0049] If nighttime power transmission is set to be performed or if a time period for nighttime power transmission is set and the time falls within the time period, the OCV is measured by the monitor cell 316. th If it is greater than the HVDC side voltage V E is set to V2, and the battery unit 30 is set to the discharge mode (step S307).

[0050] At this time, V E >V D As a result, the power discharged from the bidirectional DC / DC converter 32 passes through the connection unit 40 and is transmitted to the grid by the power conditioner 20 (step S308).

[0051] When the discharge of the storage battery 31 continues and the OCV of the monitor cell becomes equal to or lower than a predetermined threshold (step S306: No), the HVDC side voltage V E With V set to V2, charging and discharging of the battery unit 30 is stopped (step S309). As a result, power transmission from the power conditioner 20 to the grid is stopped (step S310).

[0052] In this way, during the night, the OCV of the monitor cell 316 of the electrolyte of the RFB, which is the storage battery 31, is measured to monitor the amount of stored electricity, while easily and reliably controlling the charging and discharging of the entire battery unit 30.

[0053] In the power generation system 1 of the present embodiment, the charge / discharge path 43 of the connection unit 40 and the battery unit 30 can be attached or detached as desired. That is, the power generation system 1 can be switched between an operating state in which the charge / discharge path 43 and the battery unit 30 are connected to enable charging and discharging, and an operating state in which the charge / discharge path 43 and the battery unit 30 are disconnected to stop charging and discharging.

[0054] Since the battery unit 30 has a detachable configuration, it is possible to continue operation in which the electricity generated by the power generation unit 10 is directly transmitted to the grid via the connection unit 40 and the power conditioner 20, while temporarily disconnecting the battery unit 30 from the power generation system 1 to perform maintenance and inspection or to add or remove electrolyte tanks.

[0055] In addition, when connecting a new connection unit 40 and battery unit 30 to an existing power generation unit 10 and power conditioner 20, first connect the wiring from the existing power generation unit 10 to the input connection terminal of the connection unit 40, and then connect the output connection terminal of the connection unit 40 to the input end of the existing power conditioner 20.

[0056] In this state, by keeping only the main transmission line 42 of the connection unit 40 independently active, after daytime solar power generation begins, the existing power generation unit 10 and power conditioner 20 can be operated as usual. Next, the connection unit 40 and the battery unit 30 are connected, and after the trial operation of the battery unit 30 is completed, the existing power generation system can start operating as the power generation system 1 with a battery.

[0057] As described above, the power generation system 1 according to the present embodiment includes the battery unit 30 that stores surplus power that is not transmitted by the power conditioner 20 among the power generated by the power generation unit 10, and the connection unit 40 that connects the power generation unit 10, the power conditioner 20, and the battery unit 30 to each other. The battery unit 30 includes a storage battery 31, a bidirectional DC / DC converter 32 that switches between charging and discharging the storage battery 31, and a controller 33 that controls the storage battery 31 and the bidirectional DC / DC converter 32. The connection unit 40 includes an MPPT control DC / DC converter 41 that performs MPPT control of the power generated by the power generation unit 10. The controller 33 of the battery unit 30 controls the bidirectional DC / DC converter 32 to charge the battery unit 30 with surplus power among the power output by the MPPT control DC / DC converter 41, or to discharge the power stored in the battery unit 30 to the power conditioner 20. This allows a storage function to be added to the existing power generating unit 10 with a simple configuration, preventing waste of generated power and enabling flexible response to facilities after operation has begun. In other words, the power generating system 1 with a storage function can be easily constructed by simply changing the wiring, without modifying the equipment specifications of the existing power generating unit 10 and power conditioner 20.

[0058] In the power generation system 1 according to the present embodiment, the battery unit 30 includes a redox flow battery, and the OCV of the redox flow battery is monitored, and discharging is stopped when the OCV is equal to or lower than a predetermined threshold. This makes it possible to easily and reliably grasp the amount of stored electricity in the entire storage battery 31 in real time by measuring the OCV of the redox flow electrolyte of the storage battery 31, and makes it possible to appropriately control charging and discharging the battery unit 30 by using the measured value.

[0059] Furthermore, in the power generation system 1 according to this embodiment, the power conditioner 20 includes a second MPPT controlled DC / DC converter, and a voltage fluctuation absorbing unit 44 is inserted in the main power transmission line of the connection unit 40. This makes it possible to absorb voltage fluctuations caused by interference between the MPPT controlled DC / DC converter 41 (first MPPT controlled DC / DC converter) and the MPPT controlled DC / DC converter (second MPPT controlled DC / DC converter) of the power conditioner 20, and to suppress adverse effects on the charging and discharging operations of the bidirectional DC / DC converter 32 of the battery unit 30.

[0060] Furthermore, the power generation unit 10 according to this embodiment is a solar power generation unit, and discharging from the battery unit 30 via the main power transmission line 42 of the connection unit 40 is performed at night. As a result, the power generation unit 10 generates a large amount of power during the daytime when the weather is fine, and when the generated power exceeds the rated power of the power conditioner 20, the upper limit amount is transmitted to the grid, while the surplus generated power is charged in the battery unit 30 via the connection unit 40. Then, when the power generation unit 10 is not generating power, such as at night, the stored power is transmitted to the power conditioner 20, so that waste of generated power can be reduced.

[0061] (Example) Fig. 6 shows actual measurement data of generated power and surplus power for an example of the power generation system 1 having the configuration shown in the embodiment. As shown in Fig. 6, the generated power P A is drawn at the maximum power point by the MPPT controlled DC / DC converter 41 of the connection unit 40.

[0062] Power generation P A Of these, the rated power P of the power conditioner 20 B The part exceeding this is the surplus power (P A -P B) and is charged into the storage battery 31 of the battery unit 30. Then, during a predetermined time period at night after power generation stops due to sunset, the power stored in the storage battery 31 can be discharged to the power conditioner 20 via the bidirectional DC / DC converter 32 and the voltage fluctuation absorption unit 44.

[0063] Although the embodiment of the present disclosure has been described above, this embodiment is merely an example, and the scope of application of the present disclosure is not limited thereto. In other words, various modifications and applications are possible without departing from the gist of the present disclosure. [Explanation of symbols]

[0064] 1 power generation system, 10 power generation unit, 20 power conditioner (PCS), 30 battery unit, 31 storage battery, 32 bidirectional DC / DC converter, 33 controller, 40 connection unit, 41 MPPT control DC / DC converter (first MPPT DC / DC converter), 42 main transmission line, 43 charging / discharging line, 44 voltage fluctuation absorption unit, 311 RFB stack, 312, 314 electrolyte tank section, 313, 315 pump, 316 monitor cell.

Claims

1. A connection unit that connects a power generation unit, a power conditioner that transmits power generated by the power generation unit to a grid, and a battery unit to each other, a first MPPT control DC (Direct Current) / DC converter that performs MPPT (Maximum Power Point Tracking) control of the power generated by the power generation unit; a main transmission line connecting the first MPPT control DC / DC converter and the power conditioner; a charge / discharge path connecting the main power transmission path and the battery unit; By controlling a bidirectional DC / DC converter inserted between the charge / discharge path and the storage battery of the battery unit, surplus power generated by the power generation unit that is not transmitted by the power conditioner is charged to the storage battery, or power stored in the storage battery is discharged to the power conditioner. Connection unit.

2. the battery unit includes a redox flow battery; When the amount of stored electricity in the redox flow battery is equal to or less than a predetermined threshold, discharging is stopped. The connection unit according to claim 1 .

3. when charging the storage battery of the battery unit with power generated by the power generation unit, a high-voltage DC side voltage of the bidirectional DC / DC converter inserted between the charge / discharge path and the storage battery of the battery unit is set lower than a high-voltage DC side voltage of the first MPPT control DC / DC converter, and when discharging the power stored in the storage battery to the power conditioner, the high-voltage DC side voltage of the bidirectional DC / DC converter is set higher than the high-voltage DC side voltage of the first MPPT control DC / DC converter. A connection unit according to claim 1 or 2.

4. The power conditioner includes a second MPPT controlled DC / DC converter, A voltage fluctuation absorption unit is inserted in the main transmission line. A connection unit according to any one of claims 1 to 3.

5. the power generating unit is a solar power generating unit; Discharge from the battery unit through the main power transmission line of the connection unit is performed at night. A connection unit according to any one of claims 1 to 4.

6. an input connection terminal for connecting to the existing power generating unit; Further comprising an output connection terminal for connecting to the existing power conditioner; A connection unit according to any one of claims 1 to 5.

7. The charging / discharging path and the battery unit are detachably connected. A connection unit according to any one of claims 1 to 6.

8. The connection unit according to claim 7 , which is switchable between an operating state in which the charge / discharge path and the battery unit are connected to enable charging and discharging, and an operating state in which the charge / discharge path and the battery unit are disconnected to stop charging and discharging.

9. A battery unit connected to a power generation unit via a connection unit and connected to a power conditioner via the connection unit, the power conditioner transmitting power generated by the power generation unit to a power grid, the connection unit has a first MPPT control DC / DC converter between the power generation unit and the battery unit, the first MPPT control DC / DC converter performing MPPT control of the electric power generated by the power generation unit, The battery unit includes: A storage battery that stores surplus power that is not transmitted by the power conditioner out of the power generated by the power generation unit; a bidirectional DC / DC converter inserted between the first MPPT control DC / DC converter and the storage battery; and a controller that controls the bidirectional DC / DC converter to charge the surplus power to the storage battery or discharge the power stored in the storage battery to the power conditioner. Battery unit.

10. A power generation system having a power generation unit and a power conditioner that transmits power generated by the power generation unit to a power grid, a battery unit including a storage battery that stores surplus power generated by the power generation unit and not transmitted by the power conditioner, a bidirectional DC / DC converter that switches between charging and discharging the storage battery, and a controller that controls the storage battery and the bidirectional DC / DC converter; a connection unit that connects the power generation unit, the power conditioner, and the battery unit to each other and has a first MPPT control DC / DC converter that performs MPPT control of the power generated by the power generation unit; The controller of the battery unit controls the bidirectional DC / DC converter to charge the surplus power to the storage battery or to discharge the power stored in the storage battery to the power conditioner. Power generation system.

11. A method for operating a power generation system having a power generation unit and a power conditioner that transmits power generated by the power generation unit to a power grid, comprising: The power generation system includes: A battery unit including a storage battery that stores surplus power generated by the power generation unit and not transmitted by the power conditioner, and a bidirectional DC / DC converter that switches between charging and discharging the storage battery; a connection unit that connects the power generation unit, the power conditioner, and the battery unit to each other and has a first MPPT control DC / DC converter that performs MPPT control of the power generated by the power generation unit; a charging step of setting a high-voltage DC side voltage of the bidirectional DC / DC converter lower than a high-voltage DC side voltage of the first MPPT control DC / DC converter and charging the storage battery with the surplus power; a discharging step of discharging the power stored in the storage battery by setting a high-voltage DC side voltage of the bidirectional DC / DC converter higher than a high-voltage DC side voltage of the first MPPT control DC / DC converter; A method for operating a power generation system having the above structure.

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