JP6599700B2 - Grid interconnection device - Google Patents

Description

  The present invention relates to a grid interconnection device.

  2. Description of the Related Art In recent years, a grid interconnection device that connects a power company system and a power generation facility such as a solar cell and supplies power to a load in a house linked to the grid has become widespread. In such a grid interconnection device, normally, power is supplied from a grid or power generation equipment to a load in the house, and surplus power generated by the power generation equipment is supplied to the grid to perform grid connection operation. At the time of occurrence of a power failure or instantaneous voltage drop (hereinafter referred to as “instantaneous voltage drop”), it is known to perform a self-sustaining operation that disconnects from the system and supplies power generated by the power generation equipment to the load (for example, Patent Document 1, 2).

Japanese Patent Laying-Open No. 2015-6044 JP2015-61429A

  By the way, when an instantaneous drop occurs in the system, if the lines are disconnected all at once, the balance of supply and demand of the entire system may be disturbed, and a power failure or the like may occur over a wide area. Therefore, in the grid connection regulations, there is a requirement for Fault Ride Through (FRT). In order to satisfy the FRT requirements, grid interconnection operation must be continued when a voltage sag occurs. When a voltage sag occurs, the grid interconnection device is immediately disconnected from the system and switched to independent operation. Can not. Therefore, if an instantaneous drop occurs when power is supplied from the system to the load, power cannot be supplied to the load.

  An object of the present invention is to provide a grid interconnection device that can quickly supply power to a load while complying with the grid interconnection regulations at the time of an instantaneous power failure or a power failure.

  A grid interconnection device according to the present invention is a grid interconnection device that connects a power generation device that generates DC power and a system that supplies AC power, and supplies the power of the power generation device and the grid to a load. A power converter that is connected to the system, the power generation device, and the load and converts the DC power of the power generation device into AC power; and detects a voltage drop in the system; Auxiliary power conversion unit that outputs AC power of a predetermined voltage based on, a switch that switches between the power conversion unit and the system between conduction and non-conduction, and supply of AC power from the system or the power conversion unit to the load Then, when the switch between the power conversion unit and the system is conducted by the switch, the system interconnection control for supplying AC power from the power conversion unit to the system is performed, and when the voltage drop of the system is detected, At a given time During this period, AC power is supplied from the auxiliary power converter to the grid, and the switch is made non-conductive between the power converter and the grid, and AC power is supplied from the power converter to the load. A grid interconnection control unit that switches to the independent operation control.

  According to this configuration, the grid connection operation is performed to connect the power conversion unit and the system with the system, and when the voltage of the system decreases, the power conversion unit and the system are not connected to each other. The power conversion unit is made to operate independently, and power is supplied from the power conversion unit to the system via the auxiliary power conversion unit for a predetermined time. In other words, even when a voltage sag occurs, power can be continuously supplied to the grid in the same way as grid-connected operation. Can be powered.

  Further, in the grid interconnection device, the power conversion unit charges the storage battery with DC power of the power generation device, and converts the DC power discharged from the storage battery into AC power at least in the self-sustained operation control. It is good also as supplying to. According to this configuration, even when an instantaneous drop occurs, the storage battery can be charged and the power discharged from the storage battery can be supplied to the load.

  In the grid interconnection device, the auxiliary power conversion unit is connected to the power conversion unit and the system, and converts the AC power converted by the power conversion unit into a predetermined voltage corresponding to the system. May be supplied to the system. According to this configuration, the power conversion unit can be operated independently when a sag occurs, and power is continuously supplied from the power conversion unit to the system via the auxiliary power conversion unit, similar to the grid interconnection operation. be able to.

  In the grid interconnection device, the auxiliary power conversion unit is connected to the power generation device and the system, and converts the DC power of the power generation device into AC power having a predetermined voltage according to the system. It is good also as supplying to a system | strain. According to this configuration, it is possible to allow the power conversion unit to operate independently and to continuously supply power to the system when a sag occurs.

  According to the configuration of the present invention, it is possible to quickly supply power to the load while complying with the grid connection regulations at the time of a power failure or a power failure.

FIG. 1 is a configuration diagram illustrating a configuration example of grid interconnection by the grid interconnection device according to the first embodiment. FIG. 2 is an operation flowchart of the grid interconnection device according to the first embodiment. FIG. 3 is a diagram illustrating a voltage change of the system. FIG. 4 is a configuration diagram illustrating a configuration example of grid interconnection by the grid interconnection device according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<First Embodiment>
FIG. 1 is a configuration diagram showing a configuration example of grid interconnection by the grid interconnection device according to the first embodiment of the present invention. As shown in FIG. 1, the grid interconnection device 1 is connected to the grid 2 through a distribution board (not shown) connected to the wiring L, and includes a solar cell 3, a storage battery 4, and an AC load 5. It is connected.

  The solar cell 3 is an example of a power generation device, includes a solar cell module in which a plurality of cells are connected in series or in parallel, and converts sunlight into DC power by a photovoltaic effect.

  The storage battery 4 is a secondary battery that can be repeatedly charged and discharged. For example, a lithium ion battery is used. The storage battery 4 charges or discharges DC power under the control of the power conditioner 11.

  The AC load 5 is an electrical device that operates by supplying AC power, such as an OA device such as a personal computer or a server installed in a home, a television, a refrigerator, or a lighting.

  The grid interconnection device 1 includes a power conditioner 11, a cutoff switch 12, a sub-converter 13, and a linkage control unit 14. The grid interconnection device 1 can supply power supplied from the system 2 to the AC load 5 or supply power from the solar battery 3 and the storage battery 4 to the AC load 5. Further, the grid interconnection device 1 can supply (reverse power flow) the power of the solar cell 3 to the grid 2. Hereinafter, each structure of the grid connection apparatus 1 is demonstrated concretely.

  The power conditioner 11 includes a DC / DC converter and a bidirectional inverter (both not shown). The power conditioner 11 charges the storage battery 4 by converting DC power generated by the solar battery 3 into a predetermined voltage according to the voltage of the storage battery 4 by a DC / DC converter. Further, the power conditioner 11 converts the DC power generated by the solar battery 3 and the DC power discharged from the storage battery 4 into AC power of a predetermined voltage or the AC power supplied from the system 2 by the bidirectional inverter. 4 is converted into DC power of a predetermined voltage corresponding to the voltage of 4.

  The power conditioner 11 switches on / off the cutoff switch 12 under the control of the interconnection control unit 14 and changes its operation mode. Specifically, the power conditioner 11 turns on the cutoff switch 12 from the interconnection control unit 14 to bring the power conditioner 11 and the system 2 into a conductive state, and the power conditioner 11 communicates between the system 2 and the power conditioner 11. It operates in the grid connection mode that can exchange power. In addition, when a predetermined control signal indicating that a voltage drop has occurred is supplied from the interconnection control unit 14, the power conditioner 11 outputs surplus power generated by the solar cell 3 to the sub-converter 13, and a cutoff switch 12 is turned off, the power conditioner 11 and the system 2 are made non-conductive, and the operation is performed in the self-sustaining operation mode. In the self-sustained operation mode, power from the solar battery 3 or the storage battery 4 is supplied to the AC load 5. The power conditioner 11 performs constant current control in the grid connection mode, and performs constant voltage control in the independent operation mode.

  The cutoff switch 12 is constituted by, for example, an AC relay circuit, and is turned on / off by the power conditioner 11.

  The sub-converter 13 detects a voltage drop and a voltage restoration of the system 2 based on the voltage in the system 2 and outputs the detection result to the interconnection control unit 14. Further, the sub-converter 13 converts the AC power supplied from the power conditioner 11 into AC power corresponding to the voltage of the grid 2 to the grid 2 according to a predetermined control signal supplied from the interconnection control unit 14. Output. Since the sub-converter 13 only needs to be able to output AC power at least for a predetermined time, a sub-converter having a smaller capacity than the power conditioner 11 can be used.

  The interconnection control unit 14 controls the power conditioner 11 and the sub-converter 13 based on the detection result of the sub-converter 13. Specifically, when the voltage reduction of the grid 2 is detected by the sub-converter 13, the interconnection control unit 14 includes the power conditioner 11 and the sub-converter until the voltage recovery is detected within a predetermined time from the voltage drop. A predetermined control signal is output to 13, and surplus power of the solar cell 3 is supplied from the power conditioner 11 to the sub-converter 13. The interconnection control unit 14 converts the surplus power into AC power corresponding to the voltage of the grid 2 and supplies it to the grid 2 in the sub-converter 13, and turns off the shut-off switch 12 in the power conditioner 11 to be independent. Switch to operation mode. Note that this predetermined time is the time defined in the grid connection rule as the time from when the voltage of the grid 2 drops until it is disconnected (in the grid connection rule of the March 2017 version in Japan, It is set in advance to include 1 second at the time of low and power failure. In the present embodiment, for example, about 5 to 10 seconds.

  The interconnection control unit 14 stops the output of a predetermined control signal to the power conditioner 11 and the sub-converter 13 when the sub-converter 13 detects the return of the voltage of the system 2 from the voltage drop of the system 2. In the power conditioner 11, the cutoff switch 12 is turned on to switch to the grid connection mode. In addition, when the voltage of system 2 does not return within a predetermined time, the interconnection control unit 14 stops the output from the power conditioner 11 to the sub-converter 13 after the predetermined time has elapsed, and continues the operation in the independent operation mode. To do.

  That is, when the voltage drop of the grid 2 occurs, the grid interconnection device 1 supplies the surplus power to the grid 2 by the sub-converter 13 for a predetermined time from the voltage drop and maintains the operation in the grid interconnection mode. However, the power conditioner 11 is operated in the self-sustaining operation mode while the power conditioner 11 and the system 2 are not connected. Then, when the voltage of the grid 2 is restored, the grid interconnection device 1 causes the power conditioner 11 to operate in the grid interconnection mode by bringing the power conditioner 11 and the grid 2 into a conductive state.

(Operation)
FIG. 2 is a diagram illustrating an operation flow of the grid interconnection device 1. For example, the operation of the grid interconnection device 1 will be described by taking as an example the case where the voltage of the grid 2 changes as shown in FIG. In the example of FIG. 3, the voltage of the grid 2 is a normal voltage in which no voltage drop occurs between the times t0 and t1, and the voltage is, for example, 30% of the normal time between the times t1 and t2. Decreases and the voltage returns from time t2.

  The grid interconnection device 1 operates in the grid interconnection mode by turning on the cutoff switch 12 by the power conditioner 11 from time t0 to time t1 in FIG. 3 (step S11). That is, AC power based on the power generation of the solar cell 3 or AC power based on the discharge of the storage battery 4 is supplied to the AC load 5 between times t0 and t1 in FIG. It is supplied or the storage battery 4 is charged.

  When the voltage of the grid 2 decreases at time t1 in FIG. 3, the grid interconnection device 1 detects the voltage drop of the grid 2 by the sub-converter 13 (step S12: Yes), and the grid controller 14 and the power conditioner 11 A predetermined control signal is output to the sub-converter 13. Thereby, the power conditioner 11 outputs the surplus power of the solar cell 3 to the sub-converter 13, and the sub-converter 13 converts the surplus power according to the voltage of the system 2 and supplies it to the system 2. Further, the power conditioner 11 turns off the cutoff switch 12 and shifts to the self-sustained operation mode (step S13). Thereby, the power conditioner 11 can supply the electric power from the solar cell 3 to the AC load 5 or the storage battery 4, or can supply the electric power from the storage battery 4 to the AC load 5.

  At time t <b> 2 in FIG. 3, the grid interconnection device 1 detects the voltage recovery of the grid 2 by the sub-converter 13. When the voltage recovery of the grid 2 is within a predetermined time from the voltage drop (step S14: No, S15: Yes), the interconnection control unit 14 outputs a predetermined control signal to the power conditioner 11 and the sub-converter 13. Stop output. Thus, the power conditioner 11 turns on the cutoff switch 12 and operates in the grid connection mode (step S16). At this time, the power conditioner 11 outputs AC power to the grid 2 so that it becomes 80% or more of the power before the voltage drop within a certain time. Specifically, for example, AC power may be generated in the sub-converter 13 so as to be 80% or more of the power before the voltage drop, and the AC power may be output from the power conditioner 11 within a certain time.

  In the grid interconnection device 1, if the voltage recovery of the grid 2 is not detected by the sub-converter 13 within a predetermined time after the voltage drop of the grid 2, the grid control unit 14 causes the grid 2 to be out of power. Judgment is made, the output of AC power from the power conditioner 11 to the sub-converter 13 is stopped, and the operation in the self-sustaining operation mode is continued (step S14: Yes, S17).

  In the first embodiment described above, the grid interconnection device 1 monitors the voltage change of the grid 2 by the sub-converter 13, and when the voltage of the grid 2 decreases, until the voltage recovers within a predetermined time from the voltage drop, The grid connection is continued by the sub-converter 13 and the power conditioner 11 is disconnected between the grid 2 and the power conditioner 11 to operate the power conditioner 11 in the self-sustaining operation mode. Therefore, even if a voltage sag occurs, the power conditioner 11 can be operated in the self-sustaining operation mode and power can be supplied to the load while observing the FRT requirement defined in the grid connection. In addition, when the voltage of the grid 2 is restored, the grid interconnection device 1 switches the power conditioner 11 to the grid interconnection mode by bringing the power conditioner 11 and the grid 2 into a conductive state, and quickly restarts the grid interconnection. Can be made.

Second Embodiment
FIG. 4 is a configuration diagram illustrating a configuration example of grid interconnection by the grid interconnection device according to the second embodiment. As shown in FIG. 4, the grid interconnection device 1 </ b> A includes a cutoff switch 12 similar to that of the first embodiment, and includes a power conditioner 11 </ b> A, a linkage control unit 14 </ b> A, and a sub inverter 15. Hereinafter, a configuration different from the first embodiment will be described.

  The power conditioner 11A changes the operation mode by switching on / off of the cutoff switch 12 under the control of the interconnection control unit 14A. Specifically, the power conditioner 11A operates in the grid connection mode by turning on the cutoff switch 12 and conducting between the power conditioner 11A and the grid 2. Further, when a predetermined control signal indicating that the voltage drop of the system 2 has occurred is supplied from the interconnection control unit 14, the power conditioner 11 </ b> A turns off the cutoff switch 12, and connects the power conditioner 11 </ b> A and the system 2. Operates in the self-sustained operation mode.

  The sub inverter 15 is connected to the solar cell 3 and the system 2. The sub-inverter 15 detects an instantaneous drop and a voltage recovery based on the voltage of the system 2, and outputs the detection result to the interconnection control unit 14A. In addition, the sub inverter 15 converts the DC power of the solar cell 3 into AC power corresponding to the voltage of the grid 2 and supplies it to the grid 2 in accordance with a predetermined control signal supplied from the interconnection control unit 14A.

  The interconnection control unit 14A is connected to the power conditioner 11A and the sub inverter 15, and controls the power conditioner 11A and the sub inverter 15 according to the detection result of the sub inverter 15. That is, when the voltage drop of the grid 2 is detected by the sub inverter 15, the interconnection control unit 14 </ b> A applies predetermined power to the power conditioner 11 </ b> A and the sub inverter 15 until voltage recovery is detected within a predetermined time from the voltage drop. The sub-inverter 15 converts the DC power generated by the solar battery 3 into predetermined AC power and supplies it to the system 2. Then, the interconnection control unit 14A turns off the cutoff switch 12 by the power conditioner 11A and switches the power conditioner 11A to the independent operation mode.

  Further, the interconnection control unit 14A outputs a predetermined control signal to the power conditioner 11A and the sub inverter 15 when the sub inverter 15 detects the voltage return of the system 2 within a predetermined time from the voltage drop of the system 2. Stop and turn off the shut-off switch 12 by the power conditioner 11A. Then, the power conditioner 11A is switched to the grid connection mode, and the output of AC power from the sub inverter 15 to the grid 2 is stopped.

  The interconnection control unit 14A stops the output from the sub-inverter 15 when the predetermined time has elapsed unless the voltage return is detected by the sub-inverter 15 within a predetermined time from the voltage drop of the grid 2, and is independent of the power conditioner 11A. Continue operation in operation mode.

  That is, the grid interconnection device 1A monitors the voltage change of the grid 2 by the sub inverter 15, and when a voltage drop occurs in the grid 2, the sub-inverter 15 sends a predetermined voltage based on the power generation of the solar cell 3 to the grid 2. While supplying AC power, the power conditioner 11A is operated in the self-sustained operation mode by bringing the power conditioner 11A and the system 2 into a non-conductive state. Therefore, even if a voltage sag occurs in the configuration of the present embodiment, the power conditioner 11A can be operated in the self-sustained operation mode and power can be supplied to the load while observing the FRT requirement defined by the grid interconnection.

<Modification>
While the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit thereof. Hereinafter, modifications of the present invention will be described.

  (1) In the above-described embodiment, the example in which the solar cell 3 is used as the power generation device has been described. However, for example, a power generation device using wind power or a fuel cell may be used as the power generation device.

  (2) In the above-described embodiment, the example in which the storage battery 4 is connected to the power conditioners 11 and 11A has been described, but the storage battery 4 may not be connected.

  (3) In the above-described embodiment, the supply of power from the sub-converter 13 or the sub-inverter 15 to the system 2 is stopped after the voltage of the system 2 is restored. The supply of power from 15 to the grid 2 may be continued. In this case, electric power is supplied to the grid 2 from both the power conditioner 11 and the sub-converter 13, or both of the power conditioner 11 </ b> A and the sub-inverter 15.

  DESCRIPTION OF SYMBOLS 1,1A ... Grid connection apparatus, 2 ... System, 3 ... Solar cell, 4 ... Storage battery, 5 ... AC load, 11, 11A ... Power conditioner, 12 ... Cutoff switch, 13 ... sub-converter, 14, 14A ... interconnection control unit, 15 ... sub-inverter

Claims (3)

A grid interconnection device that connects a power generation device that generates DC power and a system that supplies AC power, and that supplies power from the power generation device and the system to a load,
A power conversion unit that is connected to the system, the power generation device, and the load and converts DC power of the power generation device into AC power;
An auxiliary connected to the power conversion unit and the system , detects a voltage drop of the system , converts the AC power converted by the power conversion unit into a predetermined voltage corresponding to the system, and supplies the voltage to the system A power converter,
A switch that switches between conduction and non-conduction between the power converter and the system;
System interconnection that supplies AC power to the load from the system or the power conversion unit, allows conduction between the power conversion unit and the system by the switch, and supplies AC power from the power conversion unit to the system When a voltage drop in the system is detected, the AC power converted by the power conversion unit by the constant voltage control for a predetermined time is converted into a predetermined voltage corresponding to the system by the auxiliary power conversion unit. converted to to subjected supply to the system together, and the between said power converting unit system by the switch non-conductive, self-supporting and supplies the AC power constant voltage control to the load from the power converter unit A grid interconnection control unit for switching to operation control;
A grid interconnection device comprising:   The said power conversion part charges the direct current power of the said power generator to a storage battery, converts the direct current power discharged from the said storage battery into alternating current power at least in the said independent operation control, and supplies it to the said load. Grid interconnection device. A grid interconnection device that connects a power generation device that generates DC power and a system that supplies AC power, and that supplies power from the power generation device and the system to a load,
A power conversion unit that is connected to the system, the power generation device, and the load and converts DC power of the power generation device into AC power;
Auxiliary power conversion unit that detects a voltage drop of the system and outputs AC power of a predetermined voltage based on DC power of the power generator,
A switch that switches between conduction and non-conduction between the power converter and the system;
System interconnection that supplies AC power to the load from the system or the power conversion unit, allows conduction between the power conversion unit and the system by the switch, and supplies AC power from the power conversion unit to the system When a voltage drop in the system is detected, AC power is supplied from the auxiliary power conversion unit to the system for a predetermined time, and the switch between the power conversion unit and the system is performed by the switch. A grid interconnection control unit that is switched off to a self-sustained operation control that supplies AC power from the power conversion unit to the load;
With
Said auxiliary power converter unit is connected to said and said power generator system, supplied to the grid by converting the DC power of the power generator into AC power of a predetermined voltage according to the system, the system Mitsururen system apparatus.

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