JP2014103731A - Power conversion system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion system capable of balancing between the need and the supply to ensure the stability by preventing the voltage from increasing in a power supply system even when a large number of equipment is reconnected at the same timing.SOLUTION: The power conversion system includes: a power generation system that generates the power and outputs DC power; a power conversion device that converts the DC power into AC power; a switch that switches the connection between the power conversion device and the power supply system; a control unit that controls the switch; and a detection section that detects the status of the power supply system. When the detection section detects a problem, the control unit shut off the connection of the switch. After the detection section detects the recovery of the power supply system, the control unit sets variable reconnection time for recovering the reconnection.

Description

  The present invention relates to a power conversion system that is connected to a power system.

  Conventionally, in a grid-connected power conversion system, when the system is blacked out or the quality of the system is reduced due to some influence, the system is disconnected from the system. Thereafter, when the grid interconnection power conversion system determines that the system has recovered from the power failure or the grid quality has stabilized again, the power conversion system that performs grid interconnection operation reconnects to the grid.

  Patent Document 1 shows a method for performing a reconnection time, which is a time from when it is determined that the system quality is stabilized again until a reconnection is performed, in as short a time as possible.

JP 2000-209871 A

  However, in the conventional grid-connected power conversion system, a plurality of grid-connected power conversion systems (for example, the same type of devices) that perform re-connection to the system in the same re-connection time are connected to the same system. In such a case, when the quality of the system decreases due to a power failure or for some reason, the system is disconnected once and then connected to the system at the same time. If a plurality of grid-connected power conversion systems are linked simultaneously, an excessive supply of power to the grid temporarily occurs, and the balance between power demand and supply is lost. At the same time, if there are few devices that perform reconnection, the impact on the system is small, and the imbalance between supply and demand can be absorbed on the system side. The balance cannot be absorbed on the system side, and as a result, the system voltage rises and the stability of the system is impaired.

  Until now, there were about 1 to 3 grid-connected power conversion systems connected to the same grid, and it was rare that the equipment would be re-linked to the grid at the same re-link time. In the future, due to the spread of smart towns, etc., it is assumed that all customers connected to the same grid will be connected to a grid-connected power conversion system that re-connects to the grid in the same re-link time. In that case, it is expected that the above problems will occur.

  In order to solve the conventional problems, in the grid-connected power conversion system of the present invention, a power generation device that generates power and outputs DC power, a power conversion device that converts the DC power into AC power, and the power A switch for interconnecting the converter and the power system, a control unit for controlling the switch, and a detection unit for detecting an abnormality of the power system, wherein the control unit detects the abnormality By disconnecting the switch and then performing control so as not to perform reconnection at the same timing by making the reconnection time variable, which is the time until reconnection to the power system, System stability can be maintained.

In the grid-connected power conversion system of the present invention, the reconnection time is not a fixed value, but is variable, so that when a plurality of grid-connected power conversion systems are connected to the same system, a system abnormality occurs. Later, when re-connecting to the grid, all grid-connected power conversion systems do not re-link to the grid at the same time, so the stability of the grid can be maintained.

The block diagram in the 1st Embodiment of this invention Timing chart in the first and second embodiments of the present invention Timing chart in the first and second embodiments of the present invention The block diagram in the 2nd Embodiment of this invention Connection diagram in the second embodiment of the present invention Connection diagram of grid and customer Timing chart of grid-connected power conversion system at the time of power failure

The first invention generates power and outputs DC power; and
A power converter for converting the DC power into AC power;
A switch for connecting the power converter and the power system;
A control unit for controlling the switch;
A detection unit for detecting the state of the power system;
When the detection unit detects an abnormality, the control unit disconnects the switch, and after that, the control unit detects a return from the power system to the reconnection. This is a power conversion system that makes the interconnection time variable.

  By making the reconnection time variable rather than a fixed value, when multiple grid connection power conversion systems are connected to the same system, when reconnecting to the system after the occurrence of a system abnormality, Since all grid-connected power conversion systems do not reconnect to the grid at the same time, the stability of the grid can be maintained.

A second invention is the power conversion system, further comprising:
It has an interface unit that connects to a server or other power conversion system through a network.
The power conversion system according to claim 1, wherein the control unit sets the reconnection time based on information acquired by the interface unit.

  3rd invention is a power conversion system of Claim 2 which sets the said reconnection time in the said control part in time different from the reconnection time which another power conversion system sets.

  By acquiring the reconnection time of other power conversion systems through the network, it is possible to set different reconnection times for all grid-connected power conversion systems connected to the network. When multiple systems are connected, all grid-connected power conversion systems reliably re-link to the grid at different timings when the grid is re-linked after a system failure occurs. Can maintain stability.

  4th invention selects in the said control part from the several time which can be set as the said reconnection time, The electric power in any one of Claims 1-3 which sets the said reconnection time It is a conversion system.

  The fifth invention is the power conversion system according to claim 1, wherein the control unit generates a random number and sets the reconnection time based on the generated random number.

  The power conversion system according to claim 1 or 4, wherein the control unit according to a sixth aspect of the invention sets the reconnection time based on a power generation amount generated by the power generation device.

  By setting the reconnection time based on the power generation amount before the reconnection, the influence on the system can be reduced and the stability of the system can be maintained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the present embodiment.

  FIG. 6 shows a connection diagram in the case where a plurality of grid-connected power conversion systems that perform reconnection to the system at the same reconnection time are connected to the same system. The pole transformer 1 operates to keep the voltage of the system 101 at 100V. Each of the consumers 2a to 2j consumes 1 kW of power. Each of the grid interconnection power conversion systems 102a to 102e generates 1 kW of power.

  FIG. 7 shows a timing chart when a power failure occurs in the system 101.

  A power failure occurs in the grid 101 at T1, and all the grid-connected power conversion systems 102a to 102e are disconnected from the grid. At this time, the supplied power is 0 W and the demand power is also 0 W, which balances the power demand and supply.

  Immediately after the system 101 recovers from the power failure at T2, the grid interconnection power conversion systems 102a to 102e remain disconnected because the determination of recovery from the power failure cannot be made immediately. At this time, the power supply is 10 kW, and the power demand is 10 kW before the power outage, which balances the power demand and supply.

  At T3, the grid interconnection power conversion systems 102a to 102e determine that the grid 101 has recovered from the power failure, reconnect to the grid, and 5 kW of power is newly supplied to the grid 101. At this time, the supply power is 15 kW, the demand power is 10 kW, and an excessive supply of 5 kW is created. The electric power exceeding 50% of the demand becomes surplus electric power, and the imbalance between the demand and the supply cannot be absorbed by the pole transformer, and as a result, the voltage of the grid 101 increases.

(Embodiment 1)
FIG. 1 is a block diagram of a grid-connected power conversion system according to the first embodiment of the present invention.

  FIG. 1 illustrates a grid 101 and a grid-connected power conversion system 102.

  The grid interconnection power conversion system 102 includes at least a power generation device 103, a power conversion device 104, a switch 105, a control unit 106, and a detection unit 107.

  Here, the power generation device 103 includes a fuel cell, solar power generation, storage battery, and the like, and generates DC power. The power converter 104 converts the DC power generated by the power generator 103 into AC power synchronized with the system 101.

  The switch 105 connects and disconnects the grid 101 and the grid-connected power conversion system 102. When the switch 105 is turned on, the grid interconnection power conversion system 102 is linked to the grid 101. When the switch 105 is turned off, the grid interconnection power conversion system 102 is disconnected from the grid 101.

  The control unit 106 controls on / off of the switch 105. The control is performed based on information from the detection unit 107. The detection unit 107 monitors the state of the system 101 and determines whether the system is abnormal or normal.

  FIG. 2 is an operation timing chart.

  In T101, the detection unit 107 detects a power failure in the system 101 and performs abnormality determination. The control unit 106 immediately turns off the switch 105 and enters the disconnected state.

  Although the system 101 returns to the normal state at T102, the detection unit 107 cannot determine that the system 101 has become normal until T103. This is to determine that the system has returned to normal after confirming that the system has maintained a normal state for a certain period of time.

  At T104, the control unit 106 turns on the switch 105 to perform reconnection.

  Here, T105 represents the reconnection time. T105 may be defined as the time (T104-T102) from the recovery from the power failure to the reconnection, or as the time (T104-T103) from the detection of the recovery from the detection unit 107 to the reconnection. It may be defined.

  In the present embodiment, the time of the reconnection time T105 is not set to a fixed value, but is set to a variable value, so that when a plurality of grid connection power conversion systems are connected to the same system, When the grid is reconnected after the occurrence of an abnormality in the system, all the grid-connected power conversion systems do not reconnect to the system at the same time, so that the stability of the system can be maintained.

  FIG. 3 is a timing chart when the reconnection time of the grid interconnection systems 102a to 102e is made variable and different reconnection times T201 to TT205 are set in the connection state shown in FIG.

  At T200, the system returns from the power failure. At this time, the supply power is 10 kW, and the power demand is 10 kW before the power outage, so that the balance between power supply and supply is achieved.

  After T201 from T200, only the grid interconnection power conversion system 102a is reconnected. At this time, the supply power is 11 kW and the demand power is 10 kW, which is an instantaneous supply of 1 kW. However, it is 10% of the demand, and in many cases it can be judged that the difference between the demand and the supply is small. This level of supply and demand imbalance can be absorbed by the pole transformer 1.

  In addition, for the sake of explanation, a case where 10 customers are connected to one pole transformer 1 has been described, but in an actual installation environment, one pole transformer 1 is There are many cases where 30 to 50 customers are connected, and the more consumers that are installed, the greater the effect of maintaining the stability of the system according to the present invention.

  Thereafter, the grid-connected power conversion system 102b after T200 to T202, the grid-connected power conversion system 102c after T200 to T203, the grid-connected power conversion system 102d after T200 to T204, and the T200 to T205 After the lapse of time, the grid interconnection power conversion system 102e independently reconnects to the grid, so that the grid is not affected.

  Thus, in the grid interconnection power conversion system of the present invention, when the grid interconnection power conversion system is connected to the same system by making the reconnection time not variable but a variable value, When the system is re-connected after the occurrence of the system abnormality, all the grid-connected power conversion systems do not re-connect to the system at the same time, so that the stability of the system can be maintained.

  In this embodiment, the reconnection time T105 may be set by the user at the time of shipment, installation, or any other timing of the grid interconnection power conversion system. The grid interconnection power conversion system itself may be set at the time of start-up, power failure, or the like.

  In the present embodiment, in setting the reconnection time T105, the user or the grid connection power conversion system may select and set from a plurality of preset setting values, or a random number may be set. May be used.

  In addition, regarding the setting of random numbers, specifically, by setting in units of 1 second from 0 to 100 (seconds), there is a high possibility that reconnection is performed at a different timing from other grid connection power conversion systems. . In calculating the random number, the calculation may be performed based on the total power generation time, the total number of power generations, the generated power before disconnection from the system, and the like.

(Embodiment 2)
FIG. 4 is a block diagram of a grid-connected power conversion system in the second embodiment of the present invention.

  Here, FIG. 4 is different from FIG. 1 in order to exchange information with the server 110 or another grid-connected power conversion system 102, and newly connects the network 108 and the network 108 to exchange information. 109 is different. In FIG. 4, the same components as those in FIG.

  FIG. 5 is a connection diagram of the grid-connected power conversion system in the second embodiment of the present invention. The server 110 acquires the reconnection time T105 information of all the grid connection power conversion systems 102a to 102e connected through the network 108, so that each grid connection time T105 does not become the same time. Give instructions to the grid-connected power conversion system.

  FIG. 2 is an operation timing chart. Since the operation is the same as in (Embodiment 1), description thereof is omitted.

  FIG. 3 is a timing chart when the grid interconnection power conversion systems 102a to 102e are connected to the network as shown in FIG. 5 in the connection state shown in FIG. Since the operation is the same as in (Embodiment 1), description thereof is omitted.

  In this embodiment, the time of the reconnection time T105 is not set to a fixed value, but by setting the reconnection time T105 different from other devices through the network, a plurality of grid connection power conversion systems are provided in the same system. When connected to a stand, when any system abnormality occurs, when reconnecting to the system, all grid-connected power conversion systems do not reconnect to the system at the same time. it can.

  In setting the reconnection time T105, the interface unit 109 acquires information on the reconnection time T105 of another grid connection power conversion system connected to the same system via the network 108. The acquired information may be sent to the control unit 106, and the control unit 106 may set a reconnection time T105 different from those of other grid connection power conversion systems 102.

Note that the reconnection time T105 may be set based on the power generation amount before the power failure. If a customer with a small amount of power generation before the power failure is connected to the grid, the burden on the system 101 is small. Conversely, if a customer with a large amount of power generation before the power failure is connected to the grid, the burden on the system 101 is large. Become. The reconnection time T105 of each grid-connected power conversion system may be set so as to reduce the influence on the grid by appropriately combining these.

  As described above, the grid-connected power conversion system according to the present invention can maintain the stability of the system when a plurality of units are connected to the same system. The present invention can also be applied to uses such as batteries, wind power generators, distributed power generators such as gas engines.

DESCRIPTION OF SYMBOLS 101 system | strain 102 grid interconnection power conversion system 103 power generation apparatus 104 power conversion apparatus 105 switch 106 control part 107 detection part 108 network 109 interface part 110 server

Claims (6)

A power generator that generates power and outputs DC power;
A power converter for converting the DC power into AC power;
A switch for connecting the power converter and the power system;
A control unit for controlling the switch;
A detection unit for detecting the state of the power system;
When the detection unit detects an abnormality, the control unit disconnects the switch, and after that, the control unit detects a return from the power system to the reconnection. A power conversion system that makes the interconnection time variable. The power conversion system further includes:
It has an interface unit that connects to a server or other power conversion system through a network.
The power conversion system according to claim 1, wherein the control unit sets the reconnection time based on information acquired by the interface unit.   The power conversion system according to claim 2, wherein the control unit sets the reconnection time with a time different from a reconnection time set by another power conversion system.   The power control system according to any one of claims 1 to 3, wherein the control unit selects the plurality of times that can be set as the reconnection time, and sets the reconnection time.   The power conversion system according to claim 1, wherein the control unit generates a random number and sets the reconnection time based on the generated random number.   The power conversion system according to claim 1, wherein the control unit sets the reconnection time based on a power generation amount generated by the power generation device.