JP2005295707A - Operation method of distributed power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation method of a distributed power supply that allows the distributed power supply to be extended to an arbitrary place of a system. <P>SOLUTION: As a plurality of the distributed power supplies that are operated in a manner of current control, there are used first kinds of the distributed power supplies A2 to An each having power accumulation equipment, and second kinds of the distributed power supplies B1 to Bn each having a solar battery 1 as generation equipment and not having the power accumulation equipment. A power converter 6 of the second kind of the distributed power supply is operated in a manner of current control so as to follow the maximum power point of the generation equipment such as the solar battery. The second kind of the distributed power supply can be added or extended to the arbitrary place of the system. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a parallel operation method for a plurality of distributed power sources disconnected from a power system.

In JP-A-11-89096 (Patent Document 1), a distributed power source including a solar cell, an inverter (power conversion device), and a power storage device is connected to a plurality of power systems, and each distributed type is connected to the power system. When the power source is disconnected, one distributed power source is voltage-controlled, and this single distributed power source is used as an AC voltage source, and the remaining distributed power source is used as an AC current source. There is disclosed a method of performing parallel synchronous operation of each distributed power source without exchanging information such as output power and output current.
Japanese Patent Laid-Open No. 11-89096 FIG. 1 Claims

  In the conventional method, since the solar cells of each distributed power source are directly connected to the power storage facility and output electric power according to the load, the operating point of the solar cell is determined by the storage battery voltage, and the power conversion device The current operation could not be controlled to follow the maximum power point of the solar cell. In addition, in the conventional method, when a distributed power source is added to an existing power system, if there is a part where the impedance of the system wiring is large, there is a possibility that it is biased to a specific distributed power source. For this reason, it was not possible to add a distributed power source to any part of the system.

  An object of the present invention is to provide a method of operating a distributed power source that can add a distributed power source to an arbitrary part of a system.

  Another object of the present invention is to provide a method of operating a distributed power source that can achieve leveling of the usage rate of power storage equipment included in the distributed power source that can be used as an AC voltage source.

  An object of the present invention is to provide a method of operating a distributed power source that can effectively utilize surplus power output from the distributed power source used as an alternating current source.

  Still another object of the present invention is to provide a distributed power source that can avoid stopping power supply to a load as much as possible by using another distributed power source as an AC voltage source even when the distributed power source used as an AC voltage source fails. The object is to provide a method of operating a mold power source.

  In the operation method of the distributed power source to be improved by the present invention, in order to operate a plurality of distributed power sources separated from the power system, including a power conversion device that converts DC power into AC power, First, the power converter of one distributed power source is voltage-controlled, and this one distributed power source is used as an AC voltage source for independent operation. Then, the remaining multiple distributed power sources are synchronized with the output voltage of the AC voltage source, and each of the remaining multiple distributed power sources is synchronized with the AC voltage source. Connected operation as a current source. Up to here, it is the same as the conventional driving method.

  In the method of the present invention, a first type of distributed power source having a power storage facility is used as a plurality of distributed power sources that are operated under current control, and natural energy such as a solar cell or a wind-hydraulic power generation facility is used as a power generation facility. A second type of distributed power source that includes all power generation facilities including a natural energy generation power generation facility that generates power and does not have power storage facilities is used. Then, the power converter of the second type of distributed power source is operated in a current control manner so as to follow the maximum power point of the power generation facility. Such a second type of distributed power supply is capable of current-controlling the power conversion device without being affected by the storage voltage of the storage facility. Therefore, the second type of distributed power supply can be attached to or added to any part of the system, and a stable load sharing can be achieved to realize parallel operation of a plurality of distributed power supplies.

  It is to be noted that a bi-directional conversion type power converter having a function of converting AC power into DC power is provided as a power converter of the distributed power source provided with a storage device for storing surplus power in a distributed power source serving as an AC voltage source. May be. In this case, the system power is measured to determine that surplus power is generated, or the generation of surplus power is automatically determined without measuring the system power using a known technique. In this case, the surplus power can be regenerated by the power conversion device of the distributed power source serving as the AC voltage source to charge the surplus power storage power storage facility. Therefore, surplus power can be used effectively. Note that grid power measurement and charging control can be easily realized by providing a predetermined control device for the grid.

  In addition, as a plurality of distributed power sources to be used, a plurality of first power converters including a power conversion device having a bidirectional conversion function for converting AC power into DC power and converting DC power into AC power and a power storage facility are used. You may make it use a kind of distributed power supply and one or more 2nd types of distributed power supplies which are equipped with a solar cell as a power generation equipment, and do not have an electrical storage equipment. In this case, the first type of distributed power supply can be any AC voltage source. Therefore, when the first type of distributed power source used as the AC voltage source fails, the operation of the first type of distributed power source that has failed is stopped and the other first type of distributed power source is stopped. It is possible to continue operation by performing a switching operation using as an AC voltage source. In this way, the possibility of power supply to the load being stopped is reduced, and the distributed power source can be operated stably. Also, in this case, one distributed power source selected alternately from a plurality of first type distributed power sources at an appropriate time is used as an AC voltage source, and the remaining first type distributed power sources and Two types of distributed power sources may be interconnected by current control operation. Thus, when the distributed voltage source used as the AC voltage source is used alternately, it is possible to level the usage rate of the power storage equipment of a plurality of first type distributed power supplies, and the life of the storage battery of the power storage equipment Can be extended.

  Of course, the first type of distributed power source may include a power generation facility including a natural energy utilization power generation facility.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to attach or add a distributed power supply to any part of the system, and it is possible to realize a parallel operation of distributed power supplies with stable load sharing. Further, there is an advantage that the usage rate of the power storage equipment provided in the distributed power source that can be used as an AC voltage source can be leveled. Furthermore, surplus power output from a distributed power source used as an alternating current source can be effectively utilized. Further, even when a distributed power source used as an AC voltage source fails, it is possible to avoid stopping power supply to the load as much as possible by using another distributed power source as an AC voltage source.

  Hereinafter, an example of an embodiment of an operation method of a distributed power source according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a single-line system diagram showing an example of a system configuration for carrying out the method of the present invention. In FIG. 1, what is indicated by a symbol AC is a commercial power source, and blocks indicated by L are representative of loads connected to the system. In this example, the distributed power sources connected to the system are divided into a first type of distributed power sources A1 to An and a second type of distributed power sources B1 to Bn.

  First, the first type of distributed power sources A1 to An each have a solar cell 1, a changeover switch circuit 3, and a power having a bidirectional conversion function for converting DC power into AC power and converting AC power into DC power. The converter 5 and the electrical storage equipment 7 provided with electrical storage means, such as a storage battery, are provided. A solar cell 1 made of a PV panel or the like is installed on a factory or building roof or a dedicated installation stand. The first type of distributed power sources A1 to An may be concentrated at one place, or may be distributed at some distance from each other. The changeover switch circuit 3 connects the solar cell 1 and the power storage facility 7 to the power converter 5 when the solar cell 1 is generating power, and stores the power storage facility when the solar cell 1 is not generating power. 7 is connected to the power converter 5. The power conversion device 5 is not only used when the system is normal, but also when the commercial power supply or the system power supply AC is out of power, or when a disconnection occurs in a part of the system, from the solar cell 1 or the power storage facility 7. It functions as an inverter that converts the obtained DC power into AC power and outputs it to the system. When the solar cell 1 is not generating power, when the amount of power stored in the power storage means of the power storage facility 7 is low, or when charging the power storage means of the power storage facility 7 with regenerative power described later, AC power on the system side Functions as a converter that converts DC power to DC power.

  As shown in FIG. 2, the power converter 5 includes a switching circuit 5A composed of a bridge circuit of power semiconductor switching elements, a control means 5B composed of a microcomputer and the like, and a current on the system side. It comprises an instrument current transformer 5C that measures i and an instrument transformer 5D that detects the voltage on the system side. The control means 5B includes a plurality of switching circuits 5A that constitute the switching circuit 5A according to an operation mode selected from a plurality of predetermined operation modes based on outputs of the instrument current transformer 5C and the instrument transformer 5D and various contact signals. A conduction control signal is output to the semiconductor switching element. Among the plurality of operation modes, there are an operation mode in which the power converter 5 is voltage-controlled and the distributed power source is an AC voltage source, and the power converter 5 is current-controlled and the distributed power source is an AC current. If one of the distributed power sources operating as an AC voltage source and one distributed power source operating as an AC voltage source fails, one of the remaining distributed power sources of the first type is controlled by current control. In the operation mode in which an AC voltage source is used instead of the voltage control operation, and in the plurality of first type distributed power sources, each distributed power source that is an AC voltage source is changed in a predetermined order. The operation mode in which the power source is operated, and the operation mode for executing the function of charging the power storage means of the power storage facility 7 using the power conversion device 5 as a converter when surplus power is generated in the system are included.

  On the other hand, the second type of distributed power sources B1 to Bn each include a solar cell 1 and a power conversion device 6 having only a function of converting DC power into AC power. Unlike the first type of distributed power sources A1 to An, the second type of distributed power sources B1 to Bn do not include a power storage facility. The power converters of these second types of distributed power sources B1 to Bn are operated in a current controlled manner so as to follow the maximum power point of the solar cell 1, and the first type of distributed power sources A1 to An and Is different. The second type of distributed power sources B1 to Bn can perform the current control operation of the power converter 6 without being affected by the storage voltage of the storage facility. Therefore, the second type of distributed power sources B1 to Bn can be attached to or added to any part of the system. The configuration of the power converter used in the second type of distributed power sources B1 to Bn is substantially the same as that of the first type of distributed power sources A1 to An, except that reverse conversion cannot be performed. It has the same composition as.

  The control device 9 determines a system state based on the system voltage Vout and the system current or the load current IL, and particularly monitors the operation state (presence or absence of failure) of the first type of distributed power sources A1 to An. And, it has a function of outputting operation start and operation stop commands to each of the distributed power sources A1 to An and B1 to Bn. That is, the control device 9 has a function of coordinating the movement of each distributed power source. The control device 9 and each distributed power source are connected by wire or wirelessly. It is also possible to communicate with each other using a distribution line of the system.

  When the system in which the system power supply AC of the power system supplies power to the load L is normal, the outputs of the solar cells 1 of the distributed power sources A1 to Bn are mainly converted into power converters during the day when the solar cell 1 generates power. The system is operated in parallel with the power system by controlling the interconnection operation modes 5 and 6, and the DC power from each solar cell 1 is converted into AC power by the power converters 5 and 6 and supplied to the load L in parallel. Is done. At this time, each of the distributed power sources A1 to Bn is operated by current control, and each output current is in phase with the voltage of the system power source AC, and is operated in synchronization with the system power source AC. When the system power supply AC fails for some reason, each distributed power supply is disconnected from the power system in order to prevent electric shock or the like due to so-called single operation. A cross mark in FIG. 1 is a separation point.

  When power is supplied to the load L only from the distributed power source, each distributed power source A1 to Bn starts operation according to the respective operation mode in response to a command from the control device 9. In this example, the first type of distributed power source A1 is operated by voltage control so as to be operated independently to be an AC voltage source. Then, the other distributed power sources A2 to An and B1 to Bn are subjected to current control operation in synchronism with the output voltage of the AC voltage source, whereby these are operated as an AC current source. If it is night, only the first type of distributed power sources A1 to An are operated in parallel.

  At this time, the first type of distributed power sources A1 to An operate in a mode as shown in FIG. The distributed power sources A2 to An that perform the current control operation, that is, the grid operation, obtain the measurement result of the system power and perform the operation according to the operation mode shown in FIG. Then, the second type of distributed power sources B1 to Bn supply power to the load system while obtaining the maximum output of the solar cell 1 by the maximum output tracking control. Here, the maximum output follow-up control means that the power conversion device 6 is current-operated controlled so that all the maximum outputs output by the power generation equipment such as the solar cell 1 are converted into AC power and output. In the operation mode of FIG. 3, the response of the distributed power source that controls the current operation is delayed by the amount of the system power measured when the load suddenly changes. On the other hand, the distributed power source A1 performing the voltage control operation covers this delay. For example, immediately after a sudden load change from 0 kW to 50 kW, the distributed power supply A1 for autonomous operation outputs 50 kW. Then, the load of the distributed power sources A2 to Bn that are operated by other current control increases with a delay of the measurement time, and the distributed power source A1 and the other distributed power sources share 25 kW and 25 kW, respectively. Immediately after a sudden load change of 100 kW to 50 kW, the output of the distributed power supply A1 in the self-sustained operation becomes 0 kW, and the other distributed power supplies that are operated by current control bear all of the load. After that, the burden ratio between the distributed power source and the other distributed power source operated by current control becomes 25 kW at a delay of the measurement time. During this operation, the distributed power sources A2 to An that are current-controlled operate only for current operation control, so there is no need to control the phase or amplitude of the output voltage between the distributed power sources.

  According to this embodiment, the voltage of the load power supply is determined by the output voltage of the distributed power source serving as the AC voltage source, and the output current of the power converter of the remaining distributed power source is the output of the distributed power source serving as the AC voltage source. The output of these remaining distributed power supplies is synchronized with the output of the distributed power supply serving as the reference AC voltage source, so that no information related to the output is exchanged between the distributed power supplies. Each distributed power source can be operated in parallel synchronously. Therefore, a plurality of distributed power sources can be operated in parallel and synchronous with an inexpensive configuration without laying communication lines between the distributed power sources.

  Since power is supplied to the load system also from the second type of distributed power sources B1 to Bn by the maximum output tracking control, naturally, surplus power may be generated. In such a case, the distributed power source A1 that is operating independently performs a regenerative operation to charge the power storage means of the power storage facility 7 of the distributed power source A1. The generation of surplus power may be detected by measuring system power, but the generation of surplus power may be determined based on a known technique, and the surplus power may be regenerated automatically and continuously. . In the present embodiment, the latter technique of automatically regenerating surplus power continuously is employed. In this way, power can be used effectively. If the power storage means of the power storage facility 7 of the distributed power source A1 is in a fully charged state, this is monitored by the control device 9 so as to stop the operation of the second type of distributed power sources B1 to Bn. You can do it.

  In the first type of distributed power sources A1 to An used, any of the distributed power sources can be an AC voltage source. Therefore, when the first type of distributed power source used as the AC voltage source fails, the operation of the first type of distributed power source that has failed is stopped and the other first type of distributed power source is stopped. It is possible to continue operation by performing a switching operation using as an AC voltage source. In this way, the possibility of power supply to the load being stopped is reduced, and the distributed power source can be operated stably. Further, in this case, one distributed power source selected alternately at a suitable time from the plurality of first type distributed power sources A1 to An is used as an AC voltage source, and the remaining first type distributed power sources are used. The power source and the second type of distributed power source may be interconnected by current control operation. Thus, when the distributed voltage source used as the AC voltage source is used alternately, it is possible to level the usage rate of the power storage equipment of a plurality of first type distributed power supplies, and the life of the storage battery of the power storage equipment Can be extended.

  In carrying out the present invention, it is not always necessary to provide power storage equipment in the first type of distributed power source. Further, it is not necessary to use a solar cell as a direct current power source in the first type of distributed power source.

  In the above embodiment, solar cells are used as the power generation facilities of the first and second types of distributed power sources. However, in the present invention, it is possible to use various types of power generation facilities including a natural energy generation power generation facility using natural energy, such as a solar cell and a wind-hydraulic power generation facility, in any type of power generation facility of a distributed power source. Of course.

It is a single track | line system diagram which shows an example of the structure of the system | strain for implementing the method of this invention. It is a figure which shows the structure of a power converter device. It is a figure used in order to demonstrate an example of the operation mode of an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solar cell 3 Changeover switch circuit 5,6 Power converter 7 Power storage equipment 9 Control apparatus A1-An 1st distributed power supply B1-Bn 2nd distributed power supply

Claims (7)

A power conversion device that converts direct current power into alternating current power, and among a plurality of distributed power sources separated from the power system,
Voltage-controlled operation of the power conversion device of one of the distributed power sources to make the one distributed power source an AC voltage source for independent operation,
The power converters of the remaining plurality of distributed power supplies are synchronized with the output voltage of the AC voltage source, and the current control operation is performed to synchronize the remaining plurality of distributed power supplies with the AC voltage source. A method of operating a distributed power source that operates in an interconnected manner as an alternating current source,
As the plurality of distributed power sources operated in current control, a first type distributed power source having a power storage facility and a second type distributed power source having a power generation facility but not a power storage facility are used.
A method of operating a distributed power source, wherein the power conversion device of the second type of distributed power source is operated in a current control manner so as to follow the maximum power point of the power generation facility.   The method of operating a distributed power source according to claim 1, wherein the power generation facility includes a natural energy generation power generation facility that generates power using natural energy, such as a solar battery or a wind-hydraulic power generation facility. A power conversion device that converts direct current power into alternating current power, and among a plurality of distributed power sources separated from the power system,
Voltage-controlled operation of the power conversion device of one of the distributed power sources to make the one distributed power source an AC voltage source for independent operation,
The power converters of the remaining plurality of distributed power supplies are synchronized with the output voltage of the AC voltage source, and the current control operation is performed to synchronize the remaining plurality of distributed power supplies with the AC voltage source. A method of operating a distributed power source that operates in an interconnected manner as an alternating current source,
As the plurality of distributed power sources that are operated under current control, the first type distributed power source having a power storage facility, and a power generation facility using a natural energy generation power generation facility that generates power using natural energy are provided. Using a second type of distributed power supply that does not have
The current conversion operation of the power conversion device of the second type of distributed power supply so as to follow the maximum power point of the power generation facility,
Bidirectional conversion type power conversion device having a power storage device for storing surplus power in the distributed power source serving as the AC voltage source and having a function of converting AC power to DC power as the power conversion device of the distributed power source Use
When it is determined that surplus power is generated, the surplus power is regenerated by the power conversion device of the distributed power source serving as the AC voltage source to charge the surplus power storage power storage facility. To operate a distributed power supply. With a power conversion device that converts DC power to AC power, among multiple distributed power sources that are disconnected from the power system,
A voltage control operation is performed on the power conversion device of the one distributed power source, and the one distributed power source is used as an AC voltage source for independent operation,
AC that synchronizes the remaining plurality of distributed power sources with the AC voltage source by performing current control operation of the power converters of the remaining plurality of distributed power sources in synchronization with the output voltage of the AC voltage source. It is a method of operating a distributed power source that operates in an interconnected manner as a current source,
As the plurality of distributed power sources, a plurality of first types of power supplies having a bidirectional conversion function for converting AC power into DC power and converting DC power into AC power and power storage equipment One or more second-type distributed power sources that include a distributed power source and a natural energy generating power generation facility that uses natural energy such as a solar cell or a wind-hydraulic power generation facility as a power generation facility and that does not have a power storage facility And
One distributed power source selected from the plurality of first type distributed power sources is the AC voltage source, and the remaining first type distributed power source and second type distributed power source are By the current control operation, the AC current source is connected and operated,
The current conversion operation of the power conversion device of the second type of distributed power supply is performed so as to follow the maximum power point of the power generation facility,
When it is determined that surplus power is generated, the surplus power is regenerated by the power conversion device of the first type distributed power source serving as the AC voltage source to charge the power storage facility. A method for operating a distributed power source. A power conversion device that converts direct current power into alternating current power, and among a plurality of distributed power sources separated from the power system,
Voltage-controlled operation of the power conversion device of one of the distributed power sources to make the one distributed power source an AC voltage source for independent operation,
The power converters of the remaining plurality of distributed power sources are each operated in a current controlled manner in synchronization with the output voltage of the AC voltage source, whereby the remaining plurality of distributed power sources are connected to each other as an AC current source. A method of operating a distributed power source,
As the plurality of distributed power sources, a plurality of first types of power supplies having a bidirectional conversion function for converting AC power into DC power and converting DC power into AC power and power storage equipment Using a distributed power source and one or more second type distributed power sources that include solar cells as power generation facilities and do not have power storage facilities,
One of the plurality of first-type distributed power supplies selected alternately at an appropriate time is used as the AC voltage source, and the remaining first-type distributed power supplies and the second A distributed power source of a kind is connected to the current controlled operation, and
The current conversion operation of the power conversion device of the second type of distributed power source so as to follow the maximum power point of the solar cell,
When it is determined that surplus power is generated, the surplus power is regenerated by the power conversion device of the first type distributed power source serving as the AC voltage source to charge the power storage facility. A method for operating a distributed power source. When the first type of distributed power supply used as the AC voltage source fails, the operation of the failed first type of distributed power supply is stopped,
6. The method of operating a distributed power supply according to claim 4 or 5, wherein the operation is continued by performing a switching operation using another one of the first type distributed power supplies as the AC voltage source. .   The said 1st type distributed power supply is equipped with the power generation equipment containing the natural energy utilization power generation equipment which generate | occur | produces using natural energy, such as a solar cell and a wind-hydraulic power generation equipment. Of operating distributed power supply.

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