JP2015107033A - Parallel-off control device, parallel-off control method and power conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a parallel-off control device capable of performing parallel-off of a distributed power source and a commercial power supply system during single operation without affecting detection of single operation in another distributed power supply system.SOLUTION: The parallel-off control device includes: a single operation determination part 27 for determining occurrence of single operation of a distributed power supply system 1 which is operated while being interconnected with a commercial power supply system 11; a phase detection part 26 for detecting a phase of an AC voltage of the commercial power supply system 11; a delay part 28 in which, when it is determined by the single operation determination part 27 that the single operation occurs, while defining the phase of the AC voltage at the time of the determination as a reference, a delay signal is generated that is delayed by a half cycle of the phase or more; and an instruction part 29 in which, when the delay signal is received, a parallel-off signal instructing the parallel-off of the commercial power supply system and the distributed power supply system is generated.

Description

  The present invention relates to a disconnection control device, a disconnection control method, and a power conditioner.

  2. Description of the Related Art A distributed power supply system that supplies electric power by distributing power generators (power supplies) that are relatively small compared to commercial power supplies near power consumers is known. There are cases where the power supply by the commercial power supply is stopped due to various causes such as construction and accidents. A state in which power is supplied from the distributed power supply system to the system load in a state where power supply by the commercial power supply is stopped (power failure state) is referred to as single operation. When the isolated operation occurs, the commercial power supply system that should be essentially non-voltage is charged, and there is a possibility that problems such as security will occur in the operation of the system. Accordingly, it is necessary to take measures such as detecting the isolated operation of the distributed power supply system and eliminating the isolated operation.

  As a method for detecting the isolated operation of the distributed power supply system, a passive method and an active method are known. The passive method is a method of monitoring a system voltage and detecting a change appearing during an independent operation in the case of a system power failure. In the active method, a disturbance signal (active signal) is applied from the side of the distributed power supply system in order to change the system voltage, and a frequency change that appears during an isolated operation in the case of a system power failure is detected.

  In addition, as a method of eliminating the isolated operation, an interconnection relay for paralleling or disconnecting the distributed power supply system and the commercial power supply system is provided. A method of disconnecting a system from a commercial power supply system is known. The interconnection relay is disclosed in Patent Document 1, for example.

JP 2009-44910 A

  In recent years, the spread of distributed power supply systems has progressed, and there are many cases where a plurality of distributed power supply systems are arranged in parallel in a relatively close region and range. Here, when a power failure occurs in the commercial power supply system, the following problems occur when the isolated operation is detected and the interconnection relay is shut off in each distributed power supply system.

  The plurality of neighboring distributed power systems are not necessarily synchronized, and the detection timing of the independent operation by the active method may be shifted between the plurality of distributed power systems. In this way, when the detection timing of isolated operation is shifted, if a distributed power supply system detects isolated operation before other systems and shuts off the interconnection relay, system fluctuations and signal Mutual interference can affect distributed systems that are still connected to the grid. For example, in a distributed system that is still connected to the grid, the frequency of the detected voltage may change, making it impossible to detect changes that appear during isolated operation. In this case, an isolated operation occurs in the distributed power supply system during a power failure.

  The present invention has been made in view of the above circumstances, and when isolated operation occurs, it does not affect the detection of isolated operation in other distributed power systems, and disconnects the distributed power system from the commercial power system. An object of the present invention is to provide a disconnection control device, a disconnection control method, and a power conditioner.

  In order to achieve the above object, the disconnection control device includes an isolated operation determination unit, a phase detection unit, a delay unit, and an instruction unit. The isolated operation determination unit determines whether or not an isolated operation of the distributed power supply system that operates in conjunction with the commercial power supply system is generated, and generates a determination signal when the isolated operation occurs. The phase detection unit converts an AC voltage of a commercial power supply or an AC voltage output from the distributed power supply system into a phase. When the delay unit receives the determination signal indicating that there is an isolated operation from the isolated operation determination unit, the delay unit is based on the phase information transmitted from the phase detection unit and performs delay processing (at least a half cycle or more based on the phase of the AC voltage at the determination time). After waiting), a delay signal is generated in the instruction unit. When the instruction unit receives the delay signal from the delay unit, the instruction unit generates a disconnection signal for disconnecting the distributed power supply system from the commercial power supply system.

  The disconnection control method includes an isolated operation determination step, a phase detection step, and a disconnection instruction step. In the isolated operation determination step, it is determined whether or not an isolated operation of the distributed power supply system that operates in conjunction with the commercial power supply system is generated. In the phase detection step, the phase of the AC voltage of the commercial power supply system is detected. In the disconnection instruction step, when it is determined in the isolated operation determination step that the isolated operation has occurred, the commercial power supply system and the distributed power supply system are used after a half cycle or more of the phase has elapsed with reference to the phase of the AC voltage at the time of the determination. Instructing the disconnection with.

  According to the disconnection control device, the disconnection control method, and the power conditioner described above, when it is determined that there is an isolated operation, the distributed power supply system and the distributed power supply system after at least half a cycle have elapsed with reference to the phase of the AC voltage at the time of determination The commercial power system is disconnected. Therefore, even if a plurality of distributed power supply systems are arranged in parallel and the timing of the isolated operation detection in each distributed power system is shifted, the actual disconnection is executed only in all the distributed power systems. After the determination. In other words, the disconnection operation executed by the distributed power supply system that has been preceded by the occurrence of isolated operation does not affect the isolated operation detection of other distributed power supply systems. Thereby, in all the distributed power supply systems arranged in parallel, the isolated operation detection and the disconnection can be reliably executed at the time of a power failure.

It is a conceptual diagram which shows a mode that the some distributed power supply system is connected to the commercial power supply system. It is a figure which shows the grid connection schematic structure of the distributed power supply system which concerns on this invention. It is a conceptual diagram which shows a mode that several power conditioners are connected to a commercial power supply system. It is a figure which shows the detection timing of the independent driving | operation in each power conditioner. It is a figure explaining the principle which the misdetection of a single operation generate | occur | produces. It is a figure which shows the grid connection schematic structure of the other distributed power supply system which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may differ from the actual ratios.

  FIG. 1 is a conceptual diagram showing a state in which a plurality of distributed power supply systems are connected to a commercial power supply system.

  FIG. 1 shows an example in which a distributed power supply system 1 is provided for each consumer. The distributed power supply system 1 according to the present embodiment is a system that can supply power from a power supply 10 to a load 12 in conjunction with a commercial power supply system 11. As shown in FIG. 1, a power source 10 and a power conditioner 13 are provided. In the distributed power system 1, a power conditioner 13 is connected between a power supply 10 and a commercial power supply system 11.

  The power supply 10 is a small-scale power generation device that is distributed in the vicinity of a power receiving facility of a person who uses the power supplied (hereinafter referred to as a “customer”). For example, the power supply 10 is a solar cell, a fuel cell, an engine generator, or a storage battery. In FIG. 1, the form which uses the solar cell connected to the solar panel as the power supply 10 is shown.

  The commercial power supply system 11 is a system that integrates power generation, power transformation, power transmission, and power distribution for supplying power to a power receiving facility of a consumer. That is, it is a system that supplies electric power from a power company to factories, ordinary homes, and the like.

  The load 12 is a device that consumes the electric power supplied from the commercial power supply system 11 to the power receiving facility of the customer.

  The power conditioner 13 converts power (DC power) generated by the power source 10 into power (AC power) that can be used by the commercial power system 11 and the load 12. The power conditioner 13 supplies insufficient power from the commercial power supply system 11 to the load 12 when the power generated by the power supply 10 is smaller than the demand power of the load 12. Conversely, in the case of a solar cell system, for example, if the power generated by the power supply 10 is larger than the demand power of the load 12, surplus power is supplied to the commercial power supply system 11.

  In general, when power transmission from a substation to a distribution line is stopped due to a ground fault or a short-circuit accident, a planned power outage, etc. in a distribution line of the commercial power system 11 (hereinafter referred to as “power failure”), work on the distribution line Safety must be ensured. Therefore, when the commercial power supply system 11 fails, the distributed power supply system 1 needs to be disconnected from at least the distribution line in operation and stop the power supply from the distributed power supply system 1. Therefore, the power conditioner 13 detects that the distributed power supply system 1 is operating alone (hereinafter referred to as “single operation”), that is, a power failure of the commercial power supply system 11 by a disconnection control device described later. The distributed power system 1 is disconnected from the commercial power system 11.

  The configuration of the power conditioner 13 will be described in more detail.

  FIG. 2 is a schematic configuration example of the distributed power supply system according to the first embodiment, and particularly shows a detailed configuration of the power conditioner 13.

  The power conditioner 13 includes an inverter unit 20, an interconnecting relay 21, a measurement unit 22, a current command value generation unit 23, a current control unit 24, a gate control unit 25, a phase detection unit 26, an isolated operation determination unit 27, a delay unit 28, And an instruction unit 29.

The inverter unit 20 is connected between the power supply 10 and the commercial power supply system 11, and has an inverter circuit that converts DC power output from the power supply 10 into AC power. The inverter circuit mainly includes a switching circuit (not shown), a frequency control circuit (not shown), and a filter circuit (not shown). The switching circuit includes a plurality of bridge-connected switching elements, and switches each switching element (ON / OFF) to convert DC power into AC power. An IGBT (Insulated Gate Bipolar Transistor) or the like is used as the switching element. However, the present invention is not limited to this, and a monopolar transistor such as an FET (Field Effect Transistor) or a bipolar transistor other than an IGBT may be used. The frequency control circuit controls the output current frequency of the power conditioner 13. The filter circuit blunts the current waveform converted to AC by the switching circuit into a curve close to the AC waveform of the commercial power supply system 11. Further, the inverter unit 20 has a DC / DC converter on the front stage side of the inverter circuit that generates a desired DC voltage (for example, 300 to 400 V) from the DC power output from the power supply 10 and supplies the DC voltage to the inverter circuit. It may be.

  The interconnection relay 21 is a switch that is connected between the inverter unit 20 and the commercial power supply system 11 and that causes the distributed power supply system 1 to be parallel or disconnected from the commercial power supply system 11.

  The measurement unit 22 measures at least the AC voltage output from the inverter unit 20. For example, the measurement unit 22 measures the AC voltage output from the inverter unit 20 using an AC voltmeter.

  The current command value generation unit 23 creates a sine wave synchronized with the AC voltage of the commercial power supply system 11 measured by the measurement unit 22, and adds a reactive current component based on an instruction from the isolated operation determination unit as necessary. Generate a value.

  The current control unit 24 controls the inverter unit 20 via the gate control unit 25 described later so that the alternating current output from the inverter unit 20 follows the current command value generated by the current command value generation unit 23.

  The gate control unit 25 outputs a control signal for turning on / off a switching element provided in the inverter unit 20 in order to convert a direct current into an alternating current. Specifically, the gate control unit 25 receives a disconnection signal generated by an instruction unit 29 described later, and turns off all switching elements for controlling the output of the inverter unit 20. The power supply from the power supply 10 to the outside of the distributed power supply system 1 can be stopped by turning off all switching elements for controlling the output of the inverter unit 20 (gate block).

  The phase detection unit 26 converts the AC voltage measured by the measurement unit 22 into a phase, and transmits phase information to a delay unit 28 described later. The phase detected here is governed by the AC voltage of the commercial power system 11 when the commercial power system 11 is normal, and the AC from the inverter unit 20 when the commercial power system 11 is out of power. Since it is dominated by voltage, for convenience of explanation, the AC voltage phase of the commercial power supply system 11 and the AC voltage phase of the inverter unit 20 may be treated synonymously.

  The isolated operation determination unit 27 monitors the measurement value by the measurement unit 22 to determine whether or not the isolated operation of the distributed power supply system 1 has occurred. If it is determined that an isolated operation has occurred, a determination signal is generated to notify that an isolated operation has occurred.

  The delay unit 28 is disposed between the isolated operation determination unit 27 and an instruction unit 29 described later. When the delay unit 28 receives a determination signal indicating that there is an isolated operation from the isolated operation determination unit 27, the delay unit 28 is based on the phase information transmitted from the phase detection unit 26 and is at least a half cycle or more based on the phase of the AC voltage at the determination time. After the delay process (standby), a delay signal is transmitted to the instruction unit 29 described later. For example, when the AC voltage is 50 Hz, since one cycle is 20 milliseconds, the delay unit 28 transmits a delay signal to the instruction unit 29 after 10 milliseconds or more have elapsed since the determination signal was received.

When the instruction unit 29 receives the delay signal from the delay unit 28, the instruction unit 29 transmits to the interconnection relay 21 a disconnection signal for disconnecting the interconnection relay in order to disconnect the distributed power supply system 1 from the commercial power supply system 11. Alternatively, when the instruction unit 29 receives the delay signal from the delay unit 28, the instruction unit 29 causes the gate control unit 25 to turn off all switching elements for controlling the output of the inverter unit 20 and stop the output of the inverter unit 20. A disconnect signal instructing execution of control is transmitted. The instruction unit 29 may transmit a disconnection signal to one or both of the interconnection relay 21 and the gate control unit 25.

  As shown in FIG. 6, the delay unit 28 may be a partial function of the instruction unit 29. Further, the disconnection signal may be a signal that the delay unit 28 determines a delay time based on the determination signal and the phase information, and is transmitted from the instruction unit 29 at the determined timing, or may be delayed by a hardware circuit. The determination signal subjected to the above may be used as a disconnection signal from the instruction unit 29.

  The disconnection control device includes at least a phase detection unit 26, an isolated operation determination unit 27, a delay unit 28, and an instruction unit 29. With respect to various value acquisition functions and control signals used for the operation of the disconnection control device, the disconnection control device may be provided, and the function provided in the power conditioner 13 on which the disconnection control device is mounted. You may also use it.

  According to the distributed power supply system 1 of the present embodiment, the following effects can be obtained.

  When the single operation determination unit 27 determines that the single operation of the distributed power supply system 1 has occurred, after at least a half cycle or more has elapsed from the phase of the AC voltage at the time of determination as a reference, the interconnection relay 21 and / or A disconnection signal for disconnecting the distributed power supply system 1 from the commercial power supply system 11 is transmitted to the gate control unit 25. As a result, even when the timing of the active isolated operation detection is shifted between the plurality of distributed power supply systems 1 as shown in FIG. Disconnection is executed after all the distributed power supply systems 1 have been determined to be isolated. In other words, since the disconnection operation executed by the distributed power supply system 1 that has been preceded by the occurrence of isolated operation does not affect the isolated operation detection of other distributed power supply systems 1, it is paralleled at the time of a power failure. In all of the distributed power supply systems 1 that are connected, it is possible to reliably detect the isolated operation and execute the disconnection from the commercial power supply system 11.

  Here, in order to clarify the effect of the present embodiment, the cause of the shift in the determination timing of the occurrence of isolated operation between the conventional distributed power systems will be described. Furthermore, the cause of erroneous detection occurring in isolated operation when the determination timing is shifted will be described.

  FIG. 3 is a conceptual diagram showing a state in which a plurality of power conditioners respectively provided in a plurality of distributed power systems are connected to a commercial power system. FIG. 4 shows the detection timing of isolated operation in each power conditioner. FIG. 5 is an explanatory diagram for explaining the principle of erroneous detection of isolated operation.

  As shown in the conceptual diagram of FIG. 3, it is assumed that four power conditioners 53 a to 53 d that operate the four power supplies 50 a to 50 d are connected to the commercial power supply system 11, respectively. Here, as shown by being surrounded by a dotted line in the figure, only the power conditioner 53b is connected to the commercial power supply system 11 with the U phase and the V phase being reversed with respect to the power conditioners 53a, 53c, 53d.

  In the power conditioners 53a to 53d, the measurement unit operates in synchronization with the frequency of the voltage on the commercial power supply system 11, so that only the power conditioner 53b has a measurement cycle shifted by a half cycle as shown in FIG.

When the measurement timing is shifted by a half cycle, for example, as shown in FIG. 5, the measurement of the AC voltage from the inverter unit 20 by the measurement unit 22 is performed only for the power conditioner 53b and for the half cycle earlier than the power conditioners 53a, 53c, and 53d. It will be.

  Here, as an example, in the distributed power supply system 1 in which reactive power is injected into the commercial power supply system 11 to determine whether or not a single operation occurs, the change rate of the measurement frequency by the measurement unit 22 exceeds a predetermined threshold value three times. A determination operation in a form in which it is determined that an isolated operation has occurred when continuously exceeding will be described. The predetermined threshold value may be common to all times, or a different threshold value may be set for each measurement time. For example, the threshold value can be gradually set larger as the first time, the second time, and the third time. Further, a change amount threshold value may be set instead of the change rate.

  When a power failure occurs, the rate of change of the frequency of the AC voltage measured by the measurement unit 22 (hereinafter referred to as “change rate”) increases. The power conditioner 53b measures the frequency at times t2, t4, t6, and t8, half a cycle earlier than the other power conditioners 53a, 53c, and 53d. When a power failure has occurred, as shown in FIG. 5, the rate of change does not exceed the threshold at time t2, and the rates of change C1, C2, and C3 at times t4, t6, and t8 exceed the threshold for three consecutive times. The power conditioner 53b of the prior art executes disconnection from the commercial power supply system 11 at time t8.

  The disconnection of the power conditioner 53b may affect the rate of change in other nearby distributed power systems. Specifically, at the time t9 after the time t8, the change rate C6 at the time t9 does not exceed the threshold value due to the influence of the disconnection of the power conditioner 53b, although it should originally exceed the threshold value. There is a case. As a result, the power conditioners 53a, 53c, and 53d do not exceed the threshold value for three consecutive times, and thus are not determined to be in isolated operation, and the isolated operation continues.

  On the other hand, according to the power conditioner 13 in the embodiment of the present invention, even if it is determined that there is an independent operation at the time t8 half a cycle earlier than the other power conditioners 53a, 53c, 53d, like the power conditioner 53b, The distributed power supply system 1 is disconnected from the commercial power supply system 11 after a period or more. Therefore, at time t9 in FIG. 5, the other power conditioners 53a, 53c, and 53d are not affected by the frequency due to the disconnection of the power conditioner 53b, and thus the rate of change exceeds the threshold value. As a result, all the power conditioners 13 are reliably determined as having an isolated operation, and the distributed power supply system 1 can be disconnected from the commercial power supply system 11.

  As mentioned above, although the said embodiment was described as an example of invention, this invention is not limited to the said embodiment. Various modifications are possible within the scope of the technical idea of the present invention.

  The present invention only needs to be able to absorb such a shift in the determination timing, and can be applied to cases where the determination timing is shifted for any reason other than when the three-phase connection is reversed. In any case, the determination timing of the occurrence of isolated operation does not deviate by more than one cycle between the plurality of distributed power supply systems 1, and for more certainty, the phase of the AC voltage at the determination time is used as a reference. The disconnection signal may be transmitted after one or more cycles have elapsed.

  Moreover, although the lower limit for delaying the disconnection instruction is a half cycle, the upper limit conforms to a standard determined by an agreement between electric utilities. For example, when the isolated operation period is defined as 0.2 seconds or less in the standard, the upper limit for delaying the instruction for disconnection is 0.2 seconds or less.

  The functional units 22 to 29 constituting the disconnection control device and the power conditioner 13 are realized by a CPU (not shown) reading out and executing it in a program memory installed in the storage. Further, the present invention is not limited to this, and hardware such as ASIC may be used.

  In the above description, it has been described that the occurrence of an isolated operation is determined by an active method, but the isolated operation determination unit 27 may include a function of determining the occurrence of an isolated operation by a passive method. A detailed description of the passive method is omitted.

1 Distributed power system,
10 power supply,
11 Commercial power system,
12 load,
13 Power conditioner,
20 Inverter part,
21 interconnected relay,
22 Measuring unit,
23 current command value generation unit,
24 current control unit,
25 Gate control unit,
26 phase detector,
27 Independent operation determination unit,
28 delay part,
29 Instruction unit.

Claims (9)

An isolated operation determination unit that determines the occurrence of isolated operation of a distributed power system that operates in conjunction with a commercial power supply system and generates a determination signal when an isolated operation occurs,
A phase detector for detecting the phase of the AC voltage of the commercial power supply system or the phase of the AC voltage output by the distributed power system;
When receiving the determination signal from the isolated operation determination unit, a delay unit that generates a delay signal delayed by a half cycle or more of the phase with reference to the phase of the AC voltage at the time of the reception,
When the delay signal is received, an instruction unit that generates a disconnection signal that instructs disconnection between the commercial power supply system and the distributed power supply system;
A disconnection control device comprising:   2. The disconnection control device according to claim 1, wherein the disconnection signal is a signal for instructing disconnection to a connection relay for paralleling or disconnecting the commercial power supply system and the distributed power supply system.   The disconnection signal is supplied to a gate control unit that controls an output of the inverter unit by operating a switching element included in an inverter unit that converts DC power from a power source included in the distributed power system into AC power. The disconnection control device according to claim 1, wherein the signal is an instruction to execute gate control to turn off the inverter and stop the output of the inverter. An isolated operation determination step for determining the occurrence of isolated operation of the distributed power supply system operating in conjunction with the commercial power supply system;
A phase detection step for detecting the phase of the AC voltage of the commercial power supply system;
When it is determined in the isolated operation determination step that the isolated operation has occurred, the commercial power supply system and the distributed power supply system after the elapse of a half cycle or more of the phase with reference to the phase of the AC voltage at the time of the determination A sequence instruction step for instructing the sequence with
A disconnection control method.   5. The disconnection control method according to claim 4, wherein in the instructing step, a disconnection signal for instructing disconnection is transmitted to an interconnection relay for paralleling or disconnecting the commercial power supply system and the power supply.   6. The disconnection control method according to claim 4, wherein in the instruction step, the disconnection signal is transmitted to a gate control unit that controls an inverter that converts a current from a power source included in the distributed power supply system. An isolated operation determination unit that determines the occurrence of isolated operation of a distributed power system that operates in conjunction with a commercial power supply system;
A phase detector for detecting the phase of the AC voltage of the commercial power supply system or the phase of the AC voltage output by the distributed power system;
An interconnected relay for paralleling or disconnecting the commercial power system and the distributed power system;
An inverter unit that has a switching element and converts DC power from a power source included in the distributed power system into AC power;
A gate control unit for controlling an output of the inverter unit by operating a switching element of the inverter unit;
When the single operation determination unit determines that there is an occurrence of single operation, with reference to the phase of the AC voltage at the time of the determination, a delay unit that generates a delay signal delayed by a half cycle or more of the phase;
When the delay signal is received, an instruction unit that transmits a disconnection signal that instructs disconnection between the commercial power system and the distributed power system;
Power conditioner with   The power conditioner according to claim 7, wherein the disconnection signal is a signal that instructs the interconnection relay to cut off the interconnection.   9. The power according to claim 7, wherein the disconnection signal is a signal that instructs the gate control unit to execute gate control that turns off a switching element of the inverter unit and stops output from the inverter unit. conditioner.