JP6082689B2 - Isolated operation detection device and isolated operation detection method - Google Patents

Description

  The present invention relates to an isolated operation detection device and an isolated operation detection method.

  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 a commercial power supply near a consumer is known. Commercial power may be stopped due to various causes such as construction or accidents. A state where electric power is supplied from the distributed power supply system to the system load when the commercial power supply is stopped (power failure state) is referred to as an independent operation. When an isolated operation occurs, a system that should originally be 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.

  There are a passive method and an active method as a method for detecting the isolated operation of the distributed power supply system. The passive method is a method of monitoring a system voltage and detecting a change appearing during a single operation in the case of a system power failure. In the active method, a disturbance signal (active signal) is applied in order to change the system voltage from the distributed power supply system side, and a change that appears during an independent operation in the case of a system power failure is detected. In addition, there are many patent documents of isolated operation detection (for example, patent document 1).

JP 2010-074943 A

  A typical example of the active method is a frequency shift method. In this method, the output frequency is shifted in a period lower than the period of the fundamental wave of the system, and if there is a change in the system frequency, the shift direction is fixed. .If it lasts for 5 seconds, the gate block and the interconnection relay will be disconnected.

  Another representative example of the active method is a reactive power fluctuation method. In this method, the reactive power is changed at a period lower than the fundamental wave of the system, and if the system frequency change of a predetermined value or more continues for a predetermined time or more, it is determined as an independent operation, and the gate block and the interconnection relay are disconnected. It is.

  Another example of the active method is a slip mode frequency shift method. In this method, by giving a characteristic that shifts the frequency of the output current according to the frequency change from the rated frequency, the frequency is changed by positively feeding back the minute frequency change that occurs even when active and reactive power are balanced, When a predetermined frequency is reached, it is determined that the operation is independent, and the gate block and the interconnection relay are disconnected.

  However, in these systems, even if an active signal is applied, when the generated power of the power source provided in the distributed power system and the load power are equal and no current is flowing in the system, the frequency does not change, so the isolated operation is detected. May not be possible. On the other hand, when there is no frequency change and a change in voltage or harmonic is detected, reactive power is injected to generate a frequency change. If no is detected, this is also not possible, and there is a possibility that isolated operation cannot be detected.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an isolated operation detection device and an isolated operation detection method that can reliably detect an isolated operation.

  An isolated operation detection device for achieving the above object is an isolated operation determination device for a distributed power system including an inverter unit that converts direct current to alternating current and outputs the alternating current, and is specific to a fundamental alternating current of a specific frequency. A current command generation unit that generates a current command for causing the inverter unit to output an alternating current on which harmonic AC of a dimension is superimposed, and an invalidity command that generates a reactive current addition command for adding a reactive current to the alternating current An AC voltage output from the inverter unit according to at least the current command among the current command generated by the current command generation unit and the current command generated by the current command generation unit and the reactive current command generated by the reactive current addition command generation unit And the distributed power supply system according to whether or not the voltage measured by the measurement unit includes harmonic alternating current exceeding a reference amount. When the possibility of isolated operation is tentatively determined and the possibility of isolated operation is determined in the tentative determination, it is determined whether or not the frequency of the voltage has changed beyond a reference amount. A single operation determination unit that makes a main determination of the single operation.

  In addition, an islanding operation determination method for achieving the above object is an islanding operation determination method used for a distributed power system including an inverter unit that converts a direct current into an alternating current and outputs the alternating current. A second stage for generating a harmonic alternating current of a specific dimension, a third stage for superimposing the harmonic alternating current of the specific dimension on the fundamental alternating current of the specific frequency, and the specific A fourth stage of outputting an alternating current obtained by superimposing the harmonic alternating current of the specific dimension on a fundamental alternating current of a frequency of 5% from the inverter unit, and a fifth stage of measuring an alternating voltage output from the inverter unit, A sixth stage for tentatively determining the possibility of isolated operation of the distributed power supply system based on whether or not the harmonic voltage exceeding a reference amount is included in the voltage measured in the fifth stage; When the temporary judgment of the floor is considered to be a single operation, the inverter unit outputs a reactive current to the AC current and outputs it from the inverter unit, and the inverter unit outputs the seventh step. An eighth stage of measuring an AC voltage, and a ninth stage of main determination of the isolated operation of the distributed power source system based on whether or not the frequency of the voltage measured in the eighth stage has changed beyond a reference amount And having.

  According to the present invention, harmonics are superimposed on the output current of the distributed power source, and the single operation is detected by the two-stage determination of temporary determination and main determination. Therefore, reactive power can be appropriately injected according to changes in harmonics, and single operation of the distributed power supply system can be reliably detected.

1 is a diagram illustrating a schematic configuration example of a distributed power supply system according to an embodiment. It is a flowchart which shows the procedure of an independent driving | operation detection process. It is a wave form diagram for demonstrating the superimposition method of a harmonic. It is a figure for demonstrating the method of temporary determination. It is a wave form diagram of an alternating voltage when a commercial power supply system is operating normally. It is a wave form diagram of an alternating voltage when a commercial power system has a power failure. It is a figure for demonstrating the method of this determination. It is a waveform diagram of an alternating voltage when a reactive current is injected when a commercial power supply system is operating normally. It is a wave form diagram of an alternating voltage at the time of injecting a reactive current when the commercial power supply system has a power failure. It is a figure for demonstrating the modification of the method of temporary determination.

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 be different from the actual ratios.

  FIG. 1 is a diagram illustrating a schematic configuration example of a distributed power supply system according to the present embodiment.

  Hereinafter, a schematic configuration of the distributed power supply system will be described with reference to FIG.

<Distributed power supply system>
The distributed power supply system according to the present embodiment is a system that can supply the power of the power supply 10 to the load 12 in conjunction with the commercial power supply system 11. The distributed power supply system includes a power supply 10 and a power conditioner 13. A power conditioner 13 is connected between the power supply 10 and the 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 receives and uses power (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.

  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, a short-circuit accident, a planned power failure, or the like (hereinafter referred to as “power failure”) in the distribution line of the commercial power supply system 11, Work safety must be ensured. For this reason, when the commercial power supply system 11 has a power failure, the distributed power supply system needs to be disconnected from at least the working distribution line and stop the power supply from the distributed power supply system. Therefore, the power conditioner 13 detects that the distributed power supply system is operating independently (hereinafter referred to as “single operation”), that is, a power failure of the commercial power supply system 11, and detects the power supply system 11 as a commercial power supply system 11. It is decided to disconnect from.

  In order to realize the above functions, the power conditioner 13 includes an inverter unit 20, an interconnection relay 21, a measurement unit 22, an isolated operation determination unit 23, a harmonic determination unit 24, as shown in FIG. A current command generation unit 25, a reactive current addition command generation unit 26, and a gate control unit 27 are provided.

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 (on, off) each switching element 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. 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. Also good.

  The waveform of the alternating current and the alternating voltage output from the inverter unit 20 is converted into a fundamental wave of a sine wave (hereinafter referred to as “fundamental wave alternating current”) having a predetermined fundamental frequency (for example, 50 Hz or 60 Hz). It becomes a waveform in which harmonics having a frequency that is an integral multiple of alternating current (hereinafter referred to as “harmonic alternating current”) are superimposed. In addition, a reactive current may be injected into the alternating current output from the inverter unit 20. Here, the reactive current refers to a current component that becomes invalid due to a phase shift between the AC voltage output from the inverter unit 20 and the AC current.

  The interconnecting relay 21 is a switch that is connected between the inverter unit 20 and the commercial power supply system 11 and causes the distributed power supply system 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. Moreover, the measurement part 22 calculates | requires statistical data, such as an average value for a predetermined period, about the frequency of an alternating voltage from the measured value.

  The isolated operation determination unit 23 monitors the measurement value by the measurement unit 22 and determines the occurrence of isolated operation of the distributed power supply system.

  (A) Specifically, the isolated operation determination unit 23 can perform the isolated operation of the distributed power supply system depending on whether or not the AC voltage measured by the measurement unit 22 includes harmonic AC exceeding the reference amount. Temporarily determine sex.

  (A1) When the commercial power supply system 11 is operating normally, even if an alternating current on which harmonic alternating current is superimposed is output from the inverter unit 20, it is affected by the commercial power supply system 11 and its harmonic components. Will be countered. Therefore, the AC voltage measured by the measurement unit 22 does not include harmonic AC exceeding the reference amount. At this time, the isolated operation determination unit 23 determines that there is no possibility that the distributed power supply system is operating independently.

  (A2) On the other hand, when the commercial power supply system 11 has a power failure, when an alternating current on which harmonic alternating current is superimposed is output from the inverter unit 20, the AC voltage measured by the measuring unit 22 includes a reference amount. More than harmonic harmonics are included. At this time, the isolated operation determination unit 23 determines that there is a possibility that the distributed power supply system is operating independently.

  (B) When the isolated operation determination unit 23 determines that there is a possibility that the distributed power supply system is operating independently (temporary determination), a reactive current is injected into the alternating current output from the inverter unit 20. . At this time, the isolated operation determination unit 23 makes a main determination on the isolated operation of the distributed power supply system based on whether or not the frequency of the AC voltage measured by the measurement unit 22 has changed beyond the reference amount.

(B1) When the commercial power supply system 11 is operating normally, even if a reactive current is injected into the alternating current output from the inverter unit 20, the measurement is performed by the measurement unit 22 under the influence of the commercial power supply system 11. Almost no change in frequency occurs in the AC voltage. At this time, the isolated operation determination unit 23 determines that the distributed power supply system is not operated independently.

  (B2) On the other hand, when the commercial power system 11 has a power failure, the alternating current output from the inverter unit 20 is not affected by the commercial power system 11. For this reason, the AC current output from the inverter unit 20 is not adjusted to have the same phase by the commercial power supply system 11, and when measured by the measurement unit 22, the frequency may change. As described above, when a change in frequency occurs in the AC voltage measured by the measurement unit 22, a further reactive current is injected into the AC current output from the inverter unit 20 based on the change amount (may be a change rate). The Therefore, when the reactive current injection is continued, the change (change amount, change rate, etc.) of the frequency of the alternating voltage measured by the measurement unit 22 is expanded. At this time, the isolated operation determination unit 23 determines that the isolated operation of the distributed power supply system is occurring when the frequency of the AC voltage measured by the measurement unit 22 changes beyond the reference amount.

  Further, when the isolated operation determination unit 23 determines that the distributed power system is operating independently, the connected relay 21 causes the connected relay 21 to disconnect the distributed power system from the commercial power system 11. A control signal for turning off 21 is transmitted. Alternatively, a control signal is transmitted to the gate control unit 27 to instruct execution of gate control for turning off all switching elements for controlling the output of the inverter unit 20 and stopping the output of the inverter unit 20. The isolated operation determination unit 23 may transmit a control signal to one or both of the interconnection relay 21 and the gate control unit 27.

  The harmonic determination unit 24 determines the type and amount of harmonic alternating current included in the alternating current output from the inverter unit 20 based on the value measured by the measurement unit 22 and the output power. Examples of the type of harmonic alternating current include single Nth order harmonic alternating current (N is a natural number), or harmonic alternating current in which a plurality of different dimensions of harmonic alternating current are arbitrarily combined. Moreover, the harmonic alternating current which has a specific distortion factor may be sufficient.

  The current command generation unit 25 generates a current command for causing the inverter unit 20 to output a fundamental alternating current (sine wave) having a specific fundamental frequency (for example, 50 Hz or 60 Hz).

  In addition, the current command generation unit 25 superimposes a harmonic alternating current (a harmonic alternating current of a specific dimension) having a frequency that is an integral multiple of the fundamental alternating current on the fundamental alternating current (which may be injected with a reactive current). A current command for causing the inverter unit 20 to output the AC current thus generated is generated. Specifically, the current command generation unit 25 generates a current command value obtained by adding a current value corresponding to at least one harmonic AC to a current value corresponding to the fundamental AC.

  The reactive current addition command generation unit 26 adds a reactive current to the alternating current output from the inverter unit 20 when the isolated operation determination unit 23 determines that there is a possibility that the distributed power system is operating independently. A reactive current addition command for generating the Specifically, the reactive current addition command generation unit 26 is a current command value (reactive current addition command) obtained by shifting the phase of the AC current output from the inverter unit 20 with respect to the AC voltage measured by the measurement unit 22. It is. Then, the current command value is transmitted to the gate control unit 27. At this time, the amount by which the phase is shifted is determined according to the frequency deviation of the AC voltage measured by the measuring unit 22.

  The reactive current addition command generation unit 26 does not generate a reactive current addition command when the isolated operation determination unit 23 determines that there is no possibility that the distributed power system is operating independently. At this time, the reactive current addition command generation unit 26 may transmit the current command (current command value) generated by the current command generation unit 25 to the gate control unit 27 as it is.

  The gate control unit 27 controls the operation of the inverter unit 20 using the current command generated by the reactive current addition command generation unit 26. Specifically, the gate control unit 27 controls on / off of each switching element in the inverter unit 20. If it is determined that there is no possibility of independent operation, the current command value generated by the current command generator 25 and the current command value generated by the reactive current addition command generator 25 are the same value.

  At least some of the functions of the functional units 22 to 27 described above are realized by a CPU (not shown) reading out a program installed in a storage (not shown) to a memory (not shown) and executing it. The Further, the present invention is not limited to this, and hardware such as ASIC may be used. With respect to various value acquisition functions and control signals used for the operation of the isolated operation detection device, the isolated operation detection device may be provided, and the function provided in the power conditioner 13 in which the isolated operation detection device is mounted. You may also use it.

  Detailed operation of the distributed power supply system will be described in detail below.

<Operation of distributed power supply system>
FIG. 2 is a flowchart showing a procedure of the isolated operation detection process. FIG. 3 is a waveform diagram for explaining a method of superimposing harmonic alternating current. FIG. 4 is a diagram for explaining a provisional determination method. FIG. 5A is a waveform diagram of an AC voltage when the commercial power supply system is operating normally. FIG. 5B is a waveform diagram of an AC voltage when the commercial power supply system has a power failure. FIG. 6 is a diagram for explaining the method of this determination. FIG. 7A is a waveform diagram of an AC voltage when a reactive current is injected when the commercial power supply system is operating normally. FIG. 7B is a waveform diagram of an AC voltage when a reactive current is injected when the commercial power supply system has a power failure.

  Hereinafter, the procedure of the isolated operation detection process will be described with reference to FIGS.

(Single operation detection process)
When the AC power is output from the power conditioner 13, the power conditioner 13 starts the isolated operation detection process shown in FIG. However, the timing for starting the isolated operation detection process is not limited to this.

[Step S101]
When the isolated operation detection process is started, the current command generator 25 generates a fundamental alternating current having a specific frequency (for example, a fundamental frequency of 50 Hz or 60 Hz). Specifically, the current command generator 25 generates a current value for causing the waveform of the alternating current output from the inverter unit 20 to be a fundamental alternating current as shown in FIG.

[Step S102]
Subsequently, the current command generation unit 25 generates a harmonic alternating current (a harmonic alternating current of a specific dimension) having a frequency that is an integer multiple of the fundamental alternating current generated in step S101. Specifically, the current command generation unit 25 generates a current value for making the waveform of the alternating current output from the inverter unit 20 an Nth order harmonic alternating current (N is a natural number). Note that the Nth order harmonic alternating current (N is a natural number) includes a third order harmonic alternating current having a frequency three times that of the fundamental wave alternating current and a fifth order having a frequency five times that of the fundamental wave alternating current as shown in FIG. At least one odd harmonic alternating current such as a harmonic alternating current and a seventh harmonic alternating current having a frequency seven times that of the fundamental alternating current is included. When the applied harmonics are even harmonics, multiple distributed power supply systems are connected in parallel, and if some of them include a distributed power supply system in which wiring is reversely connected, harmonics are canceled out. May end up. Therefore, by including at least one kind of odd harmonic alternating current, harmonics can be reliably detected even when a plurality of units are reversely connected.

  The amount and type of the harmonic alternating current generated in the current command generation unit 25 is determined by the harmonic determination unit 24. Specifically, the output power of the inverter unit 20 is determined so as to include a predetermined amount of harmonic alternating current. For example, it may include harmonic alternating current at a predetermined rate or a proportion proportional to the output power. If a certain amount of harmonic alternating current is superimposed regardless of the output power, the amount of harmonics may become excessive or small due to fluctuations in the output power, but harmonic alternating current should be superimposed at a suitable ratio according to the output power. Thus, the possibility of independent operation can be provisionally determined more stably. For example, the order of the harmonic alternating current is determined according to the measurement value of the measurement unit 22 and the output power. When a plurality of harmonic alternating currents having different orders are combined, the combination is determined. Further, the distortion rate of harmonic alternating current may be determined.

[Step S103]
The current command generator 25 superimposes the harmonic alternating current generated in step S102 on the fundamental alternating current generated in step S101. Specifically, the current command generation unit 25 generates a current command (current command value) by adding a current value corresponding to harmonic AC to a current value corresponding to fundamental AC. Thereby, for example, as shown in FIG. 3, a superimposed waveform alternating current in which the third harmonic alternating current, the fifth harmonic alternating current, and the seventh harmonic alternating current are superimposed on the fundamental alternating current is generated.

  Then, the current command generation unit 25 transmits the current command (current command value) generated in step S103 to the reactive current addition command generation unit 26. At this time, a signal indicating that there is no possibility that the distributed power supply system is operating independently is supplied to the reactive current addition command generating unit 26 from the isolated operation determining unit 23. Therefore, the reactive current addition command generation unit 26 transmits the current command (current command value) transmitted from the current command generation unit 25 to the gate control unit 27 without generating the reactive current addition command.

[Step S104]
The gate control unit 27 causes the inverter unit 20 to output an alternating current corresponding to the superimposed waveform alternating current generated in step S103. Specifically, the gate control unit 27 controls each switching element in the inverter unit 20 using the current command (current command value) transmitted from the reactive current addition command generation unit 26.

[Step S105]
The measurement unit 22 measures at least the AC voltage output from the inverter unit 20. Specifically, the measurement unit 22 measures the AC voltage output from the inverter unit 20 using a predetermined AC voltmeter.

[Step S106]
The isolated operation determination unit 23 temporarily determines the possibility of isolated operation of the distributed power supply system based on whether or not the alternating current voltage measured in step S105 includes harmonic alternating current exceeding the reference amount.

  A specific provisional determination method in step S106 is as follows.

  First, the isolated operation determination unit 23 is between any m cycles including the latest cycle of the AC voltage measured by the measurement unit 22 (m ≧ 2) and between any n cycles not including the latest cycle among the m cycles. (N and m are natural numbers, and an average harmonic voltage effective value at n <m) is obtained. Therefore, in the example shown in FIG. 4 (m = 6, n = 3), the average harmonic voltage effective value X in the three periods from N4 to N2 is obtained. In the case of n = 1, the harmonic voltage effective value X in one period is obtained instead of the average.

  Next, the isolated operation determination unit 23 calculates the harmonic voltage effective value Y in each period other than the n period during the m period. Therefore, in the example shown in FIG. 4, the harmonic voltage effective value during each period of N5, N1, and N0 is obtained.

  Thereafter, the isolated operation determination unit 23 obtains a difference (XY) between both obtained values, and if the obtained difference (XY) is outside a predetermined reference value, sets the reference amount to the AC voltage. It is determined that there is no higher harmonic AC included, and it is determined that there is a possibility of isolated operation of the distributed power system. At this time, the isolated operation determination unit 23 supplies a signal indicating that the distributed power supply system may be operated independently to the reactive current addition command generation unit 26.

  On the other hand, if the obtained difference (X−Y) does not deviate from the reference value, the isolated operation determination unit 23 regards that the AC voltage does not include harmonic AC exceeding the reference amount, and It is determined that there is no possibility of isolated operation. At this time, the isolated operation determination unit 23 supplies a signal indicating that there is no possibility that the distributed power system is operating independently to the reactive current addition command generation unit 26.

  If the isolated operation determination unit 23 determines that there is a possibility of isolated operation of the distributed power supply system (step S106: YES), the process proceeds to step S107. On the other hand, if the isolated operation determination unit 23 determines that there is no possibility of isolated operation of the distributed power supply system (step S106: NO), the process returns to step S101.

  When the commercial power supply system 11 is operating normally, as shown in FIG. 5A, the AC voltage has a waveform that does not include harmonic AC exceeding the reference amount. On the other hand, when the commercial power supply system 11 has a power failure, as shown in FIG. 5B, the AC voltage has a waveform including harmonic AC exceeding the reference amount.

[Step S107]
The reactive current addition command generation unit 26 is an invalid injection injected into the alternating current output from the inverter unit 20 in order to confirm whether or not the determination that the distributed power supply system may be operating independently in step S106 is correct. Calculate the current. Specifically, the reactive current addition command generation unit 26 determines the reactive current to be injected according to the change (change amount, change rate, etc.) of the frequency of the AC voltage measured by the measurement unit 22. For example, the amount of change (rate of change) between the latest frequency (average value for a predetermined period) of the AC voltage obtained in the measuring unit 22 and the frequency (average value for the predetermined period) of the AC voltage obtained before that. It is calculated so that the reactive current to be injected increases as the value increases.

  Then, the reactive current addition command generation unit 26 transmits a current command (reactive current addition command) including the reactive current determined by the calculation to the gate control unit 27.

[Step S108]
The gate control unit 27 injects a reactive current into the alternating current output from the inverter unit 20. Specifically, the gate control unit 27 controls each switching element in the inverter unit 20 using the current command generated by the current command generation unit 25 and the reactive current addition command generated by the reactive current addition command generation unit 26. To do.

[Step S109]
The measurement unit 22 measures at least the AC voltage output from the inverter unit 20. Specifically, the measurement unit 22 measures the AC voltage output from the inverter unit 20 using a predetermined AC voltmeter.

[Step S110]
Thereafter, the isolated operation determination unit 23 makes a final determination (main determination) as to whether or not the distributed power supply system is operating independently.

  The specific method of this determination in step S110 is, for example, as follows.

  First, the isolated operation determination unit 23 obtains the average frequency (r is a natural number) of the AC voltage during an arbitrary r cycle including the latest cycle of the AC voltage measured by the measurement unit 22. Therefore, in the example shown in FIG. 6 (r = 4), the average frequency P of the AC voltage during four periods from N3 to N0 is obtained. In addition, when r = 1, the frequency P of the AC voltage in one period is obtained instead of the average.

  Next, the isolated operation determination unit 23 obtains the average frequency (s is a natural number) of the AC voltage during an arbitrary s period that does not include the latest period. Therefore, in the example shown in FIG. 6 (s = 3), the average frequency Q of the AC voltage during three periods from N4 to N2 is obtained. In the case of s = 1, the frequency Q of the AC voltage in one cycle is obtained instead of the average.

  Thereafter, the isolated operation determination unit 23 obtains a difference (PQ) between both obtained values, and if the obtained difference (PQ) deviates from a predetermined reference value, the frequency of the AC voltage is the reference. It is determined that the distributed power system is operating independently, assuming that the amount has changed over the quantity.

  On the other hand, if the obtained difference (PQ) does not deviate from the reference value, the isolated operation determination unit 23 assumes that the frequency of the AC voltage has not changed beyond the reference amount, and the distributed power supply system It is determined that the vehicle is not operating alone.

  If the isolated operation determination unit 23 determines that the distributed power supply system is operating independently (step S110: YES), the process proceeds to step S111. On the other hand, when the isolated operation determination unit 23 determines that the distributed power supply system is not operating independently (step S110: NO), the operation returns to step S101.

  When the reactive current is injected when the commercial power supply system 11 is operating normally, as shown in FIG. 7A, the change in the frequency of the AC voltage does not expand beyond the reference amount, and the distributed power supply The system is considered not operating alone. On the other hand, when the reactive current is injected when the commercial power supply system 11 has a power failure, as shown in FIG. 7B, the change in the frequency of the AC voltage expands beyond the reference amount, and the distributed power system alone Driving is considered to have occurred.

[Step S111]
When it is determined in step S110 that the distributed power supply system is operating independently, the isolated operation determination unit 23 transmits a control signal for turning off the interconnection relay 21, and the distributed power supply system is disconnected from the commercial power supply system 11. To line up. In addition, you may transmit to the gate control part 27 the control signal which instruct | indicates execution of the gate control which turns off all the switching elements for controlling the output of the inverter part 20, and stops the output of the inverter part 20. The isolated operation determination unit 23 may transmit a control signal to one or both of the interconnection relay 21 and the gate control unit 27.

  Thereafter, the power conditioner 13 ends the isolated operation detection process.

By executing the above isolated operation detection process in the power conditioner 13, harmonic alternating current is superimposed on the output power of the power supply 10 (alternating current output from the inverter unit 20). Therefore, it becomes easy to detect the change in the harmonic alternating current superimposed on the output current in the power conditioner 13, and the reactive current can be appropriately injected according to the change in the harmonic alternating current. Furthermore, the single operation of the distributed power supply system can be reliably detected by the two-stage determination of the temporary determination and the main determination.

  Each processing unit in the above-described flowchart is divided according to main processing contents in order to facilitate understanding of the power conditioner 13. The invention of the present application is not limited by the method of classification of the processing steps and the names thereof. The processing performed in the power conditioner 13 can be divided into more processing steps. One processing step may execute more processes.

<Modification>
In addition, said embodiment intends to illustrate the summary of this invention, and does not limit this invention. Many alternatives, modifications, and variations will be apparent to those skilled in the art.

  For example, in the above embodiment, the current command generator 25 generates a current command value by adding a current value corresponding to a harmonic AC to a predetermined fundamental wave AC current value, thereby generating a fundamental AC current. Is superimposed with harmonic AC. However, the present invention is not limited to this, and the current command generation unit 25 may generate a current command value that uses a sine wave on which a harmonic alternating current is superimposed in advance as a fundamental alternating current. According to this method, the process of superimposing the harmonic alternating current on the fundamental alternating current is omitted, and the load on the power conditioner 13 is reduced.

  Moreover, the method of temporary determination by the independent operation determination unit 23 is not limited to the above method, and may be performed by the method described below.

  FIG. 8 is a diagram for explaining a modification of the provisional determination method.

  First, the isolated operation determination unit 23 includes the oldest cycle among the m ′ cycles in any m ′ cycle including the latest cycle of the AC voltage measured by the measurement unit 22 (m ′ ≧ 2), and Then, an average harmonic voltage effective value in an arbitrary n ′ period not including the latest period (n ′ and m ′ are natural numbers and n ′ <m ′) is obtained. Therefore, in the example shown in FIG. 8 (m ′ = 6, n ′ = 3), the average harmonic voltage effective value X ′ during three periods from N5 to N3 is obtained. In the case of n ′ = 1, the harmonic voltage effective value X ′ for one period is obtained instead of the average.

  Next, the isolated operation determination unit 23 obtains the harmonic voltage effective value Y ′ in each period other than the n ′ period during the m ′ period. Therefore, in the example shown in FIG. 8, the harmonic voltage effective value during each period of N2, N1, and N0 is obtained.

  Thereafter, the isolated operation determination unit 23 obtains a difference (X′−Y ′) between both obtained values, and if the obtained difference (X′−Y ′) deviates from a predetermined reference value, the AC voltage Therefore, it is determined that there is a possibility of isolated operation of the distributed power supply system.

  On the other hand, if the obtained difference (X′−Y ′) does not deviate from the reference value, the isolated operation determination unit 23 considers that the AC voltage does not include higher harmonic AC exceeding the reference amount, and the distributed power source Determine that there is no possibility of system independent operation.

  In the modified example, the above provisional determination is executed instead of the process of step S106.

  The above-described configuration of the distributed power supply system has been described with reference to the main configuration in describing the features of the above-described embodiments and modifications, and is not limited to the above-described configuration. In addition, the configuration of a general distributed power supply system is not excluded.

  Further, each functional configuration of the power conditioner 13 described above is classified according to main processing contents in order to facilitate understanding of each functional configuration. The present invention is not limited by the way of classification and names of the constituent elements. Each functional configuration can be classified into more components according to the processing content. Moreover, it can also classify | categorize so that one component may perform more processes.

  The processing of each functional configuration of the power conditioner 13 described above can also be realized by a dedicated hardware circuit. In this case, it may be executed by one hardware or a plurality of hardware.

  The program for operating the power conditioner 13 may be provided by a computer-readable recording medium such as a USB memory, a flexible disk, or a CD-ROM, or may be provided online via a network such as the Internet. . In this case, the program recorded on the computer-readable recording medium is usually transferred to and stored in a memory or storage. Further, this program may be provided as, for example, a single application software, or may be incorporated in the software of each device as one function of the power conditioner 13.

10 power supply,
11 Commercial power system,
12 load,
13 Power conditioner,
20 Inverter part,
21 interconnected relay,
22 Measuring unit,
23 islanding determination unit,
24 harmonic determination unit,
25 current command generator,
26 reactive current addition command generator,
27 Gate controller.

Claims (13)

An independent operation determination device for a distributed power supply system including an inverter unit that converts direct current into alternating current and outputs it,
A current command generation unit that generates a current command for causing the inverter unit to output an alternating current obtained by superimposing a harmonic alternating current of a specific dimension on a fundamental alternating current of a specific frequency;
A reactive current addition command generating unit for generating a reactive current addition command for adding a reactive current to the alternating current; and
A measuring unit that measures an AC voltage output from the inverter unit according to at least the current command among the current command generated by the current command generation unit and the reactive current addition command generated by the reactive current addition command generation unit;
While the voltage measured by the measurement unit includes a harmonic alternating current exceeding a reference amount, the possibility of isolated operation of the distributed power system is provisionally determined, and the possibility of isolated operation is determined by the provisional determination. When it is determined that there is an isolated operation determination unit that determines whether or not the distributed operation of the distributed power system is independent depending on whether the frequency of the voltage has changed beyond a reference amount,
A harmonic determination unit that determines the type of harmonic alternating current to be superimposed on the fundamental alternating current of the specific frequency in the current command generation unit;
I have a,
The harmonic determination unit is an isolated operation determination device that determines the amount of harmonic alternating current according to output power . The reactive current addition command generator is
When it is determined that there is no possibility of isolated operation of the distributed power system in the temporary determination by the isolated operation determination unit, the reactive current addition command is not generated, and there is a possibility of isolated operation in the temporary determination. The isolated operation determination device according to claim 1, wherein the reactive current addition command is sometimes generated. A gate control unit that controls the operation of the inverter unit using at least the current command among the current command generated by the current command generation unit and the reactive current addition command generated by the reactive current addition command generation unit;
A power source is connected to the DC side of the inverter unit, and a commercial power system is connected to the AC side of the inverter unit via a connection relay.
The islanding determination unit
When the single operation of the distributed power system is determined, a gate block command is output to the gate control unit to stop the operation of the inverter unit, and an open command is output to the interconnection relay to output the inverter unit. The isolated operation determination device according to claim 1 or 2, wherein the AC side of the power source and the commercial power supply system are disconnected. The provisional determination by the isolated operation determination unit is
Between any m periods including the latest period of the voltage measured by the measurement unit (m ≧ 2), between any n periods not including the latest period among the m periods (n and m are natural numbers, and n The difference between the harmonic voltage effective value or the average harmonic voltage effective value in <m) and the harmonic voltage effective value in each period other than the n period during the m periods deviates from a predetermined reference value. Depending on whether or not
If the difference deviates from the reference value, it is considered that the voltage includes harmonic alternating current exceeding a reference amount, and it is determined that there is a possibility of independent operation of the distributed power system.
If the difference does not deviate from the reference value, it is considered that the harmonic AC exceeding the reference amount is not included in the voltage, and it is determined that there is no possibility of independent operation of the distributed power supply system. The isolated operation determination device according to any one of 3. This determination by the isolated operation determination unit is
The frequency or average frequency of the voltage in an arbitrary r cycle including the latest cycle of the voltage measured by the measurement unit (r is a natural number), and the frequency or average of the voltage in an arbitrary s cycle not including the latest cycle Depending on whether the difference between the frequency and (s is a natural number) deviates from a predetermined reference value,
If the difference is outside the reference value, it is determined that the frequency of the voltage has changed beyond a reference amount, and it is determined that the distributed power supply system is operating alone,
5. If the difference does not deviate from the reference value, it is considered that the frequency of the voltage has not changed beyond a reference amount, and it is determined that the distributed power supply system is not operating independently. The isolated operation determination device according to any one of the above. Before SL harmonic determining unit, as the type of harmonic AC, N harmonic AC alone (N is a natural number), or to determine the harmonic alternating current in any combination of several different dimensions harmonics alternating current, The isolated operation determination device according to any one of claims 1 to 5 , wherein the determined type of harmonic alternating current is output to the current command generation unit. The harmonic alternating current, characterized in that it comprises at least one odd harmonic AC, isolated operation determination apparatus according to claim 1. A single operation determination method used in a distributed power supply system including an inverter unit that converts direct current into alternating current and outputs it,
A first stage for generating a fundamental alternating current of a specific frequency;
A second stage that generates harmonic alternating current of a particular dimension;
A third step of superimposing the harmonic alternating current of the specific dimension on the fundamental alternating current of the specific frequency;
A fourth stage in which an alternating current obtained by superimposing the harmonic alternating current of the specific dimension on the fundamental alternating current of the specific frequency is output from the inverter unit;
A fifth step of measuring the alternating voltage output by the inverter unit;
A sixth stage that tentatively determines the possibility of single operation of the distributed power supply system based on whether or not a harmonic alternating current exceeding a reference amount is included in the voltage measured in the fifth stage;
A seventh stage in which a reactive current is added to the alternating current and output from the inverter unit when there is a possibility of isolated operation in the provisional determination of the sixth stage;
An eighth stage of measuring the AC voltage output from the inverter unit in the seventh stage;
A ninth stage for determining whether or not the distributed power system is operated independently depending on whether the frequency of the voltage measured in the eighth stage has changed beyond a reference amount;
An eleventh step of determining a type of harmonic alternating current to be superimposed on the fundamental alternating current of the specific frequency in the second step;
I have a,
The eleventh stage is an isolated operation determination method for determining the amount of harmonic alternating current according to the output power . A power source is connected to the DC side of the inverter unit, and a commercial power system is connected to the AC side of the inverter unit via a connection relay.
When it is determined in the ninth stage that the distributed power system is operating independently, the operation of the inverter unit is stopped and the interconnection relay is opened to connect the AC side of the inverter unit and the commercial The tenth stage of disconnecting the power supply system,
The isolated operation determination method according to claim 8 , further comprising: The provisional determination of the sixth stage is
Between any m periods including the latest period of the voltage measured in the fifth stage (m ≧ 2), between any n periods not including the latest period among the m periods (n and m are natural numbers, and , N <m), the difference between the harmonic voltage effective value or the average harmonic voltage effective value and the harmonic voltage effective value in each period other than the n period during the m periods is a predetermined reference value. Depending on whether or not
If the difference deviates from the reference value, it is considered that the voltage includes harmonic alternating current exceeding a reference amount, and it is determined that there is a possibility of independent operation of the distributed power system.
If the difference is not out of the reference value, it is considered that does not contain the harmonic alternating current exceeds the reference amount of the voltage, the distributed power supply system alone and there is no possibility of the operation judges claim 8 or The islanding operation determination method according to 9 . The main determination in the ninth stage is as follows.
The frequency or average frequency of the voltage in an arbitrary r cycle including the latest cycle of the voltage measured in the eighth stage (r is a natural number), and the frequency of the voltage in an arbitrary s cycle not including the latest cycle Alternatively, the difference between the average frequency and (s is a natural number) is determined based on whether or not a predetermined reference value is exceeded.
If the difference is outside the reference value, it is determined that the frequency of the voltage has changed beyond a reference amount, and it is determined that the distributed power supply system is operating alone,
If the difference is not out of the reference value, is regarded as the frequency of the voltage does not change by more than the reference amount, the distributed power supply system itself not driving the determining claims 8 to 10 The isolated operation determination method according to any one of the above. Claim before Symbol eleventh step, as the type of harmonic AC, N harmonic AC alone (N is a natural number), or, to determine the harmonic alternating current in any combination of several different dimensions of the harmonic AC The isolated operation determination method according to any one of 8 to 11 . 9. The islanding operation determination method according to claim 8 , wherein in the eleventh stage, at least one odd harmonic alternating current is determined as the type of harmonic alternating current.