JP2011055678A - Method for detecting islanding, controller, device for detecting islanding, and distributed power system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly detect islanding at reactive-power balance. <P>SOLUTION: A method for detecting islanding includes:determining, when additional injection reactive power of a predetermined phase is injected additionally for a fixed period when an immediate injection reactive power is balanced with a load reactive power, the phase of the immediate injection reactive power on the basis of the sign of a system frequency deviation after a period shorter than the fixed period passes after the injection of an additional reactive power;injecting, when the phase of the immediate injection reactive power from the sign of the system frequency deviation at the time of the decision is in antiphase with the predetermined phase of the additional injection reactive power, the additional injection reactive power of the phase corresponding to the sign of the system frequency deviation for the fixed period again;and continuing, when the phase of the immediate injection reactive power from the sign of the system frequency deviation at the time of the deviation is in phase with the predetermined phase of the additional injection reactive power, the injection of the additional injection reactive power by the same phase for the period left until the fixed period elapses after the injection of the additional injection reactive power. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an isolated operation detection method for detecting whether or not a distributed power source is disconnected from a power system and operated independently, a control device for detecting an isolated operation of a distributed power source, an isolated operation detection device, and a distributed power system. .

  Independent operation is a state in which a distributed power source supplies power to a local system load when the power system is stopped due to an accident or other circumstances. A distributed power source can generate power by installing a power source at or near a demand location. There are various types of distributed power sources such as an engine generator, a turbine generator, a power storage device, and a fuel cell that are linked to a power system. In addition, in order to use such a distributed power supply in conjunction with system power, many power conditioners that adapt the frequency and voltage to the power system have been proposed.

  A distributed power source that feeds loads such as home appliances by connecting a distributed power source facility including the distributed power source described above and a power conditioner that converts the output of the distributed power source into alternating current with a commercial power system The system is implemented. In this distributed power system, in order to ensure the safety of maintenance work for the commercial power system, the operation of the power conditioner on the distributed power facility side should be stopped immediately in the event of an unexpected power outage and work outage of the commercial power system. Alternatively, it is essential to have a function of disconnecting the distributed power source from the commercial power system by operating the switch immediately to release the interconnection and preventing the distributed power source from operating independently.

  FIG. 14 shows an image diagram of a multi-unit interconnection of distributed power sources. The independent operation detection time of the inverter is 0.5 to 1.0 seconds in the active method. This is a characteristic that assumes (i) isolated operation in units of houses, and there was no problem at the stage of the spread of distributed power sources in small quantities. Recently, however, distributed power sources are in the period of widespread use, and a multi-unit interconnection as shown in FIG. 14 is being implemented. In this case, there is a possibility of independent operation in units of (ii) pole transformers, (iii) units of section switches, and (iv) units of circuit breakers. When these high-pressure systems are included, it is necessary to detect an isolated operation assuming a high-low pressure mixed accident.

  One of the methods for detecting such an isolated operation is that a reactive power is injected into the power system, and when the isolated operation occurs, a power fluctuation is caused by the injected reactive power, and this power fluctuation is detected, and a distributed power source is detected. An electric power fluctuation method for detecting a single operation of the vehicle has already been proposed. However, in the isolated operation detection method in which reactive power is injected into the power system, the isolated operation may continue even though reactive power is injected from the isolated operation detection device.

  As a result of earnest research on the cause of the continuation of the above-mentioned isolated operation, the applicant has balanced the injected reactive power and the load reactive power. As a result, it has become possible to investigate that the isolated operation state is continued without detecting the isolated operation.

  Therefore, the present applicant has already inadvertently injected into the power system when the reactive power injection from the isolated operation detection device and the reactive load of the load are balanced and injection of reactive power for isolated operation detection is insufficient when the isolated operation occurs. Research progressed on an isolated operation detection method that can detect isolated operation by enabling additional injection of reactive power (additionally injected reactive power) to reactive power being injected (existing injected reactive power) . Then, the present applicant has filed an application that includes a technique relating to additional injection reactive power in which the phase is set by changing the sign of the system frequency deviation, for example, the already injected reactive power (see, for example, Patent Document 1). ).

  FIG. 15 is a diagram showing reactive power injected into the power system for the isolated operation detection proposed in Patent Document 1 (the already injected reactive power). The horizontal axis represents the system frequency deviation Δf, and the vertical axis represents Indicates the reactive power amount Q.

  As shown in FIG. 15, reactive power is injected according to the system frequency deviation Δf. When the system frequency deviation Δf is positive, the phase advance reactive power is used. When the system frequency deviation Δf is negative, The reactive power with phase lag is injected respectively.

  In the above-mentioned Patent Document 1, when reactive power (existing injected reactive power) and load reactive power in FIG. 15 are balanced and reactive power injection for isolated operation is insufficient, additional reactive power (additional injection invalid power) is further reduced. Additional injection of power). At this time, the phase advance / delay of the pre-injection reactive power and the phase advance / delay of the additional injection reactive power are matched so that the pre-injection reactive power and the additional injection reactive power are not offset. That is, as shown in FIG. 16, the additional injection reactive power additionally injects phase advance reactive power when the system frequency deviation Δf is positive, and phase delay reactive power when the system frequency deviation Δf is negative. I am doing so.

JP2009-11037A

  In Patent Document 1, since the phase advance / delay of already injected reactive power is matched with the phase advance / delay of additional injected reactive power, the reactive power is not offset by one single operation detection device. As shown in P1 of FIG. 17 (a), since there are variations in frequency measurement in a plurality of isolated operation detection devices, for example, 2 isolated operation detection devices, when the system frequency deviation is near “0”. In addition, one isolated operation detection device additionally injects phase-advanced reactive power, and the other isolated operation detection device additionally injects phase-added reactive power as indicated by P2 in FIG. The injected reactive power is canceled out and power fluctuation cannot be caused, and as a result, the isolated operation state may be continued without being detected as an isolated operation.

  Therefore, the problem to be solved by the present invention is that the reactive power injected into the power system is prevented from being canceled, and even if the reactive power and the load reactive power are balanced, the balance state is broken and the independent operation is ensured. The purpose is to enable detection.

(1) The isolated operation detection method according to the present invention injects reactive power into the power system and detects whether the distributed power source is disconnected from the power system and is operating independently. In the isolated operation detection method that detects the isolated operation based on the electrical fluctuation that occurs,
Reactive power (pre-injected reactive power) is injected into the power system based on electrical fluctuations and the reactive power having a predetermined phase is applied to the power system when the already injected reactive power is balanced with the load reactive power. A first step of additionally injecting (additional injection reactive power) for a certain period;
A second step of determining a sign of the electrical variation after a period shorter than the predetermined period has elapsed since the additional reactive power injection in the first step;
From the sign of the electrical fluctuation at the time of the determination, when it is determined that the phase of the already injected reactive power is opposite to the predetermined phase of the additional injected reactive power injected in the first step A third step of injecting the additional injection reactive power of the phase corresponding to the sign of the electrical variation again for the predetermined period;
From the sign of the electrical fluctuation at the time of the determination, when it is determined that the phase of the already injected reactive power is the same as the predetermined phase of the additional injected reactive power injected in the first step, A fourth step of continuing the injection of the additional injection reactive power in the same phase as the additional injection reactive power injected in the first step for the remaining period after the additional injection reactive power injection in one step until a certain period of time elapses;
It is characterized by including.

  The predetermined phase is preferably an advance phase or a delay phase.

  According to the present invention, in the first step, reactive power (pre-injected reactive power) is injected into the power system based on electrical fluctuations in the first step, and when the already-injected reactive power balances with the load reactive power, Predetermined phase, for example, lagging phase reactive power (additional injection reactive power) is additionally injected for a certain period, so that a plurality of isolated operation detection devices additionally inject lagging phase reactive power. Thus, the reactive power is not canceled out among a plurality of single operation detection devices.

  In the second step, the electrical fluctuation sign is determined after a period shorter than the predetermined period. In the third step, as a result of the determination, the electrical fluctuation sign at the time of determination is already injected. When it is determined that the phase of the reactive power is opposite to the phase of the additional injection reactive power injected in the first step, the additional injection reactive power having the phase corresponding to the sign of the electrical fluctuation is changed again. Since the injection is performed for a certain period, the additional injection reactive power does not have to be canceled out by the already injected reactive power, and it becomes possible to detect the isolated operation by breaking the reactive power balance with the additional injection reactive power.

  In the fourth step, the phase of the already injected reactive power is the same as the phase of the additional injected reactive power of the predetermined phase injected in the first step from the sign of the electrical fluctuation at the time of the determination. In the case of the determination, the injection of the additional injection reactive power is continued in the same phase as the additional injection reactive power injected in the first step for the remaining period after the additional injection reactive power injection in the first step until a certain period elapses. Therefore, in this case, it becomes possible to detect the isolated operation by breaking the reactive power balance with the additional injection reactive power.

  In the present invention, a preferred aspect is that the electrical variation is a system frequency deviation, and the phase advance / delay determination of the reactive power is performed based on the sign of the system frequency deviation.

  In a preferred aspect of the present invention, the electrical fluctuation is a system frequency fluctuation, a system voltage fluctuation, or a harmonic fluctuation.

  In a further preferred aspect of the present invention, the certain period is a period that is three times the system period, and a period shorter than the certain period is a period that is twice the system period.

  (2) A control device according to the present invention is a control device that controls a detection operation of an isolated operation detection device that detects whether or not a distributed power source is disconnected from an electric power system and is operating alone. It is possible to carry out the method (1).

  (3) The isolated operation detection device according to the present invention is the isolated operation detection device that injects reactive power into the power system for detecting whether the distributed power source is disconnected from the power system and is operating independently. It is characterized by including the control device described in 1.

  (4) A distributed power supply system according to the present invention is a distributed power supply system including a distributed power supply and an isolated operation detection device that detects whether or not the distributed power supply is disconnected from the power system and is operated independently. The islanding operation detection device is the islanding operation detection device described in (3) above.

  The isolated operation detection device according to the present invention is not limited to the name, and includes a case where it is referred to as a power conditioner or other names.

  According to the present invention, it is possible to reliably detect a single operation of a distributed power source even when reactive power is balanced.

FIG. 1 is a diagram showing a configuration of a distributed power supply system to which an isolated operation detection method according to an embodiment of the present invention is applied. FIG. 2 is a functional block diagram of the control device of FIG. FIG. 3 is a diagram for explaining the calculation of the period deviation. FIG. 4 is a diagram illustrating the relationship between the period deviation and the reactive power amount. FIG. 5 is a diagram showing the configuration of another distributed power supply system to which the isolated operation detection method according to the embodiment of the present invention is applied. FIG. 6 is a diagram used for explaining the system voltage and harmonic distortion voltage of each system period and the average value of the system voltage and harmonic distortion voltage for three periods. FIG. 7A is a diagram used to explain whether or not the system frequency change satisfies the determination conditions (a1) and (a2) when the system voltage and the harmonic distortion voltage suddenly change to the rising side, and FIG. FIG. 6 is a diagram used for explaining whether or not the system frequency change satisfies the determination conditions (a1) and (a2) when the system voltage and the harmonic distortion voltage change suddenly to the lower side. FIG. 8A is a diagram used for explaining whether or not the system voltage change satisfies the determination condition (b1) when the system voltage suddenly changes to the rising side, and FIG. 8B shows the system voltage suddenly changing to the decreasing side. FIG. 8C is a diagram used for explaining whether or not the system voltage change satisfies the determination condition (b1), and FIG. 8C shows the harmonic distortion voltage change when the harmonic distortion voltage suddenly changes to the rising side. FIG. 8D is a diagram used for explaining whether or not (b2) is satisfied. FIG. 8D is whether or not the harmonic distortion voltage change when the harmonic distortion voltage suddenly changes to the lower side satisfies the determination condition (b2). It is a figure used for description. 9A is a diagram used for explaining reactive power injection when the system voltage and the harmonic distortion voltage suddenly change to the rising side, and FIG. 9A is a case where the system voltage and the harmonic distortion voltage suddenly change to the decreasing side. It is a figure used for description of no reactive power injection. FIG. 10 is a diagram for explaining a predetermined phase of reactive power injection. FIG. 11 is a flowchart used for explaining the isolated operation detection method according to the embodiment. FIG. 12 is a diagram used for explaining the phase control of the additional injection reactive power when the system frequency deviation continues to be positive. FIG. 13 is a diagram used for explaining the phase control of the additional injection reactive power when the system frequency deviation changes from plus to minus. FIG. 14 is an image diagram of a multi-unit interconnection of distributed power sources. FIG. 15 is a diagram for explaining already injected reactive power. FIG. 16 is a diagram for explaining additional injection reactive power. FIG. 17 is a diagram for explaining offset of the additional injection reactive power.

  Hereinafter, an isolated operation detection method according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a schematic configuration of a distributed power supply system including an isolated operation detection device that detects an isolated operation by the isolated operation detection method of the embodiment. In the embodiment, a description will be given using a total harmonic distortion voltage or a harmonic distortion voltage as a harmonic, but the present invention is not limited to this.

  A distributed power system 10 shown in FIG. 1 generates DC power, for example, a distributed power source 12 such as a solar power generator or a gas engine generator, and a power system 14 connected to the distributed power source 12. A power conditioner 16 disposed between the distributed power source 12 and the power system 14 and having a power conversion function, and a power conditioner 16 disposed between the power conditioner 16 and the power system 14. The power conditioner 16 converts the DC power generated by the distributed power source 12 into the AC power of the power system 14 through the power conversion function, and the converted AC current. Electric power is supplied to loads outside the figure such as general household appliances.

  The isolated operation detection device 18 includes interconnection relays 20 and 22, a control device 24, an inverter control unit 26, an inverter 28, and a current detector 30.

  The control device 24 is connected to the power system line 32 through the input lines P, L, and M, and measures the system voltage, the harmonic distortion voltage, and the system frequency of the power system 14. By outputting the isolated operation detection output to the relays 20 and 22, the interconnection relays 20 and 22 are turned off, and a current control command value for injecting injection reactive power through the output line Q is output to the inverter control unit 26. It has become.

  The control device 24 calculates a system frequency deviation within a predetermined system cycle from the measured system frequency, calculates a reactive power to be injected into the power system based on the calculated system frequency deviation, While power is being injected into the power system, the system frequency deviation continues from the measured system frequency, system voltage, and harmonic distortion voltage for a predetermined number of system cycles continuously. It is determined whether or not the condition that the system voltage and the harmonic distortion voltage have suddenly changed with a change exceeding the predetermined voltage fluctuation range is satisfied, and whether or not the above condition has been satisfied, the above injection is already performed. In addition to the reactive power that is being used, additional reactive power is injected.

  The control device 24 may be constituted by a microcomputer. For example, when the control device 24 is configured by a microcomputer, the control device 24 includes a CPU, a memory, an interface, and the like. The memory stores a control program for carrying out the isolated operation detection method of the embodiment. The CPU executes various calculations based on the system voltage, system current, system power, etc. input through the interface, and opens / closes the interconnection relays 20 and 22 through the interface from the execution result. An independent operation detection output that is a command is output, and current control command values that are various commands to the inverter control unit 26 are output.

  In the embodiment, for understanding of the explanation, a microcomputer is built in the control device 24, and functions described below are executed by a control program of the microcomputer. FIG. 2 shows the functional configuration of the microcomputer.

  The function of the control device 24 will be described in detail with reference to FIG. FIG. 2 is a block diagram for understanding the function of the control device 24, and this block configuration does not exist as hardware in the microcomputer. Of course, since it can be configured as hardware, the embodiment is not limited to any of them.

  The control device 24 measures the system voltage measurement unit 34a that measures the voltage of the system power input from the power system line 32 through the input line L1, and the harmonic distortion voltage of the system power input from the power system line 32 through the input line L2. The isolated harmonic determination is performed from the measured value of the system frequency measuring unit 36, the system frequency measuring unit 36b for measuring the system frequency of the system power input from the power system line 32 through the input line M, and the harmonic distortion measuring unit 34b. According to the determination, the isolated operation determination unit 38 that outputs the isolated operation detection output for turning on / off the interconnection relays 20 and 22 to the output line P, the moving average value of the current system frequency from the measured value of the system frequency measuring unit 36, and the past And a system frequency deviation calculating unit 40 for calculating a system frequency deviation from the calculated value and calculating a moving average value of the system frequency of the system frequency, And a reactive power calculation unit 42 for calculating the amount of reactive power to be injected from the grid frequency deviation of the difference computation unit 40 to the power grid.

  The control device 24 continues the state in which the system frequency deviation is continuously below a predetermined number of system cycles, the system frequency is not substantially changed, and the system voltage is within a predetermined voltage range set in advance. A first reactive power injection determining unit 44a that performs control to determine that the system voltage has suddenly changed due to the occurrence of isolated operation and to inject additional reactive power.

  Further, the control device 24 continues the state in which the system frequency deviation is continuously below a predetermined number of system cycles, the system frequency does not change substantially, and the harmonic distortion voltage is set in a predetermined voltage range set in advance. A second reactive power injection determining unit 44b that performs control to additionally inject reactive power when the harmonic distortion voltage suddenly changes due to the occurrence of isolated operation when it changes along the inside.

  Further, the control device 24 ORs the OR outputs of the determination outputs of the first and second reactive power injection determining units 44a and 44b, the calculated reactive power from the reactive power amount calculating unit 42, and the first output from the OR gate 45. 1 and an addition unit 46 for adding the additional reactive power from the second reactive power injection determination units 44a and 44b, and an output current control signal is output to the inverter control unit 26 through the output line Q in accordance with the output of the addition unit 46. An output current control unit 48.

  The system frequency deviation calculating unit 40 includes a current moving average calculating unit 40a that calculates a moving average value of a current system frequency, a past moving average calculating unit 40b that calculates a moving average value of a past system frequency, and both of these calculated values. And a calculation unit 40c for calculating the system frequency deviation.

  The system frequency measuring unit 36 sequentially measures the system frequency of the power system from the system voltage in a measurement cycle unit, for example, 5 msec unit. When the system frequency of the power system is 50 Hz (one system period is 20 milliseconds), the system period unit is desirably 1/3 or less of the system period of the power system, for example, 5 milliseconds unit.

  In the system frequency deviation calculation unit 40, based on the system period in units of 5 milliseconds sequentially measured by the system frequency measurement unit 36, the moving average value of the system period for a continuous predetermined moving average time, for example, 40 milliseconds is sequentially calculated. Is. The predetermined moving average time is preferably set to, for example, 40 milliseconds because it is longer than one cycle of the system period, for example, 20 milliseconds, and is as short as possible for a desired detection speed, for example, 100 milliseconds. .

  In the present embodiment, a reactive power injection phase re-determination unit 51 is provided in addition to the above configuration. In this reactive power injection phase re-determination unit 51, the system frequency deviation from the system frequency deviation calculating unit 40 and the OR gate 45 output for ORing the determination outputs of the first and second reactive power injection determining units 44a and 44b, Based on the above, the following determination operation is performed, and the determination result is fed back to the reactive power injection determination units 44a and 44b. Then, the reactive power injection determination units 44a and 44b control reactive power injection control as described later with reference to FIGS. 11 to 13 in accordance with the re-determination result of the reactive power injection phase re-determination unit 51. ing.

  FIG. 3 is an operation explanatory diagram related to the system frequency measuring unit 36 and the system frequency deviation calculating unit 40, where C0 is a system period currently measured by the system frequency measuring unit 36, C1 is a system period measured 5 ms before, Cn Indicates the measured value of the system cycle n * 5 ms before. Therefore, the system frequency deviation calculation unit 40 sequentially calculates the latest moving average value in units of 5 milliseconds by moving average the system period for 40 milliseconds of C0-C7.

  The past moving average value is calculated by moving average the system cycle for 40 ms of C40-C47 200 ms before C0 and sequentially calculating in 5 ms units when the latest moving average value of C0-C7 is used. is there. The current system frequency deviation is calculated by the past moving average value (C40-C47) -the latest moving average value (C0-C7).

  The reactive power amount calculation unit 42 uses the characteristic of the reactive power amount versus the system frequency deviation of FIG. 4 corresponding to FIG. 15 described above, and based on the system frequency deviation calculated by the system frequency deviation calculation unit 42 The amount is calculated, and this reactive power amount is notified to the output current control unit 48 via the addition unit 46. The reactive power amount vs. system frequency deviation characteristic shown in FIG. 4 is such that when the system frequency deviation is small, the change rate of the reactive power amount with respect to the change of the system frequency deviation is reduced, that is, the slope of the characteristic line L1 is reduced to increase the isolated operation detection sensitivity. When the system frequency deviation is large, the low sensitivity band range R1, which is the range to be lowered, increases the rate of change of the reactive power amount with respect to the change of the system frequency deviation, that is, increases the slope of the characteristic line L1 to increase the isolated operation detection sensitivity. Sensitive band ranges R21 and R22, which are ranges, are set.

  The reactive power amount is decreased in the high frequency range R21, the reactive power amount is increased in the high frequency range R22, and the change rate of the reactive power with respect to the system frequency deviation is set small in the low frequency range R1. To do. That is, reactive power can be injected even in the low-risk range R1 where the system frequency deviation is small to detect the isolated operation of the distributed power source 12, and the change rate of the reactive power amount can be set to the high-sensitive range R21, R21, By making it smaller than in the case of R22, it is possible to reliably prevent the influence of the distributed power source 12 on the power system 14 without being affected by the slow fluctuation of the system voltage.

  The distributed power supply system described above is the same as the system shown in FIG. In this system, an independent operation detection device is built in the power conditioner 16. Parts corresponding to those in FIG. 1 are denoted by the same reference numerals.

  In the embodiment, one independent operation detection system in which the system voltage measurement unit 34a and the first reactive power injection determination unit 44a inject reactive power into the power system as one electrical variation indicating the system voltage variation in the single operation state. Configure. In addition, the harmonic distortion measurement unit 34b and the second reactive power injection determination unit 44b inject reactive power into the power system as one electrical variation indicating the harmonic distortion voltage variation (harmonic variation) in the single operation state. One isolated operation detection system is configured. And, in these plurality of isolated operation detection systems, reactive power is injected into the power system from the isolated operation detection system side that previously performed the isolated operation detection based on the electrical fluctuation. . It should be noted that this isolated operation detection system is an example in the embodiment, and may be another isolated operation detection system. Of course, the number of isolated operation detection systems may be three or more.

  This will be described below. In the description, both independent operation detection systems will be described together in order to avoid duplication of description.

  As shown in FIG. 6, the system voltage measurement unit 34a and the harmonic distortion measurement unit 34b measure M0 with the system voltage N0 and the total harmonic distortion voltage for each system period N0. In FIG. 6, “T0”, “T1”, “T2”,..., “T13” are system cycles, and “N0”, “N1”, “N2”, “N3”, “N4”, “N5”; “M0”, “M1”, “M2”, “M3”, “M4”, and “M5” are the system voltage and the total harmonic distortion voltage in each system cycle. N0 and M0 are the system voltage and total harmonic distortion voltage at the current system period T0, N1 and M1 are the system voltage and total harmonic distortion voltage at the system period T1,..., N5 and M5 are systems at the system period T5. Voltage and total harmonic distortion voltage. In the embodiment, Navr and Mavr are the average values of the system voltage and the total harmonic distortion voltage of a total of 3 system cycles from the system cycle T3 of 3 system cycles before the current system cycle T0 to the system cycle T5 of 5 system cycles before. . Of course, the average values Navr and Mavr of the system voltage and the total harmonic distortion voltage are not limited to the three system periods of the embodiment, and can be determined as appropriate.

Total harmonic distortion voltage is THD, second harmonic distortion voltage is V ₂ , third harmonic distortion voltage is V ₃ , fourth harmonic distortion voltage is V ₄ , fifth harmonic distortion voltage is V ₅ , sixth order Assuming that the harmonic distortion voltage is V ₆ and the seventh harmonic distortion voltage is V ₇ , the total harmonic distortion voltage squares the respective harmonic distortion voltages V ₂ to V ₇ ,
It is given as

THD = √ (V ₂ ) ² + (V ₃ ) ² + (V ₄ ) ² + (V ₅ ) ² + (V ₆ ) ² + (V ₇ ) ²
However, the total harmonic distortion voltage of the above equation is given by the above equation from the second to seventh harmonic distortion voltages, but does not exclude higher harmonic voltages.

  The harmonic distortion measurement unit 34b measures the total harmonic distortion voltage. However, for example, the third-order harmonic distortion voltage V3 may be measured, or another order harmonic distortion voltage may be measured. Good.

  In that sense, in the following description, it is not referred to as a total harmonic distortion voltage, but simply described as a harmonic distortion voltage.

  Further, in the embodiment, the single operation detection is performed with the total harmonic voltage or the second or higher harmonic distortion voltage, but the total harmonic distortion current, the total harmonic distortion power, or the second or higher harmonic distortion current, Second-order or higher harmonic distortion power may be used.

  In the first reactive power injection determination unit 44a, the measured value of the system voltage from the system voltage measuring unit 34a, the measured value of the system frequency from the system frequency measuring unit 36, and the system frequency deviation from the system frequency deviation calculating unit 40 From these, as a condition (a1), a state in which the system frequency deviation is continuously within a certain range for a predetermined number of system cycles continues and there is no substantial change in the system frequency, and the condition ( Whether or not the above two conditions (a1) and (b1), that is, whether the system voltage has changed within a predetermined voltage fluctuation range set in advance, is determined as b1).

  In the second reactive power injection determining unit 44b, the measured value of the harmonic distortion from the harmonic distortion measuring unit 34b, the measured value of the system frequency from the system frequency measuring unit 36, and the system from the system frequency deviation calculating unit 40 The frequency deviation is input, and from these, as a condition (a2), a state in which the system frequency deviation is continuously within a certain range for a predetermined number of system cycles continues and there is no substantial change in the system frequency, and It is determined whether or not the above two conditions (a2) and (b2), that is, whether the harmonic distortion voltage has changed within a preset voltage range as the condition (b2).

  This determination is divided into the system voltage and the harmonic distortion voltage in the rising and falling directions, and FIGS. 7 (a), 7 (b), 8 (a), (b), (c), (d), and FIGS. ) Will be described.

  7 (a) and 7 (b) are the determination conditions (a1) and (a2), FIGS. 8 (a) and 8 (b) are the determination conditions (b1), FIGS. 8 (c) and 8 (d) are the determination conditions (b2), and FIG. (A) and (b) are the reactive power injection states from the first and second reactive power injection determination units 44a and 44b when the determination conditions (a1) (b1) or (a2) (b2) are both satisfied, Indicates.

  FIGS. 7 (a), 8 (a), 8 (c), and 9 (a) are respectively shown in FIGS. 7 (b), 8 (b), and 9 (a) when the system voltage suddenly changes in the upward direction. 8 (d) and FIG. 9 (b) show cases where the system voltage suddenly changes in the downward direction.

  Regarding determination conditions (a1) and (a2), T0, T1, T2, T3, T4, and T5 in the horizontal direction in FIGS. 7A and 7B are the system cycle described above, and the vertical axis is the system frequency deviation. The dotted line f1 has a system frequency deviation of 0.5 Hz from the deviation 0 Hz to the plus (+) side, and f2 has a system frequency deviation of 0.5 Hz from the deviation 0 Hz to the minus (−) side. If the system frequency deviation is within a certain range of ± 0.5 Hz (deviation range ΔT = 1.0 Hz) for a predetermined number of system cycles, in the embodiment, for example, continuously for 6 system cycles, the system frequency is substantially reduced. Judge that there is no change. Of course, in the above determination, the number of system cycles in which the system frequency deviation continues continuously within the certain range is not limited to 6 system cycles, and may be at least 2 system cycles.

  As shown in FIG. 7A, when the system voltage and the harmonic distortion voltage change suddenly in the increasing direction, the system frequency deviation is from the system cycle T1 to the plus (+) side from the deviation 0 Hz, and is shown in FIG. 7B. Thus, when the system voltage and the harmonic distortion voltage change suddenly in the downward direction, the system frequency deviation is from the system cycle T1 to the minus (−) side from the deviation 0 Hz. In addition, in order to calculate a system | strain frequency deviation for every system | strain period, the system | strain frequency deviation between a system | strain period and a system | strain period changes digitally. In the embodiment, the system frequency deviation calculation unit 40 calculates the system frequency deviation for each system period, but the present invention is not limited to this.

  In FIGS. 7A and 7B, for the sake of understanding, it is assumed that the system frequency deviation is continuously within the predetermined range from the current system period T0 for the past three system periods or more, and the system frequency is not substantially changed. a2) is shown in an established state.

  Next, the determination conditions (b1) and (b2) will be described with reference to FIGS.

  8A and 8B, the horizontal axis represents the system cycle, the vertical axis represents the system voltage (V), FIGS. 8C and 8D, the horizontal axis represents the system period, and the vertical axis represents the harmonic distortion voltage (V). is there. Solid lines (Nave) and (Mave) indicate the average value Navr of the system voltage and the average value Mavr of the harmonic distortion voltage in the three system periods T3, T4, and T5 from the current system period T0 to 3 periods before and 5 periods before, respectively. Is a line. N0, N1, N2, N3, N4, and N5; M0, M1, M2, M3, M4, and M5 are system voltages and harmonic distortion voltages in the system periods T0, T1, T2, T3, T4, and T5, respectively. .

  A dotted line (Ni) is a line connecting them in order to show a change in each system voltage, and a dotted line (Mi) is a line connecting them in order to show a change in each harmonic distortion voltage.

  As shown in FIGS. 8A and 8C, the determination conditions (b1) and (b2) of the system voltage, the system voltage in the increasing direction of the harmonic distortion voltage, and the harmonic distortion voltage fluctuation are as follows. The voltage is the voltage in the shaded areas S1a and S1b in FIGS. Regarding the shaded areas S1a and S1b, specific conditional expressions are shown as (1a) and (1b) below. The black circles (●) in FIGS. 8A and 8C are marks indicating the system voltage and the harmonic distortion voltage. In this determination conditional expression, system voltages N0, N1, N2, N3, N4, N5 for each system period T0, T1, T2, T3, T4, T5; each system period T0, T1, T2, T3, T4, T5 Harmonic distortion voltages M0, M1, M2, M3, M4, and M5 for each of the system periods T0, T1 with respect to the system voltage average value Navr and the harmonic distortion voltage average value Mavr of each of the plurality of system periods in the past, respectively. , T2, T3, T4, and T5, it is determined that the system voltage and the harmonic distortion voltage have fluctuated when changing within a predetermined voltage fluctuation range. The same applies to FIGS. 8B and 8D.

  In this case, in the determination conditional expressions (1a) and (1b), among the system voltages N0, N1, N2, N3, N4, and N5, N0 and N1 are the difference from the system voltage average value Navr, and the harmonic distortion voltage. Among M0, M1, M2, M3, M4, and M5, M0 and M1 are different from the harmonic distortion voltage average value Mavr in terms of other system voltages N2, N3, N4, and N5, and harmonic distortion voltage M2, respectively. A system voltage change pattern and a harmonic distortion voltage change pattern that increase more rapidly than M3, M4, and M5 are included in the determination conditions. This makes it possible to distinguish between cases caused by isolated operation and other causes that are not. Further, the difference between the system voltages N3, N4, and N5 and the system voltage average value Navr was within a predetermined voltage change range (−0.5 to +0.5 V), but the system voltage average value Navr at the system voltage N2. And the difference between the system voltage N0 and N1 and the system voltage average value Navr in the embodiment (system voltage change width) exceeds 3V, The wave distortion voltage system voltages M3, M4, and M5 have changed within a predetermined voltage change range (−0.5 to +0.5 V), but the harmonic distortion voltage M2 has a difference from the harmonic distortion voltage average value Mavr. The difference from the harmonic distortion voltage average value Mavr (harmonic distortion voltage change width) at the harmonic distortion voltages M0 and M1 exceeds the predetermined voltage +0.5, and rapidly increases beyond 2 V in the embodiment. It is a judgment condition to do.

  As described above, in the embodiment, when the system voltage and the harmonic distortion voltage exhibit changes corresponding to the system voltage change pattern and the harmonic distortion voltage change pattern set in advance along a plurality of system cycles in the past, the single operation occurs. Therefore, reactive power is injected into the power system.

In the embodiment, the determination output of each of the first and second reactive power injection determination units 44a and 44b that performs the above determination can be output from the OR gate 45, so that it corresponds to the isolated operation generation mode. It is possible to inject the reactive power at a high speed through the power system with the determination output on the side and detect the isolated operation, and to increase the speed of the isolated operation detection.

[(N0-Navr)> 3V] and
[(N1-Navr)> 3V] and
[(N2-Navr)>-0.5V] and
[-0.5 <(N3-Navr) <0.5V] and
[-0.5 <(N4-Navr) <0.5V] and
[−0.5 <(N5-Navr) <0.5V] (1a)

[(M0-Mavr)> 2V] and
[(M1-Mavr)> 2V] and
[(M2-Mavr)>-0.5V] and
[−0.5 <(M3-Mavr) <0.5V] and
[−0.5 <(M4-Mavr) <0.5V] and
[-0.5 <(M5-Mavr) <0.5V] (1b)

As shown in FIGS. 8B and 8D, the determination conditions (b1) and (b2) for the system voltage, the system voltage fluctuation in the descending direction of the harmonic distortion voltage, and the harmonic distortion voltage fluctuation are as follows. The distortion voltage is the voltage in the shaded areas S2a and S2b in FIGS. 8B and 8D. Regarding the hatched areas S2a and S2b, specific conditional expressions are shown as the following expressions (2a) and (2b). The black circles (●) in FIGS. 8B and 8D are marks indicating the system voltage and the harmonic distortion voltage. (Navr) (Ni) (Mavr) (Mi) in FIGS. 8B and 8D corresponds to (Navr) (Ni) (Mavr) (Mi) in FIGS. 8A and 8B. () Is for distinguishing from the average value Navr of the system voltage, the average value Mavr of the harmonic distortion voltage, the system voltage N0 to N5, and the harmonic distortion voltage M0 to M5.
[(N0-Navr) <-3V] and
[(N1-Navr) <-3V] and
[(N2-Navr) <0.5V] and
[-0.5 <(N3-Navr) <0.5V] and
[-0.5 <(N4-Navr) <0.5V] and
[−0.5 <(N5-Navr) <0.5V] (2a)

[(M0-Mavr) <-2V] and
[(M1-Mavr) <-2V] and
[(M2-Mavr) <0.5V] and
[−0.5 <(M3-Mavr) <0.5V] and
[−0.5 <(M4-Mavr) <0.5V] and
[-0.5 <(M5-Mavr) <0.5V] (2b)

In the embodiment, for the sake of understanding, as a representative example, the system voltage for each system period is in the shaded areas S1a and S2a, and the harmonic distortion voltage for each system period is in the shaded areas S1b and S2b. Whether the voltage or harmonic distortion voltage increases or decreases, the system voltage fluctuation determination condition (b1) and the harmonic distortion voltage fluctuation determination condition (b2) are satisfied. The determination conditions (b1) and (b2) are the system voltage average values Navr and harmonics of the three system periods T3, T4 and T5 from the previous system period T0 to the previous five periods as shown in the above conditional expression. This is when the system voltage and harmonic distortion voltage of each of the past six periods T0 to T5 are within the shaded areas S1a, S1b, S2a, and S2b for each system period with respect to the distortion voltage average value Mavr.

  The first reactive power injection determination unit 44a determines whether or not the determination conditions (a1) and (b1) are satisfied as shown in FIGS. 7 (a), 7 (b), 8 (a), and 8 (b). When it is determined that it is established, control for injecting additional reactive power into the power system is performed as shown in FIGS. The second reactive power injection determination unit 44b determines whether or not the determination conditions (a2) and (b2) are satisfied as shown in FIGS. 7 (a), 7 (b), 8 (c), and 8 (d). When it is determined that it is established, control for injecting additional reactive power into the power system is performed as shown in FIGS.

  9 (a) and 9 (b), the horizontal axis represents the system cycle corresponding to each of FIGS. 7 (a) and 7 (b) and FIGS. 8 (a) to 8 (d), and the vertical axis represents the reactive power injection determination unit 44. The reactive power (Var) to be additionally injected is shown. In the embodiment, for the purpose of illustration, the value of reactive power (Var) is shown in FIG. 9 (a) and FIG. 9 (b) as the phase delay side 200Var, but this is not intended to limit the value of injection reactive power.

  In this embodiment, as described above, between a plurality of isolated operation detection devices, for example, a plurality of power conditioners, in the vicinity of the system frequency deviation of “0”, due to variations in frequency measurement, When the determination conditions (a1) (b1); (a2) (b2) are satisfied in the current system cycle T0 in order to prevent the reactive power to be additionally injected from being canceled, FIGS. 7 (a) and (b) Regardless of the sign of the system frequency deviation, as shown in FIGS. 9A and 9B, 200 Var is injected as reactive power having a predetermined phase, for example, reactive power having a phase delay.

  As a result, the reactive power additionally injected in the vicinity of the system frequency deviation of “0” becomes a reactive power with phase delay in any of the plurality of power conditioners, and is injected between the plurality of power conditioners. The reactive power is not canceled out, and when a single operation occurs, a power fluctuation can be caused by the additionally injected reactive power, and this power fluctuation can be detected to detect a single operation.

  9 (a) and 9 (b), when one system cycle is 20 milliseconds, the reactive power injection periods Ta1 and Ta2 are both 100 milliseconds, but the injection periods Ta1 and Ta2 It is not limited to. The injection periods Ta1 and Ta2 are preferably not less than 100 milliseconds and not more than 200 milliseconds because it is easy to cause power fluctuations in the power system line 32 and is preferable for high speed operation detection.

  In the embodiment, the case where the system voltage and the harmonic distortion voltage are suddenly changed to the rising side and the case where the system voltage is suddenly changed to the falling side has been described. The determination condition (b) may be satisfied only when it suddenly changes to one side, or only when it suddenly changes to either side.

  As described above, when reactive power is injected from the reactive power amount calculation unit 42, whether or not the injected reactive power and the load reactive power are balanced, the active power of the distributed power source 12 and the load active power are balanced. Whether the first determination condition (a1) (b1) is satisfied or both the second determination conditions (a2) (b2) are satisfied. If established, the first reactive power injection determining unit 44a or the second reactive power injection determining unit 44b additionally injects the reactive power in the delayed phase regardless of the phase of the reactive power injection from the reactive power amount calculating unit 42. As a result, the reactive power additionally injected between the plurality of power conditioners is not canceled out, and the power fluctuation is caused when the power system line 32 is operated independently, so that the isolated operation can be detected. Uninaru.

  From the above description, in the state where reactive power is injected into the power system to detect whether or not the distributed power source 12 is disconnected from the power system 14 and is operating independently, the system frequency is substantially over a plurality of system cycles in the past. When the system voltage or harmonic distortion voltage fluctuates beyond the specified fluctuation range when there is no change, reactive power is additionally injected into the power system. As a result of breaking the balanced state between the mold power source 12 side and the load side (not shown), it is possible to reliably detect an isolated operation.

  However, if the phase of reactive power to be additionally injected is fixed to the phase delay as shown in FIG. 10 regardless of the sign of the system frequency deviation, when the system frequency deviation Δf changes to the positive side, for example, it is shown in P2. The phase-added additional injection reactive power and the phase-advanced existing reactive power shown in P3 of FIG. 15 may cancel each other.

  Therefore, in the present embodiment, after additional reactive power injection by the reactive power injection determination units 44a and 44b, the additional injection is disabled due to the phase advance and delay between the already injected reactive power and the additional injected reactive power. A reactive power injection phase re-determination unit 51 for controlling the phase of the additional injection reactive power is provided so that the power is not canceled by the already injected reactive power.

  Hereinafter, the prevention of reactive power cancellation by the reactive power injection phase re-determination unit 51 will be described with reference to FIGS. 11 to 13.

  FIG. 11 is an operation flowchart of the reactive power injection phase re-determination unit 51. FIG. 12A is a case where the system frequency deviation is (a), and the system frequency deviation is positive at the timing t0 and is positive thereafter. (C) shows the phase control waveform of the already injected reactive power, FIG. 13 (a) shows the system frequency deviation, and (b) shows the system frequency deviation is positive at timing t0. Shows the control waveform of the phase of the additional injection reactive power when it changes to minus, and (c) shows the control waveform of the phase of the already injected reactive power. The following description will be divided into the combinations of FIGS. 11 and 12 and the combinations of FIGS. 11 and 13.

  In FIG. 11, in step n1, the reactive power injection determining units 44a and 44b determine whether or not to add additional reactive power. As described above, this determination is made when the already injected reactive power based on the system frequency deviation calculated by the system frequency deviation calculating unit 40 and the load reactive power are balanced, and the reactive power injection determining units 44a and 44b disable additional injection. It is determined that power is to be injected, and in step n2, additional injection reactive power with a phase delay that is a predetermined phase is output.

  The injection timing at this time is t0 shown in FIG. FIG. 12A shows that the system frequency deviation is positive at timing t0, and FIG. 12B shows that the phase of the additional injection reactive power is delayed at timing t0. As described above, in the reactive power injection determination units 44a and 44b, the phase of the reactive power from the reactive power injection determination units 44a and 44b is set to a predetermined delay phase regardless of the sign of the system frequency deviation.

  Then, the reactive power injection phase re-determination unit 51 can know the injection timing t0 of additional reactive power from the output change of the reactive power injection determination units 44a and 44b. The reactive power injection phase re-determination unit 51 controls steps from this injection timing t0. In addition, the output period of the additional injection reactive power from the reactive power injection determination units 44a and 44b is, for example, three periods in the system cycle in the embodiment.

  When the reactive power injection phase re-determination unit 51 determines in step n3 that it has reached the determination timing t1 when two cycles have elapsed in the system cycle before the three cycles have elapsed from the injection timing t0, the determination timing At t1, as shown in step n4, it is determined from the sign of the system frequency deviation whether the phase of the reactive power from the reactive power calculation unit 42 is advanced or delayed. In this determination, since the sign of the system frequency deviation is on the plus side as shown in FIGS. 12 (a), 12 (b), and 12 (c), the phase of the already injected reactive power from the reactive energy calculation unit 42 is on the advance side. Is determined.

  As a result of the determination, the reactive power injection phase re-determination unit 51 changes the injection direction of the additional reactive power so as to change the phase of the additional reactive power to the advancing side so as to coincide with the already injected reactive power, and step n5 Then, a determination result for injecting reactive power in the changed injection direction (advancing phase) is input to the reactive power injection determination units 44a and 44b.

  The reactive power injection determination units 44a and 44b change the injection direction of the additional reactive power according to this determination.

  The reactive power injection phase re-determination unit 51 determines in step n6 whether or not three cycles have elapsed in the system cycle after the additional reactive power injection direction has been changed, and three cycles have elapsed in the system cycle. If it is determined that it has been performed, this is input to the reactive power injection determination units 44a and 44b.

  In response to this input, reactive power injection determining units 44a and 44b stop injection of additional reactive power at step n9, and determine whether or not five cycles have elapsed since the stop of additional reactive power injection at step n10. In step 5, when five cycles have elapsed since the stop of additional reactive power injection, the process returns to step n1.

  FIGS. 13A, 13B, and 13C correspond to FIGS. 12A, 12B, and 12C, respectively. At the determination timing t0, the phase of the additional reactive power is on the lag side regardless of the sign of the system frequency deviation. Since the sign of the system frequency deviation is negative at the determination timing t1, in the determination at Step n4, the reactive power injection phase re-determination unit 51 indicates the determination result that the reactive power injection direction is not changed as the reactive power injection. It inputs into the determination parts 44a and 44b.

  From this determination result, the reactive power injection determination units 44a and 44b continue to inject reactive power (delayed phase) for one more cycle from the timing t1 as shown in step n7. When it is determined in step n8 that the reactive power injection has passed one cycle in the system cycle, the reactive power injection is stopped in step n9. The subsequent steps are the same as above.

  As described above, in the present embodiment, reactive power is injected into the power system as already injected reactive power based on the system frequency deviation in the power system, and when this already injected reactive power balances with the load reactive power, Regardless of the sign of the system frequency deviation, the delay phase reactive power (additional injection reactive power), which is a predetermined phase, is additionally injected for three periods of the system period as a fixed period.

  Then, until the above-described fixed period elapses, the phase of the additional injection reactive power is determined after two cycles have elapsed in the system cycle that is shorter than the fixed period after the injection of the additional reactive power. This determination is made based on the sign of the system frequency deviation. As a result of this determination, when it is determined that the phase of the additional injection reactive power is opposite to the phase of the additional injection reactive power from the sign of the system frequency deviation at the time of determination, the sign of the system frequency deviation is used. The additional injection reactive power of the matched phase is injected again for the above-mentioned fixed period, so that the additional injection reactive power does not need to be offset by the existing injection reactive power, and the reactive power balance is broken by the additional injection reactive power and the single operation is detected. It becomes possible.

  Further, when it is determined that the phase of the additional injection reactive power is the same phase based on the sign of the system frequency deviation at the time of the determination, it is a remaining period until a fixed period elapses after the additional injection reactive power injection 1 Since the injection of the additional injection reactive power is continued in the same phase for the period, it becomes possible to effectively perform the isolated operation detection by effectively breaking the reactive power balance with the additional injection reactive power.

  The present invention is not limited to the above-described embodiment, and includes various changes or modifications within the scope described in the claims.

  The present invention is useful for detecting an isolated operation of a distributed power supply system.

DESCRIPTION OF SYMBOLS 10 Distributed type power supply system 12 Distributed type power supply 14 Electric power system 16 Power conditioner 18 Independent operation detection apparatus 20,22 Interconnection relay 24 Control apparatus 26 Inverter control part 28 Inverter 34a System voltage measurement part 34b Harmonic distortion measurement part 36 System frequency Measurement unit 38 Isolated operation determination unit 40 System frequency deviation calculation unit 42 Reactive power amount calculation unit 44a First reactive power injection determination unit 44b Second reactive power injection determination unit 46 Reactive power addition unit 51 Reactive power injection phase re-determination unit

Claims (7)

In order to detect whether the distributed power source is disconnected from the power system and operating independently, reactive power is injected into the power system, and isolated operation is detected based on electrical fluctuations that occur in the power system due to this injection. In the isolated operation detection method,
Reactive power (pre-injected reactive power) is injected into the power system based on electrical fluctuations and the reactive power having a predetermined phase is applied to the power system when the already injected reactive power is balanced with the load reactive power. A first step of additionally injecting (additional injection reactive power) for a certain period;
A second step of determining a sign of the electrical variation after a period shorter than the predetermined period has elapsed since the additional reactive power injection in the first step;
From the sign of the electrical fluctuation at the time of the determination, when it is determined that the phase of the already injected reactive power is opposite to the predetermined phase of the additional injected reactive power injected in the first step A third step of injecting the additional injection reactive power of the phase corresponding to the sign of the electrical variation again for the predetermined period;
From the sign of the electrical fluctuation at the time of the determination, when it is determined that the phase of the already injected reactive power is the same as the predetermined phase of the additional injected reactive power injected in the first step, A fourth step of continuing the injection of the additional injection reactive power in the same phase as the additional injection reactive power injected in the first step for the remaining period after the additional injection reactive power injection in one step until a certain period of time elapses;
An islanding operation detection method comprising: The electrical fluctuation is the system frequency deviation,
The method according to claim 1, wherein the phase advance / delay determination of the reactive power is performed based on a sign of the system frequency deviation.   The method according to claim 1, wherein the electrical fluctuation is a system frequency fluctuation, a system voltage fluctuation, or a harmonic fluctuation.   The method according to any one of claims 1 to 3, wherein the certain period is a period that is three times the system period, and a period shorter than the certain period is a period that is twice the system period.   5. A control device for controlling the detection operation of an isolated operation detection device that injects reactive power into the power system for detecting whether or not the distributed power source is disconnected from the power system and operating independently. A control apparatus characterized in that the method according to any one of the above can be implemented.   An isolated operation detection device for detecting whether or not a distributed power source is disconnected from an electric power system and operated independently, comprising the control device according to claim 5.   A distributed type comprising a plurality of distributed power sources and a plurality of isolated operation detection devices that are individually provided for each distributed power source and detect whether or not the distributed power source is disconnected from the power system and operated independently In the power supply system, each isolated operation detection device is the isolated operation detection device according to claim 6.

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