JP2009136095A - Islanding operation detecting method, controller, islanding operation detecting apparatus and distribution type power supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an islanding operation detecting method capable of maintaining the sensitivity of detecting islanding operation at excellent or comparatively excellent state as a whole while reducing the effect on a power system, irrespective of the state of islanding operation. <P>SOLUTION: In this islanding operation detecting method, a plurality of kinds of islanding operation detecting systems for applying electrical variation for detecting isolating operation to a power system, and the isolating operation detecting systems are combined with each other to remove or reduce a dead zone in detection of isolating operation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides an electrical active signal to the power system to detect whether or not the distributed power source is disconnected from the power system and is operating independently, and based on this electrical fluctuation. The present invention relates to an isolated operation detection method for performing isolated operation detection. The present invention also relates to a control device for detecting an isolated operation of a distributed power source, an isolated operation detecting 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.

  As one of the methods for detecting such an isolated operation, reactive power is injected as an active signal into the power system, and when the isolated operation occurs, an electrical variation is caused by the injected reactive power, and this electrical variation is detected. Thus, an active method for detecting the isolated operation of a distributed power source has already been proposed.

  In addition, the applicant of the present invention disclosed in Japanese Patent Application No. 2006-2225016 an isolated operation detection method in which the electrical variation is a system frequency variation, and in Japanese Patent Application No. 2007-168421, an isolated operation detection method in which the electrical variation is a system voltage. No. 209285 has filed for an isolated operation detection method in which the electrical fluctuation is a harmonic fluctuation.

  However, in each of these isolated operation detection methods, as the isolated operation state, the injection reactive power and the load reactive power from the isolated operation detection device are balanced and not balanced, and the injection reactive power Even if the load reactive power and the load reactive power are balanced, the case where the injection active power from the isolated operation detection device and the load active power are balanced and the case where they are not balanced are independent. While there is a single operation detection method with high and high operation detection sensitivity, there is an individual operation detection method in which the single operation detection sensitivity is significantly low.

In addition, there are many patent documents of isolated operation detection, and typical examples are given below.
Japanese Patent Laid-Open No. 02-144615 Japanese Patent Laid-Open No. 08-98411 Japanese Patent No. 3397912 Japanese Patent No. 3424443

  Therefore, the applicant of the present invention is able to detect single operation over a wide range of single operation states by combining a plurality of single operation detection methods regardless of the single operation state such as the power balance. He has eagerly studied what can be done with sensitivity.

  However, on the other hand, when a plurality of islanding detection methods are combined and an active signal such as reactive power is injected into the power system at the same time, it may adversely affect the power system. It is simply not possible to combine a plurality of islanding detection methods.

  Therefore, in the present invention, by combining the single operation detection system in the single operation detection method, the single operation detection sensitivity is generally reduced while reducing the influence on the power system regardless of the single operation state. It is an object of the present invention to provide an isolated operation detection method that can be maintained in good or relatively good condition.

  (1) The islanding operation detection method according to the present invention causes an electrical fluctuation by giving an electrical active signal to the power system for detecting whether the distributed power source is disconnected from the power system and operating independently. In the islanding operation detection method for detecting islanding based on the electrical fluctuation, a plurality of islanding operations are detected corresponding to each of a plurality of types of electrical fluctuations that occur in the power system due to the application of the active signal. An independent operation detection system is provided, and the dead zone of the isolated operation detection is eliminated or reduced by combining the individual operation detection systems.

  The dead zone for detecting an isolated operation is a relative sensitivity in the isolated operation detection sensitivity. That is, when the isolated operation detection sensitivity is relatively divided into, for example, a high sensitivity zone and a low sensitivity zone, it is a sensitivity zone having a lower sensitivity than the low sensitivity zone. Alternatively, the sensitivity below the normal sensitivity can be referred to as a dead zone. These can define dead zones according to user settings. In any case, in the plurality of isolated operation detection systems, at least one of the isolated operation detection systems is relatively compared with other isolated operation detection systems, and depending on the type of electrical fluctuation, When the sensitivity is insufficient, the dead zone is supplemented by another isolated operation detection system.

  Therefore, even if various electrical fluctuations occur by applying an active signal to the power system, it is possible to detect a single operation from a single operation detection system having a detection sensitivity that is impossible to detect a single operation. Since there are also systems, the isolated operation detection system is equipped with a plurality of isolated operation detection systems, and a combination of these isolated operation detection systems (including meanings of independent operation) makes it possible to detect a wide range of isolated operation conditions. The zone is set as a dead zone, and each islanding detection system relatively covers the detection sensitivity so that other islanding detection systems can be detected.

  In the present invention, since the single operation detection system is singly or combined, it is possible to maintain the single operation detection sensitivity as a whole while reducing the influence on the power system for a wide range of single operation states. it can.

  In a preferred aspect of the present invention, when a plurality of the above-mentioned individual operation detection systems are combined, when at least any one of the single operation detection systems has a single operation detection dead band, the other single operation detection systems have the dead band. It is to perform an isolated operation detection operation.

  In a preferred aspect of the present invention, the active signal is reactive power.

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

  (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, independent operation detection can be performed with good sensitivity as a whole while reducing the influence on the electric power system regardless of the isolated operation state.

  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 L1, L2, and M, and measures the system voltage, the harmonic distortion voltage, and the system frequency of the power system 14, and from these, the connection is made through the output line P. 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 being used, it is possible to perform control for injecting reactive power further.

  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 energy injected 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 also maintains a state in which the system frequency deviation is continuously below a predetermined number of system cycles for a certain number of continuous periods, 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 computing unit 44a that performs control to determine that the system voltage has suddenly changed due to the occurrence of isolated operation and to inject constant reactive power.

  Further, the control device 24 further maintains a state in which the system frequency deviation continuously becomes constant or less over a predetermined number of system cycles, the system frequency does not substantially change, and the harmonic distortion voltage is set in a predetermined voltage range set in advance. A second reactive power injection computing unit 44b that performs control to determine that the harmonic distortion voltage has suddenly changed due to the occurrence of an isolated operation when it is changed along the inside, and to inject constant reactive power.

  Further, the control device 24 selects and outputs one of the reactive powers from the first and second reactive power injection arithmetic units 44a and 44b, and the reactive power that controls the selection operation of the selection gate 45. Reactive power addition unit that adds the calculation reactive power from the injection method determination unit 47, the reactive power amount calculation unit 42, and the reactive power from the first and second reactive power injection calculation units 44a and 44b from the selection gate 45. 46, and an output current control unit 48 that outputs an output current control signal to the inverter control unit 26 through the output line Q in accordance with the output of the reactive power adding unit 46.

  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 units of measurement periods, for example, 5 milliseconds. When the system frequency of the power system is 50 Hz (one system period is 20 msec), the system cycle unit is desirably 1/3 or less of the system period of the power system, for example, 5 msec 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. .

  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 energy injection calculating unit 42 calculates the reactive power amount based on the system frequency deviation calculated by the system frequency deviation calculating unit 40 using the characteristic of the reactive power amount versus the system frequency deviation of FIG. The reactive power amount is notified to the output current control unit 48 through 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, and 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.

  Then, a single operation detection system (system) in which the system frequency deviation calculation unit 40 and the reactive power amount injection calculation unit 42 inject reactive power into the power system as one electrical fluctuation indicating the system frequency fluctuation in the single operation state. A frequency fluctuation type isolated operation detection system).

  In addition, one independent operation detection system (system) in which the system voltage measuring unit 34a and the first reactive power injection calculating unit 44a inject reactive power into the power system as one electrical variation indicating the system voltage variation in the single operation state. A voltage fluctuation type isolated operation detection system).

  Further, the harmonic distortion measuring unit 34b and the second reactive power injection calculating unit 44b inject reactive power into the power system as one electrical fluctuation indicating the harmonic distortion voltage fluctuation (harmonic fluctuation) in the single operation state. One isolated operation detection system (harmonic fluctuation type isolated operation detection system) is configured.

  In addition, each said independent operation detection system | strain is an example, and of course, other independent operation detection systems may be sufficient. Of course, the number of isolated operation detection systems may be three or more.

  This will be further described below. In the description, the system voltage fluctuation type and harmonic fluctuation type single operation detection systems will be described together to avoid duplication of explanation.

  The system voltage measurement unit 34a and the harmonic distortion measurement unit 34b measure the system voltage and the total harmonic distortion voltage for each system period, as shown in FIG. 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 is the square root of each of the harmonic distortion voltages V ₂ to V _7, and the sum of these squares. It is given by

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.

  In the above, the isolated 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, or the second or higher harmonic distortion voltage. Harmonic distortion power may be used.

  In the first reactive power injection calculating 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 calculating 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. The solid lines (Navr) and (Mavr) 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 the previous three periods to five periods. 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 judgment condition formula, 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.

  From the above, when the system voltage and harmonic distortion voltage show changes corresponding to the system voltage change pattern and harmonic distortion voltage change pattern set in advance along multiple past system cycles, the system voltage related to the occurrence of isolated operation Reactive power can be injected into the power system by determining that there is fluctuation or harmonic fluctuation.

In addition, since it is possible to select and output either of the determination outputs of the first and second reactive power injection calculating units 44a and 44b that perform the above determination from the selection gate 45, the side corresponding to the isolated operation generation mode. With this determination output, reactive power can be injected at high speed through the power system to detect the isolated operation, and the isolated operation can be detected at high speed.

[(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] (1a)

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)

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 harmonic distortion voltage rises or falls, 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, as shown in the above conditional expression, the system voltage average value Navr, harmonic distortion of each of the three system periods T3, T4, T5 from the current system period T0 to three periods before to five periods. This is when the system voltage and the harmonic distortion voltage in each of the past six cycles T0 to T5 are within the shaded areas S1a, S1b, S2a, and S2b for each system cycle with respect to the voltage average value Mavr.

  The first reactive power injection calculating 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 reactive power into the power system can be performed as shown in FIGS. 9 (a) and 9 (b).

  The second reactive power injection calculating 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 reactive power into the power system can be performed as shown in FIGS. 9 (a) and 9 (b).

  9 (a) and 9 (b), the horizontal axis represents the system cycle corresponding to FIGS. 7 (a) and 7 (b) and FIGS. 8 (a) to (d), and the vertical axis represents the reactive power injection calculation unit 44. Reactive power (Var) additionally injected to the phase advance side or the phase delay side is shown. In the embodiment, for the purpose of illustration, the values of reactive power (Var) are entered in FIG. 9 (a) and FIG. 9 (b) as phase advance side 200Var and phase lag side 200Var. is not.

  Further, the determination conditions (a1) (b1); (a2) (b2) are satisfied in the current system cycle T0, and the sign of the system frequency deviation is positive in the current system period T0 in FIG. In b), since it is on the negative side, the phase advances when the system voltage rises and the harmonic distortion voltage rises at the current system cycle 0, and 200 Var is injected as reactive power with phase lag when the system voltage falls and the harmonic distortion voltage falls. Yes.

  This is because when the sign of the system frequency deviation is positive, the reactive power from the reactive power injection calculating section 42 is in phase advance, and when the sign of the system frequency deviation is negative, the reactive power from the reactive power injection calculating section 42 is out of phase. Therefore, the reactive power from the reactive power injection arithmetic unit 42 is not canceled by the adding unit 46 so that the reactive power from the reactive power injection arithmetic unit 42 and the reactive power from the reactive power injection arithmetic units 44a and 44b are not offset. This is because the phase delay advance and the phase delay advance of the reactive power from the reactive power injection calculating units 44a and 44b are made to coincide.

  In the above description, in the present embodiment, as shown in FIG. 10, the following islanding operation is performed with respect to the above-described system frequency variation type, system voltage variation type, and harmonic variation type independent operation detection system. A detection method can be provided.

  That is, regarding the injection of reactive power into the power system, first, at step n0, the system frequency, system voltage, and harmonics from the system frequency measurement unit 36, system voltage measurement unit 34a, and harmonic distortion measurement unit 34b are measured. From these measurements, at step n1, the system frequency deviation calculating unit 40 calculates the system frequency deviation. In step n2, the reactive power injection calculation unit 42 in the system frequency fluctuation type isolated operation detection system calculates the injection reactive power amount, and in step n3, the calculated reactive power is converted to the reactive power addition unit. 46 is input. Step n3 is a step of adding the reactive power in step n2 and one reactive power in steps n6 and n8 described later. And step n4 is output current control in the output current control part 48 by these added reactive power.

  On the other hand, when the system frequency deviation calculated in step n1 is 0.1 Hz or less and the electrical fluctuation in the single operation state is the system voltage fluctuation, the reactive power injection method determination unit 47 determines that the system voltage fluctuation type single unit By switching the selection gate 45 so as to select the reactive power from the first reactive power injection calculation unit 44a that is the operation detection system, the process proceeds from step n5 to step n6, and in step n3, the first reactive power injection calculation unit A certain amount of reactive power from 44 a is input to the reactive power adding unit 46.

  Moreover, although the system | strain frequency deviation calculated by step n1 is 0.1 Hz or less, when the electrical fluctuation | variation in a single operation state is not a system | strain voltage fluctuation | variation, it transfers to step n7. In step n7, when the system frequency deviation is 0.1 Hz or less and the electrical fluctuation in the single operation state is a harmonic fluctuation, the reactive power injection method determination unit 47 determines that the harmonic fluctuation type single By switching the selection gate 45 so as to select the reactive power from the second reactive power injection calculation unit 44b that is the operation detection system, the process proceeds from step n7 to step n8, and in step n3, the second reactive power injection calculation unit A certain amount of reactive power from 44 b is input to the reactive power adding unit 46.

  At the time of isolated operation detection, among the above three independent operation detection systems, any of the reactive power from the system frequency fluctuation type independent operation detection system and any of the system voltage fluctuation type or harmonic fluctuation type independent operation detection systems One of the reactive powers is output from the output current control unit 48 to the inverter control unit 26 in step n4.

  The output form of the above reactive power will be described with reference to the table of FIG. In this table, when the reactive power is injected from the reactive power injection calculating unit 42 based on the system frequency deviation, whether or not the injected reactive power and the load reactive power are balanced, the injected reactive power and the load reactive power. Whether the active power of the distributed power source 12 and the load active power are balanced in the case where the power source is balanced and the case where the power source is not balanced, and whether or not the harmonic power is present or not. It is a table | surface which shows which combination of a driving | operation detection system | strain is preferable. In this table, a circle indicates that the isolated operation detection sensitivity is high and the isolated operation can be detected. Indicates that there is.

  That is, in the system frequency variation type, the mark is ◯ over the whole area where the reactive power is not balanced, and the mark △ is over the whole area where the reactive power is balanced.

  In the system voltage fluctuation type, all the regions where the active power is not balanced are indicated by a circle, and all the regions where the active power is balanced are indicated by a cross.

  In the harmonic fluctuation type, all the symbols with a harmonic are indicated by a circle, and all symbols without a harmonic are indicated by a cross.

  In FIG. 11, by combining the above three independent operation detection systems, it is possible to detect the independent operation in all the balance states of the reactive power and the active power, and the reactive power amount balances the active power. Even in the isolated operation detection state without harmonics, the isolated operation detection system of the system frequency variation type can detect the isolated operation.

  And, in order to reduce the influence on the power system, rather than injecting reactive power from the above three independent operation detection systems, the system frequency variation type isolated operation detection system for independent operation detection alone Reactive power injection or reactive power detection for islanding operation detection with either system frequency fluctuation type isolated operation detection system and either system frequency fluctuation type or harmonic fluctuation type isolated operation detection system Since injection is performed, it is possible to perform isolated operation detection with good sensitivity in a wide range of isolated operation states while reducing the influence on the power system as much as possible.

  Another embodiment of the present invention will be described with reference to FIGS. In this embodiment, the selection gate 49 selects any one of the above three. In step n9 of FIG. 13, if the system frequency deviation is not 0.1 Hz or less, the process proceeds to step n2, and if the system frequency deviation is 0.1 Hz or less, the process proceeds to step n5 'and subsequent steps. Therefore, step n5 in FIG. 10 is equivalent to steps n9 and n5 ′ in FIG. 13, and step n7 in FIG. 10 is equivalent to steps n9 and n7 ′ in FIG. Therefore, even in the case of this embodiment, it is possible to perform isolated operation detection with good sensitivity for a wide range of isolated operation states from the table in FIG. 11 while reducing the influence on the power system as much as possible.

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

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, the harmonic distortion voltage, the system voltage for three periods, and the average value of the harmonic distortion voltage for each system period. 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. 9B 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 flowchart relating to the explanation of the operation of the embodiment. FIG. 11 shows the isolated operation detection state with or without reactive power balance, active power balance, and harmonics in the three-way isolated operation detection system corresponding to the above-described flowchart. FIG. FIG. 12 is a functional block diagram of a control device according to another embodiment. FIG. 13 is a flowchart for explaining the operation of another embodiment. FIG. 14 is an image diagram of a multi-unit interconnection of distributed power sources.

Explanation of symbols

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

Claims (7)

In order to detect whether the distributed power source is disconnected from the power system and operated independently, an electrical active signal is given to the power system to cause electrical fluctuations, and the isolated operation detection is performed based on the electrical fluctuations. In the isolated operation detection method to be performed,
A plurality of single operation detection systems for detecting single operation corresponding to each of a plurality of types of electrical fluctuations that occur in the power system due to the application of the active signal are provided,
Eliminate or reduce the dead zone of isolated operation detection by combining the above isolated operation detection systems,
An isolated operation detection method characterized by the above.   When a plurality of the above-mentioned individual operation detection systems are combined, when there is a dead zone for detecting an independent operation in at least one of the individual operation detection systems, the other independent operation detection system is caused to perform an independent operation detection in the dead zone. The method of claim 1, wherein:   The method according to claim 1 or 2, wherein the active signal is reactive power.   The method according to claim 1, wherein the type of electrical fluctuation is system frequency fluctuation, system voltage fluctuation, or harmonic fluctuation.   5. A control device that controls the 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, according to any one of claims 1 to 4. A control device, characterized in that the described isolated operation detection method can be implemented. In a single operation detection device that injects reactive power into a power system for detection of whether a distributed power source is disconnected from the power system and is operating independently,
An isolated operation detection device comprising the control device according to claim 5.   The distributed operation system comprising: a distributed power supply; and an isolated operation detection device that detects whether or not the distributed power supply is isolated from the electric power system and operates independently. A distributed power supply system characterized by being a single operation detection device.

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