JP4872826B2 - Isolated operation detection method, control device, isolated operation detection device, and distributed power supply system - Google Patents

Description

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

  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.

  FIG. 10 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. 10 is 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 to inject reactive power into the power system based on the system frequency deviation, and when the isolated operation occurs, it causes the power fluctuation by the injected reactive power and detects this power fluctuation. Thus, there has already been proposed a power fluctuation method for detecting isolated operation of a distributed power source.

  However, in the islanding operation detection method that injects reactive power into the power system based on the system frequency deviation, when the system frequency deviation is small, the islanding operation detection device is less injecting reactive power and the islanding operation is continued. There is.

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

  As a result of earnest research on the cause of the continuation of the above-mentioned isolated operation, the applicant has a balance between the output reactive power and the load reactive power of the distributed power source, and therefore the system frequency deviation is small even in the case of independent operation. Thus, the injected reactive power is small and power fluctuation is not caused. As a result, it has been found that the isolated operation state is continued without being detected as an isolated operation.

  Therefore, the problem to be solved by the present invention is to make it possible to reliably detect an isolated operation even when the injection reactive power and the load reactive power from the isolated operation detection device are balanced.

(1) An islanding operation detection method according to the present invention is an islanding operation detection method in which reactive power is injected into an electric power system to detect whether or not the distributed power source is disconnected from the electric power system and operates independently. When the system voltage fluctuates when there is no substantial change over multiple system cycles, reactive power is injected into the power system, and each system system compares the system voltage with the average value of the system voltage for each of the past system periods. It is determined that the system voltage has changed when the system voltage for each period changes with a predetermined voltage fluctuation range determined for each system period .

  While reactive power is balanced on the distributed power supply side and load side, active power is not balanced on the distributed power supply side and load side. There is no system voltage fluctuation. The present invention utilizes this, and firstly, there are two conditions that the system frequency does not substantially change over a plurality of system cycles in the past, and secondly, the system voltage fluctuates when an isolated operation occurs. When the above is established, by injecting reactive power, the balance state with respect to the reactive power is positively broken, and as a result, power fluctuation is caused in the power system, and single operation can be detected reliably. become able to.

  The present invention preferably determines that there is no substantial change in the system frequency when the system frequency deviation continues within a certain range continuously over a plurality of system periods in the past.

In the present invention , the system frequency preferably extends over a plurality of system cycles in the past on the assumption that the reactive power of the amount of power calculated based on the system frequency deviation within a predetermined system cycle is injected into the power system for detection of isolated operation. When the system voltage fluctuates when there is no substantial change, additional reactive power is injected into the power system.

  In such a case, when the reactive power to be injected is equally balanced with the load reactive power, the balance state can be lost and the reactive power for detecting the independent operation can be reliably injected.

  The present invention is preferably such that the phase advance / delay of the additional reactive power coincides with the phase advance / delay of the reactive power to be injected.

  In such a case, it is preferable that the reactive powers do not cancel each other because the phase lag advance of the reactive powers coincides.

(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 and operated independently. Independent operation that turns on and off the interconnection relay with the power system by determining the independent operation from the measured value of the system frequency measurement unit that measures the voltage, the system frequency measurement unit that measures the system frequency of the power system, and the measured value of this system frequency measurement unit A determination unit, a system frequency deviation calculation unit that calculates a system frequency deviation from the measurement value of the system frequency measurement unit, and a reactive power amount that calculates a reactive power amount to be injected into the power system from the system frequency deviation of the system frequency deviation calculation unit A calculation unit and a reactive power injection determination unit that performs control to inject reactive power based on a system frequency deviation and a system voltage, and the system frequency has passed over a plurality of system cycles in the past Injecting reactive power into the power grid when the grid voltage when the real change the absence varies, the system voltage of each system cycle system voltage with respect to the average value of the past plurality of system cycles each of the system voltage Is determined to have changed with a predetermined voltage fluctuation range determined for each system cycle, it is determined that the system voltage has changed .

  (3) An isolated operation detection device according to the present invention is an isolated operation detection device for injecting reactive power into an electric power system for detecting whether or not a distributed power source is disconnected from the electric power system and operating independently. It is characterized by having.

  (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 isolated operation detection device is the isolated operation detection device according to claim 5.

  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.

  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.

  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 mainly composed of a microcomputer, and is connected to the power system line 32 through the input lines L and M, respectively, measures the system voltage and system frequency of the power system 14, and outputs the output line P from these. The isolated operation detection output is output to the interconnection relays 20 and 22 through the power supply, and 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 is supposed to be.

  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 and system voltage for a predetermined number of system cycles, and the system frequency continuously changes. It is determined whether or not the condition that the system voltage has suddenly changed due to a change exceeding the predetermined voltage fluctuation range is satisfied, and if the above condition is satisfied, it is additionally invalidated in addition to the reactive power already injected. Control to inject power.

  The control device 24 can also be configured by hardware other than the microcomputer. When the control device 24 is configured by a microcomputer, the control device 24 includes a CPU, a memory, an interface, and the like. A software program for executing the isolated operation detection method of the embodiment is stored in the memory. 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, in order to understand the description, a microcomputer is built in the control device 24, and functions described below are executed by a software program of the microcomputer. FIG. 2 shows a functional configuration of the microcomputer.

  The function of the control device 24 will be described in detail with reference to FIG. The control device 24 includes a system voltage measuring unit 34 that measures the voltage of the system power input from the power system line 32 through the input line L, and a system that measures the system frequency of the system power input from the power system line 32 through the input line M. A frequency measurement unit, and a single operation determination unit that outputs a single operation detection output for turning on / off the interconnection relays 20 and 22 to the output line P according to the determination, from the measurement value of the system frequency measurement unit 36 A system frequency deviation calculating unit 40 that calculates a moving average value of the current system frequency and a moving average value of the past system frequency from the measured value of the system frequency measuring unit 36 and calculates a system frequency deviation from the calculated value; The reactive power amount calculating unit 42 for calculating the reactive power amount injected into the power system from the system frequency deviation of the system frequency deviation calculating unit 40, and the system frequency deviation Is continuously injected for a certain number of system cycles, and when there is no substantial change in the system frequency and the system voltage suddenly changes with a change exceeding the specified voltage fluctuation range, reactive power is additionally injected. The reactive power injection determining unit 44 that performs control, the adding unit 46 that adds the calculated reactive power from the reactive power amount calculating unit 42 and the additional reactive power from the reactive power injection determining unit 44, and the output of the adding unit 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.

  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. .

  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 calculation unit 42 calculates the reactive energy based on the system frequency deviation calculated by the system frequency deviation calculation unit 42 using the characteristic of the reactive power amount vs. system frequency deviation in FIG. The amount of electric power 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, the system voltage measuring unit 34 and the reactive power injection determining unit 44 are provided. This will be described below.

  As shown in FIG. 6, the system voltage measurement unit 34 measures the system voltage N0 for each system cycle N0. In FIG. 6, “T0”, “T1”, “T2”,..., “T13” are system cycles, and “N0”, “N1”, “N2”, “N3”, “N4”, “N5” are The system voltage in each system cycle. N0 is a system voltage in the current system cycle T0, N1 is a system voltage in the system cycle T1,... N5 is a system voltage in the system cycle T5. In the embodiment, Navr is an average value of the system voltage of a total of three system cycles from the system cycle T3 three system cycles before the current system cycle T0 to the system cycle T5 five system cycles before. Of course, the average value Navr of the system voltage is not limited to the three system periods of the embodiment, and can be determined as appropriate.

  In the reactive power injection determination unit 44, the measured value of the system voltage from the system voltage measuring unit 34, the measured value of the system frequency from the system frequency measuring unit 36, the system frequency deviation from the system frequency deviation calculating unit 40, From these, as a condition (a), a state in which the system frequency deviation is continuously within a predetermined range for a predetermined number of system cycles continues and there is no substantial change in the system frequency, and the condition (b) As described above, it is determined whether or not the above two conditions (a) and (b) that the system voltage has suddenly changed with a change exceeding a predetermined voltage fluctuation range are satisfied.

  This determination will be described with reference to FIGS. 7A, 7B, 9A, and 9B by dividing the system voltage into the rising and falling directions.

  7 (a), 8 (a), and 9 (a) show the case where the system voltage suddenly changes in the upward direction. FIG. 7 (b), FIG. 8 (b), and FIG. The case where the system voltage suddenly changes in the downward direction is shown.

  Regarding the determination condition (a), in FIGS. 7A and 7B, T0, T1, T2, T3, T4, and T5 in the horizontal direction are the system cycle described above, and the vertical axis is the system frequency deviation. The dotted line a1 has a system frequency deviation of 0.5 Hz from the deviation 0 Hz to the plus (+) side, and a2 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 Δf = 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.

  However, 0.5 Hz on the plus (+) side and 0.5 Hz on the minus (−) side are merely examples and are not limited thereto.

  When the system voltage suddenly changes in the upward direction as shown in FIG. 7A, the system frequency deviation is from the system cycle T1 to the deviation 0 Hz plus (+) side, and the system voltage is as shown in FIG. 7B. In the case of sudden change in the descending direction, the system frequency deviation is from the system period T1 to the minus (−) side from 0 Hz deviation.

  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 within the predetermined range continuously from the current system cycle T0 for the past three system cycles or more, and the determination condition (a) is not substantially changed. It is shown in a state where it is established.

  Next, the determination condition (b) will be described with reference to FIGS.

  8A and 8B, the horizontal axis represents the system cycle, and the vertical axis represents the system voltage (V). A solid line a3 is a line indicating the average value Navr of the system voltages in the three system periods T3, T4, and T5 from the current system period T0 to three periods before and five periods before. N0, N1, N2, N3, N4, and N5 are system voltages in the system periods T0, T1, T2, T3, T4, and T5, respectively. A dotted line a4 is a line connecting the system voltages N0, N1, N2, N3, N4, and N5 in order to show changes.

 As shown in FIG. 8 (a), the determination condition (b) of the system voltage fluctuation in the system voltage increasing direction is that each of the system voltages N0, N1, N2, N3, N4 and N5 is the network in FIG. 8 (a). That is, the voltage is within the multiplying region S1. A determination condition expression using specific numerical values for the shaded area S1 is (1) below.

  However, Formula (1) is an example and is not limited thereto.

  The black circles (●) in FIG. 8A are marks indicating the system voltages. In this determination conditional expression, the system voltages N0, N1, N2, N3, N4, and N5 for each system period T0, T1, T2, T3, T4, and T5 are set to the average value Navr of the system voltages for each of the plurality of system periods in the past. On the other hand, when the system voltages N0, N1, N2, N3, N4, and N5 for each system cycle T0, T1, T2, T3, T4, and T5 change with a predetermined voltage fluctuation range determined for each system cycle, It is determined that the voltage has changed. The same applies to FIG. 8B.

[(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] (1)
As shown in FIG. 8B, the determination condition (b) of the system voltage fluctuation in the system voltage decreasing direction is that each of the system voltages N0, N1, N2, N3, N4, and N5 is the network in FIG. That is, the voltage is within the multiplying region S2. A determination condition expression using specific numerical values for the shaded area S2 is (2) below.

  However, Formula (2) is an example and is not limited thereto.

  A black circle (●) in FIG. 8B is a mark indicating each system voltage.

[(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] (2)
In the embodiment, for the sake of understanding, as a representative example, the system voltage for each system cycle is in the shaded areas S1 and S2, and the system voltage fluctuation judgment condition (b) whether the system voltage rises or falls To be satisfied. As shown in the conditional expression, this determination condition (b) is the past six cycles with respect to the system voltage average value Navr of each of the three system cycles T3, T4, T5 from the current system cycle T0 to three cycles before and five cycles before. This is when the system voltages of T0 to T5 are all within the shaded areas S1 and S2 for each system period.

  The reactive power injection determination unit 44 determines whether or not the determination conditions (a) and (b) are satisfied as shown in FIGS. 7 (a) and 7 (b) and FIGS. 8 (a) and 8 (b). Based on the determination that it is established, control is performed to inject additional reactive power into the power system as shown in FIGS. 9A and 9B, the horizontal axis represents the system period corresponding to each of FIGS. 7A, 7B, 8A, and 8B, and the vertical axis represents the phase from the reactive power injection determination unit 44. Reactive power (Var) additionally injected to the leading side or the phase lag 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.

  In this embodiment, the determination conditions (a) and (b) are satisfied in the current system cycle T0, and the system frequency deviation is positive in the current system cycle T0 in FIG. 9A and negative in FIG. 9B. Therefore, in the current system cycle 0, the phase advances when the system voltage rises, and 200 Var is injected as phase reactive power when the system voltage falls. This is because the reactive power from the reactive power calculation unit 42 is advanced in phase when the system frequency deviation is positive, and the reactive power from the reactive power calculation unit 42 is delayed in phase when the system frequency deviation is negative. So that the reactive power from the reactive power calculation unit 42 and the reactive power from the reactive power injection determination unit 44 are not canceled out, and the reactive power injection determination unit This is to match the phase delay advance of the reactive power from 44.

  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 suddenly changes to the rising side and the case where the system voltage suddenly changes to the falling side has been described, but it is not limited to satisfying the determination condition (b) even if suddenly changing to any side, The determination condition (b) may be satisfied only when suddenly changing to any one side, or the determination condition (b) may be satisfied only when suddenly changing to any other 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. Is determined by the determination conditions (a) and (b). When both determination conditions (a) and (b) are satisfied, the reactive power injection determination unit 44 injects the reactive power from the reactive power calculation unit 42. As a result of injecting reactive power in which the reactive power and the phase of advance and delay are matched, a current control command value for causing power fluctuation in the power system line 32 can be input to the inverter control unit 26. When the line 32 is in an isolated operation, a power fluctuation is caused, and the isolated operation can be detected.

  As described above, in the embodiment, in the isolated operation detection method in which reactive power is injected into the power system for detecting whether or not the distributed power source 12 is disconnected from the power system 14 and operated independently, the system frequency is the past. Since reactive power is injected into the power system when the system voltage fluctuates when there is no substantial change over a plurality of system cycles, the reactive power is distributed between the distributed power source 12 side and the load side outside the figure. As a result of being able to break the balanced state, it is possible to reliably detect an isolated operation.

  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 for each system period and the average value of the system voltage for three periods. FIG. 7A is a diagram used for explaining whether or not the system frequency change satisfies the determination condition (a) when the system voltage suddenly changes to the rising side, and FIG. 7B shows the system voltage suddenly changing to the decreasing side. It is a figure used for description of whether a system frequency change fulfills judgment conditions (a) when doing. FIG. 8A is a diagram used for explaining whether or not the system voltage change when the system voltage suddenly changes to the rising side satisfies the determination condition (b), and FIG. 8B shows the system voltage suddenly changing to the decreasing side. It is a figure used for description of whether the system voltage change in the case of satisfying determination conditions (b). FIG. 9A is a diagram used for explaining reactive power injection when the system voltage suddenly changes to the rising side, and FIG. 9A is a diagram used for explaining reactive power injection when the system voltage suddenly changes to the decreasing side. is there. FIG. 10 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 device 20,22 Interlinked relay 24 Control device 34 System voltage measurement part 36 System frequency measurement part 38 Independent operation determination part 40 System frequency deviation calculation Unit 42 reactive energy calculation unit 44 reactive power injection determination unit 46 addition unit 26 inverter control unit 28 inverter

Claims (7)

In the isolated operation detection method of injecting reactive power into the power system for detecting whether the distributed power source is disconnected from the power system and operating independently,
When the grid voltage fluctuates when the grid frequency has not changed substantially over the past multiple grid cycles, reactive power is injected into the power grid .
It is determined that the system voltage fluctuates when the system voltage for each system period changes with a predetermined voltage fluctuation range determined for each system period with respect to the average value of the system voltage for each of a plurality of system periods in the past. An isolated operation detection method characterized by:   2. The islanding operation detection method according to claim 1, wherein it is determined that there is no substantial change in the system frequency when a state in which the system frequency deviation is continuously within a certain range continues over a plurality of system cycles in the past. . A state in which the system frequency has not changed substantially over a plurality of system cycles in the past, assuming that reactive power of the amount of power calculated based on the system frequency deviation within a predetermined system cycle is injected into the power system for islanding detection 3. The islanding operation detection method according to claim 1, wherein reactive power is additionally injected into the power system when the system voltage fluctuates at the time. The isolated operation detection method according to claim 3 , wherein the phase advance / delay of the additional reactive power coincides with the phase advance / delay of the reactive power injected based on the system frequency deviation. In the control device that controls the detection operation for the single operation detection device that detects whether the distributed power source is disconnected from the power system and is operating alone,
The system voltage measurement unit that measures the voltage of the power system, the system frequency measurement unit that measures the system frequency of the power system, and the on-off of the interconnection relay with the power system by making an independent operation determination from the measured value of this system frequency measurement unit An independent operation determination unit, a system frequency deviation calculation unit that calculates a system frequency deviation from the measurement value of the system frequency measurement unit, and a reactive power amount to be injected into the power system from the system frequency deviation of the system frequency deviation calculation unit A reactive energy calculation unit, and a reactive power injection determination unit that performs control to inject reactive power based on the system frequency deviation and system voltage,
When the grid voltage fluctuates when the grid frequency has not changed substantially over the past multiple grid cycles, reactive power is injected into the power grid .
It is determined that the system voltage fluctuates when the system voltage for each system period changes with a predetermined voltage fluctuation range determined for each system period with respect to the average value of the system voltage for each of a plurality of system periods in the past. A control device characterized by that. 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 . A distributed power supply, in a distributed power supply system and a independent operation detecting apparatus to which the distributed power supply is detected whether or not the isolated operation is disconnected from the power system, the isolated operation detecting apparatus according to claim 6 A distributed power supply system characterized by being a single operation detection device.

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