JP5630047B2 - Isolated operation detection device, distributed power supply device, grid interconnection system, isolated operation detection method, and grid interconnection control method - Google Patents

Description

  The present invention, for example, between a solar power generator, a fuel cell generator, a gas engine generator, a wind power generator, a hydroelectric generator, etc., and a distributed power source (also simply referred to as “power source”) and a system power source (commercial power source). And an isolated operation detection device that detects an isolated operation of the generated power source during a grid-connected operation of the generated power source, and a distributed power supply device including the isolated operation detection device.

  In recent years, a distributed power source such as a solar cell installed in a house of a general power consumer is connected to an existing power system (commercial power system) via an inverter, and the amount of power generated by the distributed power source is increased. The surplus power when the power usage exceeds the power usage of the power source is transmitted to the grid side (reverse power flow) and purchased by the power company. The grid-connected system, which is covered by the power supply from the country, is spreading.

  In such a grid-connected system, when the power supply from the grid power supply stops, such as during an accidental power outage or work blackout on the system side, the distribution line is reversely charged by the distributed power source. Because of the possibility of electric shock or damage to power distribution equipment, safety is ensured by disconnecting the grid and inverter when the independent operation of the grid-connected inverter is detected. . In addition, an inverter, a control device for the inverter, a relay device for disconnecting the grid connection, and the like that can accommodate all types of devices necessary for grid connection of distributed power sources are all-in-one. It is generally called a conditioner, and one power conditioner is generally arranged at a predetermined position in a house with respect to one power generation source. Further, a distributed power source including a distributed power source such as a solar cell and a power conditioner is referred to as a distributed power device.

  The driving detection method is roughly classified into a passive method and an active method. The passive method is a method of detecting an isolated operation by capturing changes in the voltage waveform, phase, frequency, etc. at the connection point when shifting from the connected operation to the isolated operation. Examples of the isolated operation detection method include a “voltage phase jump detection method”, a “frequency change rate detection method”, and a “third harmonic voltage distortion rapid increase detection method”. The “voltage phase jump detection method” is a method for detecting a sudden change in voltage phase due to an imbalance between the power generation output and the load at the time of shifting to a single operation. The “frequency change rate detection method” detects a change in frequency due to an imbalance between the supplied power and the load before and after the occurrence of an isolated operation. The “third-order harmonic voltage distortion rapid increase detection method” is a method that uses a current control type inverter (inverse conversion device) to detect a rapid increase in the third-order harmonic voltage that depends on the transformer when shifting to an independent operation.

  On the other hand, the active method positively gives fluctuation elements (reactive power, frequency, etc.) from the distributed power supply to the system side, and changes in interconnection points (changes in voltage waveform, frequency, etc.) due to these fluctuation elements This is a method for detecting an isolated operation by making the value appear largely during isolated operation. Examples of the active method include “frequency shift method”, “reactive power fluctuation method”, and “harmonic superposition method”. Among these, the “frequency shift method” is a method in which a frequency bias is applied to an internal transmitter of an inverter and the like, and a frequency change that appears at the time of shifting to an independent operation is detected. The “reactive power fluctuation method” is a system in which a periodic reactive power fluctuation is given to a power generation output, and a voltage fluctuation or the like that appears at the time of shifting to an independent operation is detected. The “harmonic superposition method” is a method of superimposing a reference harmonic on the output of the distributed power supply device.

  Among these, the reactive power fluctuation method is a system that gives periodic reactive power fluctuations to the power generation output of the power generation source, and detects periodic voltage fluctuations and frequency fluctuations that appear during the transition to isolated operation. With regard to this reactive power fluctuation method, the number of high-voltage interconnection inverters (several hundred kW class) installed in elementary and junior high schools is increasing, and it is considered that the reactive power fluctuation method will often be used in the future. However, when a plurality of distributed power supply devices are connected to the system, disturbance signals for detecting the isolated operation of each distributed power supply device may cause mutual interference, lower detection sensitivity, and detect isolated operation. There is a risk that it will not be possible.

  In order to solve this, each distributed power supply is connected by wire, or a radio clock signal, AM / FM radio time signal, TV signal, GPS signal, telephone line time signal, Internet and power line communication synchronization There is a technique for synchronizing signals so as not to cause interference (see Patent Document 1).

JP 2006-262557 A

  However, in the isolated operation detection device described in Patent Document 1, the active signal cannot be synchronized if the period of the active signal (reactive power fluctuation signal) injected from each distributed power supply device is not known in advance. There is a problem. Furthermore, since some kind of communication line or receiving device is required, the equipment cost becomes high, which becomes a factor that hinders the spread of distributed power supply devices.

  The present invention has been made in view of such a situation, and the object of the present invention is even when the fluctuation period of the active signal (reactive power fluctuation signal) of each distributed power supply device linked to the power system is not known. The isolated operation detection device, the distributed power supply, the system connection, which can detect the occurrence of isolated operation in the distributed power supply device by synchronizing the active signals output from each distributed power supply device to avoid mutual interference An object of the present invention is to provide a system system, an isolated operation detection method, and a system interconnection control method.

(1) The present invention has been made in order to solve the above-mentioned problems, and the isolated operation detection device of the present invention is an isolated operation detection device used for grid connection of a distributed power supply device. A detection unit that detects voltage information based on the voltage at the connection point that connects the power supply device to the system, and at least one of the frequency and voltage at the connection point due to reactive power fluctuations based on the voltage information And a determination unit that determines that the distributed power supply device is in a single operation state.
With such an isolated operation detection device, pay attention to the fact that the active signal (reactive power fluctuation signal) fluctuates the system voltage, and this is detected by the isolated operation detection device installed in each distributed power supply device. A change in the frequency and voltage of the interconnection point due to the fluctuation is determined, and it is detected that the distributed power supply device (for example, an inverter) is in a single operation state.
As a result, even when the fluctuation period of the active signal (reactive power fluctuation signal) of each distributed power supply device connected to the system is not known, mutual interference due to the active signal output from each distributed power supply device is avoided. The occurrence of an isolated operation in the distributed power supply device can be detected.
The isolated operation detection device of the present invention is synchronized with the voltage fluctuation when it is determined that the magnitude of the voltage fluctuation in the voltage information detected by the detection unit is equal to or higher than a predetermined first reference level. And a control unit for injecting an active signal for changing the reactive power into the system.
With such an isolated operation detection device, when it is determined that the detected voltage fluctuation is greater than or equal to the first reference level, an active signal (reactive power fluctuation signal) is synchronized with the voltage fluctuation. Inject.
Thereby, when the magnitude of the detected voltage fluctuation is equal to or higher than the first reference level, an active signal (reactive power fluctuation signal) can be injected in synchronization with this single voltage fluctuation.
Further, the detection unit detects a voltage at the interconnection point at the time of activation, and extracts voltage fluctuation information having a certain period included in a predetermined period range.
With such an independent operation detection device, the voltage at the connection point (connection point voltage) is detected at the time of startup, and voltage fluctuation information in a certain cycle is extracted. For example, a band pass filter, FFT, DFT, or the like is used for extracting the voltage fluctuation information.
Thereby, the voltage fluctuation information of the period included in the predetermined range defined beforehand can be extracted from the interconnection point voltage.

(2) Further, in the isolated operation detection device of the present invention, the detection unit is based on the voltage fluctuation detection unit that detects the voltage fluctuation constantly based on the detected voltage information, and the detected constant voltage fluctuation. And a phase / period estimator for estimating a period and a phase of an active signal supplied as a signal for changing reactive power to the system.
With such an isolated operation detection device, a continuous voltage fluctuation of the system is detected, and the phase and period of the active signal (reactive power fluctuation signal) are estimated from the continuous voltage fluctuation of the system. Thereby, the period and phase of the active signal can be extracted from the constant voltage fluctuation of the system.
Furthermore, the isolated operation detection device of the present invention is characterized in that the phase / period estimation unit estimates the period and phase of the detected constant voltage fluctuation by performing a filtering process from the voltage information of the interconnection point. To do.
In such an isolated operation detection device, since the filtering process is performed from the voltage information at the interconnection point to estimate the cycle and phase of the voltage fluctuation, this allows the continuous voltage fluctuation of the grid to be linked to the grid. It is possible to easily extract the active signals of other distributed power supply devices.
Further, the isolated operation detection device of the present invention is a control unit that generates an active signal to be supplied to the system so as to synchronize with a constant voltage fluctuation detected by the detection unit based on the estimated phase and period. And a conversion unit that supplies the active signal generated in response to a command from the control unit.
In such an isolated operation detection device, the control unit is configured to detect the active signal (reactive power fluctuation signal) and the detected active signal (reactive power fluctuation signal) based on the phase and period of the active signal (reactive power fluctuation signal) detected by the determination unit. An active signal is generated to be supplied to the system so as to be synchronized. The conversion unit supplies an active signal corresponding to the command signal to the system.
Thus, the active signal can be supplied to the system in synchronization with the active signal (reactive power fluctuation signal) of the system.

(3) Moreover, the isolated operation detection apparatus of this invention is characterized by the said voltage fluctuation | variation detection part detecting the said constant voltage fluctuation | variation in the connection point connected with the said system | strain.
In such an isolated operation detection device, the voltage fluctuation detection unit detects a constant voltage fluctuation at the connection point with the system, and thereby detects a continuous voltage fluctuation of the system, The phase and period of the active signal (reactive power fluctuation signal) of another distributed power supply device linked to the system can be estimated from the constant voltage fluctuation.

(4) Further, in the isolated operation detection device of the present invention, the phase / period estimation unit estimates the period and phase of the detected constant voltage fluctuation by performing a filtering process from the voltage information of the interconnection point. It is characterized by.
In such an isolated operation detection device, since the filtering process is performed from the voltage information at the interconnection point to estimate the cycle and phase of the voltage fluctuation, this allows the continuous voltage fluctuation of the grid to be linked to the grid. It is possible to easily extract the active signals of other distributed power supply devices.

(6) Further, in the isolated operation detection device of the present invention, the control unit adjusts the phase of the active signal to be injected so that the fluctuation range of the constant voltage fluctuation is larger than a predetermined threshold value. Features.
With such an isolated operation detection device, the control unit adjusts so that an active signal (reactive power fluctuation signal) having a magnitude that enables determination of the isolated operation state of the distributed power supply device is input to the system. Thus, the isolated operation can be reliably detected.

(7) In the isolated operation detection device of the present invention, the control unit causes the active signal (reactive power fluctuation signal) having a predetermined amplitude to be injected so that a phase difference from the estimated phase is eliminated. It is characterized by.
In such an isolated operation detection device, the control unit causes an active signal (reactive power fluctuation signal) having a predetermined amplitude to be injected so that there is no phase difference from the phase estimated from the voltage fluctuation of the system. Thereby, it is possible to avoid the occurrence of mutual interference with an active signal (reactive power fluctuation signal) injected by another distributed power supply device.

(8) Further, the isolated operation detection device of the present invention is characterized in that the phase when the fluctuation range of the constant voltage fluctuation of the detected interconnection point shows the maximum value is the initial phase.
In such an isolated operation detection device, based on the estimated initial value of the phase θ of the reactive power signal of the other distributed power supply, an active signal (reactive power fluctuation signal) having a certain magnitude is converted into a phase. Change the injection to scan. Then, it is estimated that the phase at which the fluctuation range of the voltage fluctuation at the interconnection point is maximum is close to the estimated phase. Thereafter, an active signal (reactive power fluctuation signal) having a predetermined amplitude is injected so that the phase difference from the estimated phase (initial phase) is eliminated. Thereby, it is possible to avoid the occurrence of mutual interference with an active signal (reactive power fluctuation signal) injected by another distributed power supply device.

(9) In addition, in the isolated operation detection device of the present invention, the control unit determines the phase when the fluctuation range of the constant voltage fluctuation at the interconnection point shows a maximum value in a plurality of predetermined phases. The initial phase is assumed.
In such an isolated operation detection device, an active signal (reactive power fluctuation) having a certain magnitude is determined based on the initial value of the phase θ of the estimated active signal (reactive power fluctuation signal) of the other distributed power supply device. The signal) is injected so as to scan by changing the phase of the active signal according to a plurality of predetermined phases. Then, it is estimated that the phase where the fluctuation width of the constant voltage fluctuation at the interconnection point is the maximum is in the vicinity of the estimated phase. Thereafter, an active signal (reactive power fluctuation signal) having a predetermined amplitude is injected so that there is no phase difference from the estimated phase (initial phase). Thereby, it is possible to avoid the occurrence of mutual interference with an active signal (reactive power fluctuation signal) injected by another distributed power supply device.

(10) Further, the independent operation detecting apparatus of the present invention, the control unit, the deviation with respect to the estimated phase of the initial phase, and judging to be within a predetermined range defined in advance .
In such an isolated operation detection device, the fluctuation range of the constant voltage fluctuation is the initial value due to, for example, the phase of the active signal (reactive power fluctuation signal) injected from another distributed power supply device after a long time has passed. It may be possible to decrease from As a countermeasure, whether or not the deviation between the phase (initial phase) of the active signal (reactive power fluctuation signal) injected from the current other distributed power supply device and the estimated phase estimated in the previous time is within a predetermined range is determined. To detect.
Thereby, the phase difference between the active signal (reactive power fluctuation signal) injected from the other distributed power supply apparatus and the active signal (reactive power fluctuation signal) injected by the self-distributed power supply apparatus can be reduced. .

(11) Further, the independent operation detecting apparatus of the present invention, the control unit, the deviation with respect to the estimated phase of the initial phase, when it is determined that there is no the predetermined range defined in advance, the deviation is small Thus, the value of the initial phase is corrected.
With such an isolated operation detection device, it is conceivable that the fluctuation range of the voltage fluctuation always decreases from the initial value due to a phase shift after a long time. As a countermeasure, the control unit, if the phase of the current estimate, the deviation between the initial phase is not within the predetermined range, performs estimation procedure of the initial phase again, to correct the deviation.
Thereby, the phase difference between the active signal (reactive power fluctuation signal) injected from the other distributed power supply apparatus and the active signal (reactive power fluctuation signal) injected by the self-distributed power supply apparatus can be reduced. .

(12) Further, the control unit causes the initial phase to be set again when the fluctuation range of the constant voltage fluctuation is lower than a predetermined reference ratio.
With such an isolated operation detection device, it is conceivable that the fluctuation range of the voltage fluctuation always decreases from the initial value due to a phase shift after a long time. As a countermeasure, the control unit performs the initial phase estimation procedure again when the value drops by a certain value (for example, 70% or less) from the initial fluctuation range.
Thereby, the phase difference between the active signal (reactive power fluctuation signal) injected from the other distributed power supply apparatus and the active signal (reactive power fluctuation signal) injected by the self-distributed power supply apparatus can be reduced. .

(13) Further, when the fluctuation range of the constant voltage fluctuation is larger than a predetermined threshold due to the amount of fluctuation of the reactive power to be injected, the control unit generates the generation based on the detected active signal amplitude. Control to reduce the amplitude of the active signal.
With such an independent operation detection device, there is a concern that the normal voltage fluctuation increases due to the amount of reactive power fluctuation injected by the self-distributed power supply device, and the power quality may be degraded. In order to avoid this, the amplitude of the generated active signal (reactive power fluctuation signal) is controlled to be smaller than the amplitude of the detected active signal (reactive power fluctuation signal).
As a result, it is possible to avoid that the voltage fluctuation at the time of grid connection becomes excessively large and adversely affects the grid (for example, flicker occurs).

(14) Further, in the isolated operation detection device according to the present invention, when the control unit shifts to the isolated operation state and a frequency deviation equal to or greater than a predetermined reference value is detected, the generated active signal Control is performed to increase the amplitude.
In such an isolated operation detection device, the active signal of the other distributed power supply device is always a master signal (a slightly stronger signal), and the self-distributed power supply device is a slave signal (a weak signal). As a result of shifting to the single operation, when the frequency deviation is small, for example, when | Δf | ≧ 0.05 [Hz], the active signal of the self-distributed power supply device is increased.
Thereby, the voltage fluctuation at the time of grid connection can be suppressed. In addition, when an isolated operation occurs, this can be reliably detected.

(15) Further, in the isolated operation detection device of the present invention, when it is determined that the magnitude of the constant voltage fluctuation does not satisfy the predetermined first reference level, other distributed power supply devices are not activated. And an active signal (reactive power fluctuation signal) having a predetermined constant amplitude value is injected.
In such an isolated operation detection device, when the magnitude of the detected constant voltage fluctuation is smaller than the first reference level, it is determined that the other distributed power supply device is not activated, and is set to a predetermined constant. An active signal (reactive power fluctuation signal) having an amplitude value of is injected.
As a result, it is determined that the active signal (reactive power fluctuation signal) is not injected from the other distributed power supply at the grid connection point, and the active signal (reactive power fluctuation) is transmitted from the self-distributed power supply to the system. Signal) can be injected.

(17) Further, the independent operation detecting apparatus of the present invention, as the control unit, when the size of the previous SL always voltage fluctuation is determined to be the first reference level or more, synchronized to the constantly voltage variation An active signal for changing reactive power is injected into the system.
With such an isolated operation detection device, when it is determined that the detected constant voltage fluctuation is greater than or equal to the first reference level, an active signal (reactive power fluctuation) is synchronized with the constant voltage fluctuation. Signal).
Thereby, when the detected magnitude of the constant voltage fluctuation is equal to or higher than the first reference level, an active signal (reactive power fluctuation signal) can be injected in synchronization with this single voltage fluctuation.

(18) In the isolated operation detection device of the present invention, when the control unit injects the active signal, the control unit gradually maintains the phase of the active signal to be injected and gradually increases the amplitude of the active signal to be injected. It is increased to the extent that the magnitude of the always-on voltage fluctuation is less than the second reference level higher than the first reference level (the level permitted on power quality), is fixed to a constant amplitude. With such an isolated operation detection device, when the active signal (reactive power fluctuation signal) is injected, the amplitude of the active signal (reactive power fluctuation signal) is gradually increased, and the voltage fluctuation level at the interconnection point is the power quality. The amplitude is fixed to a certain level within a range that is below a certain allowable level (level 2).
Thereby, the constant voltage fluctuation of the interconnection point voltage can be suppressed to a certain level allowed in terms of power quality.

(19) In the isolated operation detection device according to the present invention, in a state where the amplitude of the active signal to be injected is fixed to the constant amplitude, the magnitude of the constant voltage fluctuation is higher than the second reference level. When it is detected that the reference level has been exceeded, it is determined that the single operation state is set.
With such an isolated operation detection device, an isolated operation is detected if the voltage fluctuation level exceeds a certain level (third reference level) in a state where the amplitude of the active signal (reactive power fluctuation signal) is fixed.
Thereby, the change of the amplitude of the active signal (reactive power fluctuation signal) injected into the system can be detected, and the occurrence of the isolated operation can be easily detected.

(20) In addition, the isolated operation detection device of the present invention detects the amplitude of the active signal when it is detected that the magnitude of the constant voltage fluctuation exceeds a third reference level higher than the second reference level. When it is detected that the fourth reference level that is higher than the third reference level is exceeded, it is determined that the vehicle is in the single operation state.
With such an isolated operation detection device, the isolated signal is detected when the amplitude of the active signal (reactive power fluctuation signal) is fixed and the voltage fluctuation level exceeds a certain level (third reference level). When the amplitude of the signal (reactive power fluctuation signal) is increased and further exceeds a certain level (fourth reference level), the isolated operation is detected.
Thereby, it can detect more reliably that the independent operation generate | occur | produced.

(21) In addition, the independent operation detection device according to the present invention may include the active signal if the constant voltage fluctuation of the period is already greater than or equal to the second reference level before injecting the activation active signal. Is characterized by not injecting.
In such an isolated operation detection device, if the voltage fluctuation level in the cycle is already equal to or higher than the second reference level before injection of the active signal at the time of activation, the active signal is not injected.
Thereby, the continuous voltage fluctuation of the connection point voltage can be suppressed to a certain level permitted in power quality.

(22) The isolated operation detection device of the present invention is characterized in that the injection of the active signal is started when the magnitude of the constant voltage fluctuation is lower than the second reference level.
In such an isolated operation detection device, if the voltage fluctuation level in the period is already equal to or higher than the second reference level before injecting the active signal at the time of activation, the active signal is not injected. However, the voltage fluctuation level is continuously monitored, and when the voltage falls below the second reference level, injection of an active signal (reactive power fluctuation signal) is started.
Thereby, the continuous voltage fluctuation of the connection point voltage can be suppressed to a certain level permitted in power quality.

(23) In the isolated operation detection device of the present invention, when the magnitude of the constant voltage fluctuation exceeds the second reference level in a state where the active signal is injected with a fixed amplitude, gradually. Further, the amplitude of the active signal is reduced so that the magnitude of the constant voltage fluctuation is not more than the second reference level.
In such an isolated operation detection device, when the active signal is injected and the amplitude is fixed, and the voltage fluctuation level exceeds the second reference level, the active signal (reactive power fluctuation signal) gradually increases. The amplitude is lowered so that the voltage fluctuation level is equal to or lower than the second reference level. Note that the reason why the amplitude of the active signal is gradually decreased is that there may be a case where the isolated operation is not detected if the amplitude of the active signal (reactive power fluctuation signal) is suddenly decreased during actual isolated operation.
Thereby, the continuous voltage fluctuation of the connection point voltage can be suppressed to a certain level permitted in power quality.

(24) In the isolated operation detection device of the present invention, the first reference level is a value for determining the presence or absence of an active signal from another isolated operation detection device, and the second reference level guarantees power quality. The third reference level is a value indicating a first stage for detecting the isolated operation state , and the fourth reference level is a value for detecting the isolated operation state . It is a value indicating two stages, and is set to a higher value in the order of the first reference level, the second reference level, the third reference level, and the fourth reference level.
In such an isolated operation detection device, the first reference level for determining the presence or absence of an active signal (reactive power fluctuation signal) by another isolated operation detection device and the maximum value allowed for guaranteeing power quality a second reference level is a third reference level which indicates a first step of detecting the islanding state, the fourth reference level showing a second step of detecting alone operating conditions used (first reference level <first 2 reference level <3rd reference level <4th reference level).
As a result, the active signal (reactive power fluctuation signal) can be detected and injected, and the isolated operation state can be detected while suppressing the constant voltage fluctuation of the interconnection point voltage to a certain level permitted in power quality.

(25) In addition, the isolated operation detection device of the present invention predetermines an expected value of the fluctuation period of the distributed power supply, and determines a deviation between the expected value and the estimated period, And an output unit that outputs a determination result based on the determination result of the deviation of the period.
With such an isolated operation detection device, for example, the fluctuation period of the other distributed power supply device is provided in advance by the power company side, and it is confirmed that there is no deviation from the cycle estimated by the self-distributed power supply device. .
Thereby, it is possible to confirm that the estimated period is accurate, and to verify whether or not the active signal (reactive power fluctuation signal) is detected accurately.

(26) In the isolated operation detection device of the present invention, the output unit displays an abnormal state when it is determined that the estimated period is not within a desired range with respect to the expected value.
As a result, when the active signal (reactive power fluctuation signal) is not accurately detected, this can be notified.

(27) Further, a distributed power supply apparatus according to the present invention includes any one of the above-described isolated operation detection apparatuses.
Thereby, it is possible to avoid occurrence of mutual interference due to active signals (reactive power fluctuation signals) injected from a plurality of distributed power supply devices.

(28) Further, the grid interconnection system of the present invention is characterized in that a plurality of the distributed power supply devices described above are linked to the grid.
Thereby, the mutual interference by the active signal (reactive power fluctuation signal) inject | poured from each distributed power supply device can be avoided.

  (29) Further, the isolated operation detection method of the present invention is an isolated operation detection method used for grid interconnection of a distributed power supply apparatus, wherein the voltage at an interconnection point for connecting the distributed power supply apparatus to the system is used. Detecting voltage information based on the voltage information, and determining, based on the voltage information, any one or more changes in the frequency and voltage of the interconnection point due to reactive power fluctuations, so that the distributed power supply is in a single operation state And a step of detecting that there is.

  (30) A grid interconnection control method according to the present invention is a grid interconnection control method used for grid interconnection of a distributed power supply apparatus, wherein a connection point for linking the distributed power supply apparatus to a grid is provided. A step of detecting voltage information based on the voltage; a step of detecting constant voltage fluctuation based on the detected voltage information; and estimating the period and phase of the reactive power fluctuation signal based on the detected constant voltage fluctuation And generating a reactive power fluctuation signal to be supplied to the system as an active signal so as to synchronize with the detected reactive power fluctuation signal based on the estimated phase and period. It is characterized by.

  According to the isolated operation detection device of the present invention, an active signal (reactive power fluctuation signal) injected from another distributed power supply device connected to the system is always regarded as a system voltage fluctuation, and an active signal synchronized with this is detected. Therefore, even if the fluctuation cycle of the active signal (reactive power fluctuation signal) of each distributed power supply device connected to the power system is not known, the active power output from each distributed power supply device can be obtained. It is possible to avoid mutual interference by synchronizing signals and to detect the occurrence of isolated operation in the distributed power supply device.

1 is a schematic configuration diagram of a grid interconnection system in which an isolated operation detection device according to an embodiment of the present invention is used. It is a figure for demonstrating the 1st operation example (basic operation example) of the isolated operation detection apparatus in this embodiment. It is a figure for demonstrating the 2nd operation example of the independent operation detection apparatus in this embodiment. It is a figure which shows the 1st structural example of the isolated operation detection apparatus in this embodiment. It is a figure which shows the 2nd structural example of the isolated operation detection apparatus in this embodiment. It is a figure which shows the 3rd structural example of the isolated operation detection apparatus in this embodiment. It is a figure which shows the logic of the independent operation determination process in the independent operation determination part 14 in this embodiment. It is a figure which shows the example of a waveform of an active signal (reactive power fluctuation signal). It is a figure which shows the example which two synchronous generators used as a distributed power supply device link to a high voltage power distribution system.

  FIG. 1 is a schematic configuration diagram of a grid interconnection system in which an isolated operation detection device according to an embodiment of the present invention is used. In the grid interconnection system shown in FIG. 1, the symbol PS is a system power source, the symbol UW is an ultra high voltage transmission line, the symbol ST is a distribution transformer, the symbol CB is a circuit breaker, the symbol HW is a high voltage distribution line, and the symbol HL is a high voltage. Side load, symbol TR is a pole transformer, symbol LW is a low voltage distribution line, symbol LL is a low voltage side load, symbols G1 and G2 are distributed power supply units, symbols PCS1 and PCS2 are power conditioners including a single operation detection device, Reference numerals PV1 and PV2 denote power generation sources (distributed power generation sources).

The system power source PS corresponds to a power plant such as a thermal power plant or a nuclear power plant, for example, and boosts the generated power to ultra high voltage power to the primary side of the distribution transformer ST via the ultra high voltage transmission line UW. Supply. The ultra high voltage transmission line UW is a transmission line used for connecting the system power source PS and the distribution transformer ST and transmitting ultra high voltage power from the system power source PS to the distribution transformer ST.
The distribution transformer ST converts the ultra high voltage power received via the ultra high voltage transmission line UW into high voltage power (for example, 6600 V) and converts the primary transformer TR to the primary via the circuit breaker CB and the high voltage distribution line HW. Supply to the side. The circuit breaker CB is a switchgear for stopping the supply (distribution) of high-voltage power when a system fault occurs. The distribution transformer ST and the circuit breaker CB are installed in the distribution substation. The high-voltage distribution line HW connects the distribution substation (distribution transformer ST and circuit breaker CB) and the pole transformer TR, and distributes high-voltage power from the distribution transformer ST to the pole transformer TR. It is a distribution line used for. Moreover, the high voltage | pressure side load HL is all the loads connected to the high voltage distribution line HW.

  The pole transformer TR converts the high-voltage power received via the high-voltage distribution line HW into low-voltage power (for example, 100V or 200V) that can be used by a general power consumer, and the general power demand via the low-voltage distribution line LW. Supply to the house (not shown) of the house. The low-voltage distribution line LW is a distribution line that is used to connect the pole transformer TR and the house of a general power consumer, and to distribute low-voltage power from the pole transformer TR to the house of a general power consumer. is there. Moreover, the low voltage | pressure side load LL is all the loads connected to the low voltage distribution line LW.

  The existing power system (commercial power system) is configured by the above system power supply PS, ultra high voltage transmission line UW, distribution transformer ST, circuit breaker CB, high voltage distribution line HW, pole transformer TR and low voltage distribution line LW. The power generation systems PV1 and PV2 are connected to such a power system via power conditioners PCS1 and PCS2 provided in pairs.

  The power generation source PV1 is a solar cell installed in a house of a general power consumer, for example, and supplies DC power obtained by solar power generation to the power conditioner PCS1. The power generation source PV2 is, for example, a solar battery installed in a house of a general power consumer different from the power generation source PV1, and supplies DC power obtained by solar power generation to the power conditioner PCS2. These power generation sources PV1 and PV2 are not limited to solar cells, and may be other power generation sources such as fuel cells.

  The power conditioner PCS1 is installed in a house of a general power consumer as a pair with the power generation source PV1, and is connected (connected) to an existing power system at a connection point X1 on the low-voltage distribution line LW. ing. Although details will be described later, the power conditioner PCS1 includes an inverter therein, and the power generation source PV1 is actually interconnected via the inverter. That is, the DC power generated by the power generation source PV1 is converted into AC power by the inverter in the power conditioner PCS1, and can be transmitted (reverse power flow) to the power system side (low voltage distribution line LW).

  The power conditioner PCS2 is installed in a house of a general power consumer as a pair with the power generation source PV2, and is connected (connected) to the existing power system at the connection point X2 on the low-voltage distribution line LW. ing. This power conditioner PCS2 is similarly provided with an inverter inside, and the power generation source PV2 is actually grid-connected via this inverter. That is, the DC power generated by the power generation source PV2 is converted into AC power by the inverter in the power conditioner PCS2, and can be transmitted (reverse power flow) to the power system side (low voltage distribution line LW).

  FIG. 2 is a diagram for explaining a first operation example (basic operation) of the isolated operation detection device according to the embodiment of the present invention. In this operation example, as shown in FIG. 2A, two distributed power supply devices G1 and G2 are connected to the low voltage distribution line LW, and the distributed power supply device G1 is connected to the low voltage distribution line LW. In this example, an active signal (reactive power fluctuation signal) (hereinafter, also simply referred to as “active signal”) that slightly fluctuates is injected. For this reason, a minute constant voltage fluctuation ΔV has already occurred in the low-voltage distribution line LW. Then, the distributed power supply device G1 detects the isolated operation using the increase in the frequency deviation or the voltage fluctuation ΔV when the isolated operation occurs.

  In this configuration, the distributed power supply G2 has a phase and period (for example, several seconds to 10) of a constant voltage fluctuation ΔV (also simply referred to as voltage fluctuation ΔV) due to a reactive power fluctuation signal injected from the existing distributed power supply G1. Estimate fluctuations in seconds). Specifically, the voltage V2 at the interconnection point X2 is detected, and the period and phase of the active signal are estimated from the voltage fluctuation ΔV2 that is a constant voltage fluctuation occurring at the interconnection point X2. For example, FIG. 2B shows the voltage fluctuation V2 at the interconnection point X2 and the reactive power fluctuation signal ΔQ side by side with time taken on the horizontal axis. As shown in FIG. 2B, a voltage fluctuation ΔV2 is generated at the interconnection point X2 due to the reactive power fluctuation ΔQ injected from the distributed power supply device G1, and therefore the distributed power supply is detected by detecting this voltage fluctuation ΔV2. The phase and period of the reactive power fluctuation ΔQ injected from the device G1 can be estimated. If the distributed power supply G2 injects an active signal (reactive power fluctuation signal) synchronized with the distributed power supply G1 into the system, the reactive power fluctuation signals injected from the two distributed power supply G1 and G2 Mutual interference can be prevented.

  FIG. 2C is a flowchart showing a method for estimating the phase and period of reactive power fluctuation ΔQ (voltage fluctuation ΔV2). Hereinafter, this estimation method will be described with reference to FIG. As an estimation procedure, first, the voltage variation ΔV at the interconnection point X2 is detected to generate voltage information (step S1). Then, filter processing (for example, DFT (Discrete Fourier Transform)) is performed from the voltage information of the interconnection point X2 (step S2), and the period and phase of the voltage fluctuation ΔV2 are estimated (step S3). Next, an active signal (reactive power fluctuation signal) having a certain magnitude is injected from the distributed power supply device G2 so as to scan using the phase estimated in step S1 as an initial value. Then, a characteristic curve of the voltage fluctuation ΔV2 and the reactive power injection phase θ as shown in FIG. 2D is obtained (step S5).

  Then, it is confirmed that the phase in which the fluctuation range ΔV2 of the voltage fluctuation at the interconnection point X2 is maximum is close to the estimated phase, and the confirmation result is corrected as necessary (for example, the distributed type is distributed to the power company in advance). It is also possible to receive information on the fluctuation cycle of the power supply device G1 and confirm that there is no deviation from the estimated cycle). Through the procedure of steps S1 to S5, the phase and cycle of the active signal to be synchronously injected by the distributed power supply G2 are determined (step S6).

  It can be considered that the voltage fluctuation ΔV2 indicating the fluctuation range of the voltage fluctuation always decreases from the initial value due to the phase of the active signal injected from the distributed power supply device G1 being shifted after a long time. As a countermeasure, when a certain amount of reduction (for example, 70% or less) occurs from the initial fluctuation range, the above procedure is performed again.

  Further, the amount of reactive power fluctuation injected by the distributed power supply G2 increases the constant voltage fluctuation ΔV2, and there is a concern that power quality may be degraded. As a preventive measure, the active signal of the distributed power supply G1 is a master signal (a slightly stronger signal), and the distributed power supply G2 is a slave signal (a weaker signal). As a result of the shift to the single operation, when the frequency change Δf occurs slightly due to the imbalance between the power generation output and the load at the shift to the single operation, for example, when “| Δf | ≧ 0.05 [Hz]” is satisfied. If the signal of the distributed power supply G2 is increased, it is possible to suppress the voltage fluctuation at the time of grid connection and to detect the isolated operation with certainty.

  Moreover, FIG. 3 is a figure for demonstrating the 2nd operation example of the independent operation detection apparatus of embodiment of this invention. In the first operation example (basic operation example) shown in FIG. 2, it is assumed that the other distributed power supply G1 exists in advance, and the distributed power supply G2 receives an active signal injected from the other distributed power supply G1. Although the example to detect was demonstrated, the isolated operation detection apparatus of this embodiment is not limited to this. In the isolated operation detection device of this embodiment, the presence / absence of an active signal (reactive power fluctuation signal) from another distributed power supply device itself is determined. If there is an active signal from another distributed power supply device, this active signal is detected. The period and phase of the signal (reactive power fluctuation signal) can be estimated.

  That is, in the system configuration shown in FIG. 3 (A), the distributed power supply G2 detects the connection point voltage V2 at the time of startup, and displays voltage fluctuation information in a predetermined range (for example, about several seconds to 10 seconds). Extraction is performed and the presence / absence of an active signal from another distributed power supply device is determined. The voltage fluctuation is extracted using a bandpass filter, FFT (Fast Fourier Transformation) or DFT. If it is determined that there is an active signal from the other distributed power supply device G1, the period and phase of this active signal (reactive power fluctuation signal) are estimated, and the active signal synchronized with the estimated period and phase. (Reactive power fluctuation signal) is injected into the system. The method for estimating the phase and period of the active signal injected from the other distributed power supply apparatus G1 is the same as the procedure shown in the flowchart of FIG.

  FIG. 3B is a diagram illustrating a method of injecting a reactive power fluctuation signal according to a voltage fluctuation level. In FIG. 3B, the horizontal axis represents time, the vertical axis represents the level of the voltage V2 at the interconnection point X2, the voltage fluctuation Va due to the active signal of the other distributed power supply G1, and the self-distributed power supply. The voltage fluctuation Vb when the reactive power fluctuation signal is applied from G2 to the interconnection point X2 is shown. In FIG. 3B, level 1 (first reference level) of voltage fluctuation V2 is a level for determining the presence / absence of a signal from another distributed power supply apparatus, and level 2 (second reference level) is for power quality. The allowable maximum voltage fluctuation level, level 3 (third reference level) is a level of the first stage of isolated operation detection described later, and level 4 (fourth reference level) is level of the second stage of isolated operation detection. Level (Level 1 <Level 2 <Level 3 <Level 4). Level 1, level 2, level 3 and level 4 are predetermined threshold values.

  Then, in the distributed power supply G2, if the voltage fluctuation Va does not reach a certain level (level 1), it is determined that another reactive power fluctuation power supply has not been activated, and an active signal having a certain magnitude by itself. (Reactive power fluctuation signal) is injected. If the voltage fluctuation Va is a certain level (level 1) or more, an active signal (reactive power fluctuation signal) is injected so as to be synchronized with the voltage fluctuation Va. In injecting the reactive power fluctuation signal, the amplitude of the active signal is gradually increased, and is fixed to a constant amplitude within a range where the voltage fluctuation level Vb at the interconnection point is below a certain level (level 2) permitted in power quality. To do. The estimation of the phase of the active signal is the same as the example shown in FIG.

  When the amplitude of the active signal is fixed and the voltage fluctuation level Vb exceeds a certain level (level 3), the isolated operation is detected. Alternatively, the amplitude of the active signal is increased when a certain level (level 3) is exceeded, and the isolated operation is detected when the voltage fluctuation level Vb exceeds a certain level (level 4). Further, if the voltage fluctuation level Va in the period is already equal to or higher than level 2 before injection of the reactive power fluctuation signal at startup, the reactive power fluctuation signal is not injected. However, the fluctuation level Vb of the reactive power fluctuation signal is constantly monitored, and when the fluctuation level Vb falls below level 2, injection of the fluctuation signal is started.

  Further, when the fluctuation signal is injected and the amplitude is fixed, when the voltage fluctuation level Vb exceeds level 2, the amplitude of the active signal is gradually lowered so that the voltage fluctuation level Vb becomes equal to or lower than level 2. To. Thus, the level of the reactive power fluctuation signal is gradually decreased because, if the amplitude of the active signal is suddenly decreased during actual single operation, there is a case where the single operation is not detected.

FIG. 4 is a diagram illustrating a first configuration example of the isolated operation detection device according to the embodiment of the present invention. This first configuration example is a configuration example for realizing the first operation example (basic operation) of the distributed power supply device G2 shown in FIG. 2, and the isolated operation detection device 11 in the distributed power supply device G2a. It is the figure which showed the internal structure of power conditioner PCS2 which consists of an inverter.
As shown in FIG. 4, the power conditioner PCS2 includes an interconnection switch 1, an inverter 3, and an isolated operation detection device 11 (including a voltmeter 2). The other distributed power supply device G1 may be any distributed power supply device that detects a reactive power fluctuation signal by injecting it as an active signal, and there is no limitation on the configuration method. For example, a configuration similar to that of the distributed power supply device G2a may be used (the same applies to FIGS. 5 and 6 described later).

  The interconnection switch 1 is a switch that disconnects the connection (connection) between the inverter 3 and the power system (low-voltage distribution line LW) in accordance with the disconnection signal input from the isolated operation determination unit 14. Here, “disconnection” refers to disconnecting the electrical connection between the inverter 3 and the power system (low voltage distribution line LW). The voltmeter 2 detects the voltage V2 at the connection point X2 of the low-voltage distribution line LW, and outputs it to the voltage fluctuation detection unit 12 as the connection point voltage V (t).

  The isolated operation detection device 11 estimates the phase and period of the voltage fluctuation ΔV2 due to the active signal injected from the other distributed power supply device G1 based on the interconnection point voltage V (t), and the self-distributed power supply device G2 Determines the phase and amplitude of an active signal to be injected into the power system, and includes a voltage fluctuation detection unit 12, an isolated operation determination unit 14, a phase / period estimation unit 15, an active signal generation unit 17, and a reactive power injection control unit. 18 and a frequency deviation detector 22.

  The voltage fluctuation detection unit 12 detects a voltage fluctuation ΔV2 included in the connection point voltage V (t) based on the connection point voltage V (t) input from the voltmeter 2. This voltage fluctuation ΔV2 is a voltage fluctuation generated by the reactive power fluctuation ΔQ injected from the distributed power supply device G1, and for example, the period fluctuates gently in about several seconds to 10 seconds. The voltage fluctuation detection unit 12 outputs a detection result of the voltage fluctuation ΔV2 included in the interconnection point voltage V (t) to the isolated operation determination unit 14. In the voltage fluctuation detection unit 12, as a means for detecting the voltage fluctuation ΔV2 included in the interconnection point voltage V (t), when digital signal processing is performed, DFT (Discrete Fourier Transform) or FFT (Fast Fourier Transform) ) Is provided with a filter unit 13 using a digital filter.

  The phase / period estimation unit 15 estimates the voltage fluctuation period T and the phase θ of the voltage fluctuation ΔV2 based on the voltage fluctuation ΔV2 detected by the voltage fluctuation detection unit 12. The phase / period estimation unit 15 includes a phase scanning unit 16. The phase scanning unit 16 injects an active signal (reactive power) of a certain magnitude from the power conditioner PCS2 so as to scan the phase θ estimated from the voltage fluctuation ΔV2 as an initial value. In this phase θ scan, a command signal having a phase θ and a period T is output to the active signal generation unit 17, and the reactive power fluctuation ΔQ is injected into the low-voltage distribution line LW through the reactive power injection control unit 18 and the inverter 3. go.

Then, by obtaining the characteristic data of the voltage fluctuation ΔV2 and the reactive power injection phase θ as shown in FIG. 2D, the constant voltage fluctuation amount (voltage fluctuation) ΔV2 at the interconnection point X2 is maximized. The phase θ and the period T are determined. The phase / period estimation unit 15 determines the phase θ and the period T of the active signal to be synchronously injected by the distributed power supply G2a, and outputs the determined signal of the phase θ and the period T to the active signal generation unit 17. .
The active signal generation unit 17 generates a reactive power command value (active power fluctuation signal) of the active signal (reactive power fluctuation signal) to be injected into the interconnection point X2 based on the phase θ and period T signals input from the phase / period estimation unit 15. Phase θm, period Tm, and amplitude Vm) are determined, and the reactive power command value signal is output to the reactive power injection controller 18.

  The reactive power injection control unit 18 changes the reactive power based on the phase θm, the period Tm, and the active amplitude Vm of the reactive power command value (active signal to be injected to the power system side) input from the active signal generation unit 17. A control signal for controlling the inverter 3 such as a PWM (Pulse Width Modulation) signal is generated and output to the inverter 3 so that an active signal synchronized with ΔV2 is injected into the power system.

Specifically, the reactive power injection control unit 18 generates a PWM signal so that the reactive power fluctuation signal corresponding to the reactive power command value (phase θm, period Tm, and active amplitude Vm) is output from the inverter 3. . The reactive power injection control unit 18 uses a sine wave / triangular wave comparison method as a PWM signal generation method, and generates a desired PWM signal by changing the amplitude and frequency of the sine wave.
The inverter 3 converts the DC power supplied from the power generation power source PV2 into AC power by switching an internal switching element (switching element in a bridge circuit such as IGBT) based on the PWM signal, thereby converting the DC power to the power system ( Output to the low-voltage distribution line LW). That is, reactive power that becomes an active signal (reactive power) is superimposed on the active power on the output voltage of the inverter 3.
The frequency deviation detector 22 detects the frequency deviation Δf from the voltage detection signal V (t) output from the voltmeter 2 and outputs the detected frequency deviation Δf to the isolated operation determination unit 14.

  The isolated operation determination unit 14 detects the voltage fluctuation ΔV included in the interconnection point voltage V (t) input from the voltage fluctuation detection unit 12 and the detection result of the frequency deviation Δf output from the frequency deviation detection unit 22. Thus, it is determined whether or not the independent operation of the inverter 3 has occurred, and when it is determined that the independent operation has occurred, a disconnection signal for turning off (disconnecting) the interconnect switch 1 is provided. Output to. In this isolated operation detection, the circuit breaker CB is opened during isolated operation, and the voltage fluctuation ΔV at the interconnection point X2 (low voltage distribution line LW) increases due to the impedance fluctuation on the high voltage side, or at the interconnection point X2. Detection is performed using the occurrence of frequency deviation.

  FIG. 7 is a diagram illustrating the determination logic of the isolated operation determination process in the isolated operation determination unit 14. In FIG. 7, ΔVk is a constant voltage fluctuation amount (voltage fluctuation ΔV2) included in the interconnection point voltage V (t), and is represented by, for example, the following expression (1). In the following equation (1), ΔV_base is an average value of the voltage fluctuation ΔV2 in the past 100 cycles, ΔV_now is the current voltage fluctuation ΔV2, and V1base is the fundamental standard voltage (100 V or 200 V). When the absolute value | ΔVk | of the ΔVk becomes equal to or greater than the threshold value ΔVkth, the theoretical value “1” is output to the OR circuit 30.

  In FIG. 7, Δfk is the frequency deviation of the interconnection point, and is represented by the difference between the current frequency f_now and the reference frequency f_base, as shown in the following equation (2). When the absolute value | Δfk | of Δfk becomes equal to or greater than the threshold value Δfkth (for example, Δfkth = 0.2 Hz), the theoretical value “1” is output to the OR circuit 30.

  As shown in FIG. 7, in the isolated operation determination process, when at least one of the two conditions of ΔVk ≧ ΔVkth and | Δfk | ≧ Δfkth is satisfied, the logic “1” is output from the OR circuit 30 to the timer 31. Then, the timer 31 outputs a determination result that the single operation of the inverter 3 has occurred when the output state “1” continues for a predetermined time. When the islanding operation determination unit 14 determines the occurrence of islanding of the inverter 3 using the islanding operation determination process as described above, the islanding operation determination unit 14 outputs a disconnection signal for turning off (disconnecting) the interconnecting switch 1. Output to 1. Thereby, since the inverter 3 is disconnected from the power system, reverse charging of the power system due to the independent operation of the inverter 3 can be prevented, and safety can be ensured. Note that the timer 31 may be individually provided for each of the signals ΔVk and Δfk.

  FIG. 4 illustrates a configuration in which two distributed power supply devices G1 and G2a are interconnected to one pole transformer TR for easy understanding of the drawing and simplification of description. A large number of distributed power supply devices may be system-connected in parallel to one pole transformer TR. A plurality of pole transformers TR are also connected to the high voltage distribution lines HW, and a large number of distributed power supply devices are connected in parallel to the low voltage distribution lines LW of the pole transformers TR. Thus, when a large number of distributed power supply devices are connected in parallel to one pole transformer TR, first, a distributed type in which an active signal (reactive power fluctuation signal) is injected into the system. A voltage variation caused by the power supply device is detected by another distributed power supply device, and an active signal synchronized with the voltage variation is injected from the other distributed power supply device.

  Moreover, FIG. 5 is a figure which shows the 2nd structural example of the independent operation detection apparatus of embodiment of this invention. Compared with the distributed power supply G2a shown in FIG. 4, the distributed power supply G2b shown in FIG. 5 newly includes a period determination unit 19 and a determination result output unit 20 in the isolated operation detection device 11. Only the point is different. Other configurations are the same as those of the distributed power supply G2a shown in FIG. For this reason, the same code | symbol is attached | subjected to the same component and the overlapping description is abbreviate | omitted.

  The period determination unit 19 determines whether or not the period T of the constant voltage fluctuation amount (voltage fluctuation) ΔV2 of the interconnection point X2 estimated by the phase / period estimation unit 16 matches a predetermined reference period Tref. The reference period Tref may be provided in advance by the electric power company as information about the fluctuation period of the distributed power supply G1. The determination result output unit 20 outputs a signal (error signal) notifying abnormality when the period determination unit 19 determines that the estimated period does not match the reference period Tref. Thereby, it can be determined that the estimated period T is accurate, and it can be verified whether or not the reactive power fluctuation signal is accurately detected.

  Moreover, FIG. 6 is a figure which shows the 3rd structural example of the isolated operation detection apparatus of embodiment of this invention. Compared with the distributed power supply G2b shown in FIG. 5, the distributed power supply G2c shown in FIG. 6 has a point that a level control unit 21 is newly added in the isolated operation detection device 11 and a frequency deviation detection unit 22. The only difference is that the signal of the frequency deviation Δf detected in is output to the isolated operation determination unit 14, the level control unit 21, and the active signal generation unit 17. Other configurations are the same as those of the distributed power supply G2b shown in FIG. For this reason, the same code | symbol is attached | subjected to the same component and the overlapping description is abbreviate | omitted.

The level control unit 21 performs a process for realizing the operation (active signal level control operation) of the distributed power supply device G2 illustrated in FIG.
As described above, the constant voltage fluctuation ΔV2 increases due to the reactive power fluctuation amount injected by the distributed power supply device G2c, and there is a concern that the power quality may be degraded. As a preventive measure, it is preferable that the active signal of the distributed power supply G1 is a master signal (slightly stronger signal) and the distributed power supply G2c is a slave signal (weaker signal).
In addition, as a result of the shift to the single operation, when the frequency deviation Δf of the interconnection point before and after the single operation occurs is small, for example, when “| Δf | ≧ 0.05 [Hz]”, Is detected by the frequency deviation detection unit 22 and notified to the active signal generation unit 17 (or the level control unit 21) to increase the active signal injected from the distributed power supply G2c. It is possible to suppress fluctuations and reliably detect an isolated operation.

  Hereinafter, the operation in the level control unit 21 will be described. In FIG. 6, the signal of the voltage fluctuation ΔV <b> 2 at the interconnection point X <b> 2 detected by the voltage fluctuation detection unit 12 is input to the level control unit 21. The level control unit 21 determines whether there is an active signal (reactive power fluctuation signal) injected from another distributed power supply device based on the voltage fluctuation ΔV2. In this determination of the presence or absence of injection, as shown in the waveform diagram of voltage fluctuation (voltage fluctuation ΔV2) of the voltage V2 on the left side of the figure, the peak value of the voltage fluctuation ΔV2 is level 1 (for example, 0.1 V (100 V system)). Is exceeded, it is determined that there is a signal (reactive power fluctuation signal) from another distributed power supply device.

  If the voltage fluctuation ΔV2 is less than level 1 (first reference level), the level control unit 21 determines that another reactive power fluctuation power source is not activated, and activates a constant magnitude by itself. The phase θk, the period Tk, and the amplitude Vk are output to the active signal generation unit 17 so as to inject a signal (reactive power fluctuation signal). The active signal generation unit 17 generates an active signal (reactive power signal) to be injected into the reactive power fluctuation at the interconnection point X2 based on the signal having the phase θk, the period Tk, and the amplitude V input from the level control unit 21. Reactive power command value command values (phase θm, period Tm, and amplitude Vm) are determined and output to reactive power injection control unit 18.

  The reactive power injection control unit 18 causes the reactive power fluctuation signal to be injected to the power system side based on the reactive power command values (phase θm, period Tm, and active amplitude Vm) input from the active signal generation unit 17. Then, a control signal for controlling the inverter 3, for example, a PWM (Pulse Width Modulation) signal is generated and output to the inverter 3.

  On the other hand, if the level control unit 21 determines that the voltage fluctuation ΔV2 is equal to or higher than level 1 (first reference level), the active signal generation unit 17 assumes that there is an injection of an active signal from another distributed power supply device. Is instructed to synchronize with the phase θ and the period T output from the phase / period estimation unit 15. In injecting the reactive power fluctuation signal, the active signal generator 17 gradually increases the amplitude of the active signal, and the voltage fluctuation level at the interconnection point is a certain level 2 (second reference level, eg, , Fixed to a constant amplitude within a range of 1V or less in the 100V system.

  Then, the isolated operation determination unit 14 detects the isolated operation when the voltage fluctuation level ΔV2 exceeds level 3 (third reference level) in a state where the amplitude of the active signal is fixed. Alternatively, if the level 3 is exceeded, the active signal determination unit 17 (or the active signal generation unit 17 via the level control unit 21) is instructed to increase the amplitude of the active signal, and a certain level 4 (fourth) If the reference level is exceeded, isolated operation is detected.

  If the voltage fluctuation level in the period is already level 2 or higher before injection of the reactive power fluctuation signal at the time of startup, the level control unit 21 instructs the active signal generation unit 17 not to inject the reactive power fluctuation signal. Instruct. However, the fluctuation level (voltage fluctuation ΔV2) of the reactive power fluctuation signal is constantly monitored, and when it falls below level 2, an instruction is given to start injection of the fluctuation signal.

Further, the level control unit 21 gradually reduces the amplitude of the active signal when the voltage fluctuation level exceeds the level 2 at the stage where the fluctuation signal is injected and the amplitude is fixed, and the voltage fluctuation level becomes the level 2. Instruct the active signal generator 17 to: Thus, the level of the reactive power fluctuation signal is gradually decreased because, if the amplitude of the active signal is suddenly decreased during actual single operation, there is a case where the single operation is not detected.
Thus, the level control unit 21 appropriately controls the level of the active signal injected into the system according to the level of the active signal injected from the other distributed power supply device.

Further, the frequency deviation detector 22 detects a frequency change from the voltage detection signal V (t) output from the voltmeter 2. As a result of shifting to the single operation, when a deviation of a predetermined reference value or more occurs in the frequency before and after the single operation (for example, when the frequency deviation Δf is | Δf | ≧ 0.05 [Hz]), this frequency A change detection result signal is output to the isolated operation determination unit 14, the level control unit 21, and the active signal generation unit 17. When the signal from the frequency deviation detector 22 is input to the level controller 21 and the active signal generator 17, the reactive power command value (the amplitude of the active signal to be injected to the power system side) is increased so that the amplitude of the active signal is increased. The active amplitude Vm of the command value) is increased.
As a result, for example, the active signal of the other distributed power supply device is always the master signal (slightly stronger signal), and the self-distributed power supply device is always the slave signal (weaker signal). And when shifting to a single operation, the amplitude of the active signal of the self-distributed power supply device can be increased.

In the examples shown in FIGS. 4, 5, and 6, the example in which the distributed power supply device is connected to the low-voltage distribution system using the inverter has been described. However, the present invention is connected to the high-voltage distribution system. It can also be applied to distributed generators. For example, the present invention can also be applied when the synchronous generator applies an active signal to the automatic voltage regulator (AVR) to generate reactive power fluctuations during grid connection.
FIG. 9 is a diagram illustrating an example in which two synchronous generators SG1 and SG2 serving as distributed power supply devices are connected to a high-voltage distribution system. Each of the synchronous generators SG1 and SG2 has automatic voltage regulators AVR1 and AVR2 for adjusting the field voltage. Further, high voltage side loads HL1, HL2 are connected to the high voltage distribution line HW, respectively.

In the system configuration shown in FIG. 9, the synchronous generator SG1 is a generator adopting the method of the present invention, and the synchronous generator SG2 is another generator (synchronous generator of reactive power fluctuation method). This synchronous generator SG1 is provided with an independent operation detection device 11 for detecting the voltage at the connection point between the synchronous generator SG1 and the high-voltage distribution line HW and controlling the automatic voltage regulator AVR1.
In the isolated operation detection device 11 shown in FIG. 9, the connection point voltage V (t) is detected when the synchronous generator SG1 is started, and voltage fluctuation information in a predetermined range (for example, about several seconds to 10 seconds) is obtained. Extraction is performed to determine whether or not an active signal (reactive power fluctuation signal) is injected by another synchronous generator SG2. When it is determined that there is an active signal injected from the synchronous generator SG2, the period and phase of this active signal are estimated, and an active signal synchronized with the estimated period and phase is injected into the system. The injection of the active signal is performed by controlling the field voltage by the automatic voltage regulator AVR1. That is, in the case of a synchronous generator, when the field current is decreased, the advance power factor is obtained, and when the field current is increased, the delay power factor is obtained. Therefore, by changing the field voltage by the automatic voltage regulator AVR1. A desired active signal (reactive power fluctuation signal) can be injected into the distribution system.

  Compared with the isolated operation detection device 11 shown in FIG. 6, the configuration of the control unit isolated operation detection device 11 is changed from the reactive power injection control unit 18 shown in FIG. 6 to the reactive power fluctuation control unit 18 a shown in FIG. 9. The only difference is the other configuration, which is the same as that of the isolated operation detection device 11 shown in FIG. For this reason, the same code | symbol is attached | subjected to the same component and the overlapping description is abbreviate | omitted. The reactive power fluctuation control unit 18a receives an active signal (reactive power fluctuation signal) from the synchronous generator SG1 based on the reactive power command value (phase θm, period Tm, and active amplitude Vm) input from the active signal generation unit 17. The automatic voltage regulator AVR1 is controlled so that is injected into the high voltage system side. About other operation | movement, it is the same as that of the case of the isolated operation detection apparatus shown in FIG.

  4, 5, 6, and 9 has a computer system that includes a CPU, ROM, and RAM therein. And the process of a series of processes regarding the process of each part in the isolated operation detection apparatus 11 described above is stored in a computer-readable recording medium in the form of a program, and this program is read and executed by the computer. The above processing is performed.

  That is, the voltage fluctuation detection unit 12, the filter unit 13, the single operation determination unit 14, the phase / period estimation unit 15, the phase scan unit 16, the active signal generation unit 17, the reactive power injection control unit 18 in the single operation detection device 11, In the reactive power fluctuation control unit 18a, the cycle determination unit 19, the determination result output unit 20, the level control unit 21, and the frequency deviation detection unit 22, all or part of each process is performed by a central processing unit such as a CPU or a ROM. This is realized by reading the program into a main storage device such as a RAM and executing information processing and arithmetic processing.

  Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.

  In the above-described embodiment, an example in which the active signal (reactive power fluctuation signal) injected into the system is a signal that changes in a sine wave shape has been described. However, as shown in FIG. In addition to changing to, it may change to a triangular wave shape. Furthermore, it may be changed to a trapezoidal wave or a rectangular wave.

  Here, the correspondence between the present invention and the embodiment will be described supplementarily. The distributed power supply devices G2, G2a, G2b, and G2c correspond to the distributed power supply devices in the present invention. Moreover, the grid connection system in this invention respond | corresponds, for example as shown in FIG. 1 to the grid connection system by which several distributed power supply devices were linked to the low voltage distribution line. The voltage fluctuation detector 12 and the phase / period estimator 15 correspond to the detector in the present invention. The determination unit in the present invention mainly corresponds to the isolated operation determination unit 14, and the isolated operation determination unit 14 corresponds to a part that supplies a signal to the isolated operation determination unit 14. The control unit in the present invention corresponds to the isolated operation detection device 11 (except for the voltmeter 2), and the conversion unit in the present invention corresponds to the inverter 3.

In the above-described embodiment, the isolated operation detection device G2 and the like used for the grid interconnection of the distributed power supply device includes a detection unit (voltage fluctuation detection unit 12 and phase / period estimation) that detects voltage information based on the system voltage. Unit 15) and a single operation determination unit 14 that determines a change in voltage fluctuation at the interconnection point due to reactive power fluctuation and detects that the inverter 3 is in a single operation state based on the voltage information.
In the above-described embodiment, the detection unit estimates the period and phase of the active signal based on the voltage fluctuation detection unit 12 that constantly detects the voltage fluctuation ΔV2 based on the detected voltage and the detected constant voltage fluctuation ΔV2. And a phase / period estimation unit 15.
Moreover, in the said embodiment, the independent operation detection apparatus 11 which produces | generates the active signal supplied to a system | strain so that it may synchronize with this detected voltage fluctuation | variation based on the detected phase and period, and the independent operation detection apparatus 11 And an inverter 3 for supplying the active signal generated in response to a command from

Thus, in the isolated operation detection device of this embodiment, the reactive power fluctuation used as a disturbance signal (the reactive power fluctuation method and the reactive power compensation method as the active method of the isolated operation detection device) fluctuate the system voltage. Focusing on this, this is detected as a system voltage fluctuation by an isolated operation detection device installed in each distributed power supply, and this fluctuation signal is used as a synchronization signal. Disturbance signals can be synchronized without using a receiver. Furthermore, according to the isolated operation detection device of this embodiment, even if the fluctuation period of the disturbance signal of the other distributed power supply apparatus is not known, the fluctuation period and phase of the active signal injected from the other distributed power supply apparatus , And by outputting a disturbance signal synchronized therewith, mutual interference due to the active signal can be prevented.
In addition, by determining the presence or absence of active signals injected from other distributed power supply devices from the amount of system voltage fluctuation, and adjusting the level of the disturbance signal that should be output by itself, the fluctuation range required for islanding detection can be reduced. At the same time, it is possible to constantly suppress system voltage fluctuations and suppress deterioration in power quality.

  Although the embodiment of the present invention has been described above, the isolated operation detection device and the distributed power supply device of the present embodiment are not limited to the illustrated examples described above, and do not depart from the gist of the present invention. Of course, various changes can be made.

PS ... System power supply, UW ... Ultra high voltage transmission line, ST ... Transformer for distribution,
CB ... circuit breaker, HW ... high voltage distribution line, HL, HL1, HL2 ... high voltage side load,
TR ... Pole transformer, LW ... Low voltage distribution line, LL ... Low voltage side load,
G1, G2, G2a, G2b, G2c ... distributed power supply device,
PCS1, PCS2 ... power conditioner, PV1, PV2 ... distributed power generation,
SG1, SG2 ... synchronous generator, AVR1, AVR2 ... automatic voltage regulator,
1 ... interconnection switch, 2 ... voltmeter, 3 ... inverter,
11 ... Isolated operation detection device, 12 ... Voltage fluctuation detection unit, 13 ... Filter unit,
14 ... Isolated operation determination unit, 15 ... Phase / period estimation unit, 16 ... Phase scan unit, 17 ... Active signal generation unit, 18 ... Reactive power injection control unit,
18a ... reactive power fluctuation control unit, 19 ... period determination unit, 20 ... determination result output unit, 21 ... level control unit, 22 ... frequency deviation detection unit

Claims (28)

An isolated operation detection device used for grid connection of a distributed power supply device,
A detection unit for detecting voltage information based on a voltage at a connection point for connecting the distributed power supply device to a system;
A determination unit that determines, based on the voltage information, a change in any one or more of the frequency and voltage of the interconnection point due to reactive power fluctuations, and detects that the distributed power supply device is in a single operation state;
When it is determined that the magnitude of the voltage fluctuation in the voltage information detected by the detection unit is equal to or higher than a predetermined first reference level, an active signal that fluctuates the reactive power so as to be synchronized with the voltage fluctuation. A control unit to be injected into the system;
With
The detector is
Detecting the voltage of the interconnection point at the time of starting, and extracting voltage fluctuation information of a certain period included in a predetermined period range;
An isolated operation detection device. An isolated operation detection device used for grid connection of a distributed power supply device,
A detection unit for detecting voltage information based on a voltage at a connection point for connecting the distributed power supply device to a system;
A determination unit that determines, based on the voltage information, a change in any one or more of the frequency and voltage of the interconnection point due to reactive power fluctuations, and detects that the distributed power supply device is in a single operation state;
Based on the estimated phase and period, a control unit that generates an active signal to be supplied to the system so as to be synchronized with a constant voltage fluctuation detected by the detection unit;
A converter that supplies the active signal generated in response to a command from the controller;
With
The detector is
A voltage fluctuation detection unit that constantly detects voltage fluctuations based on the detected voltage information;
A phase / period estimator for estimating the period and phase of an active signal supplied as a signal for varying reactive power to the system based on the detected constant voltage fluctuation;
An isolated operation detection device comprising: The voltage fluctuation detector is
The islanding operation detection device according to claim 2, wherein the constant voltage fluctuation at an interconnection point connected to the system is detected. The phase / period estimator is
The isolated operation detection apparatus according to claim 2 or 3, wherein a filtering process is performed from voltage information of the interconnection point to estimate a period and a phase of the detected constant voltage fluctuation. The controller is
Wherein such variation width constantly voltage variation becomes larger than a predetermined threshold value, the isolated operation detecting apparatus according to any one of adjusting the phase of said active signal to be injected from claim 2, wherein 4. The controller is
The active signal of predetermined amplitude, isolated operation detecting apparatus according to any one of claims 2 to 5, characterized in that to inject so that the phase difference between the estimated phase is eliminated. The controller is
The islanding operation according to any one of claims 2 to 6 , wherein the phase when the fluctuation range of the constant voltage fluctuation at the detected interconnection point shows a maximum value is the initial phase. Detection device. The controller is
The detected fluctuation range always voltage variation of interconnection points, in a plurality of phases are predetermined, according to the phase of the case shown a maximum value to claim 7, characterized in that said initial phase Single operation detection device. The controller is
The islanding operation detection device according to claim 7 or 8 , wherein a deviation of the initial phase from the estimated phase is determined to be within a predetermined range. The controller is
The initial phase value is corrected so that the deviation becomes small when it is determined that a deviation of the initial phase from the estimated phase is not within a predetermined range. The isolated operation detection device according to any one of claims 7 to 9 . The controller is
The isolated operation according to any one of claims 7 to 10 , wherein when the fluctuation range of the constant voltage fluctuation is lower than a predetermined reference ratio, the initial phase is set again. Detection device. The controller is
When the fluctuation range of the constant voltage fluctuation is greater than a predetermined threshold due to the amount of reactive power fluctuation to be injected, control is performed so that the amplitude of the generated active signal is smaller than the amplitude of the detected active signal. The isolated operation detection device according to any one of claims 2 to 11 , wherein: The controller is
The process proceeds to the islanding state, when the reference value or more frequency deviation predetermined is detected, claims from claim 2, wherein the controller controls so as to increase the amplitude of the activity signal for the generation The isolated operation detection device according to any one of 12 . When it is determined that the magnitude of the constant voltage fluctuation does not satisfy the predetermined first reference level, it is determined that the other distributed power supply device is not activated, and the predetermined constant amplitude value is active. isolated operation detecting apparatus according to claims 2, characterized in that injecting a signal to one of claims 13. Control unit, when the size of the previous SL always voltage fluctuation is determined to be the first reference level or more, injecting an active signal to vary the reactive power in synchronization with the constant voltage variations in the system isolated operation detecting apparatus according to 請 Motomeko 14 you characterized. The controller is
When injecting the active signal, the amplitude of the active signal to be injected is gradually increased while maintaining the phase of the active signal to be injected, and the magnitude of voltage fluctuation is always higher than the first reference level. The isolated operation detection device according to claim 1 or 15 , wherein the single operation detection device is fixed to a constant amplitude within a range that is equal to or lower than a second reference level. With the amplitude of the active signal to be injected fixed to the constant amplitude,
The method according to claim 16 , wherein when it is detected that the magnitude of the constant voltage fluctuation exceeds a third reference level that is higher than the second reference level, it is determined that the single operation state is set. Single operation detection device. When it is detected that the magnitude of the constant voltage fluctuation exceeds a third reference level that is higher than the second reference level, the amplitude of the active signal is increased, and the fourth reference is higher than the third reference level. The isolated operation detection device according to claim 16 , wherein when it is detected that the level is exceeded, it is determined that the operation is in the isolated operation state. Before injecting the active signal at startup, already if the magnitude of the constant voltage fluctuation of the cycle is the second reference level or higher, according to claim claim 16, wherein the active signal is characterized in that not inject 18 The isolated operation detection device according to any one of the above. The magnitude of the constant voltage variation, the second case where the reference level below the, isolated operation detecting apparatus according to claim 18 claim 16, characterized in that to start the injection of the active signal. In a state where the active signal is injected with a fixed amplitude, when the magnitude of the constant voltage fluctuation exceeds the second reference level, the amplitude of the active signal is gradually reduced to reduce the constant voltage. isolated operation detecting apparatus according to any one of claims 20 to claim 16, the magnitude of the fluctuations is characterized in that so as to be less than the second reference level. The first reference level is a value for determining the presence or absence of an active signal by another isolated operation detection device,
The second reference level is a maximum value allowed to guarantee power quality;
The third reference level is a value indicating a first stage of detecting the isolated operation state ;
The fourth reference level is a value indicating a second stage of detecting the isolated operation state ;
The isolated operation detection device according to claim 18 , wherein higher values are set in the order of the first reference level, the second reference level, the third reference level, and the fourth reference level. The controller is
An expected value of a fluctuation period of the distributed power supply device is determined in advance, a period determination unit that determines a deviation between the expected value and the estimated period, and a determination result is output based on a determination result of the deviation of the period A determination result output unit to perform,
The islanding operation detection device according to any one of claims 2 to 15 , further comprising: The determination result output unit includes:
The isolated operation detection device according to claim 23 , wherein an abnormal state is displayed when it is determined that the estimated period is not within a desired range with respect to the expected value. A distributed power supply device comprising the isolated operation detection device according to any one of claims 1 to 24 . 26. A grid interconnection system, wherein the distributed power supply device according to claim 25 is linked to the grid. An isolated operation detection method used for grid interconnection of a distributed power supply device,
Detecting voltage information based on a voltage at a connection point for connecting the distributed power supply device to a system;
Determining any one or more changes in the frequency and voltage of the interconnection point due to reactive power fluctuations based on the voltage information, and detecting that the distributed power supply device is in a single operation state;
When it is determined that the magnitude of the voltage fluctuation in the detected voltage information is greater than or equal to a predetermined first reference level, an active signal that fluctuates reactive power is injected into the system in synchronization with the voltage fluctuation. And steps to
Detecting the voltage of the interconnection point at the time of startup, and extracting voltage fluctuation information of a certain period included in a predetermined period range;
An islanding operation detection method comprising: A grid interconnection control method used for grid interconnection of a distributed power supply device,
Detecting voltage information based on a voltage at a connection point for connecting the distributed power supply device to a system;
Constantly detecting voltage fluctuations based on the detected voltage information;
Estimating the period and phase of the reactive power fluctuation signal based on the detected constant voltage fluctuation;
Generating a reactive power fluctuation signal to be supplied to the grid as an active signal so as to be synchronized with the detected reactive power fluctuation signal based on the estimated phase and period;
A grid interconnection control method comprising:

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