JP2002199590A - Detecting method of independent operation in distributed power supplies - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect transition to independent operation for each distributed power supply due to stopped system operation separately by providing an injection means of interharmonic waves to each one or a group of the power supplies. SOLUTION: Distributed power supplies 6, 6' consisting of more than 1 but less than n-1 out of n linkage operated distributed power supplies 6, 6' are grouped as injection/detection power supplies, and the other remaining ones are grouped as non-injection/detection power supplies. The injection/detection power supplies are provided with an interharmonic wave injecting means and a first detecting means to detect their operation, and the non-injection/detection power supplies are provided with a second detecting means to detect their operation. The injection/detection power supplies inject interharmonic waves to the system in different frequencies for each power supply and detect that they are in independent operation from the voltage changes or impedance (or admittance) changes in each frequency. The non-injection/detection power supplies detect the injected frequency voltage to one of the injection/detection supplies and detect the independent operation from the voltage changes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plurality of distributed power supplies connected to an electric power system and operated to be connected to the electric power system.
Based on detection of interharmonics of non-integer multiples of the system fundamental wave injected into the system, a distributed type that detects the transition from interconnection operation of each distributed power supply to isolated operation due to system stoppage The present invention relates to a method for detecting an isolated operation of a power supply.

[0002]

2. Description of the Related Art Conventionally, a distributed power source connected to a power system such as a power distribution system and connected to the power system has been known as an inverter type power source such as a photovoltaic power generator or a rotating machine such as a gas turbine power generator. There is a rotary machine type using a rotary machine.

[0003] In these distributed power supplies, if the circuit breaker of the upper substation is opened for some reason and the system stops, there is a possibility that the operation will shift from the interconnection operation to the isolated operation.

[0004] If the grid is charged by this single operation, an electric shock accident or the like may occur.

[0005] Therefore, in this type of distributed power supply, when the operation is switched from the grid-connected operation to the isolated operation,
It is necessary to detect this transition immediately and quickly disconnect the distributed power supply from the grid.

As a method for detecting the isolated operation of this type of distributed power supply, Japanese Patent Application Laid-Open No. H10-248168 (H0
2J 3/38) and Japanese Patent Application Laid-Open No. H11-252806 (H02J 3/38) describe that an interharmonic of a non-integer multiple of the system fundamental wave synchronized with the system fundamental wave is injected into the system. Then, based on the measurement results of the voltage and current at the injection frequency of the system, the impedance or admittance of interharmonics of the injection frequency of the system is detected. A method is described for quickly and reliably detecting the migration of a chromosome.

Further, when a plurality of distributed power supplies are connected to a system, a system stop is detected in a higher system of the system to which each distributed power supply is connected, and the distributed power supplies are collectively disconnected. Therefore, it is more advantageous from the viewpoint of the withstand voltage class and the like to detect and shift the transition from the interconnection operation to the individual operation individually for each distributed power supply, and the independent operation can be detected by an inexpensive device with a low withstand voltage. For this reason, it is preferable that inter-order harmonics be injected for each distributed power supply to separately detect the transition from interconnected operation to isolated operation for each distributed power supply.
As described in the specification, drawings and the like of the application No. 2769, in order to avoid erroneous detection due to overlapping injection of interharmonics of the same frequency, the injection frequency of interharmonics is set for each distributed power source. It needs to be different.

On the other hand, in the specification, drawings and the like of the application of Japanese Patent Application No. 11-91542, the transition from the interconnection operation of the distributed power supply to the isolated operation due to the system stoppage is described by the inter-order modulation of the injection frequency of the system. It is described that detection is performed from a change in voltage of a wave.

In this case, it is only necessary to detect the voltage of the system, there is no need to calculate impedance or admittance, and there is an advantage that the islanding operation can be detected by a simple and inexpensive method.

[0010]

In the above-mentioned conventional method for detecting an isolated operation of a distributed power supply, a transition from an interconnected operation due to a system stop to an isolated operation is performed for a plurality of distributed power supplies connected to a system. If each of the distributed power sources is individually detected and disconnected, all the distributed power sources must be provided with an inter-harmonic injection means and a detection means. When detecting from a change in impedance or admittance, it is necessary to perform complicated calculation of impedance or admittance for interharmonics of the system by the detection means. Therefore, there is a problem that capital investment of the entire system is expensive.

According to the present invention, the transition from the interconnected operation of a plurality of distributed power supplies connected to the system to the isolated operation is performed by providing inter-harmonic injection means only in one or a part of the distributed power supplies. It is an object of the present invention to be able to individually perform each distributed power supply.

Further, the transition from the interconnected operation to the isolated operation can be performed separately for each distributed power supply by providing one inter-harmonic injection means independent of each distributed power supply. Is also an issue.

[0013]

In order to solve the above-mentioned problems, a method for detecting the isolated operation of a distributed power supply according to the present invention is, in the case of claim 1, connected to an electric power system and connected to this system. And n (n is an integer of 2 or more) distributed power supplies of at least one and n-1 or less are used as power supplies on the injection / detection side, and the remaining distributed power supplies are used on the non-injection / detection side. The power supply on the injection / detection side is provided with a means for injecting interharmonics of a non-integer multiple of the system fundamental wave and a first detection means in the operating state, and the power supply on the non-injection / detection side is A second detection means is provided for the state, and the power supply on the injection / detection side injects interharmonics having different frequencies for each power supply into the system by the injection means, and the first detection means adjusts the injection frequency of the system by the first detection means. Of impedance (or admittance) for voltage change or system injection frequency The transition from interconnected operation to isolated operation due to system stoppage is detected from the power supply, and the power supply on the non-injection / detection side is detected by the second detection means by using any one of the injection frequencies of the power supply on the system injection / detection side. A voltage is detected, and a transition from the interconnection operation to the islanding operation due to a system stop is detected from a change in the detected voltage.

Therefore, only one of the n distributed power supplies connected to the system or n-1 or less of the partial power supplies (power supply on the injection / detection side) is provided with the operating state detecting means (second power supply). 1
Means for injecting interharmonics is provided together with the other means, and only the operating state detecting means (second detecting means) is provided for the remaining distributed power supply (power supply on the non-injection / detection side).
No interharmonic injection means is provided.

[0015] One or more and n-1 or less distributed power supplies on the injection / detection side inject harmonics having different frequencies for each power supply from the injection means into the system, and perform first detection of the operating state. Based on the measurement result of each injection frequency of the system by means, from the voltage change of the injection frequency of the system or the impedance or admittance for interharmonics,
The transition from interconnected operation to independent operation of each distributed power supply due to a system stop is individually detected.

Further, the remaining distributed power supply on the non-injection / detection side receives a voltage change of interharmonic injected into the system from any of the power supply on the injection / detection side by the second detection means in the operating state. Is detected, and a transition from the interconnected operation to the isolated operation is individually detected from the change.

Therefore, all (n pieces) connected to the system
The inter-harmonic injection means is provided only in one or a part (n-1 or less) of the distributed power sources, and the distributed power sources are individually switched from the grid-connected operation to the isolated operation by stopping the system. Of the distributed power sources can be disconnected from the system based on this detection.

Next, in the case of claim 2, each of n (n is an integer of 2 or more) distributed power supplies connected to the power system and connected to this system is provided with operating state detecting means, 1 connected to the system separately from each of the distributed power sources
The inter-harmonics of a non-integer multiple of the system fundamental wave are injected from the common injection devices into the system, and the detection means of each distributed power supply uses the voltage change of the system injection frequency to connect the system by stopping the system. From the operation to the islanding is detected.

Therefore, in this case, all (n) distributed power supplies connected to the system are provided with only the operating state detecting means, and all the distributed power supplies are provided with means for injecting interharmonics. Absent.

Then, an appropriate interharmonic is injected into the system from a common injection device independent of each distributed power source, and the operating state of each distributed power source is detected by the means for detecting the operating state of each distributed power source from a change in the injection frequency of the system. Detects a shift from interconnection operation to islanding operation based on system shutdown.

Therefore, it is possible to detect the transition from the interconnected operation to the isolated operation due to the system stop individually by each of the distributed power sources without providing any means for injecting interharmonics into all the distributed power sources.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. (First Embodiment) First, an embodiment corresponding to claim 1 will be described with reference to FIGS. FIG. 1 shows a single-line diagram of the power system, and shows 6.6 KV / 220 V of the substation 1.
To the 220 V distribution line 4 as a power system drawn from the secondary side of the transformer 2 through the circuit breaker 3.
# 1, # 2,..., # Via a normally closed switch 5 for disconnection
n, distributed power sources 6 are connected, and these distributed power sources 6 are connected to the grid.

In this embodiment, one distributed power source # 1 is used as a power source on the injection / detection side, and the other distributed power sources # 2 to #n are used.
N-1 distributed power sources 6 are non-injection / detection-side power sources, and the # 1 distributed power source 6 has an inter-harmonic injection unit and an operating state first detection unit. A detection device 7 is provided, and the remaining distributed power supplies 6 of # 2 to #n are provided with an islanding operation detection device 8 having second detection means of the operating state.

The islanding detection device 7 is formed as shown in FIG. 2 in the case of an independent injection system in which an interharmonic current is injected into the distribution line 4 independently of the distributed power source 6.

In this case, each of the distributed power supplies 6 may be of an inverter type or a rotating machine type. During the interconnection operation, the system voltage and system current of the instrument transformer 9 and the instrument current transformer 10 are measured. Based on the signal, the power supply control unit 11 controls the operation of the power generation unit 12 including an inverter or a rotating machine, and supplies AC power synchronized with the system fundamental wave to the distribution line 4 from the power generation unit 12 via the switch 5. I do.

Next, the isolated operation detecting device 7 comprises an injection section 7a forming an injection means for interharmonics, and a detection section 7b forming a first detection means for operating the distributed power supply 6. In the injection section 7a, the current injection control section 13 performs a predetermined order of a non-integer multiple of the system fundamental wave synchronized with the system fundamental wave, for example, 2 by PLL control based on a voltage measurement signal of the instrument transformer 9 or the like. .375 order inter-harmonic control signal.

The frequency (order) of the control signal is selected in consideration of the characteristics of the distribution line 4 and the like so that a change in the impedance or admittance of the system 4 due to the stop of the system can be reliably detected.

The control signal of the current injection control unit 13 is converted into a gate signal for driving an inverter by a gate signal forming unit 14, and the inverter 15 for interharmonic injection is driven by the gate signal. From 15, a current of, for example, a 2.375 order interharmonic is injected into the distribution line 4.

In the detecting section 7b, the measuring section 1 is operated based on the measurement signals from the instrument transformer 9 and the instrument current transformer 10.
6. By digital waveform analysis such as FFT and DFT,
The voltage and current at the instantaneous injection frequency (for example, 2.375 order) of the distribution line 4 are detected and measured from the injection point of the interharmonic, and the voltage and current information of the measurement result is impedance (or admittance). ) Is supplied to the calculation unit 17.

The calculation unit 17 calculates the injection frequency fm.
Is a voltage Vm and a current Im is a voltage Vm and a current I
m, the impedance Zm or the admittance Ym = 1 / Zm for the injection frequency fm of the distribution line 4 is represented by Z
It is determined from the vector operation of m = Vm / Im and Ym = Im / Vm. Note that Vm, Im, Zm, and Ym are vector values.

Further, the impedance Zm or the admittance Ym of the calculation result of the calculation unit 17 is determined by the islanding operation determination unit 18.
The determination unit 18 determines whether or not the above-described information is supplied, for example, in Japanese Patent Application Laid-Open Nos. 10-248168 and 11-252806.
As described in Japanese Patent Application Laid-Open Publication No. H10-107, the transition from the interconnection operation of the distributed power supply 6 to the isolated operation based on the opening of the circuit breaker 3 due to the system stoppage is detected from the changes in the impedance Zm and the admittance Ym.

In the case of the detection method described in Japanese Patent Application Laid-Open No. 10-248168, the impedance or admittance Ym is converted into the short-circuit capacity of the distribution line 4, and based on the change in the short-circuit capacity, the impedance Zm, admittance due to system stoppage is determined. From the change in the magnitude of Ym, the shift of the distributed power supply 6 from the interconnected operation to the isolated operation is detected.

Further, in the case of the detection method described in Japanese Patent Application Laid-Open No. H11-252806, the interconnection of the distributed power supply 6 by stopping the system is determined based on the capacitive and inductive directions and amounts of changes in the impedance Zm or admittance Ym. Detects the transition from operation to islanding operation.

When the operation is shifted to the islanding operation, the switch 5 is opened via the disconnection control unit 19 by the detection output of the islanding operation of the determination unit 18, and the distributed power source 6 of # 1 is connected to the distribution line 4. Disconnect immediately from.

Next, the isolated operation detection device 8 of the distributed power supply 6 of # 2 to #n is connected to the order 7 injected into the distribution line 4 from the injection section 7a of the isolated operation detection device 7 of the distributed power supply 6 of # 1. In order to detect the transition from the interconnection operation to the individual operation of each distributed power supply 6 based on the voltage change of the subharmonic, as shown in FIG.
As the second detecting means of the operating state, only the detecting unit corresponding to the detecting unit 7b in FIG. 2 is provided.

Then, based on the measurement signal of the voltage of the instrument transformer 9, the order of the injection frequency (for example, 2.375 order) injected into the distribution line 4 from the injection section 7 a by digital waveform analysis of the measurement section 16 ′. Detect and measure the voltage of the subharmonic,
The information on the voltage as a result of the measurement is supplied to the islanding operation determination unit 18 '.

At this time, the voltage of the interharmonic of the injection frequency of the distribution line 4 can be determined, for example, as described in the specification and drawings of Japanese Patent Application No. 11-91542 (hereinafter referred to as an application). , And rises due to system stoppage.

As described in the above-mentioned application, the voltage change of the interharmonic at the time when the system is stopped is affected by the power factor improving capacitor equipment, load equipment and the like of the distribution line 4. However, as is clear from Table 1, 180 V
About as large.

On the other hand, when the load is switched or when other distributed power sources are disconnected, the voltage rise is about 110% or less, as is clear from Table 1 of the above-mentioned application. It is clearly different from the voltage rise at the time.

For this reason, the determination unit 18 '
An appropriate voltage higher than the voltage of 20% and lower than the voltage of 180% is set as the threshold voltage, and when the detection voltage of the injection frequency becomes higher than the threshold voltage, the interconnection operation of the distributed power supply 6 due to the system stoppage. Is determined and detected.

Then, based on this detection, # 2 to #n are passed through a parallel-off control section 19 'similar to the parallel-off control section 19 in FIG.
The respective switches 5 of the distributed power sources 6 are opened, and the distributed power sources 6 are disconnected from the system.

Therefore, only the isolated operation detecting device 7 of the distributed power source 6 of # 1 is provided with the interharmonic injection means, and
移行 #n can individually detect the transition from the grid-connected operation to the isolated operation due to the system stop, and can disconnect each distributed power supply 6 from the system.

At this time, the isolated operation detecting device 8 of the distributed power sources 6 of # 2 to #n does not need to provide an inter-harmonic injection means corresponding to the injection section 7a of the detecting device 7, and furthermore, the detecting device 7, there is no need to provide an impedance (or admittance) operation unit corresponding to the operation unit 17 of # 7.
It is possible to detect the isolated operation of the n distributed power sources 6 very simply and at low cost.

By the way, in the above embodiment, 1 of # 1
Only the distributed power supplies 6 were used as power supplies on the injection / detection side.
Of the n distributed power supplies 6, two or more and n-1 or less distributed power supplies 6 may be used as a power supply on the injection / detection side,
In this case, in order to avoid overlapping injection of interharmonics of the same frequency, these power supplies are each provided with an islanding operation detecting device 7, and from these detecting devices 7 to the distribution line 4, intermodal interharmonics of different frequencies (orders) are provided. From the change in the impedance (or admittance) of the interharmonics at the respective injection frequencies of the distribution line 4 by the respective distributed power sources 6 to individually change the operation from the grid-connected operation to the isolated operation. The transition may be detected.

In this case as well, the remaining distributed power source 6
It is not necessary to provide interharmonic injection means for
The same effect as in the above embodiment can be obtained.

Next, in the above embodiment, an independent operation detection device 7 of an independent injection type is provided in the distributed power source 6 of # 1.
Inverter 1 separates inter-harmonic current from distributed power source 6
5 was injected into the distribution line 4, but in the case of the inverter type # 1 distributed power source 6 'shown in FIG. It is preferable to provide an isolated operation detection device 7 'shared by an inverter, which is used for injecting harmonics, to reduce the number of components, and to form the device more simply and inexpensively.

In this case, the detection device 7 ′ is
a ′ is provided with only the current injection control unit 13, and a control signal of the control unit 13 is supplied to a signal addition unit 21 provided in the power generation unit 12 ′ of the distributed power supply 6 ′.
Accordingly, the control signal of the control unit 13 and the control signal of the power supply control unit 11 are added and combined.

The output signal of the adder 21 is supplied as a drive signal to the inverter 20 through the gate signal forming unit 22. The inverter 20 supplies AC power synchronized with the system fundamental wave to the distribution line 4 and For example, 2.
A current of the 375th order harmonic is injected into the distribution line 4.

The detecting unit 7b 'of the detecting device 7'
Is formed in the same manner as the detection unit 7b of the detection device 7 of FIG.
In the same manner as in b, the shift of the distributed power source 6 'from the interconnected operation to the isolated operation due to the system stop is detected, and the switch 5 is opened to disconnect the distributed power source 6' from the system.

Next, the impedance (or admittance) with respect to the interharmonic of the injection frequency of the distribution line 4 is detected by the isolated operation detection devices 7, 7 'of the distributed power sources 6, 6' as the power supply on the injection / detection side. When the transition from the interconnection operation of the distributed power sources 6 and 6 ′ to the isolated operation due to the system stoppage is detected from the change of the power supply, for example, inter-order harmonics of the same frequency of the distribution line 4 from a plurality of power sources on the injection / detection side are detected. Even if overlapping injection occurs, the voltage at the injection frequency rises at the same time, and the impedance (or admittance) of the calculation result hardly changes. Although the detection can be performed reliably, the detection units 7b and 7
It is necessary to provide a calculation unit 17 for b 'to perform complicated calculation of impedance (or admittance).

Therefore, when the calculation of the complicated impedance (or admittance) is omitted, the power supply on the injection / detection side is replaced with the single operation of FIG. 3 instead of the detection units 7b and 7b 'of FIGS. A measurement unit similar to the measurement unit 6 ', the islanding operation detection unit 18', and the parallel-off control unit 19 'of the detection device 8,
Providing a detection unit having an islanding operation determination unit and a disconnection control unit,
By the voltage change of the interharmonic of the injection frequency of the distribution line 4,
The shift of the distributed power sources 6, 6 'from the interconnected operation to the independent operation due to the system stoppage may be detected, and the power sources 6, 6' may be disconnected from the distribution line 4.

In this case, when the overlapping injection of the interharmonics of the same frequency (order) into the distribution line 4 occurs, the detection voltage of the interharmonics of the injection frequency rises to double, triple,. The detection accuracy is not as high as when detecting from a change in impedance (or admittance) because there is a possibility of causing erroneous detection. However, complicated calculation of impedance (or admittance) is unnecessary, and it is extremely simple and inexpensive. The isolated operation of the distributed power sources 6, 6 'can be detected.

(Other Embodiment) Next, another embodiment of the present invention corresponding to claim 2 will be described with reference to FIG. FIG. 5 is a single-line diagram of the power system corresponding to FIG. 1, and the same reference numerals as those in FIG. 1 indicate the same or corresponding components.

In this embodiment, all (n) distributed power supplies 6 # 1 to #n of the distribution line 4 each include an isolated operation detection device 8 as an operation state detection means. .

As a means for injecting interharmonics, one common injection device 23 is connected to the distribution line 4 separately from each distributed power source 6.

The common injection device 23 corresponds to, for example, an instrument transformer corresponding to the instrument transformer 9 of FIG. 2, and a current injection control section 13, a gate signal forming section 14, and an inverter 15 of the injection section 7a. A current injection control unit, a gate signal forming unit, and an inverter for injecting an interharmonic current of an appropriate injection frequency (order) into the distribution line 4.

Based on this injection, the isolated operation detection device 8 of each distributed power source 6 individually detects the voltage of the interharmonic of the injection frequency of the distribution line 4 and, based on the change, detects each voltage due to the system stop. When the transition of the distributed power supply 6 from the interconnection operation to the isolated operation is detected, each switch 5 is opened and each distributed power supply 6 is disconnected from the distribution line 4.

Therefore, in the case of this embodiment, it is not necessary to provide any means for injecting interharmonics into any of the distributed power supplies 6, and all of the distributed power supplies 6 are based on a simple detection of a voltage change. Since the transition from the interconnection operation to the islanding operation due to the system stoppage is detected, complicated calculation of impedance and admittance is not required, and the islanding operation of the distributed power source can be detected extremely easily and inexpensively.

[0059]

The present invention has the following effects. First, in the case of claim 1, one of n distributed power sources 6, 6 'connected to the system (distribution line 4) or n-
Only one or less power supply (power supply on injection / detection side)
An inter-harmonic injection means is provided together with the operating state detecting means (first detecting means), and the operating state detecting means (second detecting means) is provided to the remaining distributed power supply (non-injection / detection side power supply). ), It is possible to detect the transition from the interconnection operation to the isolated operation due to the system stop individually for each of the distributed power sources 6 and 6 ′ based on the inexpensive configuration. 6 'can be disconnected from the system.

In the case of claim 2, each distributed power source 6
A suitable inter-harmonic is injected into the system from the common injection device 23 independent of the above, and the operation state of each distributed power source 6 is detected by the means for detecting the operating state of each distributed power source 6 from the voltage change of the injection frequency of the system to the interconnection operation based on the system stop. Is switched to the islanding operation, and without providing any means for injecting interharmonics into any of the distributed power supplies 6, it is extremely simple and inexpensive. It is possible to detect a transition from operation to islanding operation.

[Brief description of the drawings]

FIG. 1 is a single-line diagram of one embodiment of the present invention.

FIG. 2 is a detailed connection diagram of a distributed power supply # 1 as a power supply on the injection / detection side of FIG. 1 and an islanding detection device thereof.

FIG. 3 is a detailed connection diagram of a # 2 distributed power supply as a non-injection / detection-side power supply in FIG. 1 and its isolated operation detection device.

FIG. 4 is a detailed connection diagram of another example of the distributed power supply # 1 of FIG. 1 and its isolated operation detection device.

FIG. 5 is a single-line diagram of another embodiment of the present invention.

[Explanation of symbols]

 4 Distribution line 6, 6 'Distributed power source 7, 7', 8 Islanding detection device 23 Common injection device

Claims (2)

[Claims] 1. An n-type (n is an integer of 2 or more) distributed power supply connected to an electric power system and connected to the power supply to inject one or more and n-1 or less distributed power supplies. A power source on the detection side, and the remaining distributed power source a power source on the non-injection / detection side; a power source on the injection / detection side for injecting means and an operating state of an interharmonic of a non-integer multiple of the system fundamental wave. The first power supply of the non-injection / detection side is provided with the second detection means in the operating state. The power supply of the power injection / detection side has a different frequency for each power supply due to the power supply. The interharmonic is injected into the system, and the first detection means detects a change in the injection frequency of the system or a change in the impedance (or admittance) with respect to the injection frequency of the system, and thereby stops the connection by stopping the system. The transition from system operation to islanding operation is detected. The power supply on the non-injection / detection side detects a voltage at any injection frequency of the power supply on the injection / detection side of the system by the second detection unit, and detects a change in the detected voltage from the system. A method for detecting an isolated operation of a distributed power supply, comprising detecting a transition from the interconnected operation to the isolated operation due to a stop. 2. An operation state detecting means is provided for each of n (n is an integer of 2 or more) distributed power supplies connected to an electric power system and connected to the power supply system. A single common injection device connected to the system, and injects an interharmonic of a non-integer multiple of the system fundamental wave into the system from the one common injection device. The detection means of each of the distributed power supplies respectively injects the system. A method for detecting an isolated operation of a distributed power supply, comprising detecting a shift from the interconnected operation to an isolated operation due to a system stop from a voltage change of a frequency.