JP2004072863A - Single-run detecting method for distributed power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly detect single run for a distributed power supply from a variation in the admittance (or susceptance) of a frequency injected to a system by reducing an influence to the system, by minimizing a current amount to be injected more than in conventional ways and by preventing false detection due to the background noise of the system. <P>SOLUTION: The voltage of an interdigital harmonic of an injection degree which is larger than the background noise of the interdigital harmonic of the injection degree of the system 5 and is smaller than the voltage of the interdigital harmonic of the injection degree during the system stop is set as a reference voltage value of reactive detection. A measured voltage value and the reference voltage value of the interdigital harmonic of the injection degree of the system 5 are compared with each other. Only when the measured voltage is larger than the reference value voltage, the admittance (or the susceptance) of the interdigital harmonic of the injection degree of the system 5 is calculated and detected from the measured voltage and a measured current value. The single run is detected by the variation in the detected admittance (or the susceptance). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
Disclosed is a distributed power supply that injects a current of interharmonic harmonics of a non-integer multiple frequency of a system fundamental wave into a system, and detects an isolated operation when the system is stopped when the system is operated in an interconnected manner with the system power supply. The present invention relates to an isolated operation detection method.
[0002]
[Prior art]
Conventionally, distributed power sources such as consumer photovoltaic power generation devices and fuel cell devices are connected to a system power supply by being connected to, for example, a 6.6 KV high voltage system or a higher voltage extra high voltage (extra high) system. .
[0003]
And when the system is shut down when the circuit breaker is opened due to a system fault, etc., the system power supply disappears and the distributed power source shifts from the grid operation to the single operation. May occur.
[0004]
Therefore, it is necessary to quickly disconnect the distributed power source from the system and disconnect it when the system is stopped.
[0005]
Conventionally, for example, a customer having a distributed power source is synchronized with the fundamental wave in order to detect a system stop due to a system fault or the like on the customer side (hereinafter referred to as a customer side) quickly and reliably. Injecting harmonics of the mth order (m is a band decimal number) of non-integer multiples of the fundamental frequency of the system, and measuring the harmonics of the order m of the system's injection order on the customer side. Based on the above, there has been proposed a method for detecting the isolated operation of a distributed power source that detects the admittance of inter-order harmonics of the injection order m of the system and detects the system stop from the change in the magnitude (absolute value) (for example, JP, 10-248168, A).
[0006]
In order to prevent isolated operation (with reverse power flow) of a distributed power source connected to an extra high system, the "Distributed Power System Interconnection Technical Guidelines, JEAG 9701-2001" (published by the NEC Association) As described, a so-called other-type transfer blocking device is used.
[0007]
This transfer interruption device is formed by connecting the transfer receiving device on the customer side etc. via the communication line to the transfer transmitting device on the substation side, and when a system fault occurs, the transfer is transferred from the transfer transmitter via the communication line. An accident notification signal is sent to the receiving device, and the receiving device detects a system stoppage.
[0008]
[Problems to be solved by the invention]
In the conventional detection method, the voltage of the order of injection m of the system is reliably detected by causing sufficient voltage distortion so as not to be affected by the background noise of the system. It is necessary to inject waves.
[0009]
Then, according to various experiments, harmonics between orders that do not exist originally exist as background noise of about 0.01% of the fundamental voltage in the system, so that dispersion from the change in the admittance of the injection order m of the system In order to detect the isolated operation of the power source, it is necessary to inject harmonics between orders to cause distortion of about 0.05% in the system.
[0010]
In order to cause the distortion of about 0.05%, a particularly large current injection is required particularly in an extra high system having a very short circuit capacity, and a current injection in an ampere unit is required even in a high voltage system.
[0011]
On the other hand, the other method of the above technical guidelines requires not only a receiving device and a transmitting device, but also a long-distance communication cable between the two devices, and only the customer side detects it. I can't.
[0012]
In this type of isolated operation detection, one of the extremely important issues is to reduce the injection current as much as possible to reduce the influence on the system as much as possible, and to reduce the size and weight of the injection power supply. ing.
[0013]
In addition, the isolated operation of the distributed power supply due to the system stop may be detected from the impedance change of the reciprocal of admittance. In this case, the detected impedance of the injection order m of the system when the system is normal is the short-circuit impedance of the system power supply. The detected impedance of the injection order m of the system when the system is stopped fluctuates depending on the system load, and the difference between the detected impedances when the system is normal and when the system is stopped may not be large.
[0014]
Therefore, it is difficult to reliably determine whether or not the system is stopped from the impedance change of the injection order m of the system, and it is not practical to detect the islanding operation from the change in impedance.
[0015]
The present invention reduces admittance (or its susceptance) of the injection frequency (injection order m) of the system by preventing the erroneous detection due to the background noise of the system while reducing the influence on the system by reducing the amount of injected current as compared with the prior art. It is an object of the present invention to detect isolated operation of a distributed power source reliably from the change in admittance (or susceptance).
[0016]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the isolated operation detection method for a distributed power source according to claim 1 injects inter-order harmonics into the system,
Measure the voltage and current of the harmonics between the injection orders of the system,
Calculate and detect the admittance of the harmonics between the orders of injection of the system from the measured voltage and measured current,
An isolated operation detection method for a distributed power source that detects the isolated operation of the distributed power source when the system is stopped from the detected change in admittance,
Reference invalidity voltage for detection-order harmonics that are higher than the background noise of the harmonics of the injection order of the system and lower than the harmonics of the harmonics of the order of injection when the system is stopped. Set as
Compare the measured voltage with the reference voltage,
Only when the measured voltage is greater than the reference voltage, the admittance of the harmonics between orders of the injection order of the system is calculated and detected from the measured voltage and the measured current,
An isolated operation is detected from the detected change in admittance.
[0017]
In this case, even when the interharmonic current (injection current) injected into the system is smaller than the conventional one, the system power supply is disconnected and the injection frequency (injection order m ) Increases the system impedance and decreases the admittance of the injection frequency of the system, so that the voltage (injection voltage) of the injection frequency of the system based on the injection current is sufficiently larger than the background noise, and the injection current and injection voltage are reduced. It is possible to accurately measure and detect the admittance (= injection current (measurement current) / injection voltage (measurement voltage)) of the injection frequency (harmonic between orders of the injection order) of the system with high accuracy.
[0018]
On the other hand, when the distributed power supply is normally connected to the system power supply, the system impedance is small and the admittance of the system injection frequency is large, so if the injection current is small, the injection voltage will be about the background noise level. In addition, since the level is easily changed, even if the injection current can be measured, it is difficult to measure the injection voltage.
[0019]
Therefore, in the present invention, a reference value voltage having an appropriate detection invalidity is set, and it is assumed that the measurement voltage is valid only when the measurement voltage becomes larger than the reference value voltage. The admittance of the injection frequency of the system is detected from the voltage, and the isolated operation of the distributed power source is detected from the change of the admittance.
[0020]
Therefore, when the measured voltage is lower than the reference voltage, the measured voltage can be invalidated so that the system is considered to be normal so that the single operation of the distributed power source is not erroneously detected. About the power supply, it is possible to reliably detect the single operation by reducing the injection current than before, and it is possible to detect the single operation with a small injection current for the distributed power supply of the extra high system having a small short-circuit capacity. It is possible to provide a novel autonomous active detection method for autonomous operation.
[0021]
Then, the susceptance may be detected as the admittance of the injection frequency.
Moreover, the injection current of the interharmonics may be injected into the system from the inverter of the distributed power source.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
(1 form)
First, an embodiment will be described with reference to FIGS.
FIG. 1 is a single line connection diagram of an example of an electric power system. A primary side of one or a plurality of transformers 3 of a substation 2 is connected to a higher level system 1, and a circuit breaker 4 is connected from a secondary side of each transformer 3. Thus, one or a plurality of lower power systems 5 are drawn in a branched manner.
[0023]
For example, in the case of a high voltage system of 6.6 kV, these power systems 5 are a plurality of customer facilities such as a customer facility 7 having a distributed power source 6 and a general customer facility 8 having no distributed power source 6. Is connected.
[0024]
The customer facility 7 to which the present invention is applied is connected to the power system 5 via the circuit breaker 10 of the lead-in line 9 and the load feeder 12 is connected to each load feeder 12 as with other customer facilities. Each load is connected through the transformer 13.
[0025]
Further, a circuit breaker 14 is connected to the load bus 11, a distributed power source 6 is connected to the circuit breaker 14 via a disconnecting switch 15, and a current injection device 16 for inter-order harmonics is connected. The
[0026]
The current injection device 16 is formed by a power supply unit 17 such as an inverter that outputs an inter-order harmonic injection current, and an injection transformer 18 provided between the power supply unit 17 and the load bus 11.
[0027]
Also, a power receiving point transformer 19 and a power receiving point current transformer 20 are provided on the load bus 11 side of the circuit breaker 10 of the lead-in line 9, and voltage and current measurement signals of these three phases are system stop detection processing devices. 21 is supplied to the sample and hold circuit 22.
[0028]
This sample and hold circuit 22 samples and holds the system voltage and both measurement signals by a timing signal of a sampling command of a constant frequency formed by a constant frequency generator such as a crystal oscillator, and the output thereof is the latter stage. It is converted into a digital signal by the A / D conversion circuit 24 and becomes sampling data.
[0029]
The voltage / current sampling data converted into a digital signal by the A / D conversion circuit 24 is supplied to the arithmetic processing unit 25.
[0030]
The processing unit 25 is formed by a microcomputer or the like, and performs a known Fourier transform digital filter operation on both sampling data by the software processing, and the harmonics between orders of injection injected from the current injection device 16 to the power system 5. The wave is extracted and detected, and the occurrence of a system stop that opens the circuit breaker 4 from the change, that is, the occurrence of an independent operation of the distributed power source 6 is monitored and detected.
[0031]
Furthermore, when this isolated operation is detected, a disconnection command is supplied from the arithmetic processing unit 25 to the switch 15, the switch 15 is opened, and the distributed power source 6 is disconnected from the power system 5.
[0032]
By the way, when the system is normal, all of the circuit breakers 4, 10, 14 and the switch 15 are closed, the power of the upper system 1 is supplied to the power system 5, and the power system 5 is in a power supply state.
[0033]
At this time, the distributed power source 6 is operated in conjunction with the power system 5, and the output is consumed in the own facility 7 and the surplus is output to the power system 5 through the lead-in line 9.
[0034]
Further, in the customer facility 7, the power receiving point transformer 19 and the power receiving point current transformer 20 constantly measure the voltage at the power receiving point A and the current flowing in and out of the power receiving point A.
[0035]
In addition, the arithmetic processing unit 25 periodically outputs a start command to the power source unit 17 in synchronization with a timing signal of a constant frequency of the timing command unit 23, and based on this command, the power source unit 17 synchronizes with the timing signal. A harmonic current between non-integer multiples of the system fundamental wave is formed, and this injected current is injected into the power system 5 from the power receiving point A of the customer facility 7 via the transformer 18, the load bus 11, and the lead-in line 9. Is done.
[0036]
At this time, in order to detect and monitor the admittance by distorting the system voltage by about 0.05% of the fundamental wave voltage by the injected current in consideration of the background noise of about 0.01% existing in the power system 5 in the past. The injection current is set to a relatively large current of, for example, about 1 A. However, in the case of this embodiment, the injection current is reduced to such an extent that sufficient voltage distortion is generated when the single operation is generated. To the extent.
[0037]
For this reason, the current injection has little influence on the system 5, and the current injection device 16 and the like are smaller in capacity, smaller and lighter than the conventional device.
[0038]
Based on the injection of the current from the power receiving point A, the measurement signals of the power receiving point transformer 19 and the power receiving point current transformer 20 include the voltage and current of the inter-order harmonic of the injection order m.
[0039]
These measurement signals are sampled and held by the sampling of the sample and hold circuit 22 as described above based on the timing signal of the timing command unit 23.
[0040]
Further, the voltage and current hold outputs are converted into digital signals by the A / D conversion circuit 24, and the sampling data converted into these digital signals are processed by the arithmetic processing unit 25, and the injection order of the system 5 based on the injection current is obtained. The measurement voltage and measurement current of the harmonics between the orders of m are extracted and detected.
[0041]
If these measured voltages and currents are Vih and Iih and the admittance of the injection frequency of the power system 5 viewed from the power receiving point A is Yih, the admittance Yih is detected from the calculation of Yih = Iih / Vih, and the admittance Yih The susceptance bih is obtained from bih = Im (Iih / Vih), where Im is a function indicating an imaginary component.
[0042]
When the distributed power source 6 is connected to the system power source when the system is normal (healthy), the power source impedance of the power system 5 viewed from the power receiving point A is a short-circuit impedance. At this time, the power system viewed from the power receiving point A The admittance Yih and the susceptance bih of the interharmonic harmonic of the injection order of 5 are increased.
[0043]
Next, when the circuit breaker 4 is opened due to the stop of the power system 5 due to a system fault or the like, the power source impedance of the power system 5 seen from the power receiving point A increases from the short-circuit impedance to the open impedance. The admittance Yih and the susceptance bih of the power system 5 become small, and the stop of the power system 5, that is, the independent operation of the distributed power source 6 can be detected from the change of the admittance Yih or the susceptance bih.
[0044]
However, since the injected current Iih is reduced as much as possible, the voltage Vih becomes extremely small particularly when the system is normal, and in some cases, the voltage Vih becomes less than the background noise of the power system 5, so this voltage Vih is used. If the admittance Yih or the susceptance bih is calculated, a false detection occurs.
[0045]
Therefore, in this embodiment, the voltage distortion of the background noise of the injection order m of the electric power system 5 is higher than 0.01% and is as small as possible as much as the voltage distortion of the injection order m at the time of single operation. Specifically, for example, a voltage causing a voltage distortion of 0.02% is set in the arithmetic processing unit 25 as a reference value voltage Vref that is invalid for detection. Specifically, the arithmetic processing unit 25 executes the isolated operation detection flow of FIG.
[0046]
Then, for each measurement interval is set, in step S ₁ of the detection flow, three phases of the voltage of the electric power system 5, the sampling time of momentary power system 5 of the measurement signal of the current A / D conversion k of the voltage V (k), obtains a measurement data of the current I (k), running for example regression type DFT calculation in step S _2, for each phase, injection order m represented by equation 1 the following The voltage Vm (k) and current Im (k) at each time point k of the inter-order harmonics are obtained.
[0047]
[Expression 1]
Vm (k) = (2 / N). {Vm (k-1) -V (k-N) + V (k)). X- ¹
Im (k) = (2 / N) · {Im (k−1) −I (k−N) + I (k)) × x ⁻¹
[0048]
However, N in the equation is a time-series sampling number used for the DFT calculation, and the DFT calculation is performed using the measurement data of the past N samplings.
[0049]
A specific value of N is, for example, the number of 2048 samplings (64 × 32 =) obtained by repeating 64 samplings per period of the fundamental wave over 32 fundamental wave waves of the system.
X is x = exp (j · 2π · m / N).
[0050]
Further, the voltage Vm (k) and the current Im (k) are complex values. The three phases are a phase, b phase, and c phase, and the voltage Vam (k) of each phase a, b, and c obtained from the equation (1). ), based on the Vbm (k), Vcm (k ), current Iam (k), Ibm (k ), Icm (k), in step _{S 3,} for example, from the anti-phase operation of the number of the next second power system 5 A measurement voltage V2m (k) and a measurement current I2m (k) of the injection order m are obtained.
[0051]
[Expression 2]
V2m (k) = (Vam (k) + a · a · Vbm (k) + a · Vcm (k)) / 3
I2m (k) = (Iam (k) + a · a · Ibm (k) + a · Icm (k)) / 3
[0052]
Note that the measurement voltage V2m (k) and the measurement current I2m (k) may be obtained from normal phase calculation, and a is a = exp · (2π / 3)).
[0053]
Then, the process proceeds to step _{S 4,} it compares the set reference value voltage Vref and the measured voltage V2m (k), if V2m (k)> Vref, the process proceeds to step _{S 5,} the power system 5 The susceptance bih (= b2m (k)) of the admittance Ym having the injection order m, for example, is calculated by calculating from the following equation (3). Im is a function indicating an imaginary part (imaginary component).
[0054]
[Equation 3]
bih = b2m (k) = − Im (I2m (k) / V2m (k))
[0055]
Further, the magnitude (absolute value) of the detected susceptance bih (= b2m (k)) is maintained at the settling time T by the steps S ₆ and S ₇ , and the susceptance determination value bref of the isolated operation detection, for example, 0 .6 (s) or less is monitored and detected.
[0056]
Then, the process proceeds to step S ₈ when it continues the settling time of the state of BIH ≦ bref, for example, T = 0.7 seconds, this time, that the transition to the independent operation of the dispersed type power supply 6 by the system outage By detecting this, the circuit breaker 15 is opened by this detection, the distributed power source 6 is disconnected from the power system 5, and the process is terminated.
[0057]
Next, when the system voltage is normal, the measurement voltage V2m (k) is small. If this measurement voltage V2m (k) is equal to or less than the reference value voltage Vref, the amount of injected current is small, and the measurement voltage V2m (k) is accurately determined. It is difficult, and, in most cases, since it is considered that the system normally, the process proceeds from step S ₄ to step S _9.
[0058]
Then, shifts in step _{S 9,} the susceptance bih infusion order m in this embodiment (= b2m (k)), the determination value bref larger than the set value Bfix, in step _{S 6} is fixed to e.g. 1.0 (s) To do.
[0059]
At this time, since the bih (= b2m (k)) ≧ bref, returns from step _{S 6} to Step _{S 1,} without detecting the islanding operation, starts measuring the next interval.
[0060]
For example, as shown in FIG. 3, is detected the system stop due to opening of the circuit breaker 4 at time t _1, a single distributed power supply 6 when then passed Delta] t (= 0.05 seconds) delay 0.7 seconds When operation is detected, the circuit breaker 15 is opened, and the distributed power source 6 is disconnected from the system, the fundamental voltage of the power system 5 changes as shown in FIG. The measurement voltage Vih (= V2m (k)) of 136 Hz) changes as shown in FIG.
[0061]
Further, based on the measured voltage Vih, during Vih <Vref, the susceptance bih (= b2m (k)) is fixed to the set value bfix (> bref) as shown in FIG. The susceptance bih is not detected from the calculation, and the calculation of the susceptance bih (= b2m (k)) starts from t ₁ + ΔT that detects Vih ≧ Vref, and effective detection of the single operation starts.
[0062]
If bih (= b2m (k))> bref continues until t ₂ , the isolated operation is detected and the distributed power supply 6 is disconnected. At this time, the fundamental voltage of the power system 5 disappears. To do.
[0063]
Further, by reducing the amount of injected current compared to the conventional case, the voltage Vih at the injection frequency (injection order m) of the power system 5 becomes extremely small when the system is normal, and even if the voltage Vih cannot be measured, the susceptance bih in the meantime. Is fixed to the set value bfix, so that erroneous detection of isolated operation of the distributed power source 6 can be prevented, the amount of injected current is smaller than in the prior art, and the power source unit 17 has a small capacity and a small configuration. Can be reliably detected.
[0064]
Incidentally, in the embodiment, becomes V2m (k) ≦ Vref at Step _{S 4} in FIG. 2, when the detection voltage Vih (= V2m (k)) becomes difficult, setpoint susceptance bih proceeds to step _{S 9} After fixing to bfix, the susceptance bih and the determination value bref are formally compared in steps S ₆ and S _7. However, in order to simplify the process, V2m (k) ≦ Vref is set in step S _4. becomes immediately returns to step _{S 1,} susceptance BIH, it may be omitted comparison determination bref.
[0065]
Next, in the said form, since the change by the system stop of the admittance Yih of the electric power system 5 mainly depends on the change of the susceptance bih, the independent operation detection of the distributed power source 6 was performed from the change of the susceptance bih. There may also be detected independent operation of the dispersed type power supply 6 from the change in the admittance Yih, in this case, for example, by step _{S 5} in FIG. 2, the admittance Yih, Yih = I2m (k) / V2m (k ), And in steps S ₆ and S ₇ , it is determined whether or not the absolute value | Yih | is equal to or greater than the settling time and equal to or less than the set determination value Yref. In step S ₄ , V2m (k) if ≦ Vref, may be the admittance Yih set value Yfix (≧ Yref) in step _{S 9.}
[0066]
Note that the reference voltage Vref is specifically determined assuming that the ratio of the resistive load and the inductive load of the system 5 is 6 to 4, and the maximum predicted load of the system 5 is obtained. The background noise may be predicted and set.
[0067]
(Other forms)
Next, another embodiment will be described with reference to FIG.
In the first embodiment, the injection device 16 is provided separately from the distributed power source 6. However, when the distributed power source 6 is an inverter power source or the like, for example, the power supply from the distributed power source 6 is configured as shown in FIG. An injection current may be injected into the system 5, and in this case, the current injection device 16 of FIG. 1 can be omitted.
[0068]
In FIG. 4, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, 21 'denotes a distributed power source operation control / system stop detection processing device provided in place of the detection processing device 21 in FIG. 1, and 26 denotes a distributed type. It is a main processing unit of a microcomputer configuration that controls the fundamental wave output of the power supply 6, and the sample-and-hold circuit 22 and the A / D conversion circuit 24 are used to detect the voltage and current of the injection order m and to detect the fundamental wave voltage and current. The main processing unit 26 outputs the fundamental wave voltage and current command signals of the distributed power source 6 to the adding unit 27 based on the detection of the fundamental wave voltage and current.
[0069]
In addition, the arithmetic processing unit 27 outputs an injection current command signal of the injection frequency to the addition unit 27.
[0070]
Then, both command signals are added and synthesized by the adder 27, and the inverter power source which is the distributed power source 6 is operated by the output signal, and the distributed power source 6 outputs the fundamental wave power and the injected current to the power system 5. .
[0071]
By the way, although applied to a high voltage system in both the above-mentioned forms, the present invention can be applied to an extra high system with a large short-circuit capacity in the same manner, and an autonomous independent operation detection of an extraordinary system of an extra high system that has not existed before. A method can be realized.
[0072]
In this case, even in an extra high system, the amount of injected current may be approximately the same as that of a conventional high voltage system, and there is an advantage that the influence of the injection on the system is extremely reduced.
[0073]
In both the above-described embodiments, the inter-order harmonic injection frequency (injection order m), the injection amount, the reference value voltage Vref, the determination value bref, the set value bfix, and the like are not limited to those in both the forms, and the system conditions Of course, it may be set appropriately according to the above.
[0074]
The present invention can be applied to single operation detection of distributed power sources of various power systems including high voltage systems and extra high systems.
[0075]
【The invention's effect】
The present invention has the following effects.
First, in the case of claim 1, even when the interharmonic current (injection current) injected into the electric power system 5 is less than the conventional one, the system power supply is disconnected when the distributed power supply shifts to the single operation. As a result, the impedance of the injection frequency of the system 5 increases and its admittance decreases, and the voltage (injection voltage) of the injection frequency based on the injection current becomes sufficiently larger than the background noise of the injection frequency of the system. It is possible to reliably measure and detect the admittance (= injection current (measurement current) / injection voltage (measurement voltage)) of the injection frequency (intra-order harmonics of the injection order) of the system.
[0076]
On the other hand, when the distributed power source 6 is normally operated in a system-connected manner with the system power source, the system impedance is small, so that the admittance of the injection frequency of the system 5 is large, and when the injection current is small, the injection voltage becomes the background noise. Even if the measurement level fluctuates and the injection current can be measured, the injection voltage can no longer be measured. Only when the measured voltage is larger than the reference voltage, the measured voltage is valid. Only at this time, the admittance of the injection frequency of the system 5 is detected from the measured current and the measured voltage, and the distributed power supply is operated independently from the change in the admittance. Is detected.
[0077]
Therefore, when the measured voltage is equal to or lower than the reference voltage, the measured voltage is invalidated, the system 5 is regarded as normal, and the isolated operation of the distributed power source 6 is not erroneously detected to reliably detect the isolated operation. In addition, it is possible to reliably detect the single operation of the distributed power source of the high voltage system while reducing the injected current and preventing the influence on the system 5.
[0078]
Also, an autonomous active islanding detection method that does not exist in the past can be reliably detected even with a small injection current even in isolated operation of a distributed power source of an extra high system with a small short-circuit capacity. Can do.
[0079]
Next, in the case of claim 2, since the change in admittance of the electric power system 5 mainly depends on the susceptance, the susceptance is detected as the admittance of the injection frequency, and the effect of claim 1 can be obtained. it can.
[0080]
Further, in the case of claim 3, since the interharmonic injection system is injected from the distributed power source 6 to the system 5, there is an advantage that detection can be performed while further downsizing and simplification.
[Brief description of the drawings]
FIG. 1 is a single-line diagram of a power system to which Embodiment 1 of the present invention is applied.
FIG. 2 is a flowchart for detecting an isolated operation of the distributed power source of FIG. 1;
3A is a fundamental wave voltage waveform diagram of the power system of FIG. 1, FIG. 3B is a voltage waveform diagram of an injection frequency component of the power system of FIG. 1, and FIG. 3C is a susceptance characteristic of the power system of FIG. FIG.
FIG. 4 is a single-line diagram of a part of another embodiment of the present invention.
[Explanation of symbols]
5 Power system 6 Distributed power supply

Claims (3)

Inject harmonics between orders into the system,
Measure the voltage and current of the harmonics between the injection orders of the system,
Calculate and detect the admittance of the harmonics between the orders of injection of the system from the measured voltage and measured current,
An isolated operation detection method for a distributed power source that detects the isolated operation of the distributed power source when the system is stopped from the detected change in admittance,
Reference invalidity voltage for detection-order harmonics that are higher than the background noise of the harmonics of the injection order of the system and lower than the harmonics of the harmonics of the order of injection when the system is stopped. Set as
Compare the measured voltage with the reference voltage,
Only when the measured voltage is greater than the reference voltage, the admittance of the harmonics between orders of the injection order of the system is calculated and detected from the measured voltage and the measured current,
An isolated operation detection method for a distributed power source, wherein the isolated operation is detected from a detected change in admittance. 2. The method for detecting an isolated operation of a distributed power source according to claim 1, wherein the admittance of the interharmonics of the injection frequency is the susceptance of the admittance. The method for detecting an isolated operation of a distributed power supply according to claim 1 or 2, wherein a current of an interharmonic harmonic of the injection order is injected into the system from the distributed power supply.

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