JP5990863B2 - Isolated operation detection device and method, power conditioner, and distributed power supply system - Google Patents

Description

The present invention relates to an isolated operation detection device that detects an isolated operation of a distributed power source, a power conditioner including the same, and a distributed power system.

  Conventionally, a distributed power system including a distributed power source such as a solar cell or a fuel cell and a power conditioner has been used. The distributed power source is connected to a power system for supplying commercial power to the power receiving equipment via a power conditioner that converts DC power generated by the distributed power source into AC power. With such a configuration, the power generated by the distributed power source is used integrally with the power supplied from the commercial power source.

  When an accident, emergency work, or the like occurs in a power system connected to a distributed power source, all or part of the power system may be disconnected from a commercial power source. A state in which the distributed power source supplies power to such a power system disconnected from the commercial power source is referred to as an independent operation. The power system disconnected from the commercial power supply should be essentially voltage-free, but if a single operation occurs, the power system disconnected from the commercial power supply is charged by the distributed power supply, which is a security issue for personnel and equipment. Occurs. Therefore, when a distributed power source falls into an isolated operation, it is necessary to quickly disconnect (disconnect) the distributed power source from the power system.

  In order to detect islanding, in Japan, the power conditioner is provided with at least one of a passive method and an active method according to the grid connection regulations (Non-Patent Document 1). As the passive method, a method of detecting a change in system voltage or voltage frequency or a voltage phase jump at the time of single operation is often used. As an active method, a frequency shift method, a frequency feedback method, or the like is used. In both the frequency shift method and the frequency feedback method, the power conditioner injects reactive power into the power system so that the deviation of the voltage frequency from the reference frequency (frequency deviation) increases, so that the voltage frequency changes during single operation. Is controlled to increase.

  However, when the supply power of the distributed power supply and the power consumption of the load are balanced, the voltage frequency does not change even when the distributed power supply shifts to the single operation. Therefore, the frequency shift method cannot detect that the distributed power source has shifted to the single operation. Therefore, a frequency change facilitating function that injects a reactive current into the electric power system when a change in fundamental voltage or a change in harmonic voltage is detected is used as part of the frequency feedback system (see Patent Document 1). When a single operation occurs, even if the voltage frequency does not change, the fundamental voltage fluctuation and the harmonic voltage fluctuation may occur. For this reason, when a change in fundamental wave voltage or a change in harmonic voltage is detected, reactive power is injected into the power system to cause a change in voltage frequency, so that an isolated operation can be detected by a frequency feedback method.

JP 2009-136095 A

Japan Electric Association, grid connection regulations, JEAC 9701-2010

If the power conditioner injects reactive power into the power system, the effective power that can be output by the power conditioner is reduced by the amount of reactive power. Therefore, it is not desirable for the power conditioner to output reactive power for facilitating frequency change when the distributed power source has not shifted to single operation.
However, the harmonics of the power system are not limited to harmonics resulting from isolated operation, but are harmonics that are steadily output by the power conditioner and harmonics that are generated by loads such as IH (Induction Heating) cookers. Including harmonics that exist in normal times. In order to detect the presence or absence of harmonics resulting from an isolated operation, it is necessary to remove the normal harmonics, and the conditions for determining the presence or absence of harmonics resulting from an isolated operation are complicated. For example, in the technique of Patent Document 1, with respect to the harmonic distortion voltage in each period of the fundamental wave, (1) each of the harmonic distortion voltages from 3 periods before to 5 periods and 3 periods before and 5 periods before The absolute value of the difference from the average value of the harmonic distortion voltage up to is less than 0.5 V, respectively. (2) The harmonic distortion voltage from 3 to 5 periods before the 2nd period of harmonic distortion voltage The difference with respect to the average value is larger than −0.5V. (3) The difference with respect to the average value of the harmonic distortion voltage from 3 cycles before to 5 cycles before and 1 cycle before the current harmonic distortion voltage is 2. If all three conditions of greater than 0V are satisfied, it is determined that there is a harmonic caused by the isolated operation.

  Therefore, the technology disclosed in this specification accurately detects only the harmonics generated when the distributed power supply is operating alone, and prevents false detection of harmonic fluctuations, thereby reducing reactive power for frequency change promotion. An object of the present invention is to provide an isolated operation detection device capable of suppressing injection when necessary.

  In order to solve the above-described problem, an isolated operation detection device disclosed in the present specification is an isolated operation detection device that detects an isolated operation of a distributed power source, and is an electric power system in which the distributed power source is interconnected. A voltage detection unit that detects the AC voltage of the power system, and a harmonic component of the AC voltage in the first period having a time length corresponding to one period of the AC voltage of the power system, and the same as the first period A harmonic difference calculation unit for obtaining a difference value with a magnitude of a harmonic component of the AC voltage in a second period having a time length and starting after a predetermined time from the end of the first period; and the harmonic difference When the difference value calculated by the calculation unit is greater than or equal to a threshold value, reactive power for promoting frequency change is supplied to the power system, and when the difference value is less than the threshold value, the frequency change To encourage The reactive power and a reactive power supply control unit is not supplied to the electric power system.

  According to the isolated operation detection device disclosed in the present specification, since the difference between the harmonics in the first period and the harmonics in the second period is used, whether or not the distributed power source is in the isolated operation state. Regardless of the frequency, it is possible to detect the presence or absence of harmonics caused by isolated operation, eliminating the need for reactive power to promote frequency changes due to false detection of harmonic fluctuations. In some cases, injection can be suppressed.

1 is a block diagram showing a configuration of a power conditioner 100 according to Embodiment 1. FIG. FIG. 2 is a block diagram showing a configuration of a grid interconnection protection device 107 according to the first embodiment. FIG. 3 is a block diagram showing a configuration of a phase shift setting unit 205 according to the first embodiment. 5 is a flowchart showing the operation of the isolated operation detection device 120 according to the first embodiment. 5 is a flowchart showing operations of a harmonic detection unit 310 and a harmonic amplitude sudden increase determination unit 320 according to the first embodiment. FIG. 3 is a schematic diagram illustrating an operation of a coordinate conversion unit 201 according to the first embodiment. FIG. 4 is a diagram showing an outline of difference calculation in a harmonic detection unit 310 according to the first embodiment. FIG. 4 is a block diagram showing a configuration of a harmonic detection unit 400 according to Embodiment 2. The figure which shows the outline of the difference calculation in the harmonic detection part 400 which concerns on Embodiment 2. FIG. FIG. 9 is a block diagram showing a configuration of a harmonic detection unit 500 according to a modification of the second embodiment. FIG. 6 is a block diagram showing a configuration of a phase shift setting unit 600 according to Embodiment 3. 9 is a flowchart showing a reactive power magnitude determination operation for frequency promotion by reactive power supply control unit 610 according to the third embodiment.

(Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
≪Configuration≫
FIG. 1 is a diagram illustrating a configuration of a distributed power supply system according to the first embodiment.

The distributed power supply system includes a distributed power supply 101 and a power conditioner 100.
The distributed power source 101 is a DC power source composed of, for example, a solar cell, a fuel cell, or a secondary battery. The secondary battery is, for example, a nickel metal hydride storage battery or a lithium ion storage battery.
The power conditioner 100 has a terminal Ta and a terminal Tb. The distributed power source 101 is connected to the terminal Ta of the power conditioner 100. The power system 102 and the load 103 are connected to a terminal Tb of the power conditioner 100. The power conditioner 100 is used in a form linked to the power system 102, and outputs the power generated by the distributed power source 101 to the power system 102 and the load 103.

The power system 102 is, for example, a power distribution system that connects a power plant of a power company to a distributed power system.
The load 103 is an electrical device that is connected to the power system 102 and exists in a home, a commercial facility, or a factory.
The power conditioner 100 includes an inverter 104, a connection relay 105, a measurement unit 106, a system connection protection device 107, and an inverter drive device 110.

  The inverter 104 converts the DC power input from the distributed power source 101 into AC power. The inverter 104 includes, for example, a plurality of transistors connected in a bridge, a diode connected in antiparallel to each transistor, and a gate driver. The grid interconnection protection device 107 outputs a gate block signal Sb to the inverter 104. The inverter 104 performs the gate block by stopping the ON / OFF operation of each switching element while the gate block signal Sb is being input, and stops the current output to the terminal Tb side, so that the distributed power supply 101 is disconnected. Do column. When the gate block signal Sb is not input, the inverter 104 performs a switching operation according to the gate signal Sg output from the inverter driving device 110 and outputs AC power to the terminal Tb side.

The interconnection relay 105 is inserted in a line connecting the inverter 104 and the terminal Tb. The interconnection relay 105 opens when the disconnection signal Sr is received from the grid interconnection protection device 107 and disconnects the distributed power source 101 from the power system 102.
The measuring unit 106 measures an instantaneous value of the voltage at the terminal Tb, and a digital signal obtained by A / D converting the measured value at a predetermined sampling frequency (for example, 17.5 kHz) as a voltage value V _s. It outputs to 107 and the inverter drive device 110. In addition, the measurement unit 106 measures a current value flowing from the power conditioner 100 to the power system 102 via the terminal Tb, and similarly, a digital signal obtained by A / D converting the measured value at 17.5 Hz is a current value. and outputs to the inverter driving unit 110 as I _s.

The inverter driving device 110 includes a voltage value V _s and a current value I _s obtained from the measuring unit 106, a DC voltage detection value V _{e of} the distributed power source 101, a DC current detection value I _e, and a grid connection The gate signal Sg is generated using the phase shift amount θ _sft obtained from the protection device 107. The gate signal Sg is a pulse width modulation (PWM) signal that controls ON / OFF of each switching element of the inverter 104. When the phase shift amount θ _sft is a positive value, the inverter driving device 110 has a voltage value V _s with respect to the phase so that the power factor of the inverter 104 is 1 when the phase shift amount θ _sft is 0. Te as the phase of the current I _s is advanced by θ _sft, θ _sft phase of the current value I _s is relative is negative when the value is a voltage value V _s phase | as only delayed, | theta _sft Each generates a PWM signal. That is, the inverter 104 outputs reactive power whose magnitude depends on the phase shift amount θ _sft .

When the grid connection protection device 107 detects an isolated operation or other abnormality (frequency / voltage abnormality or the like) based on the voltage value V _s , the system interconnection protection device 107 disconnects the distributed power source 101 from the power system 102, Transmission of the gate block signal Sb and transmission of the relay disconnection signal Sr to the interconnection relay 105 are performed. Hereinafter, the grid connection protection device 107 will be described in more detail.

(Configuration of grid interconnection protection device 107)
FIG. 2 is a block diagram showing a configuration of the grid interconnection protection device 107 according to the present embodiment. The grid connection protection device 107 includes an isolated operation detection device 120, a frequency relay 206, and a voltage relay 207. Incidentally, the grid interconnection protection device 107, a period measuring unit 106 outputs a voltage value V _s, i.e. a process with a period of 17.5kHz performed.

The islanding operation detection device 120 includes a coordinate conversion unit 201, a frequency detection unit 202, a phase detection unit 203, a passive islanding operation detection unit 204, and a phase shift setting unit 205.
The coordinate conversion unit 201 converts the voltage value V _s into two components on the dq coordinate, which is an orthogonal coordinate having the rotation speed of the fundamental wave frequency (eg, 50 Hz) of the system voltage, and the d axis of the system voltage V _s The component V _d and the q-axis component V _q are output.

The frequency detection unit 202 detects the frequency f _{v of the} system voltage using the vector (V _d , V _q ) acquired from the coordinate conversion unit 201, and outputs the detected frequency f _v .
The phase detection unit 203 detects the phase θ _{v of the} system voltage using the frequency f _v acquired from the frequency detection unit 202, and outputs the detected phase θ _v .
Passive islanding detection unit 204 monitors the phase theta _v of the system voltage, detects the voltage phase jump caused by a single operation. The passive islanding detection unit 204 sends a gate block signal Sb to the gate circuit 209 included in the inverter 104 when the voltage phase jump is detected.

The phase shift setting unit 205 acquires the vector (V _d , V _q ) from the coordinate conversion unit 201 and the frequency f _{v of the} system voltage from the frequency detection unit 202, and outputs the phase shift amount θ _sft to the inverter driving device 110. To do. Details will be described later.
Frequency relay 206, the upper limit value and the lower limit value of the frequency f _v of the system voltage, holds the detection timing, the frequency f _v of the system voltage exceeds the upper limit value (frequency increase), or below the lower limit (Frequency drop) is detected. When there is a frequency increase that continues beyond the detection time period or a frequency decrease that continues beyond the detection time period, the frequency relay 206 sends a gate block signal Sb to the gate circuit 209 included in the inverter 104. In addition, the disconnection signal Sr is transmitted to the interconnection relay 105.

Voltage relay 207, an upper limit value and the lower limit value of the voltage value V _s, holds the detection timing, the voltage value V _s exceeds the upper limit value (over-voltage), or below the lower limit (undervoltage) that Detection is performed. When there is an overvoltage that continues beyond the detection time limit or an undervoltage that continues beyond the detection time limit, the voltage relay 207 sends a gate block signal Sb to the gate circuit 209 included in the inverter 104. And a disconnection signal Sr is transmitted to the interconnection relay 105.

Hereinafter, the phase shift setting unit 205 will be described in more detail.
(Configuration of phase shift setting unit 205)
FIG. 3 is a block diagram showing a configuration of phase shift setting section 205 according to the present embodiment. The phase shift setting unit 205 includes a harmonic detection unit 310, a harmonic rapid increase determination unit 320, a fundamental wave detection unit 330, a fundamental wave rapid increase determination unit 340, an OR gate 350, a frequency deviation detection unit 360, and an invalidity. A power supply control unit 370.

The harmonic detection unit 310 calculates harmonics in one cycle (first period) of the fundamental wave of the voltage value V _{s and} other fundamental waves from the vector (V _d , V _q ) acquired from the coordinate transformation unit 201. The amplitude ΔVn _max of the difference harmonic from the harmonic in one cycle (second period) is calculated. The time (predetermined time) from the end of the first period to the start of the second period is a time corresponding to one period of the fundamental wave. The harmonic detection unit 310 includes an HPF (High Pass Filter) 301, a difference vector calculation unit 302, and a difference vector integration unit 303.

The HPF 301 is a filter for extracting a harmonic vector Vn (Vn _d , Vn _q ) that is a harmonic component from the vector (V _d , V _q ) acquired from the coordinate conversion unit 201.
Differential vector calculation unit 302, a harmonic vector Vn (Vn _d, Vn _q) and the harmonics vectors Vn in only two cycles prior to the time of the fundamental wave of exactly the voltage value V _s from the time the harmonic vector Vn is obtained difference vector ΔVn (ΔVn _d, ΔVn _q) and ₂ is calculated. The difference vector calculation unit 302 includes a d component delay unit 304, a d component subtracter 305, a q component delay unit 306, and a q component subtractor 307.

Difference vector integrator 303, the difference vector ΔVn (ΔVn _d, ΔVn _q) obtained from the difference vector calculating unit 302 integrates the second period, to convert the integration result to the maximum value .DELTA.Vn _max harmonic amplitude. The difference vector integration unit 303 includes a vector integrator 308 and an amplitude value converter 309.
The harmonic surge increase determination unit 320 compares the maximum value ΔVn _max of the harmonic amplitude with a preset threshold value A. If the maximum value ΔVn _max of the harmonic amplitude is larger than the threshold value A, the OR gate A harmonic surge detection signal is sent to 350.

The fundamental wave detection unit 330 is a filter for extracting a fundamental wave from the vector (V _d , V _q ) acquired from the coordinate conversion unit 201 and outputting a fundamental wave amplitude V _0. For example, the fundamental wave detection unit 330 is an LPF (Low Pass Filter). ).
The fundamental wave sudden increase determination unit 340 compares the fundamental wave amplitude V ₀ with a preset threshold value C. When the fundamental wave amplitude V ₀ is larger than the threshold value C, the fundamental wave sudden increase detection is detected by the OR gate 350. Send a signal. In the present embodiment, threshold C is 2.5V increase of fundamental wave amplitude V ₀ , and threshold C is 102.5V with respect to single-phase 100V that is the system voltage.

While receiving at least one of the harmonic rapid increase detection signal and the fundamental rapid increase detection signal, the OR gate 350 outputs the harmonic rapid increase detection signal. That is, the OR gate 350 takes a logical sum in the case of detection: 1 and detection not: 0.
The frequency deviation detector 360 acquires the frequency f _{v of the} system voltage from the frequency detector 202, and obtains a difference value (frequency deviation) Δf (Δf = f _v −f _s ) from the reference frequency f _s of the frequency f _v. Output.

The reactive power supply control unit 370 generates and outputs the phase shift amount θ _sft using the harmonic wave sudden increase detection signal and the frequency deviation Δf. Reactive power supply control unit 370, upon receiving a rapid increase detection signal such as a harmonic, sets phase shift amount θ _sft1 for facilitating frequency change to a predetermined fixed value F (F ≠ 0) for a predetermined period. Otherwise, θ _sft1 is determined to be 0. At the same time, the reactive power supply control unit 370 generates the phase shift amount θ _sft2 by the slip mode frequency shift or the frequency feedback function from Δf. Finally, reactive power supply control unit 370, a phase shift amount theta _sft1 for conducive to the frequency change is added to the phase shift amount theta _SFT2, and outputs it as theta _sft.

<< Operation >>
(Operation of the phase shift adding unit 205)
FIG. 4 is a flowchart showing the operation of the phase shift adding unit 205 in one period of the fundamental wave.
The phase shift addition unit 205 inputs the vector (V _d , V _q ) acquired from the coordinate conversion unit 201 to the harmonic detection unit 310. The harmonic detection unit 310 detects the amplitude of the differential harmonic, which indicates the amount of fluctuation of the harmonic, and the harmonic rapid increase determination unit 320 detects whether there is a rapid increase in harmonics (S101). When the harmonic rapid increase determination unit 320 determines that there is a rapid increase in harmonics, it sends a harmonic rapid increase detection signal to the OR gate 350. Details will be described later.

The phase shift addition unit 205 inputs the d component V _d of the vector (V _d , V _q ) acquired from the coordinate conversion unit 201 to the fundamental wave detection unit 330. The fundamental wave detection unit 330 extracts the fundamental wave amplitude V ₀ , and the fundamental wave rapid increase determination unit 340 detects whether there is a rapid increase of the fundamental wave (S102). The fundamental wave sudden increase determination unit 340 compares the fundamental wave amplitude V ₀ with a preset threshold value C. When the fundamental wave amplitude V ₀ is larger than the threshold value C, the fundamental wave sudden increase detection is detected by the OR gate 350. Send a signal.

  Next, the phase shift adding unit 205 determines whether or not at least one of a harmonic surge or a fundamental surge has occurred by the OR gate 350 (S103). When the OR gate 350 receives at least one of the harmonic component rapid increase detection signal and the fundamental component rapid increase detection signal, the OR gate 350 sends the harmonic rapid increase detection signal to the reactive power supply control unit 370 (S104). Further, when neither the harmonic component sudden increase detection signal nor the fundamental component rapid increase detection signal is received, the OR gate 350 does not transmit the harmonic rapid increase detection signal to the reactive power supply control unit 370 (S105).

Further, the phase shift adding unit 205 detects the frequency deviation Δf by the frequency deviation detecting unit 360 (S106).
Next, the phase shift adding unit 205 calculates the slip mode frequency shift or the phase shift amount θ _sft2 by the frequency feedback function by the reactive power supply control unit 370 (S107).

Finally, the phase shift adding unit 205 determines and outputs the phase shift amount θ _sft indicating the reactive power output from the inverter 104 by the reactive power supply control unit 370 (S108). The reactive power supply control unit 370 sets the phase shift amount θ _sft1 to a predetermined fixed value F for a predetermined period after receiving the rapid increase detection signal such as harmonics, for a period corresponding to three periods of the fundamental wave in this embodiment. In other cases, the phase shift amount θ _sft1 is set to zero. The reactive power supply control unit 370 outputs a value _obtained by adding the phase shift amount θ _sft1 to the phase shift amount θ _sft2 as the phase shift amount θ _sft .

(Detection of sudden increase in harmonic components)
Figure 5 performs the harmonics detection unit 310 and the harmonic surge determining section 320 is a flowchart showing the details of S101, showing an operation of the measurement unit 106 which outputs a single voltage value V _s.
First, the harmonics detection unit 310 extracts a vector (V _d, V _q) harmonic vector Vn from (Vn _d, Vn _q) using the HPF 301 (S201).

FIG. 6 shows vectors (V _d , V _q ). FIG. 6A shows the d-axis and q-axis on the αβ coordinate plane, the fundamental wave vector V _0, and the harmonic vector V _n . A rotational speed f ₀ for αβ plane of the fundamental wave vector V _0, and the rotational speed f ₀ for αβ plane of the d-axis and q-axis, because it is both the fundamental frequency (e.g., 50 Hz), basic on dq coordinates The wave vector V ₀ is a vector on the d axis. On the other hand, as shown in FIG. 6B, the harmonic vector V _n (Vn _d , Vn _q ) shows a unique locus depending on the order, and its maximum radius depends on the amplitude of the harmonic component.

Next, the harmonics detection unit 310, by using the difference vector calculation unit 302, the fundamental wave of the harmonic vector Vn (Vn _d, Vn _q) and just the voltage value V _s from the time the harmonic vector Vn is obtained differential harmonic vector ΔVn (ΔVn _d, ΔVn _q) of the harmonic vector _{Vn 2 (Vn d2, Vn q2} ) in only two cycles prior to the time of calculating a (S202).

次に、高調波検出部３１０は、差分ベクトル積分部３０３のベクトル積分器３０８を用いて、差分高調波ベクトルを基本波の１周期に相当する期間Ｔで積分する（Ｓ２０３）。具体的には、差分高調波ベクトルΔＶｎの大きさの２乗を算出して積分する。ベクトル積分器３０８は、積分が開始されていないときは、差分高調波ベクトルΔＶｎを受け取った時刻から積分を開始し、既に積分が開始しているときは、差分高調波ベクトルΔＶｎの大きさの２乗と、計測部１０６が電圧値Ｖ_sを出力する間隔に相当する時間（＝１／１７．５［ミリ秒］）との積を、既に積算されている積分値に加算して積分を続行する。

Next, the harmonic detection unit 310 uses the vector integrator 308 of the difference vector integration unit 303 to integrate the difference harmonic vector over a period T corresponding to one period of the fundamental wave (S203). Specifically, the square of the magnitude of the differential harmonic vector ΔVn is calculated and integrated. The vector integrator 308 starts the integration from the time when the differential harmonic vector ΔVn is received when the integration is not started, and 2 times the magnitude of the differential harmonic vector ΔVn when the integration has already started. multiply the, continue the product of the time (= 1 / 17.5 [ms]) of the measuring unit 106 corresponds to the interval of outputting the voltage value V _s, already added to the integrated value which is integrated integrated To do.

高調波検出部３１０は、Ｓ２０３の積分を開始してから基本波の１周期に相当する期間が経過していない場合（Ｓ２０４でＮｏ）、処理を終了し、計測部１０６より電圧値Ｖ_sを取得すると、再びＳ２０１から処理を開始する。

When the period corresponding to one period of the fundamental wave has not elapsed since the start of the integration in S203 (No in S204), the harmonic detection unit 310 ends the process and determines the voltage value V _s from the measurement unit 106. Once acquired, the process starts again from S201.

On the other hand, if a period of time corresponding to one period of the fundamental wave has passed from the start of the integration of the 203 (Yes in S204), the harmonics detection unit 310 outputs a Esuderuta _Vn Terminate the integration vector integrator 308 Let Amplitude converter 309 converts the integration result Esuderuta _Vn to the vector integrator 308 is output to the maximum value .DELTA.Vn _max of the difference harmonic amplitudes, and outputs the .DELTA.Vn _max harmonic surge determining section 320.

次に、高調波急増判定部３２０は、差分高調波振幅の最大値ΔＶｎ_maxと、予め設定されたしきい値Ａとを比較する（Ｓ２０６）。本実施の形態において、しきい値Ａは４．０Ｖ²とする。差分高調波振幅の最大値ΔＶｎ_maxが４．０Ｖ²より大きい場合、高調波急増判定部３２０は、ＯＲゲート３５０に高調波急増検出信号を送出する（Ｓ２０７）。差分高調波振幅の最大値ΔＶｎ_maxが４．０Ｖ²以下の場合、高調波急増判定部３２０は、ＯＲゲート３５０に高調波急増検出信号を送出しない（Ｓ２０８）。

Next, the harmonic surge determination unit 320 compares the maximum value ΔVn _max of the differential harmonic amplitude with a preset threshold A (S206). In the present embodiment, threshold A is 4.0 V ² . When the maximum value ΔVn _max of the difference harmonic amplitude is larger than 4.0 V ² , the harmonic rapid increase determination unit 320 sends a harmonic rapid increase detection signal to the OR gate 350 (S207). When the maximum value ΔVn _max of the difference harmonic amplitude is 4.0 V ² or less, the harmonic rapid increase determination unit 320 does not send the harmonic rapid increase detection signal to the OR gate 350 (S208).

(Supplementary explanation about calculation of differential harmonic vector ΔVn)
In S202 described above, the differential vector calculation unit 302, a harmonic vector Vn (Vn _d, Vn _q) and only two periods before the times of the fundamental wave of exactly the voltage value V _s from the time the harmonic vector Vn is obtained The difference from the harmonic vector Vn ₂ (Vn _d2 , Vn _q2 ) in FIG. 6 is the difference harmonic vector ΔVn. The reason will be described with reference to FIGS. 6 and 7.

  As described above, the system voltage when the islanding operation is not generated includes a fundamental wave component and a normal harmonic component. When isolated operation occurs, harmonics resulting from isolated operation are further added as a component of the system voltage. Therefore, in order to detect an isolated operation, it is important to remove the harmonic component in normal times from the harmonics and accurately detect the presence or absence of harmonics resulting from the isolated operation.

First, the reason why the harmonic vector Vn ₂ is the time just before the Vn by m periods of the fundamental wave (m is an integer) will be described. The reason for taking the difference between the harmonic vector Vn and the harmonic vector Vn ₂ is to remove the harmonic vector Vn ₂ , which is a normal harmonic, from the harmonic vector Vn. Accordingly, harmonics with the same amplitude and frequency, in the harmonic vector Vn harmonic vector Vn ₂ Prefecture, there must be a vector having the same magnitude and direction. However, as shown in FIG. 6B, the direction and magnitude of the harmonic vector Vn are not constant during the time corresponding to one period of the fundamental wave. Therefore, the time difference between the harmonic vector Vn and the harmonic vector Vn ₂ is of an arbitrary order so that harmonics having the same frequency, amplitude, and phase become harmonic vectors having the same direction and magnitude. The time just needs to correspond to the m period of the fundamental wave so as to be an integral multiple of the period corresponding to one period of the harmonic with respect to the harmonic.

Next, the reason why the harmonic vector Vn ₂ is two periods before the fundamental wave from Vn will be described. FIG. 7 shows components of the system voltage for each time. T0, T1, T2, T3, T4, and T5 are periods corresponding to one period of the fundamental wave, and are integration periods of the vector integrator 308, respectively. Note that the period from T0 to T5 is a continuous period. FIG. 7 shows a case where the distributed power source 101 shifts to a single operation during the period T2.

Suppose that the harmonic vector Vn ₂ is one period before the fundamental wave from Vn. In this case, the vector integrator 308 during the period T1, which is a second period, and the harmonic vector Vn in the period T1 which is a second period, a harmonic vector Vn ₂ in the period T0 is a first time period Are integrated with the differential harmonic vector ΔVn. Here, since the harmonics in normal times hardly change, ΔVn may be regarded as a zero vector, and the maximum value ΔVn _max of the harmonic amplitude is 0 (FIG. 7A).

Next, during the period T2, the vector integrator 308 integrates a differential harmonic vector ΔVn between the harmonic vector Vn in the period T2 and the harmonic vector Vn ₂ in the period T1. The differential harmonic vector ΔVn is a zero vector until an isolated operation occurs, and is a harmonic vector resulting from the isolated operation after the isolated operation occurs. However, T2 includes a period during which no single operation has occurred and a period during which single operation has occurred. The maximum value ΔVn _max of the difference harmonic amplitude calculated is a time average at T2 of the square of the magnitude of the difference harmonic vector ΔVn, and thus is smaller than the maximum value of the harmonic amplitude resulting from the single operation. For example, when the time when the distributed power source 101 shifts to the single operation is after a time corresponding to a quarter period of the fundamental wave from the start of T2, the maximum value ΔVn _max of the calculated differential harmonic amplitude is Therefore, it becomes 3/4 of the maximum value of the harmonic amplitude resulting from the single operation, and it cannot be correctly determined whether or not the harmonic amplitude resulting from the single operation exceeds the threshold value A (FIG. 7B). )).

Next, vector integrator 308 during a period of T3, integrating the harmonic vector Vn in the period T3, the difference harmonic vector ΔVn the harmonic vector Vn ₂ in the period T2. The differential harmonic vector ΔVn is a harmonic vector resulting from the single operation until one cycle after the fundamental wave from the time when the distributed power source 101 shifts to the single operation. However, after one cycle of the fundamental wave from the time when the distributed power source 101 shifts to the single operation, the harmonics resulting from the single operation are also removed as normal harmonics, so the differential harmonic vector ΔVn is a zero vector. Become. Therefore, the maximum value ΔVn _max of the differential harmonic amplitude calculated is smaller than the maximum value of the harmonic amplitude resulting from the single operation, and whether or not the harmonic amplitude resulting from the single operation exceeds the threshold A. Cannot be determined correctly (FIG. 7C). In addition, after T4, similarly, the harmonic vector resulting from the single operation is removed as a normal harmonic, so that it is impossible to detect the harmonic due to the single operation.

For the above reason, when the harmonic vector Vn ₂ is one cycle before the fundamental wave from Vn, the time when the distributed power source 101 shifts to the single operation coincides with the boundary of the integration period of the vector integrator 308. Or, if it is not very close, it will not be possible to detect harmonic vectors resulting from isolated operation.
On the other hand, if the harmonic vector Vn ₂ is two cycles before the fundamental wave from Vn, the above-described problem can be avoided. Vector integrator 308 during a period of T2, integrating the harmonic vector Vn in the period T2, the difference harmonic vector ΔVn the harmonic vector Vn ₂ in the period T0. In this case, the same problem as in FIG. 7 (b) described above occurs, and it cannot be correctly determined whether or not the amplitude of the harmonics resulting from the single operation exceeds the threshold A (FIG. 7 (d)).

However, during the period T3, the vector integrator 308 integrates the difference harmonic vector ΔVn between the harmonic vector Vn in the period T3 and the harmonic vector Vn ₂ in the period T1. At this time, during the period of T3, the differential harmonic vector ΔVn always indicates a harmonic vector resulting from the single operation. Therefore, since the maximum value ΔVn _max of the difference harmonic amplitude calculated is the maximum value of the harmonic amplitude resulting from the single operation, whether the harmonic amplitude resulting from the single operation exceeds the threshold A or not. Can be determined (FIG. 7E).

  In T4, there is a problem similar to that of FIG. 7C described above, and after T5, harmonics resulting from isolated operation are regarded as normal harmonics. Cannot be detected (FIG. 7F). However, since the operation has already been performed after detecting the harmonics resulting from the single operation, there is no problem in the operation of detecting the harmonics resulting from the single operation.

What is important is that the distributed power source 101 shifts to a single operation after the end of the first period, and then the second period starts. By doing in this way, the harmonic vector Vn in the second period always includes harmonics generated by the single operation, and the harmonic vector Vn ₂ in the first period always includes harmonics generated by the single operation. This is because the maximum value ΔVn _max of the differential harmonic amplitude calculated includes the maximum value of the harmonic amplitude resulting from the single operation. Therefore, the time of the harmonic vector Vn ₂ is not limited to the time just two periods before the fundamental wave from Vn, but is the time just before m periods of the fundamental wave (m is an integer of 2 or more). Also good. Note that m needs to be an integer of 100 or less, and preferably 10 or less, in order not to include the time variation of the normal harmonic in the maximum value ΔVn _max of the differential harmonic amplitude.

≪Summary≫
As described above, in this embodiment, the harmonic amplitude is calculated from the d-axis component V _d and the q-axis component V _{q of the} voltage vector obtained by coordinate transformation, and the difference from at least two cycles or more is taken. Thus, it is possible to extract only the harmonics generated by the single operation. By using coordinate transformation, compared with the conventional harmonic detection method using discrete Fourier transform, (1) the calculation load is small, (2) harmonics of each order (second harmonics, 5 Since a vector obtained by synthesizing all vectors corresponding to the second harmonic, etc., can be obtained as a harmonic vector, two advantages can be obtained that the harmonic amplitude can be easily obtained without considering the harmonic order. In addition, by comparing the integrated values of the magnitudes of the harmonic vectors during a period corresponding to one period of two fundamental waves that are spaced by a predetermined time, normal harmonics and instantaneous power pulsations can be obtained. The influence can be easily removed, and it is possible to detect the presence or absence of harmonics resulting from isolated operation with high accuracy.

Therefore, it is possible to accurately detect the harmonics generated by the single operation, prevent erroneous detection of harmonic surges, and suppress injection when reactive power for frequency change promotion is unnecessary.
(Embodiment 2)
In Embodiment 1, in order to calculate the difference between the harmonics in the second period and the harmonics in the first period, the harmonic vector at a certain moment included in the second period, and the first period And the difference vector is integrated with the harmonic vector at the moment two cycles before the instant.

In this embodiment, in order to calculate the difference between the harmonic in the second period and the harmonic in the first period, the result of integrating the harmonic vector in the second period and the harmonic vector in the first period It is characterized in that a difference from the result of integration in the period of is used.
≪Configuration≫
The power conditioner according to the present embodiment has the same configuration as that of the power conditioner 100 except that the phase shift setting unit included in the isolated operation detection device includes a harmonic integration unit 400 instead of the harmonic integration unit 310. . Hereinafter, the same reference numerals are given to the same components as those in the first embodiment, and the description thereof is omitted.

The harmonic integration unit 400 includes a harmonic integration unit 410 and an integral value difference calculation unit 420 instead of the difference vector integration unit 302 and the difference vector integration unit 303.
The harmonic integrator 410 integrates the harmonic vector Vn in each of the first period and the second period, converts the integration result into the maximum value Vn _max of the harmonic amplitude, and holds the integration result. The harmonic integration unit 410 includes four sets of vector integrators and amplitude value converters, and an integration result holding unit 405.

Integral value difference detection unit 420, the maximum value _{Vn a_max} harmonic amplitude in the first period, and a maximum value _{Vn b_max} harmonic amplitudes in the second period obtained from the harmonic integration unit 410, the maximum the difference The value ΔVn _max is calculated and output.
<< Operation >>
The operation of the power conditioner according to the present embodiment is the same as the operation of the power conditioner 100 except that the detection operation of the harmonic increase is different from that of S101. Therefore, only the operation of the harmonic detection unit 400 performed instead of S101 will be described.

(Operation of harmonic detection unit 400)
The harmonics detection unit 400, the measurement unit 106 will be described operation when outputting one voltage value V _s.
Harmonics detection unit 400, like the S201, extracts a vector (V _d, V _q) harmonic vector Vn from (Vn _d, Vn _q) using the HPF 301.

Next, the harmonic detection unit 400 uses the vector integrator group of the harmonic integration unit 410 to integrate the harmonic vector in a period T corresponding to one period of the fundamental wave. Specifically, the square of the magnitude of the harmonic vector Vn is calculated and integrated. Each vector integrator starts integration from the time when the harmonic vector Vn is received when integration is not started, and when the integration has already started, the square of the magnitude of the harmonic vector Vn is , the measurement unit 106 is the product of the time corresponding to the interval of outputting the voltage value V _s, already added to the integrated value that is integrated to continue the integration.

  As shown in FIG. 9, the integration start timings of the vector integrators 401, 402, 403, and 404 are shifted by a quarter period of the fundamental wave. That is, after the integration of the vector integrator 401 is started, the integration of the vector integrator 402 is started after ¼ period of the fundamental wave. Further, the integration of the vector integrator 403 is started after a quarter period of the fundamental wave, and the integration of the vector integrator 404 is started after a quarter period of the fundamental wave. Further, after a quarter period of the fundamental wave, the vector integrator 401 that has finished the previous integration starts the next integration.

高調波検出部４００は、どの積分器も積分を開始してから基本波の１周期に相当する期間が経過していない場合、処理を終了し、次に計測部１０６が電圧値Ｖ_sを１つ出力したとき、再び最初から処理を開始する。

The harmonic detection unit 400 ends the process when a period corresponding to one period of the fundamental wave has not elapsed since any integrator started integration, and then the measurement unit 106 sets the voltage value V _s to 1. When one is output, the process starts again from the beginning.

On the other hand, when a period corresponding to one period of the fundamental wave has elapsed since any of the integrators started integration, the harmonic detection unit 400 ends the integration and outputs S _Vn . After that, the integration result S _Vn is converted into the maximum value Vn _max of the total harmonic amplitude using the corresponding amplitude value converter, and Vn _max is output to the integration result holding unit 405.

次に、高調波検出部４００は、積分結果保持部４０５から、最新の全高調波振幅の最大値Ｖｎ_{ａ＿ｍａｘ}と、基本波の５／４周期前に受け取った全高調波振幅の最大値Ｖｎ_{ｂ＿ｍａｘ}とを積分値差分算出部４２０に出力し、差分高調波振幅の最大値ΔＶｎ_maxを算出する。

Next, the harmonic detection unit 400, from the integration result holding unit 405, the latest maximum value _{Vna_max of} the total harmonic amplitude and the maximum value _{Vnb_max} of the total harmonic amplitude received 5/4 cycles before the fundamental wave. Is output to the integrated value difference calculating unit 420 to calculate the maximum value ΔVn _max of the differential harmonic amplitude.

次に、高調波急増判定部３２０は、Ｓ２０６と同じく、差分高調波振幅の最大値ΔＶｎ_maxと、予め設定されたしきい値Ａとを比較する。差分高調波振幅の最大値ΔＶｎ_maxがしきい値Ａより大きい場合、高調波急増判定部３２０は、高調波急増検出信号を送出する（Ｓ２０７）。差分高調波振幅の最大値ΔＶｎ_maxがしきい値Ａ以下の場合、高調波急増判定部３２０は、高調波急増検出信号を送出しない（Ｓ２０８）。

Next, the harmonic rapid increase determination unit 320 compares the maximum value ΔVn _max of the differential harmonic amplitude with a preset threshold A, as in S206. When the maximum value ΔVn _max of the difference harmonic amplitude is larger than the threshold value A, the harmonic rapid increase determination unit 320 sends out a harmonic rapid increase detection signal (S207). When the maximum value ΔVn _max of the difference harmonic amplitude is equal to or less than the threshold value A, the harmonic rapid increase determination unit 320 does not send out the harmonic rapid increase detection signal (S208).

(Supplementary explanation about calculation of differential harmonic vector ΔVn)
In the above description, the harmonic determining unit 400 calculates the maximum value _{Vn a_max} of the latest total harmonic amplitudes, the difference between the maximum value _{Vn b_max} of total harmonic amplitudes received before 5/4 period of the fundamental wave doing. The reason for this will be described with reference to FIG.
In the present embodiment, the predetermined time between the first period and the second period is set to ¼ period of the fundamental wave. In the present embodiment, since the difference calculation is performed after the harmonic vector is integrated, the predetermined time does not need to be one period of the fundamental wave or an integral multiple thereof. One period of the fundamental wave is an integral multiple of one period of the harmonic for any order of harmonics. Therefore, the value obtained by integrating stationary harmonics for one period of the fundamental wave is constant regardless of the integration start time. That is, the total amount of normal harmonic integrated values in periods 1D, 2A, 2B, and 2C in FIG. 9 is equal to the total amount of normal harmonic integrated values in periods 3A, 3B, 3C, and 3D. Therefore, it is possible to remove normal harmonics by making a comparison as shown in FIG. FIG. 9 shows a case where an isolated operation occurs during the period 2D, and it is possible to detect harmonics due to the isolated operation by calculating the difference in (f).

  As described in the first embodiment, what is important is that the single operation occurs after the end of the first period, and the second period starts after the single operation occurs. Therefore, it is important that the predetermined time is not zero and that a plurality of predetermined times are continuous. For example, when only the comparison in FIG. 9 is performed, if only (a), (c), (e), and (g) are performed, the predetermined time becomes discontinuous and the isolated operation cannot be detected. That is, four sets of vector integrators and amplitude value converters, and the predetermined time is not limited to a quarter cycle of the fundamental wave. For example, three sets of integrators and amplitude value converters, and the predetermined time is 1 of the fundamental wave. Although it may be set to / 3 period, a method of setting the first period and the second period in which the predetermined time (the interval between the first period and the second period) is discontinuous is not permitted.

Further, as described in the first embodiment, the predetermined time may be any time as long as it is equal to or shorter than the time corresponding to 100 cycles of the fundamental wave, and preferably equal to or shorter than the time corresponding to 10 cycles of the fundamental wave.
≪Summary≫
As described above, in the present embodiment, after the harmonic vectors are integrated in the first period and the second period, the maximum value ΔVn _max of the difference harmonic amplitude is calculated. By doing in this way, the predetermined time which is an interval between the first period and the second period can be made shorter than one period of the fundamental wave, and higher harmonics resulting from the independent operation are detected at a higher speed. It becomes possible.

(Modification)
In the first embodiment and the second embodiment, different calculation methods of the differential harmonic vector ΔVn are shown, but each has advantages and disadvantages.
In the method according to the second embodiment, since the vector integrator also integrates the normal harmonic component, the maximum value Vn _max of the total harmonic amplitude includes the amplitude of the normal harmonic. For this reason, when the amplitude of the harmonic in the normal state is larger than the amplitude of the harmonic due to the single operation, there is a problem that the calculation accuracy is lowered and the error of the maximum value ΔVn _max of the difference harmonic amplitude is increased.

On the other hand, in the method of the first embodiment, it is necessary to always hold the harmonic vector Vn ₂ just before two cycles in order to calculate the differential harmonic vector ΔVn, compared with the case where the value after integration is held. There is a problem that the amount of information to be retained increases.
Therefore, this modification is characterized in that the calculation method is changed according to the magnitude of the harmonic vector.

≪Configuration≫
The power conditioner according to this modification has the same configuration as that of the second embodiment except that the phase shift setting unit includes a harmonic detection unit 500 instead of the harmonic detection unit 400.
In FIG. 10, the structure of the harmonic detection part 500 with which the power conditioner which concerns on this modification is provided is shown. The harmonic detection unit 500 includes a harmonic amplitude determination unit 501, a difference vector calculation unit 302, a difference vector integration unit 303, a harmonic integration unit 410, an integral value difference calculation unit 420, and a selector 502. Yes.

Harmonic amplitude determining unit 501, a harmonic vector Vn (Vn _d, Vn _q) calculating the magnitude of the harmonic vector from the harmonic vector Vn to any of the difference vector calculating unit 302 and the harmonic integration unit 410 It is determined whether to output, and the selector 502 is operated.
The selector 502 sends the maximum value ΔVn _max of the difference harmonic amplitude output by either the difference vector integration unit 303 or the integral value difference calculation unit 420 to the harmonic sudden increase determination unit 320 in accordance with an instruction from the harmonic amplitude determination unit 501. Output.

<< Operation >>
The operation of the power conditioner according to the present embodiment is the same as the operation of the power conditioner 100 except that the detection operation of the harmonic increase is different from that of S101. Therefore, only the operation of the harmonic detection unit 500 performed instead of S101 will be described.
(Operation of harmonic detection unit 500)
Harmonics detection unit 500, like the S201, extracts a vector (V _d, V _q) harmonic vector Vn from (Vn _d, Vn _q) using the HPF 301.

Next, the harmonic detection unit 500 determines the magnitude of the harmonic vector Vn in the harmonic amplitude determination unit 501. Specifically, the square of the magnitude of the harmonic vector Vn is calculated using Equation 5 described above, and compared with a preset threshold value D. In this modification, the threshold value D is 100 times the threshold value A, that is, 400 V ² .
When the square of the magnitude of the harmonic vector Vn is not less than the threshold value D, that is, not less than 400 V ² , the harmonic amplitude determining unit 501 causes the selector 502 to connect the difference vector integrating unit 303 to the harmonic sudden increase determining unit 320. The harmonic vector Vn is output to the difference vector calculation unit 302. Since the subsequent operation is the same as that of the first embodiment, the description thereof is omitted.

On the other hand, when the square of the magnitude of the harmonic vector Vn is less than the threshold value D, that is, less than 400 V ² , the harmonic amplitude determining unit 501 adds the integrated value difference calculating unit 420 to the selector 502 and the harmonic sudden increase determining unit 320. And the harmonic vector Vn is output to the harmonic integrator 410. Since the subsequent operation is the same as that of the second embodiment, the description thereof is omitted.
In the harmonic detection unit 500, the selected side of the difference vector calculation unit 303 and the integral value difference calculation unit 420 outputs the maximum value ΔVn _max of the difference harmonic amplitude to the harmonic rapid increase determination unit 320 via the selector 502. Then, the magnitude of the harmonic vector Vn is again determined by the harmonic amplitude determination unit 501, “a combination of the difference vector calculation unit 302 and the difference vector integration unit 303”, “a harmonic integration unit 410, an integrated value” Which of “combination with difference calculation unit 420” is used is determined.

≪Summary≫
As described above, in this modification, the method for calculating the difference between the integrated values of the harmonic vector Vn and the method for calculating the integrated value of the differential harmonic vector ΔVn are selectively used depending on the magnitude of the harmonic vector Vn. . In this way, when the amplitude of the harmonics in normal times is large, the harmonics resulting from the single operation are extracted with high accuracy using a method of calculating the integral value of the differential harmonic vector ΔVn with high accuracy. At the same time, when the amplitude of the harmonics in normal times is small, a method for calculating the difference between the integral values of the harmonic vectors Vn can be used to reduce the amount of information to be retained and the harmonics resulting from the single operation. The detection speed can be increased.

(Embodiment 3)
In the first and second embodiments and the modification, the case where the phase shift amount for promoting the frequency change is determined as the predetermined θ _sft1 when the harmonic surge or the fundamental surge is detected has been described. . In this embodiment, when a harmonic surge or a fundamental surge is detected, the power conditioner outputs reactive power having a magnitude depending on the amplitude of the differential harmonic or the increase in the fundamental amplitude. It is characterized by.

≪Configuration≫
The power conditioner according to the present embodiment has the same configuration as that of the power conditioner 100 except that the isolated operation detection device includes a phase shift setting unit 600 instead of the phase shift setting unit 205.
FIG. 11 shows a configuration of phase shift setting section 600 according to the present embodiment. The phase shift setting unit 600 includes a reactive power supply control unit 610 connected to the harmonic detection unit 310 and the fundamental wave detection unit 330 in place of the reactive power supply control unit 370, and has no OR gate 350 and a higher harmonic. The rapid increase determination unit 320 and the fundamental rapid increase determination unit 340 are directly connected to the reactive power supply control unit 610. Other configurations are the same as those of the phase shift setting unit 205.

The reactive power supply control unit 610 generates a phase shift amount θ _sft1 for facilitating a frequency change and a slip mode frequency shift, or a phase shift amount θ _sft2 by a frequency feedback function, and the sum is obtained as a phase shift amount θ _sft. (Θ _sft = θ _sft1 + θ _sft2 ).
(Operation)
The operation of the power conditioner according to the present embodiment is the same as the operation of the power conditioner 100 except for the operation of S108, which is a process for determining the magnitude of reactive power. Therefore, only the reactive power determination process performed instead of S108 will be described.

FIG. 12 is a flowchart showing a process of determining reactive power for frequency promotion among operations performed by reactive power supply control unit 610 instead of S108.
Hereinafter, processing for determining reactive power for frequency promotion will be described.
The reactive power supply control unit 610 determines whether or not a harmonic rapid increase detection signal has been received (S301).

The reactive power supply control unit 610 further determines whether or not a fundamental wave sudden increase detection signal is received when receiving the harmonic sudden increase detection signal (S302).
The reactive power supply control unit 610 receives the difference between the maximum value ΔVn _max of the difference harmonic amplitude and the threshold A when the harmonic surge detection signal and the fundamental surge detection signal are received. The difference between the amplitude V ₀ and the threshold value C is compared (S303).

When the difference between the maximum value ΔVn _max of the difference harmonic amplitude and the threshold A is larger than the difference between the amplitude V _{0 of the} fundamental wave and the threshold C (Yes in S303), or when a harmonic sudden increase signal is received However, when the fundamental wave sudden increase signal is not received (No in S302), the reactive power supply control unit 610 determines the phase shift amount corresponding to the reactive power for frequency promotion using the following equation (S304). ).

ここで、Ｋ１およびＢ１は予め設定された係数である。
一方、無効電力供給制御部６１０は、高調波急増信号を受信していない場合、基本波急増信号を受信したか否かを検出する（Ｓ３０６）。

Here, K1 and B1 are preset coefficients.
On the other hand, the reactive power supply control unit 610 detects whether or not a fundamental wave rapid increase signal has been received (S306).

When the difference between the maximum value ΔVn _max of the difference harmonic amplitude and the threshold A is smaller than the difference between the amplitude V _{0 of the} fundamental wave and the threshold C (No in S303), or when a fundamental wave sudden increase signal is received However, when the harmonic surge signal is not received (No in S306), the reactive power supply control unit 610 determines the phase shift amount corresponding to the reactive power for frequency promotion using the following equation (S305). ).

ここで、Ｋ２およびＢ２は予め設定された係数である。
なお、高調波急増信号も基本波急増信号も受信していない場合（Ｓ３０６でＮｏ）、無効電力供給制御部６１０は、周波数助長のための無効電力に対応する位相シフト量をゼロと決定する（Ｓ３０７）。
θ_sft1＝０
以上の動作により、無効電力供給制御部６１０は、周波数助長のための無効電力に対応する位相シフト量θ_sft1を決定する。

Here, K2 and B2 are preset coefficients.
If neither the harmonic surge signal nor the fundamental surge signal is received (No in S306), the reactive power supply control unit 610 determines that the phase shift amount corresponding to the reactive power for frequency promotion is zero ( S307).
θ _sft1 = 0
With the above operation, the reactive power supply control unit 610 determines the phase shift amount θ _sft1 corresponding to the reactive power for frequency promotion.

Finally, the reactive power supply control unit 610 _adds the calculated θ _sft1 and the phase shift amount θ _sft2 by the slip mode frequency shift or the frequency feedback function, and outputs the sum as the phase shift amount θ _sft << Summary >>
As described above, in the present embodiment, the phase shift amount θ _sft1 corresponding to the reactive power for frequency promotion is determined based on the maximum value ΔVn _max of the differential harmonic amplitude and the fundamental wave amplitude V _0. calculate.

When at least one of the maximum value ΔVn _max of the difference harmonic amplitude and the fundamental wave amplitude V ₀ is large, there is a high possibility that the distributed power source 101 is in a single operation state. In such a case, by injecting a large reactive power as a reactive power for frequency promotion, in the case of a single operation, a slip mode frequency shift function, or a frequency fluctuation by a frequency feedback function is caused quickly, It becomes possible to detect islanding earlier.

If the maximum value ΔVn _max of the difference harmonic amplitude and the fundamental wave amplitude V ₀ are both small, there is a high possibility that the fluctuation of the normal harmonic is erroneously detected as a harmonic caused by an isolated operation. Since there is a low possibility that the distributed power source 101 is in a single operation state, in such a case, it is possible to prevent unnecessary injection of reactive current.
<Other Modifications According to Embodiment>
(1) In the first or third embodiment, the harmonic detection unit 310 includes the HPF 301 for extracting the harmonic vector Vn from the vector (V _d , V _q ) acquired from the coordinate conversion unit 201. The present invention is not necessarily limited to this case. For example, the harmonic detection unit 310 may not include the HPF 301. Without change of the fundamental wave vector (V _0, 0), the vector (V _d, V _q) and, just two cycles before the vector of the fundamental wave (V _d, V _q) by taking the difference between the difference This is because the harmonic vector ΔVn is obtained.

Here, if there is a variation in the fundamental wave vector (V ₀ , 0), the difference fundamental vector is mixed into the difference harmonic vector ΔVn. In such a case, the fundamental wave suddenly increases (S103). Yes, or S302 or S306 is Yes), it is necessary to inject a large reactive power as a reactive power for frequency promotion, and even if a rapid increase in harmonics is erroneously detected, the reactive power supply control unit 370 or The operation of 610 is not greatly affected.

In the second embodiment, the harmonic detection unit 400 or 500 may not include the HPF 301. However, since the integration result of the fundamental component is added to the integration result _SVn , _{Vna_max} and _{Vnb_max} are ΔVn. It should be noted that it is coarse with respect to _max , and the accuracy is likely to deteriorate due to digit loss.
(2) In the first embodiment, the harmonic vector Vn ₂ is the time just before the Vn by m cycles of the fundamental wave (m is an integer of 2 or more), but the present invention is not limited to this case. Not. m is not limited to a constant. For example, the value of m may periodically change to 2, 3, 2, 3 for each period of the fundamental wave. By doing so, it is possible to reduce the amount of information of the harmonic vector Vn ₂ should be retained.

  (3) In the second embodiment, the case where four sets of vector integrators and amplitude value converters are set and the predetermined time is ¼ period of the fundamental wave has been described, but the present invention is not necessarily limited to this case. For example, the vector integrator and the amplitude value converter may be p sets, and the predetermined time may be a time corresponding to a 1 / p period of the fundamental wave (p is an integer of 1 or more). Further, the integration start time of each integrator is not limited to the deviation of every 1 / p period of the fundamental wave, and can be arbitrarily set as long as there is no time not included in the predetermined time. . Note that the plurality of predetermined times may overlap each other.

(4) In the first to third embodiments, although the output SVn or Esuderuta _Vn vector integrator amplitude converter was assumed to be converted to Vn _max or .DELTA.Vn _max, the present invention is not necessarily limited to this case. For example, the harmonic integration unit does not include an amplitude value converter, the harmonic surge determining section 320, for example, a difference value between SVn of SVn and the second period of the first period, or define Esuderuta _Vn in advance It may be determined whether or not the threshold value is greater than or equal to the threshold value. In this case, the threshold value is the same as that of the first to third embodiments by incorporating the reciprocal number (2T / π) of the coefficient expressed by Equation 4 or 7 into the threshold value A described above. It can be performed. Similarly, for example, vector integrator, the square of the integrated value of the magnitude of the harmonic vector Vn or differential harmonic vector ΔVn in integration period (= the SVn or Esuderuta _Vn, the measuring unit 106 A / D conversion frequency The harmonic rapid increase determination unit 320 outputs the squared integrated value of the magnitude of the differential harmonic vector ΔVn or the square of the magnitude of the harmonic vector Vn in the first period. It may be determined whether the difference value between the integrated value and the integrated value of the square of the magnitude of the harmonic vector Vn in the second period is equal to or greater than a predetermined threshold value.

In the second embodiment, for example, the harmonic integration unit 410 does not include the amplitude value converters 402, 412, 422, and 432, and the amplitude value conversion is performed between the integration result holding unit 405 and the integrated value difference calculation unit 420. Or an amplitude value converter may be included in the integral value difference calculation unit 420.
(5) In the third embodiment, when both the harmonic surge and the fundamental surge are detected, the difference between the maximum value ΔVn _max of the differential harmonic amplitude and the threshold A, the fundamental amplitude V ₀ and the threshold Although the phase shift amount θ _sft1 is determined based on the larger of the difference from C, the present invention is not necessarily limited to this case. For example, S304 and S305 are not limited to the above formulas, and any function that increases θ _sft1 as ΔVn _max or V ₀ increases may be used. Alternatively, for example, θ _sft1 may be a fixed value in either one of S304 and S305.

Further, for example, the phase shift amount θ _sft1 based on ΔVn _max is calculated when a harmonic surge is detected, and the phase shift amount θ _sft1 based on V ₀ is calculated when a fundamental surge is detected. If both the fundamental wave sudden increase is detected, the phase shift amount θ _sft1 based on ΔVn _max and the phase shift amount θ _sft1 based on V ₀ , _whichever is larger, or the average value or the sum value is used as the phase shift amount. It may be used as θ _sft1 .

  (6) Although the phase shift setting unit 600 includes the harmonic detection unit 310 in the third embodiment, the present invention is not necessarily limited to this case. For example, the phase shift setting unit 600 may include the harmonic detection unit 400 according to the second embodiment or the harmonic detection unit 500 according to the modification instead of the harmonic detection unit 310. In this case, it is needless to say that the above (1) to (4) may be applied.

  (7) In the first to third embodiments, the harmonic component rapid increase detection (S101 or its substitute operation) and the fundamental component rapid increase detection (S102) are performed in this order. It is not limited to. For example, the fundamental component rapid increase detection in S102 may be performed prior to S101 (or its substitute operation), or the harmonic component rapid increase detection (S101 or its substitute operation) and the fundamental component rapid increase detection (S102) are performed. You may do it in parallel.

Further, S106 to S108 has been assumed to be performed for each one period of the fundamental wave, for example, S106 to S108, the measurement unit 106 performs a voltage value V _s each for outputting one of the values of theta _sft1 in S108 Only updating may be performed for each period of the fundamental wave. Incidentally, S102 to S105 is also performed each time measurement unit 106 is to output a single voltage value V _s, the harmonic surge determining section 320 between detects the rapid increase of the harmonic of one period of the fundamental wave, harmonic detection The signal may continue to be transmitted.

  (8) In the first to third embodiments, the passive islanding detection unit 204 sends the gate block signal Sb to the gate circuit 209 when detecting the jump of the voltage phase. It is not limited. For example, the passive islanding detection unit 204 may transmit the gate block signal Sb to the gate circuit 209 when detecting that the frequency change rate is equal to or greater than a threshold value. The passive islanding detection unit 204 is not limited to the frequency change rate, and any passive islanding detection method may be used.

(9) In the first to third embodiments, the phase shift setting units 205 and 600 output the phase shift amount θ _sft to the inverter driving device 110, but the present invention is not necessarily limited to this case. For example, the phase shift setting unit 205 or 600 may directly output the direction (advance or delay) and magnitude of the reactive power, or the reactive power direction and the power factor (= cos θ _sft ) of the inverter 104. It may be output. Alternatively, for example, the inverter drive device 110 shares the frequency detection unit 202 and the phase detection unit 203 with the isolated operation detection device 120, and the inverter drive device 110 receives the voltage phase θ _v and the phase shift amount θ _sft from the isolated operation detection device 120. And the frequency f _v may be received.

(10) In the first to third embodiments, the case where the measurement unit 106 performs A / D conversion on the system voltage value V _s and the output current value I _s at a predetermined frequency of 17.5 kHz has been described. It is not limited to the case. As for the frequency of A / D conversion, frequency detection and phase detection of voltage frequency, coordinate conversion of current value can be performed, and when the distributed power source 101 is operated independently, the disconnection may be performed within the disconnection time limit. For example, it may be 20 kHz.

  (11) Although the case where the frequency relay 206 and the voltage relay 207 transmit both the gate block signal Sb and the disconnection signal Sr has been described in the first to third embodiments, the present invention is not necessarily limited to this case. It is not limited. For example, the frequency relay 206 may send only the gate block signal Sb when detecting a frequency increase continuously for the detection time period or longer. Whether the frequency relay 206 and the voltage relay 207 send only the gate block signal Sb or both the gate block signal Sb and the disconnection signal Sr depends on the voltage settling value (upper limit value, lower limit value) and the frequency. May be determined separately for each of the set values. Alternatively, the frequency upper limit value and the frequency lower limit value may be individually determined.

  (12) Each of the phase shift determination unit, the isolated operation detection device, and the grid interconnection protection device of the first to third embodiments may be typically realized as an LSI (Large Scale Integration) that is an integrated circuit. Each circuit may be individually configured as one chip, or may be integrated into one chip so as to include all or some of the circuits. For example, the relay operation setting device may be integrated as a system interconnection protection device in the same integrated circuit together with other circuit units, or may be a separate integrated circuit.

Although described here as LSI, depending on the degree of integration, it may also be called IC (Integrated Circuit), system LSI, super LSI, or ultra LSI.
Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

Further, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology.
(13) The description of the first to third embodiments is merely an example of the present invention, and various improvements and modifications can be made without departing from the scope of the present invention.
(Supplement)
Below, the structure and effect of the isolated operation detection apparatus and isolated operation detection method which concern on embodiment are demonstrated.

  (1) An isolated operation detection device according to an embodiment is an isolated operation detection device that detects an isolated operation of a distributed power source, and a voltage that detects an AC voltage of a power system in which the distributed power source is interconnected. The detection unit, the magnitude of the harmonic component of the AC voltage in the first period having a time length corresponding to one period of the AC voltage of the power system, and the same time length as the first period A harmonic difference calculation unit that obtains a difference value from the harmonic component magnitude of the AC voltage in a second period that starts a predetermined time after the end of the period of 1, and the difference calculated by the harmonic difference calculation unit When the value is greater than or equal to the threshold value, reactive power for promoting frequency change is supplied to the power system, and when the difference value is less than the threshold value, reactive power for promoting the frequency change is provided. To the power grid And a reactive power supply controller, not.

  In addition, the isolated operation detection method according to the embodiment is an isolated operation detection method for performing a process of changing the amount of reactive power supplied to promote frequency change, and is a power system in which distributed power sources are connected to the grid. A voltage detection step for detecting the AC voltage of the power system, and the magnitude of the harmonic component of the AC voltage in the first period having a time length corresponding to one period of the AC voltage of the power system, the same as in the first period A harmonic difference calculating step for obtaining a difference value with a magnitude of a harmonic component of the AC voltage in a second period having a time length and starting a predetermined time after the end of the first period; and the harmonic difference When the difference value calculated in the calculation step is greater than or equal to a threshold value, reactive power for promoting frequency change is supplied to the power system, and when the difference value is less than the threshold value, the frequency And a reactive power supply control step is not supplied to the power system reactive power to promote reduction.

In this way, it is possible to detect the presence or absence of harmonics generated by an isolated operation by eliminating the influence of existing harmonics regardless of whether or not the distributed power source is in an isolated operation state. It is possible to suppress injection when reactive power injection is unnecessary to promote frequency change due to erroneous detection of wave fluctuations.
(2) Further, in the isolated operation detection device according to (1) according to the embodiment, the harmonic difference calculation unit has a dq coordinate system that rotates an instantaneous value of the AC voltage at a fundamental wave period of the AC voltage. A difference vector between the vector obtained by performing the dq coordinate transformation and the vector obtained by performing the dq coordinate transformation on the instantaneous value of the alternating voltage just before the predetermined time is calculated a plurality of times in the second period. A difference vector calculation unit for calculating and a difference vector integration unit for calculating the difference value using a result obtained by integrating the magnitude of the difference vector in the second period may be included.

By doing in this way, the normal harmonic component in the first period can be removed from the instantaneous vector included in the second period, so that the distributed power source has shifted to a single operation during a predetermined time. In this case, the result of integrating the square of the magnitude of the difference vector includes only the harmonic component resulting from the single operation, and the harmonic component resulting from the single operation can be detected with high accuracy.
(3) In the isolated operation detection device according to (2) according to the embodiment, the predetermined time may be n times the time length of the first period (n is an integer of 1 or more). Good.

In this way, the harmonic vector included in the first period and having the same frequency, phase, and amplitude can be surely removed from the instantaneous vector included in the second period, and the difference The vector can be only the harmonic vector resulting from islanding.
(4) In the isolated operation detection device according to (1) according to the embodiment, the harmonic difference calculation unit integrates the square of the amplitude value of the harmonic component of the AC voltage in the first period. A harmonic integration unit that integrates the square of the amplitude value of the harmonic component of the AC voltage in the second period, an integration value in the second period calculated by the harmonic integration unit, and the harmonic It is good also as including the integrated value difference calculation part which calculates the said difference value using the difference with the integral value in the said 1st period which the wave integration part calculated.

By doing in this way, since the information regarding the 1st period should just hold an integral value, the amount of information which an isolated operation detection device should hold can be reduced. Moreover, the predetermined time is not limited to n times the time length of the first period, and can be set to a shorter time, and harmonics resulting from the single operation can be detected at high speed.
(5) Further, in the isolated operation detection device of (1) according to the embodiment, the harmonic difference calculation unit calculates a vector obtained by performing coordinate conversion on the instantaneous value of the AC voltage, and the predetermined value based on the vector. A difference vector calculation unit that calculates a difference vector from a vector obtained by performing coordinate transformation on the instantaneous value of the AC voltage just before time in the second period, and a square of the magnitude of the difference vector A difference vector integration unit that calculates the difference value using the result obtained by integrating the result of the AC voltage in the second period, and the square of the amplitude value of the harmonic component of the AC voltage is integrated in the first period, and the AC a harmonic integration section for integrating the square of the amplitude of the harmonic component of the voltage in the second period, the integral value in the second period in which the harmonic integration section has been calculated, the harmonic integration section The calculated integral value in the first period; Using the difference, it said comprising an integration value difference calculation section that calculates a difference value, if the magnitude of the harmonic component of the AC voltage in the second period is equal to or larger than the reference value, the said difference vector calculating portion The difference vector integration unit is used to calculate the difference value. When the magnitude of the harmonic component of the AC voltage in the second period is less than the reference value, the harmonic integration unit and the integration value difference calculation The difference value may be calculated using a unit.

In this way, when the amplitude of the harmonics at normal times is small, the amount of information to be retained is reduced by the method using the difference between the integral values, and the harmonic detection due to the single operation is speeded up. When the amplitude of the harmonics of the hour is large, the method of integrating the difference vector can prevent the deterioration of the calculation accuracy such as the digit loss, and the harmonic detection due to the single operation can be made highly accurate.
(6) In the isolated operation detection apparatus according to (1) according to the embodiment, the reactive power supply control unit determines the magnitude of the reactive power according to the magnitude of the difference value. Also good.

  This reduces the amount of reactive power supplied to the load when there is a high possibility that a fluctuation in harmonics during normal operation is erroneously detected as a harmonic caused by isolated operation. Injection can be suppressed.

The isolated operation detection device and the harmonic detection method disclosed in the present specification are useful in, for example, a distributed power source that is connected to an electric power system.

DESCRIPTION OF SYMBOLS 100 Power conditioner 101 Distributed type power supply 102 Electric power system 103 Load 104 Inverter 105 Interconnection relay 106 Measuring part 107,200 Power conditioner control apparatus 110 Inverter drive device 120,220 System interconnection protection apparatus 130,210 Relay operation setting apparatus 111 , 112 Coordinate conversion unit 113 Active current control unit 114 Reactive current control unit 115 PWM signal generation unit 116 Gate circuit 121 Frequency detection unit 122 Phase detection unit 123 Passive isolated operation detection unit 124, 224 Phase shift addition unit 125 Angular acceleration calculation unit 126 Protection Relay Setting Determination Unit 127 Frequency Relay 128 Voltage Relay 221 Sign Change Count Unit

Claims (9)

An isolated operation detection device for detecting isolated operation of a distributed power source,
A voltage detection unit for detecting an AC voltage of a power system in which the distributed power source is grid-connected;
The magnitude of the harmonic component of the AC voltage in the first period having a time length corresponding to one cycle of the AC voltage of the power system, and the same time length as the first period. A harmonic difference calculation unit for obtaining a difference value with the magnitude of the harmonic component of the AC voltage in a second period starting after a predetermined time from the end;
When the difference value calculated by the harmonic difference calculation unit is greater than or equal to a threshold value, the reactive power for promoting frequency change is supplied to the power system, and the difference value is less than the threshold value An isolated operation detection device comprising: a reactive power supply control unit that does not supply reactive power for facilitating the frequency change to the power system. The harmonic difference calculation unit
A vector obtained by performing dq coordinate transformation on the dq coordinate system rotating the instantaneous value of the AC voltage with the fundamental wave period of the AC voltage, and the dq coordinate to the instantaneous value of the AC voltage a predetermined time before A difference vector calculation unit that calculates a difference vector from the vector obtained by performing the conversion a plurality of times in the second period;
The isolated operation detection device according to claim 1, further comprising: a difference vector integration unit that calculates the difference value using a result obtained by integrating the magnitude of the difference vector in the second period. The isolated operation detection device according to claim 2, wherein the predetermined time is n times the time length of the first period (n is an integer of 1 or more). The harmonic difference calculation unit
A harmonic integrator that integrates the square of the amplitude value of the harmonic component of the AC voltage in the first period, and integrates the square of the amplitude value of the harmonic component of the AC voltage in the second period; ,
Integral value difference for calculating the difference value using the difference between the integrated value calculated in the second period calculated by the harmonic integrating unit and the integrated value calculated in the first period calculated by the harmonic integrating unit. The isolated operation detection device according to claim 1, further comprising: a calculation unit. The harmonic difference calculation unit
A difference vector between a vector obtained by performing coordinate conversion on the instantaneous value of the alternating voltage and a vector obtained by performing coordinate conversion on the instantaneous value of the alternating voltage just before the predetermined time is obtained as the second vector. A difference vector calculation unit that calculates a plurality of times in a period;
A difference vector integration unit that calculates the difference value using a result obtained by integrating the square of the magnitude of the difference vector in the second period;
A harmonic integrator that integrates the square of the amplitude value of the harmonic component of the AC voltage in the first period, and integrates the square of the amplitude value of the harmonic component of the AC voltage in the second period; ,
Using the difference between the integral value in the first period and the integral value, the harmonic integration unit is calculated in the second period in which the harmonic integration section has been calculated, the integral value difference to calculate the difference value Including a calculation unit,
When the magnitude of the harmonic component of the AC voltage in the second period is greater than or equal to a reference value, the difference value is calculated using the difference vector calculation unit and the difference vector integration unit ,
The difference value is calculated using the harmonic integration unit and the integral value difference calculation unit when the magnitude of the harmonic component of the AC voltage in the second period is less than the reference value. The isolated operation detection device described. The islanding operation detection device according to claim 1, wherein the reactive power supply control unit determines the magnitude of the reactive power according to the magnitude of the difference value. The isolated operation detection device according to any one of claims 1 to 6,
A power conditioner comprising: a power supply unit that supplies reactive power to a load in accordance with an instruction from the reactive power supply control unit. A power conditioner according to claim 7;
A distributed power supply system comprising: a distributed power supply that supplies generated power to the power supply unit. An isolated operation detection method for performing a process of varying the amount of reactive power supplied to promote frequency change,
A voltage detection step for detecting an AC voltage of a power system in which a distributed power source is interconnected;
The magnitude of the harmonic component of the AC voltage in the first period having a time length corresponding to one cycle of the AC voltage of the power system, and the same time length as the first period. A harmonic difference calculating step for obtaining a difference value with the magnitude of the harmonic component of the AC voltage in a second period starting after a predetermined time from the end;
When the difference value calculated in the harmonic difference calculation step is greater than or equal to a threshold value, reactive power for promoting frequency change is supplied to the power system, and the difference value is less than the threshold value And a reactive power supply control step of not supplying reactive power for promoting the frequency change to the power system.

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