JP2017051063A - Isolated operation detection system for distributed power supply - Google Patents

Isolated operation detection system for distributed power supply Download PDF

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JP2017051063A
JP2017051063A JP2015174873A JP2015174873A JP2017051063A JP 2017051063 A JP2017051063 A JP 2017051063A JP 2015174873 A JP2015174873 A JP 2015174873A JP 2015174873 A JP2015174873 A JP 2015174873A JP 2017051063 A JP2017051063 A JP 2017051063A
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frequency deviation
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JP6547528B2 (en
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長倉 孝行
Takayuki Nagakura
孝行 長倉
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Fuji Electric Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To provide an isolated operation detection system capable of surely detecting an isolated operation state of a distributed power supply in a short time.SOLUTION: An isolated operation detection system comprises frequency detection means 12, frequency deviation calculation means 13, reactive power calculation/injection means 14, and isolated operation detection means 16 and injects reactive power in which, with respect to a frequency deviation, a frequency deviation calculated next to the frequency deviation varies by a predetermined ratio, into a system 21 through an inverter 11. The isolated operation detection means 16 calculates a ratio of the present frequency deviation's increase/decrease from a past frequency deviation, as a frequency deviation ratio and determines to be in an isolated operation state when the number of times of the frequency deviation ratio having exceeded a first threshold supposed from injected reactive power has exceeded a second threshold; or when, at the time of an injected reactive power amount exceeding a threshold, the number of times of the frequency deviation ratio having exceeded a third threshold has exceeded a fourth threshold, or when the number exceeds a fifth threshold and the absolute value of the frequency deviation exceeds a sixth threshold or a system frequency exceeds a seventh threshold or is lower than an eighth threshold.SELECTED DRAWING: Figure 4

Description

本発明は、太陽光発電システム、風力発電システム、燃料電池発電システム等の分散電源がインバータを介して電力系統に連系している場合に、系統電源の事故停電や作業停電により、分散電源が系統から切り離されて単独運転状態になったことを検出する単独運転検出システムに関するものである。   In the present invention, when a distributed power source such as a solar power generation system, a wind power generation system, or a fuel cell power generation system is connected to an electric power system via an inverter, the distributed power source is The present invention relates to an isolated operation detection system that detects that the system has been disconnected from the system and has entered an isolated operation state.

電力系統に連系して運転されている分散電源が単独運転状態となり、系統電源からの電力供給が停止すると、分散電源によって配電線が逆充電されることに起因して感電や配電設備が破損するおそれがある。このため、分散電源の単独運転を速やかに検出し、電力系統からインバータ及び分散電源を切り離して安全性を確保することが求められている。   When a distributed power source connected to the power system is in a single operation state and the power supply from the system power source stops, the electric shock and power distribution equipment are damaged due to the reverse charging of the distribution line by the distributed power source. There is a risk. For this reason, it is required to quickly detect isolated operation of the distributed power source and to ensure safety by separating the inverter and the distributed power source from the power system.

この種の単独運転検出システムは、分散電源が電力系統との連系状態から切り離されて単独運転状態に移行した時に生じる電圧や位相等の変化をとらえて単独運転を検出する受動方式と、分散電源に接続されたインバータの出力に変動要因を与えておき、連系運転時にはその変動の影響が現れず、単独運転時には変動要因の影響が現れることを利用して変動の発生により単独運転を検出する能動方式と、に大別することができる。   This type of isolated operation detection system is a passive method that detects isolated operation by detecting changes in voltage, phase, etc. that occur when the distributed power source is disconnected from the interconnection state with the power system and transitions to the isolated operation state. A fluctuation factor is given to the output of the inverter connected to the power supply, and the influence of the fluctuation does not appear at the time of interconnection operation. It can be roughly divided into the active method.

上記の能動方式としては、系統に無効電力を注入してインバータの出力を変化させ、その変化を、系統周波数の偏差を判定条件として単独運転を検出するものが知られている。
例えば、最新の系統周波数と過去の系統周波数との偏差を算出し、その偏差が所定の閾値を超過した場合に単独運転と判定するものがある。
図9(a)は、周波数偏差が閾値を超過した回数が1回または複数回の場合に、分散電源の単独運転を検出する原理の説明図であり、「●」は一定周期のサンプリング点における周波数偏差を示す。
As the above-mentioned active method, there is known a method in which reactive power is injected into a system to change the output of an inverter, and the change is detected, and an isolated operation is detected using a deviation of the system frequency as a determination condition.
For example, there is one that calculates a deviation between the latest system frequency and a past system frequency, and determines that the islanding operation is performed when the deviation exceeds a predetermined threshold.
FIG. 9A is an explanatory diagram of the principle for detecting the isolated operation of the distributed power supply when the frequency deviation exceeds the threshold value once or a plurality of times, and “●” indicates a sampling point at a constant period. Indicates frequency deviation.

また、特許文献1には、階段状に単調増加/単調減少する閾値を設定し、周波数偏差が複数のサンプリング点で上記の階段状閾値を超過した時に単独運転を検出する従来技術が開示されている。
ここで、図10は、特許文献1に記載された単独運転検出装置50の構成図であり、この検出装置50は、分散型電源60と系統電源70との間に接続されている。図10において、51は系統の周波数を計測して連系リレー54,55を制御する制御装置、52は、制御装置51からの指令と系統の電圧、電流とに基づいてインバータ53を制御するインバータ制御部である。
Further, Patent Document 1 discloses a conventional technique in which a threshold value for monotonously increasing / decreasing monotonically is set in a stepwise manner, and an isolated operation is detected when the frequency deviation exceeds the above stepwise threshold value at a plurality of sampling points. Yes.
Here, FIG. 10 is a configuration diagram of the isolated operation detection device 50 described in Patent Document 1, and this detection device 50 is connected between the distributed power supply 60 and the system power supply 70. In FIG. 10, 51 is a control device that controls the interconnection relays 54 and 55 by measuring the frequency of the system, and 52 is an inverter that controls the inverter 53 based on the command from the control device 51 and the voltage and current of the system. It is a control unit.

図11は、図10における制御装置51の構成図である。この制御装置51は、系統の周波数を計測する計測部51aと、所定期間の計測周波数の変動状況(周波数偏差)に応じて補正無効電力を生成する周波数フィードバック部51bと、無効電力を定期的に変動させる定期変動部51cと、定期的に変動する無効電力と補正無効電力とを加算する加算部51dと、所定期間の周波数偏差に応じて変化パターンを生成する変化パターン生成部51eと、周波数偏差と変化パターンとを比較して単独運転の有無を判定し、その判定出力により連系リレー54,55を駆動する判定部51fと、を備えている。
図12(a)は、上記の構成により単独運転を検出する原理の説明図であり、周波数偏差が、複数のサンプリング点で階段状閾値(変化パターン)を超過したときに単独運転を検出している。
FIG. 11 is a block diagram of the control device 51 in FIG. The control device 51 includes a measurement unit 51a that measures the frequency of the system, a frequency feedback unit 51b that generates corrected reactive power according to the fluctuation state (frequency deviation) of the measurement frequency during a predetermined period, and the reactive power periodically. A periodic variation unit 51c that varies, an addition unit 51d that adds the reactive power that periodically varies and the corrected reactive power, a change pattern generation unit 51e that generates a change pattern according to a frequency deviation in a predetermined period, and a frequency deviation And a change pattern to determine whether or not an independent operation is performed, and a determination unit 51f that drives the interconnection relays 54 and 55 based on the determination output.
FIG. 12A is an explanatory diagram of the principle of detecting an isolated operation with the above-described configuration. When the frequency deviation exceeds a stepped threshold (change pattern) at a plurality of sampling points, the isolated operation is detected. Yes.

特開2007−215392号公報(段落[0041]〜[0062]、図1,図2,図5等)JP 2007-215392 A (paragraphs [0041] to [0062], FIG. 1, FIG. 2, FIG. 5, etc.)

前述したように、周波数偏差と閾値とを比較して単独運転を検出する方式では、周波数偏差が閾値に対して大きな変化分で推移するような系統の擾乱が発生すると、判定中に周波数偏差の変化率が反転するポイントが生じ、その後に周波数偏差が小さくなったとしても、単独運転ではなくても単独運転と誤検出してしまう場合がある。
図9(b)及び図12(b)は、このような誤検出状態を示したものである。何れの場合も、系統の擾乱により瞬間的に周波数が大きく変動し、その後、周波数が元に戻っていく過程で周波数偏差が次第に縮小していくが、予め設定された閾値を下回ることがないため、単独運転と誤検出してしまう。
As described above, in the method of detecting the isolated operation by comparing the frequency deviation with the threshold value, if a system disturbance occurs such that the frequency deviation changes with a large change with respect to the threshold value, the frequency deviation is determined during the determination. Even if there is a point where the rate of change is reversed and the frequency deviation becomes smaller thereafter, it may be erroneously detected as an isolated operation even if it is not an isolated operation.
FIG. 9B and FIG. 12B show such a false detection state. In any case, the frequency fluctuates instantaneously due to the disturbance of the system, and then the frequency deviation gradually decreases in the process of returning to the original frequency, but it does not fall below the preset threshold value. Incorrect operation will be detected.

上記のような単独運転の誤検出を回避するためには、閾値を微妙に調整したり、または、余裕を見て閾値を大きめに設定する必要がある。
しかし、閾値を微妙に調整するだけでは誤検出を完全になくすことが困難であり、また、閾値に余裕を持たせると、その分、周波数偏差が大きくならない限り単独運転を検出できなくなり、感度が低下して判定に要する時間が長くなる。つまり、結果的に分散電源の単独運転状態が長く続くため、安全性が低下するという問題がある。
そこで、本発明の解決課題は、分散電源の単独運転状態を短時間で確実に検出することが可能な単独運転検出システムを提供することにある。
In order to avoid the above-described erroneous detection of isolated operation, it is necessary to finely adjust the threshold value or to set a larger threshold value with a margin.
However, it is difficult to eliminate false detection completely only by finely adjusting the threshold, and if there is a margin in the threshold, it will not be possible to detect isolated operation unless the frequency deviation becomes large. Decreases and the time required for determination becomes longer. That is, as a result, the single operation state of the distributed power source continues for a long time, and there is a problem that safety is lowered.
Accordingly, an object of the present invention is to provide an isolated operation detection system capable of reliably detecting an isolated operation state of a distributed power supply in a short time.

上記課題を解決するため、本発明は、インバータを介して系統へ無効電力を注入することにより、その注入無効電力量に応じて周波数偏差が大きくなり、当該注入無効電力量から想定される周波数偏差が変化することに基づいて単独運転を検出するものである。   In order to solve the above-described problem, the present invention injects reactive power into a system through an inverter, and thus the frequency deviation increases according to the injected reactive power amount, and the frequency deviation assumed from the injected reactive power amount. The islanding operation is detected based on the change of.

まず、系統への無効電力注入による周波数偏差の挙動を、図6及び図7に基づいて説明する。
図6において、時刻t1で検出した周波数偏差をΔfとすると、その時刻t1で系統に注入する無効電力を、次のサンプリング点t2においてΔfの2倍の周波数偏差(2×Δf)の発生を期待する量とすると、理想的には、時刻t2で検出される周波数偏差は(2×Δf)となる。更に、時刻t2で検出した周波数偏差を(2×Δf)とすると、その時刻t2で系統に注入する無効電力を、次のサンプリング点t3において(2×Δf)の2倍の周波数偏差(4×Δf)の発生を期待する量とすると、理想的には、時刻t3で検出される周波数偏差は(4×Δf)となる。
本発明では、注入無効電力によって生じると予想される連続したサンプリング点間の周波数偏差の比率(図6の例では、「2.0」)を所定の閾値と比較することを基本として、分散電源の単独運転を検出するものである。
First, the behavior of the frequency deviation due to the reactive power injection into the system will be described with reference to FIGS.
In FIG. 6, assuming that the frequency deviation detected at time t1 is Δf, the reactive power injected into the system at time t1 is expected to generate a frequency deviation (2 × Δf) twice Δf at the next sampling point t2. Ideally, the frequency deviation detected at time t2 is (2 × Δf). Further, assuming that the frequency deviation detected at time t2 is (2 × Δf), the reactive power injected into the system at time t2 is twice the frequency deviation (4 × Δf) at (2 × Δf) at the next sampling point t3. Assuming that Δf) is expected to occur, ideally, the frequency deviation detected at time t3 is (4 × Δf).
In the present invention, the distributed power source is based on comparing the ratio of frequency deviations between consecutive sampling points expected to be caused by the injection reactive power (“2.0” in the example of FIG. 6) with a predetermined threshold. Is detected.

図7は、周波数偏差と注入無効電力との関係を示す図である。注入無効電力の極性が負の場合もあり得るが、ここでは、極性が正の場合について述べる。なお、注入無効電力の極性が負の場合は、図7と対称の特性となる。   FIG. 7 is a diagram showing the relationship between the frequency deviation and the injection reactive power. There may be a case where the polarity of the injection reactive power is negative. Here, a case where the polarity is positive will be described. In addition, when the polarity of the injection reactive power is negative, the characteristics are symmetrical to those in FIG.

注入無効電力の極性が正の場合について、理想的な状態について説明する。
図7において、まず、周波数偏差Δf1を検出すると、その2倍の周波数偏差Δf2(=2×Δf1)の発生を期待する無効電力Q2を注入する。そして、この無効電力Q2の注入によって発生する周波数偏差Δf2を検出する。次に、周波数偏差Δf2を検出すると、その2倍の周波数偏差Δf3(=2×Δf2)の発生を期待する無効電力Q3を注入する。そして、この無効電力Q3の注入によって発生する周波数偏差Δf3を検出する。
以後、同様にして、周波数偏差Δfnを検出すると、その2倍の周波数偏差Δfn+1(=2×Δfn)の発生を期待する無効電力Qn+1を注入する。
An ideal state will be described for a case where the polarity of the injection reactive power is positive.
In FIG. 7, first, when the frequency deviation Δf1 is detected, the reactive power Q2 that is expected to generate twice the frequency deviation Δf2 (= 2 × Δf1) is injected. Then, the frequency deviation Δf2 generated by the injection of the reactive power Q2 is detected. Next, when the frequency deviation Δf2 is detected, reactive power Q3 that is expected to generate twice the frequency deviation Δf3 (= 2 × Δf2) is injected. Then, the frequency deviation Δf3 generated by the injection of the reactive power Q3 is detected.
Thereafter, similarly, when the frequency deviation Δfn is detected, reactive power Qn + 1 that is expected to generate a frequency deviation Δfn + 1 (= 2 × Δfn) that is twice that frequency deviation is injected.

上記のような手順で系統に無効電力を注入することにより、周波数偏差は次第に増大していく。言い換えると、検出した周波数偏差Δfに対し、次に期待する周波数偏差を例えば(2×Δf)とすると、Δfが大きければ次の周波数偏差も大きくなり、Δfが小さければ次の周波数偏差も小さくなる。
この点に着目し、本発明では、周波数偏差の変化の状況に応じて、単独運転を検出するための閾値を変動させる閾値変動方法を用いることとした。
By injecting reactive power into the system according to the above procedure, the frequency deviation gradually increases. In other words, if the next expected frequency deviation is, for example, (2 × Δf) with respect to the detected frequency deviation Δf, the next frequency deviation increases as Δf increases, and the next frequency deviation decreases as Δf decreases. .
Focusing on this point, in the present invention, a threshold value fluctuation method is used in which the threshold value for detecting the isolated operation is varied according to the change state of the frequency deviation.

図8は、本発明における閾値変動方法を説明するための概念図である。本発明では、図8(a)のように周波数偏差が小さい場合には、次に期待する周波数偏差も小さくなるため、周波数偏差の比率である閾値が小さくなり、逆に、図8(b)のように周波数偏差が大きい場合には、次に期待する周波数偏差も大きくなるため、周波数偏差の比率である閾値が大きくなるように変動する。
このため、本発明では、前述の図9(b)や図12(b)に示したように、系統の擾乱によって周波数偏差が大きく変動した場合には、次の周波数偏差に対する閾値が大きくなるように変動するのに対し、その後に周波数偏差が前回よりも減少して期待通りの値にならなかった場合には、増大した閾値に対して周波数偏差の比率が下回ることになり、単独運転とは見なさないため誤検出が回避されることになる。
FIG. 8 is a conceptual diagram for explaining the threshold value fluctuation method in the present invention. In the present invention, when the frequency deviation is small as shown in FIG. 8A, the frequency deviation expected next is also small, so the threshold value, which is the ratio of the frequency deviation, becomes small, and conversely, FIG. When the frequency deviation is large as described above, the next expected frequency deviation is also large, so that the threshold value, which is the ratio of the frequency deviation, varies so as to increase.
For this reason, in the present invention, as shown in FIG. 9B and FIG. 12B, when the frequency deviation greatly fluctuates due to the disturbance of the system, the threshold for the next frequency deviation is increased. However, if the frequency deviation subsequently decreases from the previous value and does not reach the expected value, the ratio of the frequency deviation is less than the increased threshold. Misdetection is avoided because it is not considered.

すなわち、請求項1に係る発明は、分散電源が電力変換器を介して電力系統に連系せずに単独運転状態にあることを検出する分散電源の単独運転検出システムであって、
系統周波数を検出する周波数検出手段と、前記系統周波数から所定期間の周波数偏差を算出する周波数偏差算出手段と、前記所定期間の周波数偏差に対して次の所定期間の周波数偏差が所定の比率で変化するような無効電力を算出して前記電力変換器を介して系統に注入する無効電力算出・注入手段と、前記所定期間の周波数偏差と前記無効電力算出・注入手段により系統に注入される無効電力とに基づいて、前記分散電源が単独運転状態であるか否かを判定する単独運転検出手段と、を備え、
前記単独運転検出手段は、
系統への注入無効電力が所定値以上ある時に、現在の周波数偏差の過去の周波数偏差からの増減の比率を周波数偏差比率として演算し、前記周波数偏差比率が注入無効電力から想定される比率閾値としての第1閾値を超えた回数が、回数閾値としての第2閾値を超えた時に、前記分散電源が単独運転状態にあると判定すると共に、
前記無効電力算出・注入手段が算出した前記注入無効電力が注入量閾値を超えた場合、
前記無効電力算出・注入手段は前記注入無効電力を前記注入量閾値に制限し、
前記単独運転検出手段は、
現在の周波数偏差の過去の周波数偏差からの増減の比率を周波数偏差比率として演算し、前記周波数偏差比率が比率閾値としての第3閾値を超えた回数が回数閾値としての第4閾値を超えた時、または、前記周波数偏差比率が前記第3閾値を超えた回数が回数閾値としての第5閾値を超え、かつ、系統の周波数偏差の絶対値が第6閾値を超えたときに、前記分散電源が単独運転状態にあると判定するものである。
That is, the invention according to claim 1 is an isolated operation detection system for a distributed power supply that detects that the distributed power supply is in an isolated operation state without being connected to an electric power system via a power converter,
A frequency detecting means for detecting a system frequency; a frequency deviation calculating means for calculating a frequency deviation of a predetermined period from the system frequency; and a frequency deviation of a next predetermined period changes at a predetermined ratio with respect to the frequency deviation of the predetermined period. Reactive power calculation / injection means for calculating reactive power to be injected into the system via the power converter, and reactive power injected into the system by the frequency deviation of the predetermined period and the reactive power calculation / injection means And an isolated operation detecting means for determining whether or not the distributed power supply is in an isolated operation state based on
The isolated operation detecting means includes
When the injection reactive power to the system is greater than or equal to a predetermined value, the ratio of increase / decrease of the current frequency deviation from the past frequency deviation is calculated as a frequency deviation ratio, and the frequency deviation ratio is assumed as a ratio threshold assumed from the injection reactive power When the number of times exceeding the first threshold value exceeds the second threshold value as the frequency threshold value, it is determined that the distributed power source is in a single operation state,
When the injection reactive power calculated by the reactive power calculation / injection means exceeds an injection amount threshold,
The reactive power calculation / injection means limits the injection reactive power to the injection amount threshold,
The isolated operation detecting means includes
When the ratio of increase / decrease of the current frequency deviation from the past frequency deviation is calculated as the frequency deviation ratio, and the number of times the frequency deviation ratio exceeds the third threshold as the ratio threshold exceeds the fourth threshold as the frequency threshold Alternatively, when the frequency deviation ratio exceeds the third threshold exceeds a fifth threshold as a frequency threshold, and the absolute value of the frequency deviation of the system exceeds a sixth threshold, the distributed power supply It is determined that the vehicle is in a single operation state.

請求項2に係る発明は、分散電源が電力変換器を介して電力系統に連系せずに単独運転状態にあることを検出する分散電源の単独運転検出システムであって、
系統周波数を検出する周波数検出手段と、前記系統周波数から所定期間の周波数偏差を算出する周波数偏差算出手段と、前記所定期間の周波数偏差に対して次の所定期間の周波数偏差が所定の比率で変化するような無効電力を算出して前記電力変換器を介して系統に注入する無効電力算出・注入手段と、前記所定期間の周波数偏差と前記無効電力算出・注入手段により系統に注入される無効電力とに基づいて、前記分散電源が単独運転状態であるか否かを判定する単独運転検出手段と、を備え、
前記単独運転検出手段は、
系統への注入無効電力が所定値以上ある時に、現在の周波数偏差の過去の周波数偏差からの増減の比率を周波数偏差比率として演算し、前記周波数偏差比率が注入無効電力から想定される比率閾値としての第1閾値を超えた回数が、回数閾値としての第2閾値を超えた時に、前記分散電源が単独運転状態にあると判定すると共に、
前記無効電力算出・注入手段が算出した前記注入無効電力が注入量閾値を超えた場合、
前記無効電力算出・注入手段は前記注入無効電力を前記注入量閾値に制限し、
前記単独運転検出手段は、
現在の周波数偏差の過去の周波数偏差からの増減の比率を周波数偏差比率として演算し、前記周波数偏差比率が比率閾値としての第3閾値を超えた回数が回数閾値としての第4閾値を超えた時、または、前記周波数偏差比率が前記第3閾値を超えた回数が回数閾値としての第5閾値を超え、かつ、系統周波数が第7閾値を超えるか第8閾値未満であるときに、前記分散電源が単独運転状態にあると判定するものである。
The invention according to claim 2 is an isolated operation detection system for a distributed power source that detects that the distributed power source is in an isolated operation state without being connected to a power system via a power converter,
A frequency detecting means for detecting a system frequency; a frequency deviation calculating means for calculating a frequency deviation of a predetermined period from the system frequency; and a frequency deviation of a next predetermined period changes at a predetermined ratio with respect to the frequency deviation of the predetermined period. Reactive power calculation / injection means for calculating reactive power to be injected into the system via the power converter, and reactive power injected into the system by the frequency deviation of the predetermined period and the reactive power calculation / injection means And an isolated operation detecting means for determining whether or not the distributed power supply is in an isolated operation state based on
The isolated operation detecting means includes
When the injection reactive power to the system is greater than or equal to a predetermined value, the ratio of increase / decrease of the current frequency deviation from the past frequency deviation is calculated as a frequency deviation ratio, and the frequency deviation ratio is assumed as a ratio threshold assumed from the injection reactive power When the number of times exceeding the first threshold value exceeds the second threshold value as the frequency threshold value, it is determined that the distributed power source is in a single operation state,
When the injection reactive power calculated by the reactive power calculation / injection means exceeds an injection amount threshold,
The reactive power calculation / injection means limits the injection reactive power to the injection amount threshold,
The isolated operation detecting means includes
When the ratio of increase / decrease of the current frequency deviation from the past frequency deviation is calculated as the frequency deviation ratio, and the number of times the frequency deviation ratio exceeds the third threshold as the ratio threshold exceeds the fourth threshold as the frequency threshold Or when the frequency deviation ratio exceeds the third threshold exceeds a fifth threshold as a frequency threshold and the system frequency exceeds the seventh threshold or less than the eighth threshold. Is determined to be in the single operation state.

なお、請求項3に記載するように、前記単独運転検出手段は、周波数偏差比率の推移に基づいて前記第1閾値との比較回数を決定することが望ましい。   In addition, as described in Claim 3, it is desirable that the isolated operation detection means determines the number of comparisons with the first threshold based on the transition of the frequency deviation ratio.

本発明は、系統への注入無効電力とこれによって生じる周波数偏差とを関連付けた単独運転検出システムであり、無効電力注入により発生する周波数偏差の現れ方が負荷の状況によって異なる状況でも、初期の周波数変動が小さく立ち上りが遅い場合、及び、これとは逆に、初期の周波数変動が大きく注入無効電力の制限値に速く到達してしまう場合にも、単独運転検出動作が有効に働く検出システムである。
本発明によれば、分散電源の単独運転を短時間で検出可能であり、連系リレーを迅速に開放することで直ちに事故防止対策を講じることができる。
また、注入無効電力に応じた系統の周波数偏差比率に基づいて判定する単独運転検出動作と、注入無効電力に基づいて判定する単独運転検出動作とを備えることにより、検出漏れのない高精度な単独運転検出システムを実現することができる。
更に、周波数偏差比率と周波数偏差または系統周波数と、これらの変化時間とを組み合わせた判定条件を用いることにより、系統に注入する無効電力の上限値を変更した場合にも、単独運転を誤検出することなく確実に検出する機能を確保した上で、判定のための閾値の微調整も不要になる等の効果がある。
The present invention is an isolated operation detection system in which reactive power injected into a system is associated with a frequency deviation caused thereby, and even if the appearance of the frequency deviation caused by reactive power injection varies depending on the load condition, the initial frequency This is a detection system in which the isolated operation detection works effectively even when the fluctuation is small and the rise is slow, and conversely, the initial frequency fluctuation is large and the limit value of the injection reactive power is reached quickly. .
According to the present invention, it is possible to detect a single operation of a distributed power supply in a short time, and it is possible to immediately take measures to prevent accidents by quickly opening the interconnection relay.
Also, a single operation detection operation determined based on the frequency deviation ratio of the system according to the injection reactive power and a single operation detection operation determined based on the injection reactive power, thereby providing a highly accurate single operation with no detection omission. A driving detection system can be realized.
Furthermore, by using a judgment condition that combines the frequency deviation ratio and the frequency deviation or system frequency and their change time, even if the upper limit value of the reactive power injected into the system is changed, the isolated operation is erroneously detected. In addition, there is an effect that a fine adjustment of a threshold value for determination is not necessary, while ensuring a function of reliably detecting without any problem.

本発明の実施形態が適用される系統連系システムの構成図である。1 is a configuration diagram of a grid interconnection system to which an embodiment of the present invention is applied. 図1における単独運転検出手段の処理を示すフローチャートである。It is a flowchart which shows the process of the independent operation detection means in FIG. 図1における単独運転検出手段の処理を示すフローチャートである。It is a flowchart which shows the process of the independent operation detection means in FIG. 図1における単独運転検出手段の処理を示すフローチャートである。It is a flowchart which shows the process of the independent operation detection means in FIG. 図1における単独運転検出手段の処理を示すフローチャートである。It is a flowchart which shows the process of the independent operation detection means in FIG. 系統への無効電力注入による周波数偏差の挙動を示す図である。It is a figure which shows the behavior of the frequency deviation by the reactive power injection | pouring to a system | strain. 周波数偏差と注入無効電力との関係を示す図である。It is a figure which shows the relationship between a frequency deviation and injection reactive power. 本発明における閾値変動方法を説明するための概念図である。It is a conceptual diagram for demonstrating the threshold value fluctuation | variation method in this invention. 従来技術による単独運転検出原理の説明図である。It is explanatory drawing of the independent operation | movement detection principle by a prior art. 特許文献1に記載された単独運転検出装置の構成図である。It is a block diagram of the isolated operation detection apparatus described in patent document 1. 図10における制御装置の構成図である。It is a block diagram of the control apparatus in FIG. 特許文献1による単独運転検出原理の説明図である。It is explanatory drawing of the independent operation detection principle by patent document 1. FIG.

以下に、図面に基づいて本発明の実施形態を説明する。図1は、この実施形態が適用される分散電源の系統連系システムを示している。
この連系システムは、分散電源1の直流電力をパワーコンディショナー10により交流電力に変換し、この交流電力を、系統電源20から系統21を介して供給される電力と同期させながら各種事業所や家庭等の負荷30に供給するものである。
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a system interconnection system of distributed power sources to which this embodiment is applied.
This interconnection system converts the DC power of the distributed power supply 1 into AC power by the power conditioner 10, and synchronizes this AC power with the power supplied from the system power supply 20 via the system 21. Or the like to be supplied to the load 30.

図1において、分散電源1は、太陽光発電システムや風力発電システムに設けられた直流電源であり、パワーコンディショナー10に直流電力を供給する。
パワーコンディショナー10は、分散電源1から供給された直流電力を系統電源20と同期した交流電力に変換するためのインバータ11と、系統周波数を検出する周波数検出手段12と、この周波数検出手段12による現在の系統周波数と内部に保持している過去の系統周波数とから周波数偏差を算出する周波数偏差算出手段13と、前記周波数偏差に基づいて周波数変動を起こさせるために系統21に注入する無効電力を算出して出力する無効電力算出・注入手段14と、周波数偏差算出手段13からの周波数偏差と無効電力算出・注入手段14からの注入無効電力に関する情報に基づいて、分散電源1が単独運転状態であるか否かを判定し、その判定結果を出力する単独運転検出手段16と、周波数検出手段12からの周波数情報、無効電力算出・注入手段14からの注入無効電力情報、及び、単独運転検出手段16からの単独運転情報に基づいて、インバータ11を駆動制御するインバータ制御手段15と、により構成されている。
なお、17は、単独運転検出手段16から出力される検出信号によりインバータ11(分散電源1)を系統21から遮断する連系リレーである。
In FIG. 1, a distributed power source 1 is a DC power source provided in a solar power generation system or a wind power generation system, and supplies DC power to a power conditioner 10.
The power conditioner 10 includes an inverter 11 for converting DC power supplied from the distributed power supply 1 into AC power synchronized with the system power supply 20, frequency detection means 12 for detecting the system frequency, and current frequency detection means 12. The frequency deviation calculating means 13 for calculating the frequency deviation from the system frequency of the system and the past system frequency held therein, and the reactive power to be injected into the system 21 for causing the frequency fluctuation based on the frequency deviation are calculated. The distributed power source 1 is in a single operation state based on the reactive power calculation / injection means 14 to be output and the frequency deviation from the frequency deviation calculation means 13 and the information on the reactive power calculation / injection means 14. And the independent operation detection means 16 that outputs the determination result and the frequency information from the frequency detection means 12 Injecting reactive power information from the power calculating and injecting means 14, and, based on the independent operation information from the independent operation detecting means 16, and inverter control means 15 that drives and controls the inverter 11, and is composed of.
Reference numeral 17 denotes an interconnection relay that disconnects the inverter 11 (distributed power source 1) from the system 21 by a detection signal output from the isolated operation detection means 16.

周波数偏差算出手段13が算出する周波数偏差は、単周期での偏差でも良いが、測定誤差やノイズ誤差の影響を排除するために、数周期分の移動平均値から算出した値でも良い。
無効電力算出・注入手段14では、周波数偏差算出手段13から送られる周波数偏差に応じて、系統21に注入する無効電力を1段目ゲインと2段目ゲインとに分けて演算する。ここでは、周波数偏差が後述のゲイン閾値より小さい時に注入する無効電力を、検出した周波数偏差×1段目ゲイン、ゲイン閾値より大きくなった時に注入する無効電力を、検出した周波数偏差×2段目ゲイン、として演算する。
The frequency deviation calculated by the frequency deviation calculating means 13 may be a deviation in a single cycle, but may be a value calculated from a moving average value for several cycles in order to eliminate the influence of measurement errors and noise errors.
The reactive power calculation / injection unit 14 calculates the reactive power injected into the system 21 separately for the first stage gain and the second stage gain according to the frequency deviation sent from the frequency deviation calculation unit 13. Here, the reactive power injected when the frequency deviation is smaller than a gain threshold, which will be described later, is detected frequency deviation × first stage gain, and the reactive power injected when the frequency deviation is larger than the gain threshold is detected frequency deviation × second stage. Calculated as gain.

無効電力の演算に使用する1段目ゲイン/2段目ゲインを決定するための前記ゲイン閾値は、例えば、0.01[Hz]の周波数偏差とする。また、各ゲインの値としては、2段目ゲインを1段目ゲインより大きくすることにより、周波数偏差が小さい場合は1段目ゲインにより注入無効電力を小さくして系統21に与える影響を抑え、周波数偏差が大きくなってきたら、2段目ゲインにより注入無効電力を大きくして変化がより顕著になるようにする。   The gain threshold value for determining the first stage gain / second stage gain used for the reactive power calculation is, for example, a frequency deviation of 0.01 [Hz]. Further, as the value of each gain, by making the second stage gain larger than the first stage gain, when the frequency deviation is small, the injection reactive power is reduced by the first stage gain to suppress the influence on the system 21; When the frequency deviation increases, the injection reactive power is increased by the second-stage gain so that the change becomes more remarkable.

また、無効電力算出・注入手段14により決定される注入無効電力には注入量閾値が設けられており、この注入量閾値を超える無効電力は注入できないようになっている。なお、注入無効電力が注入量閾値に達した状態を、無効電力注入リミット状態というものとする。   The injection reactive power determined by the reactive power calculation / injection means 14 is provided with an injection amount threshold value, and reactive power exceeding the injection amount threshold value cannot be injected. A state where the injection reactive power reaches the injection amount threshold is referred to as a reactive power injection limit state.

次に、この実施形態における単独運転検出手段16の処理を、図2〜図5に従って説明する。これらの図に示す単独運転検出手段16の処理は、定周期にて起動される。
なお、以下の説明では、単独運転状態か否かを検出するための検査モードになっていることを「検査中」と定義し、検査中であることをフラグにて示すものとする。
Next, the processing of the isolated operation detection means 16 in this embodiment will be described with reference to FIGS. The processing of the isolated operation detecting means 16 shown in these figures is started at a regular cycle.
In the following description, “inspection” is defined as an inspection mode for detecting whether or not the vehicle is in an isolated operation state, and a flag indicates that inspection is in progress.

まず、図2において、単独運転検出手段16は、検査中フラグを参照し、検査中であれば(ステップS1 YES)、後述する第1の単独運転検出条件による処理を行うために図3の処理に移行する。
検査中でない場合には(S1 NO)、注入無効電力が2段目ゲインによるレベルか否かを、無効電力算出・注入手段14からの情報に基づいて判断する(S2)。注入無効電力が2段目ゲインによるレベルであった場合(S2 YES)には、検出条件を満たす周波数偏差が生じ始めたと判断して、第1の単独運転検出条件による処理を開始するために各カウンタ(比率超過カウンタ1及び比率超過カウンタ2)をクリアする(S3)。
First, in FIG. 2, the islanding operation detection means 16 refers to the in-inspection flag, and if inspecting (YES in step S1), the process in FIG. Migrate to
When the inspection is not in progress (NO in S1), it is determined based on information from the reactive power calculation / injection means 14 whether or not the injection reactive power is at the level of the second stage gain (S2). When the injection reactive power is at a level based on the second stage gain (S2 YES), it is determined that a frequency deviation that satisfies the detection condition has started to occur, and each process for starting the process based on the first isolated operation detection condition is performed. The counters (ratio excess counter 1 and ratio excess counter 2) are cleared (S3).

ここで、比率超過カウンタ1は、現在の周波数偏差と過去の周波数偏差との比率(周波数偏差比率)が第1閾値(比率閾値1)を超過した回数をカウントするカウンタ、比率超過カウンタ2は、無効電力注入リミット状態において現在の周波数偏差と過去の周波数偏差との比率(周波数偏差比率)が第3閾値(比率閾値2)を超過した回数をカウントするカウンタである。   Here, the ratio excess counter 1 is a counter that counts the number of times that the ratio between the current frequency deviation and the past frequency deviation (frequency deviation ratio) exceeds the first threshold (ratio threshold 1), and the ratio excess counter 2 is It is a counter that counts the number of times that the ratio between the current frequency deviation and the past frequency deviation (frequency deviation ratio) exceeds the third threshold (ratio threshold 2) in the reactive power injection limit state.

次に、図1の周波数偏差算出手段13から送られた現在及び過去の周波数偏差から周波数偏差比率を求め(S4)、この周波数偏差比率が、無効電力算出・注入手段14による注入無効電力から想定される第1閾値(比率閾値1)、例えば「2.0」を超過しているか否かを判定する(S5)。
ここで、第1閾値の例として挙げた「2.0」の根拠は、無効電流注入時には検出した周波数偏差の4倍の偏差が現れることを期待して注入し、また、2周期分の周波数を平均化して周波数偏差を算出するものとすると、想定される周波数偏差は4倍の半分の「2.0」倍となることに基づいている。これには、マージンを見込んでもよいことは言うまでもない。
Next, a frequency deviation ratio is obtained from the current and past frequency deviations sent from the frequency deviation calculation means 13 of FIG. 1 (S4), and this frequency deviation ratio is assumed from the reactive power calculation / injection means 14 injected reactive power. It is determined whether or not the first threshold value (ratio threshold value 1), for example, “2.0” is exceeded (S5).
Here, the basis of “2.0” given as an example of the first threshold is that injection is performed in the expectation that a deviation of four times the detected frequency deviation will appear when reactive current is injected, and the frequency for two cycles If the frequency deviation is calculated by averaging the values, the assumed frequency deviation is based on the fact that the frequency deviation is “2.0”, which is half of four times. It goes without saying that this may allow for margins.

周波数偏差比率が第1閾値を超過している場合は(S5 YES)、第1の単独運転検出条件による処理を開始するために検査中フラグをセットして比率超過カウンタ1をインクリメントし(S6,S7)、周波数偏差算出手段13から入力された過去の周波数偏差を前回値として保持することにより(S8)、今回の処理を終了する。   When the frequency deviation ratio exceeds the first threshold value (S5 YES), the in-inspection flag is set and the ratio excess counter 1 is incremented to start the processing based on the first islanding detection condition (S6, S6). S7) By holding the past frequency deviation input from the frequency deviation calculating means 13 as the previous value (S8), the current process is terminated.

前記ステップS5において、周波数偏差比率が第1閾値を超過していなかった場合は(S5 NO)、現在の周波数偏差と過去の周波数偏差との比率(周波数偏差比率)が第3閾値(比率閾値2)、例えば「1.2」を超過したか否かを判定する(S9)。周波数偏差比率が第3閾値を超過していた場合(S9 YES)、第2の単独運転検出条件による処理を開始するために検査中フラグをセットすると共に、比率超過カウンタ2をインクリメントし(S10,S11)、ステップS8に移行してから今回の処理を終了する。   In step S5, when the frequency deviation ratio does not exceed the first threshold (NO in S5), the ratio (frequency deviation ratio) between the current frequency deviation and the past frequency deviation is the third threshold (ratio threshold 2). For example, it is determined whether or not “1.2” is exceeded (S9). When the frequency deviation ratio exceeds the third threshold value (S9 YES), the in-inspection flag is set and the ratio excess counter 2 is incremented to start the processing based on the second islanding operation detection condition (S10, S11) After shifting to step S8, the current process is terminated.

また、前記ステップS9において、周波数偏差比率が第3閾値を超過していなかった場合(S9 NO)は単独運転検出条件を満たしていないと判断し、検査中フラグをセットせずに、ステップS8に移行してから今回の処理を終了する。
更に、前記ステップS2において、注入無効電力が2段目ゲインに相当するレベルでなかった場合(S2 NO)は、単独運転検出条件を満たす周波数偏差が発生していないため、ステップS8に移行してから今回の処理を終了する。
In step S9, if the frequency deviation ratio does not exceed the third threshold (NO in S9), it is determined that the isolated operation detection condition is not satisfied, and the in-inspection flag is not set, and the process proceeds to step S8. The current process is terminated after the migration.
Furthermore, if the injection reactive power is not at a level corresponding to the second-stage gain in step S2 (S2 NO), there is no frequency deviation that satisfies the isolated operation detection condition, and the process proceeds to step S8. To end the current process.

次に、前記ステップS1において検査中と判定された場合(S1 YES)の処理について、図3を参照しつつ説明する。この図3の処理は、第1の単独運転検出条件による処理である。   Next, the process when it is determined in step S1 that the inspection is being performed (S1 YES) will be described with reference to FIG. The process of FIG. 3 is a process based on the first isolated operation detection condition.

図3において、まず、注入無効電力が2段目ゲインによるレベルか否かを、無効電力算出・注入手段14からの情報に基づいて判断する(S12)。
注入無効電力が2段目ゲインによるレベルであった場合(S12 YES)、検出条件を満たす周波数偏差が生じていると判断して検出動作を継続し、周波数偏差算出手段13の出力情報に基づいて現在及び過去の周波数偏差比率を演算する(S13)。
In FIG. 3, first, it is determined based on information from the reactive power calculation / injection means 14 whether or not the injection reactive power is at the level of the second-stage gain (S12).
If the injection reactive power is at the level of the second-stage gain (YES in S12), it is determined that a frequency deviation that satisfies the detection condition has occurred, and the detection operation is continued. Based on the output information of the frequency deviation calculation means 13 The current and past frequency deviation ratios are calculated (S13).

次いで、比率超過カウンタ1のカウント値の有無を判定し(S14)、カウント値がある場合(S14 YES)には、ステップS13にて演算した周波数偏差比率が、無効電力算出・注入手段14による注入無効電力から想定される第1閾値(比率閾値1)、例えば「2.0」を超過しているか否かを判定する(S15)。周波数偏差比率が第1閾値を超過している場合(S15 YES)は比率超過カウンタ1をインクリメントし(S16)、更に、比率超過カウンタ1のカウント値が第2閾値(回数閾値1)を超過しているか否かを判定する(S17)。   Next, the presence / absence of the count value of the ratio excess counter 1 is determined (S14). If there is a count value (YES in S14), the frequency deviation ratio calculated in step S13 is injected by the reactive power calculating / injecting means 14. It is determined whether or not a first threshold value (ratio threshold value 1) assumed from reactive power, for example, “2.0” is exceeded (S15). When the frequency deviation ratio exceeds the first threshold (S15 YES), the ratio excess counter 1 is incremented (S16), and the count value of the ratio excess counter 1 exceeds the second threshold (number threshold 1). It is determined whether or not (S17).

比率超過カウンタ1のカウント値が第2閾値を超過していた場合(S17 YES)は、注入無効電力に応じた周波数偏差の変化が所定回数発生したことによって第1の単独運転検出条件を満足したと判断して、分散電源1が単独運転状態にあると判定する。すなわち、単独運転検出フラグをセットし(S18)、検査中フラグをクリアして検査状態を解除することにより(S19)、今回の処理を終了する。
また、単独運転検出フラグのセット(S18)と同時に、図1の連系リレー17を開放してインバータ11を系統21から遮断する。
When the count value of the ratio excess counter 1 exceeds the second threshold value (S17 YES), the first islanding operation detection condition is satisfied by the occurrence of a predetermined number of changes in the frequency deviation according to the injection reactive power. It is determined that the distributed power source 1 is in a single operation state. That is, the isolated operation detection flag is set (S18), the in-inspection flag is cleared to cancel the inspection state (S19), and the current process is terminated.
Simultaneously with the setting of the isolated operation detection flag (S 18), the interconnection relay 17 of FIG. 1 is opened to disconnect the inverter 11 from the system 21.

ステップS12において、注入無効電力が2段目ゲインによるレベルでなかった場合は、検査開始条件を満たしていないので検査中フラグをクリアし(S21)、周波数偏差算出手段13から入力された周波数偏差を前回値として保持し(S22)、今回の処理を終了する。
また、ステップS14において比率超過カウンタ1のカウント値が未だ存在しない場合、及び、ステップS15において周波数偏差比率が第1閾値を超過していなかった場合は、第1の単独運転検出条件を満足しなくなったものとして比率超過カウンタ1をクリアし(S20)、図4の処理に移る。
更に、ステップS17において比率超過カウンタ1のカウント値が第2閾値を超過していなかった場合には、第1の単独運転検出条件による処理を継続しつつ図4の処理に移る。
In step S12, if the injection reactive power is not at the level due to the second stage gain, the inspection start condition is not satisfied, so the in-inspection flag is cleared (S21), and the frequency deviation input from the frequency deviation calculating means 13 is calculated. The previous value is held (S22), and the current process is terminated.
Further, if the count value of the ratio excess counter 1 does not yet exist in step S14, and if the frequency deviation ratio does not exceed the first threshold value in step S15, the first islanding operation detection condition is not satisfied. As a result, the ratio excess counter 1 is cleared (S20), and the process proceeds to FIG.
Furthermore, when the count value of the ratio excess counter 1 does not exceed the second threshold value in step S17, the process proceeds to the process of FIG. 4 while continuing the process based on the first isolated operation detection condition.

次に、図4に基づいて第2の単独運転検出条件による処理を説明する。
無効電力注入リミット状態であり、かつ、現在の周波数偏差と過去の周波数偏差との比率(周波数偏差比率)が第3閾値(比率閾値2)を超過しているか否かを判定し(S23)、これら両方の条件を満たしていた場合(S23 YES)は、比率超過カウンタ2をインクリメントする(S24)。
Next, processing based on the second islanding operation detection condition will be described with reference to FIG.
It is in the reactive power injection limit state, and it is determined whether the ratio of the current frequency deviation and the past frequency deviation (frequency deviation ratio) exceeds the third threshold (ratio threshold 2) (S23), If both of these conditions are satisfied (S23 YES), the ratio excess counter 2 is incremented (S24).

そして、比率超過カウンタ2のカウント値が第4閾値(回数閾値2)を超過したか否かを判定し(S25)、超過していた場合(S25 YES)は、周波数偏差が大きい状態のまま十分増大する傾向が続いているため第2の単独運転検出条件を満足したものと判断して、分散電源1が単独運転状態にあると判定する。すなわち、単独運転検出フラグをセットし(S26)、その後、検査中フラグをクリアして検査状態を解除することにより(S27)、今回の処理を終了する。また、単独運転検出フラグのセットと同時に、図1の連系リレー17を開放してインバータ11を系統21から遮断する。   Then, it is determined whether or not the count value of the ratio excess counter 2 has exceeded the fourth threshold value (number of times threshold value 2) (S25). If it has exceeded (S25 YES), the frequency deviation is sufficiently large. Since the increasing tendency continues, it is determined that the second isolated operation detection condition is satisfied, and it is determined that the distributed power source 1 is in the isolated operation state. That is, the isolated operation detection flag is set (S26), and then the in-inspection flag is cleared to cancel the inspection state (S27), thereby terminating the current process. Simultaneously with the setting of the isolated operation detection flag, the interconnection relay 17 in FIG. 1 is opened to disconnect the inverter 11 from the system 21.

なお、周波数偏差に応じて系統に無効電力を注入する単独運転検出システムにおいては、単独運転の発生以外の要因によって系統周波数の擾乱が生じた場合でも、分散型電源は無効電力を注入することになる。分散型電源に対して系統が強い場合には問題がないが、分散型電源に対して系統が脆弱である場合には、分散型電源が無効電力を注入することにより、系統の擾乱を一層助長させる可能性があるため、分散型電源が系統に注入する無効電力の上限値を低く設定することが行われている。   In the isolated operation detection system that injects reactive power into the system according to the frequency deviation, the distributed power supply injects reactive power even when the system frequency is disturbed by factors other than the occurrence of isolated operation. Become. There is no problem when the system is strong against the distributed power supply, but when the system is vulnerable to the distributed power supply, the distributed power supply injects reactive power to further promote disturbance of the system. Therefore, the upper limit value of the reactive power that the distributed power source injects into the system is set low.

このように、分散型電源が系統に注入する無効電力の上限値を低く設定した状態では、周波数偏差に応じて無効電力注入量が変化する場合、無効電力の上限値が高く設定されている場合に比べて、小さい周波数偏差により無効電力注入リミット状態に到達した後の周波数の増加が抑制されるため、周波数偏差比率の低下が早くなる。
すなわち、前記ステップS23において周波数偏差比率が第3閾値を超過している時間が短くなるので、ステップS25では比率超過カウンタ2のカウント値が回数閾値としての第4閾値を超過しなくなり(S25 NO)、単独運転を検出することができない恐れがある。
In this way, when the upper limit value of reactive power injected into the system by the distributed power source is set low, the reactive power injection amount changes according to the frequency deviation, or the reactive power upper limit value is set high. As compared with, since the increase in the frequency after reaching the reactive power injection limit state is suppressed by the small frequency deviation, the frequency deviation ratio is rapidly reduced.
That is, since the time during which the frequency deviation ratio exceeds the third threshold is shortened in step S23, the count value of the ratio excess counter 2 does not exceed the fourth threshold as the frequency threshold in step S25 (NO in S25). There is a risk that isolated operation cannot be detected.

この場合、第3閾値を低く設定すれば、周波数偏差比率が第3閾値を超過している時間が長くなり、比率超過カウンタ2のカウント値が第4閾値を超過して単独運転を検出することが可能になる。しかし、このようにすると、単独運転の発生以外の要因によって系統周波数の擾乱が生じた場合にも単独運転と誤検出してしまう恐れがある。
従って、単独運転を確実に検出するためには第3閾値の微調整が必要になるが、その結果、汎用性が低下するという新たな問題を生じる。
In this case, if the third threshold value is set low, the time during which the frequency deviation ratio exceeds the third threshold value becomes longer, and the count value of the ratio excess counter 2 exceeds the fourth threshold value to detect an isolated operation. Is possible. However, if this is done, there is a risk of erroneous detection as isolated operation even when system frequency disturbances occur due to factors other than the occurrence of isolated operation.
Therefore, fine adjustment of the third threshold value is necessary to reliably detect an isolated operation, but as a result, a new problem that versatility is reduced occurs.

そこで、請求項1に相当する本実施形態では、周波数偏差比率が第3閾値を超過していても(S23 YES)、比率超過カウンタ2のカウント値が単独運転と判定するための第4閾値を超過していない場合(S25 NO)の判断ステップ(S101)を備えている。
すなわち、比率超過カウンタ2のカウント値が第4閾値を超過していない場合(S25 NO)には、そのカウント値が第5閾値(回数閾値3)を超過し、かつ、周波数偏差の絶対値が第6閾値を超過したか否かを判断する(S101)。カウント値が第5閾値を超過した場合、つまり、単独運転がある程度想定される状態において、周波数偏差の絶対値が第6閾値を超過した場合には(S101 YES)、単独運転と判定して単独運転検出フラグをセットする(S26)。
Therefore, in the present embodiment corresponding to claim 1, even if the frequency deviation ratio exceeds the third threshold value (S23 YES), the fourth threshold value for determining that the count value of the ratio excess counter 2 is the single operation is set. A determination step (S101) for not exceeding (NO in S25) is provided.
That is, when the count value of the ratio excess counter 2 does not exceed the fourth threshold value (S25 NO), the count value exceeds the fifth threshold value (number of times threshold value 3), and the absolute value of the frequency deviation is It is determined whether the sixth threshold is exceeded (S101). If the count value exceeds the fifth threshold value, that is, if the absolute value of the frequency deviation exceeds the sixth threshold value in a state where a single operation is assumed to some extent (YES in S101), it is determined that the single operation is performed. An operation detection flag is set (S26).

ステップS101における第5閾値,第6閾値は、分散型電源が連系する系統で求められるFRT(系統擾乱時運転継続)要件における周波数変動や実際の系統擾乱時の周波数変動波形から算出される周波数偏差に余裕度を加えた値などに基づいて設定すればよい。
このステップS101を設けることにより、分散型電源が運転継続を求められる範囲では単独運転を誤検出することがないような第3閾値を、微調整なしに設定することができる。
The fifth threshold value and the sixth threshold value in step S101 are the frequency calculated from the frequency fluctuation in the FRT (continuous operation during system disturbance) requirement obtained in the system connected to the distributed power source or the frequency fluctuation waveform at the actual system disturbance. What is necessary is just to set based on the value which added the margin to the deviation.
By providing this step S101, it is possible to set the third threshold without fine adjustment so as not to erroneously detect isolated operation within the range where the distributed power source is required to continue operation.

ステップS101の判定条件が満たされない場合(S101 NO)は、第2の単独運転検出条件による処理は継続しつつ、図1の周波数偏差算出手段13から入力された周波数偏差を前回値として保持し(S28)、今回の処理を終了する。   When the determination condition of step S101 is not satisfied (NO in S101), the frequency deviation input from the frequency deviation calculation means 13 in FIG. 1 is held as the previous value while continuing the processing based on the second isolated operation detection condition ( S28), the current process is terminated.

また、前述のステップS23の判定条件を満足しなかった場合(S23 NO)は、第2の単独運転検出条件を満足しなくなったものと判断して比率超過カウンタ2をクリアする(S29)。次に、第1の単独運転検出動作を行うための比率超過カウンタ1のカウント値の有無を判定し(S30)、比率超過カウンタ1のカウント値がなければ(S30 NO)、第1の単独運転検出条件は既に満足しておらず、第1,第2の単独運転検出条件を満足していないため、検査中フラグをクリアして検査状態を解除する(S31)。そして、図1の周波数偏差算出手段13から入力された周波数偏差を前回値として保持し(S32)、今回の処理を終了する。
なお、ステップS30において、比率超過カウンタ1のカウント値が存在する場合(S30 YES)は、第1の単独運転検出条件による処理が継続しているので、検査中フラグをクリアせず、ステップS32を経た後に今回の処理を終了する。
If the determination condition in step S23 is not satisfied (NO in S23), it is determined that the second islanding operation detection condition is no longer satisfied, and the ratio excess counter 2 is cleared (S29). Next, the presence / absence of the count value of the ratio excess counter 1 for performing the first isolated operation detection operation is determined (S30), and if there is no count value of the ratio excess counter 1 (S30 NO), the first isolated operation is performed. Since the detection conditions are not already satisfied and the first and second isolated operation detection conditions are not satisfied, the in-inspection flag is cleared and the inspection state is released (S31). Then, the frequency deviation input from the frequency deviation calculating means 13 of FIG. 1 is held as the previous value (S32), and the current process is terminated.
In step S30, if there is a count value of the ratio excess counter 1 (YES in S30), the process under the first isolated operation detection condition is continued, so the in-inspection flag is not cleared and step S32 is executed. After this, the current process is terminated.

ここで、図5に示すように、前記ステップS101に代えてステップS102を設け、比率超過カウンタ2のカウント値が第4閾値を超過していない場合(S25 NO)に、そのカウント値が第5閾値(回数閾値3)を超過し、かつ、系統周波数が第7閾値を超過し、もしくは系統周波数が第8閾値未満であるか否かを判断しても良い。この実施形態は、請求項2に相当する。
すなわち、比率超過カウンタ2のカウント値が第4閾値を超過していない場合(S25 NO)には、そのカウント値が第5閾値(回数閾値3)を超過し、かつ、系統周波数が第7閾値を超過し、もしくは系統周波数が第8閾値未満であるか否かを判断する(S102)。カウント値が第5閾値を超過した場合、つまり、単独運転がある程度想定される状態において、系統周波数が第7閾値を超過し、もしくは系統周波数が第8閾値未満である場合には(S102 YES)、単独運転と判定して単独運転検出フラグをセットする(S26)。
ステップS102における第5閾値,第7閾値,第8閾値は、前記FRT要件における系統周波数や実際の系統擾乱時の系統周波数に余裕度を加えた値などに基づいて設定すればよい。
この実施形態においても、第3閾値を微調整なしに設定することができる。
Here, as shown in FIG. 5, step S102 is provided instead of step S101, and when the count value of the ratio excess counter 2 does not exceed the fourth threshold value (S25 NO), the count value is the fifth value. It may be determined whether the threshold (number threshold 3) is exceeded and the system frequency exceeds the seventh threshold or the system frequency is less than the eighth threshold. This embodiment corresponds to claim 2.
That is, if the count value of the ratio excess counter 2 does not exceed the fourth threshold value (NO in S25), the count value exceeds the fifth threshold value (number threshold value 3), and the system frequency is the seventh threshold value. Or whether the system frequency is less than the eighth threshold (S102). When the count value exceeds the fifth threshold value, that is, when the system frequency exceeds the seventh threshold value or the system frequency is less than the eighth threshold value in a state where a single operation is assumed to some extent (YES in S102). Then, it is determined as an isolated operation, and an isolated operation detection flag is set (S26).
The fifth threshold value, the seventh threshold value, and the eighth threshold value in step S102 may be set based on the system frequency in the FRT requirement or the value obtained by adding a margin to the system frequency at the time of actual system disturbance.
Also in this embodiment, the third threshold value can be set without fine adjustment.

次に、図1の単独運転検出手段15における周波数偏差比率の演算処理(図2のステップS4)について説明する。
いま、周波数偏差の増加比率が大きいと、早く無効電力注入リミット状態に達するため、増加比率が頭打ちになり、第1の単独運転検出条件を満足できなくなる。そこで、第1の単独運転検出条件を満足しているか否かの判定を2段階に分けることで、第1の単独運転検出条件の判定精度を高めるようにした。
Next, the frequency deviation ratio calculation process (step S4 in FIG. 2) in the isolated operation detection means 15 in FIG. 1 will be described.
Now, if the increase rate of the frequency deviation is large, the reactive power injection limit state is reached quickly, so that the increase rate reaches its peak and the first isolated operation detection condition cannot be satisfied. Therefore, the determination accuracy of the first isolated operation detection condition is increased by dividing the determination of whether or not the first isolated operation detection condition is satisfied into two stages.

ここでは、例として、周波数が50[Hz](周期が20[ms])の系統電力に対し、5[ms]ごと、つまり1周期あたり4回、系統周波数を検出するものとする。この時の第1閾値(比率閾値1)との比較回数は、例えば次のようにする。   Here, as an example, it is assumed that the system frequency is detected every 5 [ms], that is, four times per period with respect to the system power having a frequency of 50 [Hz] (period is 20 [ms]). The number of comparisons with the first threshold (ratio threshold 1) at this time is, for example, as follows.

(1)周波数偏差の増加率が「3.0」を超えるような高い比率の状態が1周期に4回継続する場合には、第1閾値との比較回数の合計値を、1周期半に相当する6回とする。
(2)その他の場合には、第1閾値との比較回数の合計値を、2周期強に相当する9回とする。
上記(1),(2)の何れの場合も、累積の周波数偏差比率(増加率)は「18.0」以上である。
なお、ここで示した各数値はあくまで一例であり、本発明はこれらの数値に何ら限定されるものではない。
(1) When a high ratio state in which the rate of increase in frequency deviation exceeds “3.0” continues four times in one cycle, the total value of the number of comparisons with the first threshold is set to one and a half. Corresponding 6 times.
(2) In other cases, the total value of the number of comparisons with the first threshold value is 9 times corresponding to a little over 2 cycles.
In both cases (1) and (2), the cumulative frequency deviation ratio (increase rate) is “18.0” or more.
In addition, each numerical value shown here is an example to the last, and this invention is not limited to these numerical values at all.

1:分散電源
10:パワーコンディショナー
11:インバータ
12:周波数検出手段
13:周波数偏差算出手段
14:無効電力算出・注入手段
15:インバータ制御手段
16:単独運転検出手段
17:連系リレー
20:系統電源
21:系統
30:負荷
1: distributed power supply 10: power conditioner 11: inverter 12: frequency detection means 13: frequency deviation calculation means 14: reactive power calculation / injection means 15: inverter control means 16: isolated operation detection means 17: interconnection relay 20: system power supply 21: System 30: Load

Claims (3)

分散電源が電力変換器を介して電力系統に連系せずに単独運転状態にあることを検出する分散電源の単独運転検出システムであって、
系統周波数を検出する周波数検出手段と、前記系統周波数から所定期間の周波数偏差を算出する周波数偏差算出手段と、前記所定期間の周波数偏差に対して次の所定期間の周波数偏差が所定の比率で変化するような無効電力を算出して前記電力変換器を介して系統に注入する無効電力算出・注入手段と、前記所定期間の周波数偏差と前記無効電力算出・注入手段により系統に注入される無効電力とに基づいて、前記分散電源が単独運転状態であるか否かを判定する単独運転検出手段と、を備え、
前記単独運転検出手段は、
系統への注入無効電力が所定値以上ある時に、現在の周波数偏差の過去の周波数偏差からの増減の比率を周波数偏差比率として演算し、前記周波数偏差比率が注入無効電力から想定される比率閾値としての第1閾値を超えた回数が、回数閾値としての第2閾値を超えた時に、前記分散電源が単独運転状態にあると判定すると共に、
前記無効電力算出・注入手段が算出した前記注入無効電力が注入量閾値を超えた場合、
前記無効電力算出・注入手段は前記注入無効電力を前記注入量閾値に制限し、
前記単独運転検出手段は、
現在の周波数偏差の過去の周波数偏差からの増減の比率を周波数偏差比率として演算し、前記周波数偏差比率が比率閾値としての第3閾値を超えた回数が回数閾値としての第4閾値を超えた時、または、前記周波数偏差比率が前記第3閾値を超えた回数が回数閾値としての第5閾値を超え、かつ、系統の周波数偏差の絶対値が第6閾値を超えたときに、
前記分散電源が単独運転状態にあると判定することを特徴とした分散電源の単独運転検出システム。
An isolated operation detection system for a distributed power source that detects that the distributed power source is in an isolated operation state without being connected to an electric power system via a power converter,
A frequency detecting means for detecting a system frequency; a frequency deviation calculating means for calculating a frequency deviation of a predetermined period from the system frequency; and a frequency deviation of a next predetermined period changes at a predetermined ratio with respect to the frequency deviation of the predetermined period. Reactive power calculation / injection means for calculating reactive power to be injected into the system via the power converter, and reactive power injected into the system by the frequency deviation of the predetermined period and the reactive power calculation / injection means And an isolated operation detecting means for determining whether or not the distributed power supply is in an isolated operation state based on
The isolated operation detecting means includes
When the injection reactive power to the system is greater than or equal to a predetermined value, the ratio of increase / decrease of the current frequency deviation from the past frequency deviation is calculated as a frequency deviation ratio, and the frequency deviation ratio is assumed as a ratio threshold assumed from the injection reactive power When the number of times exceeding the first threshold value exceeds the second threshold value as the frequency threshold value, it is determined that the distributed power source is in a single operation state,
When the injection reactive power calculated by the reactive power calculation / injection means exceeds an injection amount threshold,
The reactive power calculation / injection means limits the injection reactive power to the injection amount threshold,
The isolated operation detecting means includes
When the ratio of increase / decrease of the current frequency deviation from the past frequency deviation is calculated as the frequency deviation ratio, and the number of times the frequency deviation ratio exceeds the third threshold as the ratio threshold exceeds the fourth threshold as the frequency threshold Or when the frequency deviation ratio exceeds the third threshold exceeds the fifth threshold as the frequency threshold, and the absolute value of the frequency deviation of the system exceeds the sixth threshold,
A distributed power supply isolated operation detection system, wherein the distributed power supply is determined to be in an isolated operation state.
分散電源が電力変換器を介して電力系統に連系せずに単独運転状態にあることを検出する分散電源の単独運転検出システムであって、
系統周波数を検出する周波数検出手段と、前記系統周波数から所定期間の周波数偏差を算出する周波数偏差算出手段と、前記所定期間の周波数偏差に対して次の所定期間の周波数偏差が所定の比率で変化するような無効電力を算出して前記電力変換器を介して系統に注入する無効電力算出・注入手段と、前記所定期間の周波数偏差と前記無効電力算出・注入手段により系統に注入される無効電力とに基づいて、前記分散電源が単独運転状態であるか否かを判定する単独運転検出手段と、を備え、
前記単独運転検出手段は、
系統への注入無効電力が所定値以上ある時に、現在の周波数偏差の過去の周波数偏差からの増減の比率を周波数偏差比率として演算し、前記周波数偏差比率が注入無効電力から想定される比率閾値としての第1閾値を超えた回数が、回数閾値としての第2閾値を超えた時に、前記分散電源が単独運転状態にあると判定すると共に、
前記無効電力算出・注入手段が算出した前記注入無効電力が注入量閾値を超えた場合、
前記無効電力算出・注入手段は前記注入無効電力を前記注入量閾値に制限し、
前記単独運転検出手段は、
現在の周波数偏差の過去の周波数偏差からの増減の比率を周波数偏差比率として演算し、前記周波数偏差比率が比率閾値としての第3閾値を超えた回数が回数閾値としての第4閾値を超えた時、または、前記周波数偏差比率が前記第3閾値を超えた回数が回数閾値としての第5閾値を超え、かつ、系統周波数が第7閾値を超えるか第8閾値未満であるときに、
前記分散電源が単独運転状態にあると判定することを特徴とした分散電源の単独運転検出システム。
An isolated operation detection system for a distributed power source that detects that the distributed power source is in an isolated operation state without being connected to an electric power system via a power converter,
A frequency detecting means for detecting a system frequency; a frequency deviation calculating means for calculating a frequency deviation of a predetermined period from the system frequency; and a frequency deviation of a next predetermined period changes at a predetermined ratio with respect to the frequency deviation of the predetermined period. Reactive power calculation / injection means for calculating reactive power to be injected into the system via the power converter, and reactive power injected into the system by the frequency deviation of the predetermined period and the reactive power calculation / injection means And an isolated operation detecting means for determining whether or not the distributed power supply is in an isolated operation state based on
The isolated operation detecting means includes
When the injection reactive power to the system is greater than or equal to a predetermined value, the ratio of increase / decrease of the current frequency deviation from the past frequency deviation is calculated as a frequency deviation ratio, and the frequency deviation ratio is assumed as a ratio threshold assumed from the injection reactive power When the number of times exceeding the first threshold value exceeds the second threshold value as the frequency threshold value, it is determined that the distributed power source is in a single operation state,
When the injection reactive power calculated by the reactive power calculation / injection means exceeds an injection amount threshold,
The reactive power calculation / injection means limits the injection reactive power to the injection amount threshold,
The isolated operation detecting means includes
When the ratio of increase / decrease of the current frequency deviation from the past frequency deviation is calculated as the frequency deviation ratio, and the number of times the frequency deviation ratio exceeds the third threshold as the ratio threshold exceeds the fourth threshold as the frequency threshold Or, when the frequency deviation ratio exceeds the third threshold exceeds the fifth threshold as the frequency threshold, and the system frequency exceeds the seventh threshold or less than the eighth threshold,
A distributed power supply isolated operation detection system, wherein the distributed power supply is determined to be in an isolated operation state.
請求項1または2に記載した分散電源の単独運転検出システムにおいて、
前記単独運転検出手段は、前記周波数偏差比率の推移に基づいて前記第1閾値との比較回数を決定することを特徴とする分散電源の単独運転検出システム。
In the isolated operation detection system of the distributed power supply according to claim 1 or 2,
The isolated operation detection system for a distributed power source, wherein the isolated operation detection means determines the number of comparisons with the first threshold based on a transition of the frequency deviation ratio.
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