CN102565598A - Island detection method based on negative sequence voltage divider - Google Patents

Abstract

The invention discloses an island detection method based on a negative sequence voltage divider in a distributed power generation system detection technology field. The method is characterized by: firstly extracting an effective value of the negative sequence voltage at a position of a micro-grid common connection point; then calculating a ratio of the effective value to the effective value of a negative sequence voltage source which is added on the common connection point; when the ratio is less than a set threshold, determining that the island is not generated; when the ratio is greater than or equal to the set threshold, determining that the island is generated. By using the method of the invention, under various kinds of fault conditions and other scurviness situations, the island can be effectively detected. The detection is only related to a network topology structure and a pseudo island can not influence the detection. An on-site application requirement can be satisfied and the method possesses actual engineering significance.

Description

Translated fromChinese

基于负序分压器的孤岛检测方法Islanding Detection Method Based on Negative Sequence Voltage Divider

技术领域technical field

本发明属于分布式发电系统检测技术领域，尤其涉及一种基于负序分压器的孤岛检测方法。The invention belongs to the technical field of distributed power generation system detection, and in particular relates to an island detection method based on a negative sequence voltage divider.

背景技术Background technique

近年来，随着分布式发电技术的发展，由分布式电源(distributed generation，DG)与本地负荷组成的微网系统，成为大电网的有益补充。微网既能与大电网相连，向电网供电，又能孤岛运行，独立向本地负荷供电。由于微网在并网运行与孤岛运行时的控制方式不同，微网由并网状态转为孤岛状态时，要求内部DG能快速、准确地得到信号，实现控制模式的顺利切换。因此，孤岛检测具有十分重要的意义。In recent years, with the development of distributed generation technology, the micro-grid system composed of distributed generation (DG) and local loads has become a useful supplement to the large power grid. The microgrid can not only be connected to the large power grid to supply power to the grid, but also can operate in an isolated island to independently supply power to local loads. Since the control methods of the microgrid are different between grid-connected operation and islanded operation, when the microgrid changes from the grid-connected state to the island state, it is required that the internal DG can quickly and accurately obtain signals to realize the smooth switching of the control mode. Therefore, island detection is of great significance.

目前，孤岛检测方法分为三类：(1)开关状态检测法，该方法需要借助通信设备，结构复杂，成本较高。(2)被动检测法，通过检测微网的电压与频率的变化来判断孤岛的发生，该方法有较大的盲区，且门槛值难以确定。(3)主动检测法，该方法向系统加入扰动信号，来放大微网内部的某些电气量，从而判断孤岛，该方法会对电能质量造成一定影响。At present, islanding detection methods are divided into three categories: (1) switch state detection method, which requires communication equipment, has a complex structure and high cost. (2) Passive detection method, which judges the occurrence of islands by detecting changes in the voltage and frequency of the microgrid. This method has a large blind area, and the threshold value is difficult to determine. (3) Active detection method. This method adds a disturbance signal to the system to amplify some electrical quantities inside the microgrid to judge isolated islands. This method will have a certain impact on power quality.

发明内容Contents of the invention

针对上述背景技术中提到的现有孤岛检测结构复杂，成本高等不足，本发明提出了一种基于负序分压器的孤岛检测方法。In view of the disadvantages of the existing islanding detection, such as complex structure and high cost mentioned in the above background technology, the present invention proposes an islanding detection method based on a negative-sequence voltage divider.

本发明的技术方案是，基于负序分压器的孤岛检测方法，其特征是该方法包括以下步骤：The technical scheme of the present invention is, based on the island detection method of negative sequence voltage divider, it is characterized in that the method comprises the following steps:

步骤1：提取微网公共连接点处负序电压有效值，并计算该值与附加在公共连接点上负序电压源的有效值的比值；Step 1: Extract the effective value of the negative sequence voltage at the common connection point of the microgrid, and calculate the ratio of this value to the effective value of the negative sequence voltage source attached to the common connection point;

步骤2：当所述比值小于设定阈值时，则判定未发生孤岛；当所述比值大于或等于设定阈值时，则判定发生孤岛。Step 2: When the ratio is smaller than the set threshold, it is determined that no islanding occurs; when the ratio is greater than or equal to the set threshold, it is determined that islanding occurs.

所述微网公共连接点的负序电压有效值与附加在公共连接点上负序电压源的有效值的比值的计算公式为：The formula for calculating the ratio of the effective value of the negative-sequence voltage at the common connection point of the microgrid to the effective value of the negative-sequence voltage source attached to the common connection point is:

$\mathrm{<span><span>K</span>K</span>}<span><span>=</span>=</span>\frac{{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>2</span>2</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}{{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>G</span>G</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}<span><span>=</span>=</span>\frac{{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>2</span>2</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}{{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>1</span>1</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}<span><span>+</span>+</span>{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>2</span>2</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}$

其中：in:

K为微网公共连接点的负序电压有效值与附加在公共连接点上负序K is the effective value of the negative sequence voltage of the common connection point of the microgrid and the negative sequence voltage added to the common connection point

电压源的有效值的比值；The ratio of the effective value of the voltage source;

为微网公共连接点的负序电压有效值；

is the effective value of the negative sequence voltage at the common connection point of the microgrid;

为附加在公共连接点上负序电压源的有效值； is the effective value of the negative sequence voltage source attached to the common connection point;

为公共连接点处等值负序阻抗； is the equivalent negative sequence impedance at the common connection point;

为负序电压源所串联阻抗的负序值。

is the negative sequence value of the series impedance of the negative sequence voltage source.

所述

的计算公式为：said

The calculation formula is:

${\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>2</span>2</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}<span><span>=</span>=</span>\frac{{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>s</span>the\; s</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>DG</span>DG</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}{{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>s</span>the\; s</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}<span><span>+</span>+</span>{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>DG</span>DG</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}$

其中：in:

为配电网的等值负序阻抗；

is the equivalent negative sequence impedance of the distribution network;

为微网等值负序阻抗。

is the equivalent negative sequence impedance of the microgrid.

所述设定阈值为0.2。The set threshold is 0.2.

本发明有益效果是利用负序电源分压器提出了孤岛检测的方法具有以下优点：The beneficial effect of the present invention is that the islanding detection method proposed by using the negative-sequence power supply voltage divider has the following advantages:

(1)本发明能在IEEE Std.1547标准所规定的最恶劣情况下，在30毫秒内正确地检测出孤岛；(1) The present invention can correctly detect the island within 30 milliseconds under the worst case stipulated in the IEEE Std.1547 standard;

(2)孤岛检测成功时，电能质量未受到破坏，具有非破坏性和无盲区的优点；(2) When the islanding detection is successful, the power quality is not damaged, which has the advantages of non-destructiveness and no blind zone;

(3)在单相断路和两相断路的情况下依然能正确判断孤岛的发生；(3) In the case of single-phase open circuit and two-phase open circuit, the occurrence of islanding can still be correctly judged;

(4)当伪孤岛发生时，不会出现误判断。(4) When false islands occur, there will be no misjudgment.

该方法原理简单，适用范围广，在各种故障条件及其他恶劣情况下均能有效地检测出孤岛，只与网络拓扑结构有关，且不受伪孤岛的影响，能够满足现场的应用要求，具有工程实际意义。The method is simple in principle and has a wide range of applications. It can effectively detect isolated islands under various fault conditions and other harsh conditions. It is only related to the network topology and is not affected by pseudo-isolated islands. It can meet the application requirements of the site. practical significance of engineering.

附图说明Description of drawings

图1为应用于本发明的主电路系统示意图与各个序网图；Fig. 1 is a schematic diagram of the main circuit system and each sequence network diagram applied to the present invention;

图1a为主电路系统示意图；图1b为全网络电路；图1c为正序网络电路；Figure 1a is a schematic diagram of the main circuit system; Figure 1b is a full network circuit; Figure 1c is a positive sequence network circuit;

图1d为负序网络电路；Figure 1d is a negative sequence network circuit;

图2为三相断路对称故障下发生孤岛的孤岛检测各特征量波形图；Fig. 2 is the waveform diagram of each feature quantity of the island detection when the island occurs under the symmetrical fault of the three-phase open circuit;

图2a为负序电压源的三相电压曲线图；图2b为公共连接点处比值K波形图；图2c为微网电压曲线图；图2d为微网频率波形图；Figure 2a is a three-phase voltage curve of a negative sequence voltage source; Figure 2b is a waveform diagram of the ratio K at the common connection point; Figure 2c is a microgrid voltage curve; Figure 2d is a microgrid frequency waveform;

图3为非对称故障下发生孤岛的公共连接点处比值K曲线图；Fig. 3 is a curve diagram of the ratio K at the common connection point where an island occurs under an asymmetrical fault;

图3a为单相断路情况下公共连接点处比值K曲线图；图3b为两相断路情况下公共连接点处比值K曲线图；Figure 3a is a curve diagram of the ratio K at the common connection point under the condition of single-phase disconnection; Figure 3b is a curve diagram of the ratio K at the common connection point under the condition of two-phase disconnection;

图4为伪孤岛情况下，本发明检测孤岛的各特征量波形图；Fig. 4 is a waveform diagram of each characteristic quantity of the isolated island detected by the present invention in the case of a false isolated island;

图4a为电网电压波形图；图4b为公共连接点处比值K曲线图。Fig. 4a is a waveform diagram of grid voltage; Fig. 4b is a curve diagram of the ratio K at the common connection point.

具体实施方式Detailed ways

下面结合附图，对优选实施例作详细说明。应该强调的是，下述说明仅仅是示例性的，而不是为了限制本发明的范围及其应用。The preferred embodiments will be described in detail below in conjunction with the accompanying drawings. It should be emphasized that the following description is only exemplary and not intended to limit the scope of the invention and its application.

本发明的目的在于克服现有技术存在的不足，提供一种基于负序分压器的孤岛检测方法。孤岛是并网运行的微网系统在发生大电网故障的情况下，与大电网断开并继续向本地负载供电、独立运行的情况。The purpose of the present invention is to overcome the shortcomings of the prior art and provide an islanding detection method based on a negative-sequence voltage divider. Islanding refers to the situation in which a grid-connected microgrid system is disconnected from the large grid and continues to supply power to local loads in the event of a large grid failure.

微网内部可简化为DG与本地负荷的模型，微网通过公共连接点与配电网相连。配电网的容量较大，等值阻抗较小，而微网的容量较小、等值阻抗较大。微网并网运行时，与配电网相连，公共连接处的等值阻抗为微网阻抗与配电网阻抗的并联，通常非常小。而当微网孤岛运行时，公共连接点处开关断开，等值阻抗为微网阻抗，数值较大。为了反映孤岛前后这一测量阻抗的变化规律，在公共连接点处加入负序电压源，通过公共连接点处的负序电压有效值与附加的负序电压源的有效值的比值的变化来反映测量阻抗(这里指负序阻抗)的变化，从而判断出孤岛的发生。具体步骤如下：The interior of the microgrid can be simplified as a model of DG and local loads, and the microgrid is connected to the distribution network through a common connection point. The distribution network has a large capacity and a small equivalent impedance, while the microgrid has a small capacity and a large equivalent impedance. When the microgrid is in grid-connected operation, it is connected to the distribution network, and the equivalent impedance at the common connection is the parallel connection of the microgrid impedance and the distribution network impedance, which is usually very small. When the microgrid is running in an isolated island, the switch at the common connection point is turned off, and the equivalent impedance is the impedance of the microgrid, which has a larger value. In order to reflect the change law of the measured impedance before and after the island, a negative sequence voltage source is added at the common connection point, and it is reflected by the change of the ratio of the effective value of the negative sequence voltage at the common connection point to the effective value of the additional negative sequence voltage source Measure the change of impedance (referred to here as negative sequence impedance), so as to judge the occurrence of islanding. Specific steps are as follows:

首先，提取公共连接点的负序电压有效值

用与所附加的负序电压源的有效值

的比值K，作为孤岛检测的判断量。K的计算公式为：First, the effective value of the negative sequence voltage at the common connection point is extracted

use with the rms value of the negative sequence voltage source attached

The ratio K of is used as the judgment quantity of island detection. The calculation formula of K is:

$\mathrm{<span><span>K</span>K</span>}<span><span>=</span>=</span>\frac{{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>2</span>2</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}{{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>G</span>G</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}<span><span>=</span>=</span>\frac{{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>2</span>2</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}{{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>1</span>1</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}<span><span>+</span>+</span>{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>2</span>2</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}<span><span>-</span>-</span><span><span>-</span>-</span><span><span>-</span>-</span><span><span>(</span>(</span>\mathrm{<span><span>1</span>1</span>}<span><span>)</span>)</span>$

其中，；in,;

为负序电压源所串联阻抗的负序值； is the negative sequence value of the series impedance of the negative sequence voltage source;

为公共连接点处等值负序阻抗，$Z_2^{\left(2\right)}=\frac{Z_s^{\left(2\right)}{Z}_{\mathrm{DG}}^{\left(2\right)}}{Z_s^{\left(2\right)}+Z_{\mathrm{DG}}^{\left(2\right)}};$

is the equivalent negative sequence impedance at the common connection point,$Z_2^{\left(2\right)}=\frac{Z_{\mathrm{the\; s}}^{\left(2\right)}{Z}_{\mathrm{DG}}^{\left(2\right)}}{Z_{\mathrm{the\; s}}^{\left(2\right)}+Z_{\mathrm{DG}}^{\left(2\right)}};$

为配电网的等值负序阻抗；

is the equivalent negative sequence impedance of the distribution network;

为微网等值负序阻抗。

is the equivalent negative sequence impedance of the microgrid.

其次，设定K的阈值ε₁。Next, the threshold ε₁ of K is set.

然后，根据K的大小判断是否发生孤岛，判据如下：Then, judge whether islanding occurs according to the size of K. The criteria are as follows:

(1)当K未超过预先设定的阈值ε₁，则判定微网未发生孤岛；(1) When K does not exceed the preset threshold ε₁ , it is determined that there is no islanding in the microgrid;

(2)当K超过或等于预先设定的阈值ε₁，则判定微网发生孤岛。(2) When K exceeds or is equal to a preset threshold ε₁ , it is determined that the microgrid is isolated.

本发明选用负序电源作为外加电源，与一定值阻抗串联接在公共连接点处。外加电源与微网、配电网组成孤岛检测电路。微网内部可简化为DG与本地负荷的模型，微网通过公共连接点与配电网相连，微网与配电网可看作是并联电路的分支。In the present invention, the negative sequence power supply is selected as the external power supply, which is connected in series with a certain value impedance at the common connection point. The external power supply, microgrid and distribution network form an island detection circuit. The interior of the microgrid can be simplified as a model of DG and local loads. The microgrid is connected to the distribution network through a common connection point, and the microgrid and distribution network can be regarded as branches of a parallel circuit.

在检测电路的正序网络中，外加负序电压源输出为零，不会对正序网络产生影响。在检测电路的负序网络中，微网等效电源与配电网等效电源输出为零，形成仅含单一外加负序电压源的简单网络。该网络中，公共连接点处等值负序阻抗

与负序电压源所串联阻抗的负序值

形成串联的分压电路。微网并网运行时，与配电网相连，公共连接点处的等值阻抗为微网阻抗与配电网阻抗的并联，

较小，同时考虑到

为恒定负序阻抗，因此，由式(1)计算出的K值较小。当微网孤岛运行时，公共连接点断开，等值阻抗为微网阻抗，

较大，由式(1)可知，K值亦较大。通过K值判断孤岛的发生。In the positive-sequence network of the detection circuit, the output of the external negative-sequence voltage source is zero, which will not affect the positive-sequence network. In the negative-sequence network of the detection circuit, the output of the equivalent power supply of the microgrid and the equivalent power supply of the distribution network is zero, forming a simple network with only a single external negative-sequence voltage source. In this network, the equivalent negative sequence impedance at the point of common connection

Negative sequence value of impedance in series with negative sequence voltage source

Form a series voltage divider circuit. When the microgrid is connected to the grid, it is connected to the distribution network, and the equivalent impedance at the common connection point is the parallel connection of the microgrid impedance and the distribution network impedance.

smaller, taking into account

It is a constant negative sequence impedance, therefore, the K value calculated by formula (1) is small. When the microgrid is running in isolation, the public connection point is disconnected, and the equivalent impedance is the microgrid impedance,

Larger, as can be seen from formula (1), the K value is also larger. The occurrence of isolated islands is judged by the K value.

本发明具体的操作过程：在一台采用TI公司DSPTMS320F240做主控芯片的逆变电源上进行实验。如图1(其中，P_L+jQ_L为微网中本地负荷的视在功率，P+jQ为微网中DG的输出视在功率，ΔP+jΔQ为微网流向配电网的视在功率)所示，并在公共连接点处加入负序电压源，在IEEE Std.1547标准中所定义的最恶劣情况下仿真验证。各元件参数如下所示：电网线电压为380V，频率50Hz(含有幅值很小的高次谐波)，逆变器额定参考功率为50kW，直流母线电压为800V，LC滤波器(L_f＝0.6mH，C_f＝1500μF，等效电阻R＝0.01Ω)，负载额定功率为50kW(R＝2.904Ω，L＝3.698mH，C＝2740.2μF，Q_f＝2.5)。负序电压源的线电压有效值为3.8V，串联阻抗Z₁＝50Ω。系统通过变压器接入220V的市电电网。The concrete operation process of the present invention: carry out experiment on the inverter power supply that adopts DSPTMS320F240 of TI company as main control chip. As shown in Figure 1 (wherein, P_L + jQ_L is the apparent power of the local load in the microgrid, P + jQ is the output apparent power of DG in the microgrid, ΔP + jΔQ is the apparent power flowing from the microgrid to the distribution network ), and a negative-sequence voltage source is added at the common connection point, and the simulation verification is performed under the worst case defined in the IEEE Std.1547 standard. The parameters of each component are as follows: the grid line voltage is 380V, the frequency is 50Hz (including high-order harmonics with small amplitude), the rated reference power of the inverter is 50kW, the DC bus voltage is 800V, and the LC filter (L_f = 0.6mH, C_f = 1500μF, equivalent resistance R = 0.01Ω), the load rated power is 50kW (R = 2.904Ω, L = 3.698mH, C = 2740.2μF, Q_f = 2.5). The effective value of the line voltage of the negative sequence voltage source is 3.8V, and the series impedance Z₁ =50Ω. The system is connected to the 220V mains grid through a transformer.

公共连接点处比值K值的阈值ε₁取为0.2，我国国家标准GB/T 15543-1995规定，电力系统的公共连接点正常工作电压不平衡度允许值为2％，短时不超过4％。The threshold ε₁ of the ratio K value at the public connection point is taken as 0.2. China’s national standard GB/T 15543-1995 stipulates that the allowable value of the normal working voltage unbalance of the public connection point of the power system is 2%, and the short-term does not exceed 4%. .

仿真开始时，微网处于并网运行状态；在0.5s时刻公共连接点处开关断开，微网进入孤岛运行状态。为了防止过大的外加负序电源对微网电压质量造成破坏，外加电源相电压有效值仅为微网相电压有效值的1％，如图2a所示。图2b给出了K值变化曲线，可以看出，当微网并网运行时，由于公共连接点处的等效负序阻抗极小，因此该处的负序测量电压

占外加负序电源

的比重也极小，K值接近于0；在0.5s时刻，微网进入孤岛运行状态，公共连接点处的等效负序阻抗增加，该处的

占

的比重也增加，造成K值出现上升的趋势，并在一周波后仍然非常明显，由此可判断孤岛的发生。在孤岛检测过程中，微网电压幅值与频率分别如图2c和图2d所示，由图可知，两者均处于国家标准GB/T 14549-93规定的正常运行范围，电能质量未遭到破坏，实现了非破坏性和无盲区检测。At the beginning of the simulation, the microgrid is in the grid-connected operation state; at 0.5s, the switch at the common connection point is turned off, and the microgrid enters the island operation state. In order to prevent damage to the voltage quality of the microgrid caused by an excessively large external negative sequence power supply, the effective value of the phase voltage of the external power supply is only 1% of the effective value of the phase voltage of the microgrid, as shown in Figure 2a. Figure 2b shows the change curve of K value. It can be seen that when the microgrid is connected to the grid, due to the equivalent negative sequence impedance at the common connection point is extremely small, so the negative-sequence measurement voltage here

accounted for external negative sequence power supply

The proportion of the microgrid is also very small, and the K value is close to 0; at the moment of 0.5s, the microgrid enters the island operation state, and the equivalent negative sequence impedance at the common connection point increase, where the

occupy

The proportion of K also increases, resulting in an upward trend in the K value, and it is still very obvious after one cycle, so it can be judged that the occurrence of islands. During the islanding detection process, the voltage amplitude and frequency of the microgrid are shown in Figure 2c and Figure 2d respectively. It can be seen from the figure that both are within the normal operating range specified by the national standard GB/T 14549-93, and the power quality has not been affected. Destruction, to achieve non-destructive and no blind detection.

再者，公共连接点处断路器可能出现一相或者两相断开的情况，这两种情况下，K值的变化曲线分别如图3a和图3b所示，与三相断路器断开情况类似，一相或者两相断路器在0.5s断开后，K值也呈现出上升的趋势，并在一周波后仍然非常明显，因此，非全相运行情况下利用本方法依然能够实现孤岛检测。Furthermore, one phase or two phases of the circuit breaker at the common connection point may be disconnected. Similarly, after a one-phase or two-phase circuit breaker is disconnected in 0.5s, the K value also shows an upward trend, and it is still very obvious after one cycle. Therefore, this method can still achieve islanding detection under the condition of non-full-phase operation .

对于风力发电系统，在电网发生故障导致电压突然降低的情况下，要求风电机组继续与电网保持连接，只有当故障严重时才允许脱网，这就要求风力发电机组具有较强的低电压穿越能力。特别地，当风电机组机端电压下降到额定电压的15％时，要求风电机组继续运行0.625s。这就给孤岛检测技术提出了新的挑战，传统的被动检测方法在低电压穿越现象发生时可能出现误判，但是本发明可以有效地解决这一问题。图4给出了0.5s时刻，微网电压突然降低到额定值的15％的情况下，K值的变化曲线。For wind power generation systems, in the event of a sudden drop in voltage due to a grid failure, the wind turbines are required to remain connected to the grid, and are only allowed to disconnect from the grid when the fault is serious, which requires the wind turbines to have strong low-voltage ride-through capabilities . In particular, when the wind turbine terminal voltage drops to 15% of the rated voltage, the wind turbine is required to continue running for 0.625s. This poses a new challenge to the islanding detection technology. The traditional passive detection method may misjudgment when the low voltage ride through phenomenon occurs, but the present invention can effectively solve this problem. Figure 4 shows the change curve of K value when the microgrid voltage suddenly drops to 15% of the rated value at the moment of 0.5s.

低电压穿越现象发生后，由于微网依然与电网相连，公共连接点处的等效负序阻抗未发生变化，K值经过一个周波的波动后下降至接近于零的一个极小值，小于门槛值，因此，低电压穿越现象不会造成本方法误判。After the low voltage ride through phenomenon occurs, since the microgrid is still connected to the grid, the equivalent negative sequence impedance at the common connection point There is no change, and the K value drops to a minimum value close to zero after one cycle of fluctuation, which is less than the threshold value. Therefore, the low voltage ride through phenomenon will not cause misjudgment by this method.

图2～图4表明本发明所提供的基于负序分压器的孤岛检测方法在IEEEStd.1547标准中所定义的最恶劣情况下，可快速有效地检测出孤岛的发生，在电网单相及两相断路情况下仍然有效，且不受伪孤岛问题的影响。能够实现非破坏性无盲区孤岛检测，原理简单，具有良好的工程实用性。Figures 2 to 4 show that the islanding detection method based on the negative-sequence voltage divider provided by the present invention can quickly and effectively detect the occurrence of islanding under the worst case defined in the IEEE Std.1547 standard. It is still effective in the case of two-phase disconnection and is not affected by the pseudo-islanding problem. It can realize non-destructive and non-blind zone island detection, has a simple principle and has good engineering practicability.

以上所述，仅为本发明较佳的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到的变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应该以权利要求的保护范围为准。The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (4)

Translated fromChinese

1.基于负序分压器的孤岛检测方法，其特征是该方法包括以下步骤：1. based on the island detection method of negative sequence voltage divider, it is characterized in that the method comprises the following steps:步骤1：提取微网公共连接点处负序电压有效值，并计算该值与附加在公共连接点上负序电压源的有效值的比值；Step 1: Extract the effective value of the negative sequence voltage at the common connection point of the microgrid, and calculate the ratio of this value to the effective value of the negative sequence voltage source attached to the common connection point;步骤2：当所述比值小于设定阈值时，则判定未发生孤岛；当所述比值大于或等于设定阈值时，则判定发生孤岛。Step 2: When the ratio is smaller than the set threshold, it is determined that no islanding occurs; when the ratio is greater than or equal to the set threshold, it is determined that islanding occurs.2.根据权利要求1所述的基于负序分压器的孤岛检测方法，其特征是所述微网公共连接点的负序电压有效值与附加在公共连接点上负序电压源的有效值的比值的计算公式为：2. The islanding detection method based on negative-sequence voltage divider according to claim 1, characterized in that the effective value of the negative-sequence voltage of the common connection point of the microgrid and the effective value of the negative-sequence voltage source attached to the common connection point The formula for calculating the ratio is:$\mathrm{<span><span>K</span>K</span>}<span><span>=</span>=</span>\frac{{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>2</span>2</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}{{\mathrm{<span><span>U</span>u</span>}}_{\mathrm{<span><span>G</span>G</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}<span><span>=</span>=</span>\frac{{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>2</span>2</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}{{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>1</span>1</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}<span><span>+</span>+</span>{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>2</span>2</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}$其中：in:K为微网公共连接点的负序电压有效值与附加在公共连接点上负序K is the effective value of the negative sequence voltage of the common connection point of the microgrid and the negative sequence voltage added to the common connection point电压源的有效值的比值；The ratio of the effective value of the voltage source;

为微网公共连接点的负序电压有效值；

is the effective value of the negative sequence voltage at the common connection point of the microgrid;

为附加在公共连接点上负序电压源的有效值；

is the effective value of the negative sequence voltage source attached to the common connection point;

为公共连接点处等值负序阻抗；

is the equivalent negative sequence impedance at the common connection point;

为负序电压源所串联阻抗的负序值。

is the negative sequence value of the series impedance of the negative sequence voltage source.3.根据权利要求2所述的基于负序分压器的孤岛检测方法，其特征是所述

的计算公式为：3. the islanding detection method based on negative sequence voltage divider according to claim 2, is characterized in that said

The calculation formula is:${\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>2</span>2</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}<span><span>=</span>=</span>\frac{{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>s</span>the\; s</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>DG</span>DG</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}{{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>s</span>the\; s</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}<span><span>+</span>+</span>{\mathrm{<span><span>Z</span>Z</span>}}_{\mathrm{<span><span>DG</span>DG</span>}}^{<span><span>(</span>(</span>\mathrm{<span><span>2</span>2</span>}<span><span>)</span>)</span>}}$其中：in:

为配电网的等值负序阻抗；

is the equivalent negative sequence impedance of the distribution network;

为微网等值负序阻抗。

is the equivalent negative sequence impedance of the microgrid.4.根据权利要求1所述的基于负序分压器的孤岛检测方法，其特征是所述设定阈值为0.2。4. The islanding detection method based on negative-sequence voltage divider according to claim 1, characterized in that the set threshold is 0.2.

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