CN107681688A - Possess the grid-connected converter and its isolated island method of discrimination and device of VSG features - Google Patents
Possess the grid-connected converter and its isolated island method of discrimination and device of VSG features Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for AC mains or AC distribution networks
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Abstract
本发明涉及具备VSG特征的并网变流器及其孤岛判别方法与装置，本发明针对采用VSG技术的并网变流器，采用电网侧的电压扰动方法，对电网电压进行小幅度的正向电压扰动或负向电压扰动，并将扰动后的电压作为并网变流器的输出电压给定参考值，当电压持续扰动后的电网侧电压大于第一电压阈值或小于第二电压阈值时，判定发生孤岛。本发明可以快速识别出孤岛现象，并且每次进行扰动的电压很小，不影响对电网系统的稳定性和可靠性。
The invention relates to a grid-connected converter with VSG characteristics and an islanding method and device thereof. The invention aims at a grid-connected converter using VSG technology, adopts a voltage disturbance method on the grid side, and conducts a small-amplitude positive adjustment to the grid voltage. Voltage disturbance or negative voltage disturbance, and the disturbed voltage is used as the given reference value of the output voltage of the grid-connected converter. When the grid side voltage after the continuous voltage disturbance is greater than the first voltage threshold or less than the second voltage threshold, Determine the occurrence of islands. The invention can quickly identify the islanding phenomenon, and the voltage of each disturbance is very small, which does not affect the stability and reliability of the power grid system.
Description
技术领域technical field
本发明属于智能电网技术领域，具体涉及具备VSG特征的并网变流器及其孤岛判别方法与装置。The invention belongs to the technical field of smart grids, and in particular relates to a grid-connected converter with VSG characteristics and an islanding discrimination method and device thereof.
背景技术Background technique
随着分布式电源渗透率的不断增加，电力系统中的旋转备用容量及转动惯量相对减少，这对电网的安全稳定运行带来了严峻挑战。近年来，虚拟同步发电机(VirtualSynchronous Generator，VSG)技术成为国内外学者的研究热点。VSG技术本质上就是将并网变流器的控制策略中植入传统同步发电机的下垂特性以及惯性和阻尼特性，进而可以参与电网的调压、调频，避免扰动情况下电压和频率的快速变化及系统振荡，具备了变流器的“电网友好型”特征和组网特性。With the increasing penetration rate of distributed power generation, the rotating reserve capacity and moment of inertia in the power system are relatively reduced, which poses a serious challenge to the safe and stable operation of the power grid. In recent years, virtual synchronous generator (Virtual Synchronous Generator, VSG) technology has become a research hotspot of domestic and foreign scholars. VSG technology essentially embeds the control strategy of the grid-connected converter into the droop characteristics, inertia and damping characteristics of the traditional synchronous generator, and then can participate in the voltage regulation and frequency regulation of the power grid to avoid rapid changes in voltage and frequency under disturbance And system oscillation, with the "grid-friendly" characteristics and networking characteristics of the converter.
现有技术中，常规的并网变流器一般采用功率控制或直接电流控制，其主动式孤岛判别基本都是对并网逆变器的输出采用频移、功率扰动或谐波注入等方法，这类检测方法都是针对电流控制型的并网变流器。In the prior art, conventional grid-connected converters generally adopt power control or direct current control, and the active islanding discrimination basically uses methods such as frequency shift, power disturbance or harmonic injection on the output of the grid-connected inverter. These detection methods are all aimed at current-controlled grid-connected converters.
而基于VSG技术的并网变流器在电网断开后，其仍保持电压源外特性，电压和频率都保持稳定，现有的频移或功率等引入扰动的检测方法因不能打破电网中电压或频率的平衡导致孤岛判别失效，因此需要一种主动孤岛判别方法对具有VSG特征的变流器进行孤岛检测。However, after the power grid is disconnected, the grid-connected converter based on VSG technology still maintains the characteristics of the voltage source, and the voltage and frequency remain stable. Or the balance of frequency leads to the failure of islanding discrimination, so an active islanding discrimination method is needed to perform islanding detection on converters with VSG characteristics.
发明内容Contents of the invention
本发明的目的是提供一种具备VSG特征的并网变流器及其孤岛判别方法与装置，用于解决现有主动孤岛检测技术无法检测出具备VSG特征的并网变流器存在孤岛的问题。The purpose of the present invention is to provide a grid-connected converter with VSG characteristics and its islanding method and device, which is used to solve the problem that the existing active island detection technology cannot detect the existence of islands in grid-connected converters with VSG characteristics .
为解决上述技术问题，本发明提出一种具备VSG特征的并网变流器孤岛判别方法，包括以下步骤：In order to solve the above technical problems, the present invention proposes a grid-connected converter islanding method with VSG characteristics, including the following steps:
所述具备VSG特征的并网变流器并网后，对电网侧电压进行持续的正向或负向电压扰动，并将每次正向或负向电压扰动后的电网侧电压值作为所述并网变流器的输出电压给定参考值，检测每次正向或负向电压扰动后的电网侧电压情况，当正向电压持续扰动后的电网侧电压大于设定的第一电压阈值时，或当负向电压持续扰动后的电网侧电压小于设定的第二电压阈值时，判定孤岛发生。After the grid-connected converter with VSG characteristics is connected to the grid, it performs continuous positive or negative voltage disturbance on the grid side voltage, and uses the grid side voltage value after each positive or negative voltage disturbance as the The output voltage of the grid-connected converter is given a reference value, and the grid-side voltage after each positive or negative voltage disturbance is detected. When the grid-side voltage after the continuous positive voltage disturbance is greater than the first set voltage threshold , or when the grid-side voltage after the continuous negative voltage disturbance is lower than the set second voltage threshold, it is determined that islanding occurs.
进一步，当正向或负向电压持续扰动后的电网侧电压恢复到正常运行状态的电压时，判定孤岛没有发生。Further, when the voltage on the grid side after the continuous positive or negative voltage disturbance returns to the voltage in the normal operation state, it is determined that the islanding does not occur.
进一步，所述具备VSG特征的并网变流器在并网前，还包括将并网变流器输出侧电压与电网侧电压的幅值差和相位差进行预同步并网调整的步骤。Further, before the grid-connected converter with VSG feature is connected to the grid, it also includes the step of pre-synchronizing the grid-connected adjustment of the amplitude difference and phase difference between the output side voltage of the grid-connected converter and the grid side voltage.
为解决上述技术问题，本发明还提出一种具备VSG特征的并网变流器孤岛判别装置，包括以下单元：In order to solve the above technical problems, the present invention also proposes a grid-connected converter islanding identification device with VSG features, including the following units:
扰动单元：用于所述具备VSG特征的并网变流器在并网后，对电网侧电压进行持续的正向或负向电压扰动，将每次正向或负向电压扰动后的电网侧电压值作为所述并网变流器的输出电压给定参考值；Disturbance unit: used for the grid-connected converter with VSG characteristics to perform continuous positive or negative voltage disturbance on the grid side voltage after the grid-connected converter with VSG characteristics, and convert the grid side voltage after each positive or negative voltage disturbance The voltage value is used as a given reference value of the output voltage of the grid-connected converter;
比较单元：用于比较采集的每次正向电压扰动后的电网侧电压和设定的第一电压阈值，或比较采集的每次负向电压扰动后的电网侧电压和设定的第二电压阈值；Comparison unit: used to compare the collected grid-side voltage after each positive voltage disturbance with the set first voltage threshold, or compare the collected grid-side voltage after each negative voltage disturbance with the set second voltage threshold;
判断单元：用于当正向电压持续扰动后的电网侧电压大于第一电压阈值时，或当负向电压持续扰动后的电网侧电压小于第二电压阈值时，判定孤岛发生。Judging unit: used to determine that islanding occurs when the grid-side voltage after continuous positive voltage disturbance is greater than the first voltage threshold, or when the grid-side voltage after negative voltage continuous disturbance is less than the second voltage threshold.
进一步，还包括用于当正向或负向电压持续扰动后的电网侧电压恢复到正常运行状态的电压时，判定孤岛没有发生的单元。Further, it also includes a unit for judging that islanding does not occur when the grid side voltage after the positive or negative voltage continuous disturbance returns to the voltage of the normal operation state.
进一步，还包括用于在将并网变流器输出侧电压与电网侧电压的幅值差和相位差进行预同步并网调整的单元。Further, it also includes a unit for performing pre-synchronous grid-connection adjustment on the amplitude difference and phase difference between the output side voltage of the grid-connected converter and the grid-side voltage.
为解决上述技术问题，本发明还提出一种具备VSG特征的并网变流器，包括变流器主电路和控制系统，其中，控制系统包括励磁控制器，和孤岛判别模块，该孤岛判别模块包括以下单元：In order to solve the above technical problems, the present invention also proposes a grid-connected converter with VSG features, including the main circuit of the converter and a control system, wherein the control system includes an excitation controller, and an island discrimination module, the island discrimination module Includes the following units:
扰动单元：用于所述具备VSG特征的并网变流器在并网后，对电网侧电压进行持续的正向或负向电压扰动，将每次正向或负向电压扰动后的电网侧电压值作为所述并网变流器的输出电压给定参考值；Disturbance unit: used for the grid-connected converter with VSG characteristics to perform continuous positive or negative voltage disturbance on the grid side voltage after the grid-connected converter with VSG characteristics, and convert the grid side voltage after each positive or negative voltage disturbance The voltage value is used as a given reference value of the output voltage of the grid-connected converter;
比较单元：用于比较采集的每次正向电压扰动后的电网侧电压和设定的第一电压阈值，或比较采集的每次负向电压扰动后的电网侧电压和设定的第二电压阈值；Comparison unit: used to compare the collected grid-side voltage after each positive voltage disturbance with the set first voltage threshold, or compare the collected grid-side voltage after each negative voltage disturbance with the set second voltage threshold;
判断单元：用于当正向电压持续扰动后的电网侧电压大于第一电压阈值时，或当负向电压持续扰动后的电网侧电压小于第二电压阈值时，判定孤岛发生。Judging unit: used to determine that islanding occurs when the grid-side voltage after continuous positive voltage disturbance is greater than the first voltage threshold, or when the grid-side voltage after negative voltage continuous disturbance is less than the second voltage threshold.
进一步，所述孤岛判别模块还包括用于当正向或负向电压持续扰动后的电网侧电压恢复到正常运行状态的电压时，判定孤岛没有发生的单元。Furthermore, the islanding identification module further includes a unit for determining that no islanding occurs when the grid-side voltage returns to the voltage in the normal operation state after the positive or negative voltage continues to be disturbed.
进一步，所述孤岛判别模块还包括用于在所述具备VSG特征的并网变流器在并网前，将并网变流器输出侧电压与电网侧电压的幅值差和相位差进行预同步并网调整的单元。Further, the island discrimination module also includes a method for pre-setting the amplitude difference and phase difference between the output side voltage of the grid-connected converter and the grid-side voltage before the grid-connected converter with VSG characteristics is connected to the grid. Synchronous grid-connected adjustment unit.
本发明的有益效果是：本发明针对具备VSG技术的并网变流器，采用电网侧的电压扰动方法，对电网电压进行小幅度的正向电压扰动或负向电压扰动，并将扰动后的电压作为并网变流器的输出电压给定参考值，当电压持续扰动后的电网侧电压大于第一电压阈值或小于第二电压阈值时，判定发生孤岛。本发明可以快速识别出孤岛现象，并且每次进行扰动的电压很小，不影响对电网系统的稳定性和可靠性。The beneficial effect of the present invention is that: for the grid-connected converter with VSG technology, the present invention adopts the voltage disturbance method on the grid side to carry out small positive voltage disturbance or negative voltage disturbance on the grid voltage, and convert the disturbed The voltage is used as a given reference value for the output voltage of the grid-connected converter. When the grid-side voltage after continuous voltage disturbance is greater than the first voltage threshold or less than the second voltage threshold, it is determined that islanding occurs. The invention can quickly identify the islanding phenomenon, and the voltage of each disturbance is very small, which does not affect the stability and reliability of the power grid system.
附图说明Description of drawings
图1是具备VSG特征的并网变流器接入电网的总体架构图；Figure 1 is an overall architecture diagram of a grid-connected converter with VSG characteristics connected to the grid;
图2是本发明实施的控制算法框图；Fig. 2 is the control algorithm block diagram that the present invention implements;
图3是本发明主动孤岛判别方法的实现流程图；Fig. 3 is the implementation flowchart of the active island discrimination method of the present invention;
图4是本发明的孤岛判别方法的仿真图。Fig. 4 is a simulation diagram of the island discrimination method of the present invention.
具体实施方式detailed description
下面结合附图对本发明的具体实施方式作进一步的说明。The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings.
如图1所示，VSG主要包括变流器主电路与控制系统。其中，变流器主电路为常规的并网逆变器拓扑，包括直流侧电压源(一般为光储或风储等，可视为原动机)、DC/AC变流器等(对应同步发电机的电能量转换过程)，其中DC/AC变流器包括变流器的变流及滤波环节；控制系统是实现VSG的核心，主要包括控制算法、预同步算法及主动孤岛判别算法。As shown in Figure 1, the VSG mainly includes the main circuit of the converter and the control system. Among them, the main circuit of the converter is a conventional grid-connected inverter topology, including the DC side voltage source (generally solar storage or wind storage, etc., which can be regarded as the prime mover), DC/AC converter, etc. (corresponding to synchronous power generation The electric energy conversion process of the machine), in which the DC/AC converter includes the conversion and filtering links of the converter; the control system is the core to realize the VSG, mainly including the control algorithm, the pre-synchronization algorithm and the active islanding discrimination algorithm.
控制算法如图2所示，虚拟励磁控制器和虚拟调速器以及惯性阻尼环节都属于VSG的控制算法，其分别输出电压幅值参考值E*和相位θ0，经幅值和相位调整单元，将变流器输出侧电压与电网侧电压的相位差和幅值差调整到很小范围内后进行合闸并网，并网后，将电网侧电压和变流器输出侧电压送入主动孤岛判别模块，该模块经过本发明的孤岛判别方法进行孤岛判别后，最后送入电压电流双闭环进行PWM控制。The control algorithm is shown in Figure 2. The virtual excitation controller, the virtual governor and the inertial damping link all belong to the control algorithm of the VSG, which respectively output the voltage amplitude reference value E * and phase θ 0 , and the amplitude and phase adjustment unit , adjust the phase difference and amplitude difference between the voltage on the output side of the converter and the voltage on the grid side to a small range, and then close the switch and connect to the grid. After connecting to the grid, send the voltage on the grid side and the output side of the converter to the active An island discrimination module, after the island discrimination is carried out by the island discrimination method of the present invention, the module is finally sent into a voltage and current double closed loop for PWM control.
本发明的具备VSG特征的并网变流器孤岛判别方法(即上述控制算法)的流程如图3所示，包括以下步骤：The process flow of the islanding method for grid-connected converters with VSG characteristics (that is, the above-mentioned control algorithm) of the present invention is shown in Figure 3, including the following steps:
步骤一，初始化相关参数：包括VSG控制算法涉及的额定频率fN、额定电压E0、初始有功功率P0、无功功率QN以及惯量J和阻尼参数D，还包括预同步和孤岛判别方法涉及的相位差阈值ξθ、电压差阈值ξu、相位调节步长stepTheta、电压调节步长stepU、实际相位差调节量dθ、实际幅值差调节量dU、电压最低阈值Umin以及扰动步长step等参数。Step 1, initialize relevant parameters: including rated frequency f N , rated voltage E 0 , initial active power P 0 , reactive power Q N , inertia J and damping parameter D involved in the VSG control algorithm, as well as pre-synchronization and islanding discrimination methods Involved phase difference threshold ξ θ , voltage difference threshold ξ u , phase adjustment step size stepTheta, voltage adjustment step size stepU, actual phase difference adjustment amount dθ, actual amplitude difference adjustment amount dU, voltage minimum threshold U min and disturbance step size Step and other parameters.
步骤二，VSG特征的并网变流器在并网前，需要进行预同步，将并网变流器输出侧电压与电网侧电压的幅值差和相位差进行调整，具体如下：Step 2. Before the grid-connected converter with VSG characteristics is connected to the grid, pre-synchronization is required to adjust the amplitude difference and phase difference between the output side voltage of the grid-connected converter and the grid side voltage, as follows:
如图1所示，开关K2闭合，K1和K3断开，并网变流器空载运行，采集电网侧的三相电压Ugabc，变流器输出侧的三相电压Uabc，经VSG控制算法后获取变流器输出侧的电压给定幅值E*和相位θ0，读取电网侧电压经锁相环后得到的幅值Udg和相位θg，定义变流器输出侧电压与电网侧电压的幅值差和相位差，计算式为：As shown in Figure 1, the switch K2 is closed, K1 and K3 are disconnected, the grid-connected converter runs without load, the three-phase voltage U gabc on the grid side is collected, and the three-phase voltage U abc on the output side of the converter is controlled by VSG After the algorithm, obtain the given amplitude E* and phase θ 0 of the voltage on the output side of the converter, read the amplitude U dg and phase θ g of the voltage on the grid side after passing through the phase-locked loop, and define the voltage and phase θ g on the output side of the converter. The amplitude difference and phase difference of the grid side voltage are calculated as:
式中，Urefout为对电网进行扰动下VSG的输出电压峰值，ΔU为变流器输出侧电压和电网侧电压的幅值差，Δθ为变流器输出侧电压和电网侧电压的相位差，dU为可调幅值差变量，dθ为可调相位差变量，其中dθ和dU的初值设定为0，θ为变流器输出侧电压的相位。In the formula, U refout is the peak output voltage of VSG when the power grid is disturbed, ΔU is the amplitude difference between the output side voltage of the converter and the grid side voltage, Δθ is the phase difference between the output side voltage of the converter and the grid side voltage, dU is an adjustable amplitude difference variable, dθ is an adjustable phase difference variable, where the initial values of dθ and dU are set to 0, and θ is the phase of the output side voltage of the converter.
如图3所示的预同步算法，比较Δθ的绝对值是否小于或等于设定的相位差阈值ξθ，ΔU的绝对值是否小于或等于设定的电压差阈值ξu，对实际幅值差调节变量dU和实际相位差调节变量dθ进行修正：The pre-synchronization algorithm shown in Figure 3 compares whether the absolute value of Δθ is less than or equal to the set phase difference threshold ξ θ , whether the absolute value of ΔU is less than or equal to the set voltage difference threshold ξ u , and the actual amplitude difference The adjustment variable dU and the actual phase difference adjustment variable dθ are corrected:
式中，stepTheta为相位调节步长，stepU为电压调节步长，sign1和sign2为修正系数，取值分别为1、-1或0，当Δθ＞ξθ时，sign1＝1，当Δθ＜-ξθ时，sign1＝-1，当|Δθ|≤ξθ时，sign1＝0；当ΔU＞ξu时，sign2＝1，当ΔU＜ξu时，sign2＝-1，当|ΔU|≤ξu时，sign2＝0。In the formula, stepTheta is the phase adjustment step size, stepU is the voltage adjustment step size, sign1 and sign2 are correction coefficients, the values are 1, -1 or 0 respectively, when Δθ>ξ θ , sign1=1, when Δθ<- When ξ θ , sign1=-1, when |Δθ|≤ξ θ , sign1=0; when ΔU＞ ξu , sign2=1, when ΔU＜ ξu , sign2=-1, when |ΔU|≤ When ξ u , sign2=0.
幅值差调节变量dU和相位调节差变量dθ进行不断修正后，当Δθ的绝对值小于或等于设定的相位差阈值ξθ，ΔU的绝对值小于或等于设定的电压差阈值ξu时，认为预同步完成，满足合闸并网条件，随时可以闭合并网开关K1，闭合K1后随即实现无冲击并网，然后闭合负载开关K3带载运行。After the amplitude difference adjustment variable dU and the phase adjustment difference dθ are continuously corrected, when the absolute value of Δθ is less than or equal to the set phase difference threshold ξ θ , and the absolute value of ΔU is less than or equal to the set voltage difference threshold ξ u , it is considered that the pre-synchronization is completed, and the grid-connection conditions are met, and the grid-connection switch K1 can be closed at any time. After closing K1, the grid-connection without impact is realized immediately, and then the load switch K3 is closed to run with load.
步骤三，变流器并网后的孤岛判别过程为：将电网侧电压幅值Udg减小步长step，即进行了一次负扰动(其实也可以进行正向扰动，这里以负扰动作介绍)，其中step设置的值非常小(比如设为0.02V或其他很小的值)，扰动后的值作为变流器输出侧电压的给定参考值，计算式为：Step 3, the islanding identification process after the converter is connected to the grid is as follows: reduce the voltage amplitude U dg on the grid side by a step size step, that is, a negative disturbance is performed (in fact, positive disturbance can also be performed, and the negative disturbance action is introduced here ), where the value set by step is very small (for example, set to 0.02V or other very small values), and the value after disturbance is used as a given reference value of the voltage on the output side of the converter. The calculation formula is:
Urefout＝Udg-stepU refout = U dg -step
式中，将电网电压减少step，即进行了一次负向扰动，将扰动后的值作为变流器输出侧电压参考幅值，该扰动不断循环进行，则下一次扰动时，程序继续读取电网电压Udg，若电网正常连接，则Udg保持不变(即使电网电压存在波动，那么Udg也会在正常范围内)；若电网断开，由于失去电网支撑，则电网侧三相电压就是变流器输出侧三相电压，其电压幅值Udg＝Urefout，对Udg的循环扰动就会使得Urefout一直减小，当Urefout小于电压最低阈值Umin时，即可判别出孤岛现象。In the formula, the grid voltage is reduced by step, that is, a negative disturbance is performed, and the value after the disturbance is used as the voltage reference amplitude of the output side of the converter. Voltage U dg , if the grid is normally connected, U dg will remain unchanged (even if the grid voltage fluctuates, then U dg will be within the normal range); if the grid is disconnected, due to the loss of grid support, the three-phase voltage on the grid side is The three-phase voltage on the output side of the converter, its voltage amplitude U dg = U refout , the cyclic disturbance to U dg will make U refout keep decreasing, when U refout is less than the minimum voltage threshold U min , the island can be identified Phenomenon.
本发明属于一种新的主动孤岛判别方法，针对具备VSG技术的并网变流器，其主动孤岛判别方法是根据将电网电压进行自扰动，扰动的方式既可以是本实施例所提的负向电压的持续扰动，也可以是正向电压的持续扰动，其区别在于：当电网发生孤岛时，施加负向电压扰动方式使电网侧的电压值不断减小，当减小到电压最低阈值Umin时，判定发生孤岛，而施加正向电压扰动方式则是使电网侧的电压值不断增大，当增大到一个设定的电压阈值时判定发生孤岛；当电网没有发生孤岛时，无论在电网侧电压持续进行负向电压扰动还是正向电压扰动，电网侧的电压终会恢复到正常运行电压。本发明对电网侧进行扰动后的电压值赋予变流器输出电压的给定值，扰动值非常小，对系统稳定性基本没有影响，并且该方法效果显著，可以快速识别出孤岛现象。The present invention belongs to a new active islanding identification method. For grid-connected converters equipped with VSG technology, the active islanding identification method is based on self-disturbance of grid voltage. The continuous disturbance of the positive voltage can also be the continuous disturbance of the positive voltage. The difference is that when the power grid is isolated, the voltage value of the power grid side is continuously reduced by applying the negative voltage disturbance mode. When it is reduced to the minimum voltage threshold U min , it is determined that islanding occurs, and the way of applying positive voltage disturbance is to increase the voltage value on the grid side continuously. When it increases to a set voltage threshold, it is determined that islanding occurs; Whether the side voltage continues to undergo negative or positive voltage disturbances, the voltage on the grid side will eventually return to the normal operating voltage. The invention assigns the given value of the output voltage of the converter to the voltage value after the disturbance on the grid side, the disturbance value is very small, basically has no influence on the system stability, and the method has remarkable effect, and can quickly identify the islanding phenomenon.
本发明还分别提出了一种具备VSG特征的并网变流器孤岛判别装置，及一种具备VSG特征的并网变流器。其中，具备VSG特征的并网变流器孤岛判别装置包括以下三个单元：The present invention also proposes a grid-connected converter islanding device with VSG features and a grid-connected converter with VSG features. Among them, the islanding identification device of grid-connected converter with VSG features includes the following three units:
扰动单元：用于具备VSG特征的并网变流器在并网后，对电网侧电压进行持续的正向或负向电压扰动，将每次正向或负向电压扰动后的电网侧电压值作为并网变流器的输出电压给定参考值；Disturbance unit: used for grid-connected converters with VSG characteristics to perform continuous positive or negative voltage disturbances on the grid side voltage after grid connection, and convert the grid side voltage value after each positive or negative voltage disturbance As the reference value of the output voltage of the grid-connected converter;
比较单元：用于比较采集的每次正向电压扰动后的电网侧电压和设定的第一电压阈值，或比较采集的每次负向电压扰动后的电网侧电压和设定的第二电压阈值；Comparison unit: used to compare the collected grid-side voltage after each positive voltage disturbance with the set first voltage threshold, or compare the collected grid-side voltage after each negative voltage disturbance with the set second voltage threshold;
判断单元：用于当正向电压持续扰动后的电网侧电压大于第一电压阈值时，或当负向电压持续扰动后的电网侧电压小于第二电压阈值时，判定孤岛发生。Judging unit: used to determine that islanding occurs when the grid-side voltage after continuous positive voltage disturbance is greater than the first voltage threshold, or when the grid-side voltage after negative voltage continuous disturbance is less than the second voltage threshold.
而具备VSG特征的并网变流器即为图1所示VSG中的DC/AC变流器，其硬件结构为现有技术，其控制系统包括励磁控制器、电压电流双闭环及孤岛判别模块，该孤岛判别模块包括的三个单元，与具备VSG特征的并网变流器孤岛判别装置包括的三个单元相同。The grid-connected converter with VSG characteristics is the DC/AC converter in VSG shown in Figure 1. Its hardware structure is the existing technology, and its control system includes excitation controller, voltage and current double closed-loop and island discrimination module. , the three units included in the islanding identification module are the same as the three units included in the islanding identification device for grid-connected converters with VSG features.
上述所指的具备VSG特征的并网变流器孤岛判别装置，实际上是基于本发明方法流程的一种计算机解决方案，即一种软件构架，可以应用到VSG的控制系统中，上述装置即为与方法流程相对应的处理进程。同样，具备VSG特征的并网变流器中孤岛判别模块，也是与方法流程相对应的处理进程。由于对上述方法的介绍已经足够清楚完整，而本发明声称的并网变流器孤岛判别装置和孤岛判别模块实际上是一种软件构架，故不再详细进行描述。The islanding identification device for grid-connected converters with VSG features mentioned above is actually a computer solution based on the method flow of the present invention, that is, a software framework that can be applied to the VSG control system. The above-mentioned device is is the processing process corresponding to the method flow. Similarly, the island discrimination module in the grid-connected converter with VSG characteristics is also a processing process corresponding to the method flow. Since the introduction of the above method is clear and complete enough, and the grid-connected converter islanding identification device and islanding identification module claimed in the present invention are actually a software framework, no detailed description is given here.
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