CN106208059A - Adjustable impedance formula distributed photovoltaic power generation cluster resonance inhibiting system and suppressing method - Google Patents

一种可调阻抗式分布式光伏发电集群谐振抑制系统及抑制方法，系统包括有分别通过系统母线与分布式光伏发电集群并联连接在公共连接点上，并与分布式光伏发电集群共同通过配电网线路等效电感L_g并入配电网的中央控制单元、谐振抑制单元和无功调节单元，无功调节单元的信号输出端连接中央控制单元的信号输入端，无功调节单元的信号输入端连接中央控制单元的信号输出端，谐振抑制单元的信号输入端连接中央控制单元的信号输出端。方法是当中央控制单元检测到系统发生谐振时，谐振抑制单元中的电抗器组从中间级开始依次循环投切，直至系统的并联谐振得到抑制。本发明在不改变原有光伏逆变器控制算法的基础上，有效实现了对分布式光伏发电集群系统谐振的抑制。

An adjustable impedance-type distributed photovoltaic power generation cluster resonance suppression system and suppression method, the system includes parallel connection with the distributed photovoltaic power generation cluster on the public connection point through the system bus, and the distributed photovoltaic power generation cluster through the power distribution The equivalent inductance L _g of the network line is incorporated into the central control unit, resonance suppression unit and reactive power adjustment unit of the distribution network. The signal output end of the reactive power adjustment unit is connected to the signal input end of the central control unit, and the signal input end of the reactive power adjustment unit The terminal is connected to the signal output terminal of the central control unit, and the signal input terminal of the resonance suppression unit is connected to the signal output terminal of the central control unit. The method is that when the central control unit detects the resonance of the system, the reactor groups in the resonance suppression unit are cycled and switched from the middle stage until the parallel resonance of the system is suppressed. On the basis of not changing the control algorithm of the original photovoltaic inverter, the invention effectively realizes the suppression of the resonance of the distributed photovoltaic power generation cluster system.

可调阻抗式分布式光伏发电集群谐振抑制系统及抑制方法Adjustable impedance distributed photovoltaic power generation cluster resonance suppression system and suppression method

技术领域technical field

本发明涉及一种光伏发电集群谐振抑制方法。特别是涉及一种可调阻抗式分布式光伏发电集群谐振抑制系统及抑制方法。The invention relates to a method for suppressing the resonance of a photovoltaic power generation cluster. In particular, it relates to an adjustable impedance distributed photovoltaic power generation cluster resonance suppression system and suppression method.

背景技术Background technique

近年来，我国分布式光伏呈现出连片开发，集群并网的特点。光伏发电的波动性、间歇性、随机性的特点，使得光伏集群系统的输出包含丰富的谐波频谱的电压电流。同时，分布式光伏发电集群系统中存在大量的LCL滤波器，与配网阻抗构成复杂的高阶电网络，使光伏集群系统存在大量的固有谐振点。因此，当分布式光伏发电集群入网系统电压电流谐波频率与该系统固有谐振点频率相匹配时，将发生谐振。谐振问题将影响逆变器的控制回路，引起光伏并网发电系统失稳等问题，目前已有的分布式光伏并网工程中，已出现了多起逆变器并联运行产生谐振导致并网失败甚至损坏并网设备的案例，因此有必要研究合适的方案抑制光伏集群并网系统的谐振问题。In recent years, my country's distributed photovoltaic has shown the characteristics of continuous development and cluster grid connection. The fluctuation, intermittent and random characteristics of photovoltaic power generation make the output of photovoltaic cluster system contain voltage and current with rich harmonic spectrum. At the same time, there are a large number of LCL filters in the distributed photovoltaic power generation cluster system, which constitute a complex high-order electrical network with the impedance of the distribution network, so that there are a large number of inherent resonance points in the photovoltaic cluster system. Therefore, when the voltage and current harmonic frequency of the distributed photovoltaic power generation cluster grid-connected system matches the frequency of the natural resonance point of the system, resonance will occur. The resonance problem will affect the control loop of the inverter, causing problems such as instability of the photovoltaic grid-connected power generation system. In the existing distributed photovoltaic grid-connected projects, there have been many inverters running in parallel to cause resonance and grid-connection failure. There are even cases where the grid-connected equipment is damaged, so it is necessary to study a suitable solution to suppress the resonance problem of the photovoltaic cluster grid-connected system.

逆变器并联谐振的抑制主要采用虚拟阻抗等有源阻尼的方法，通过增加系统阻尼对系统谐振峰进行抑制。然而，上述有源阻尼方法着重从单个逆变器的谐振抑制出发，而实际中逆变器往往是并联运行的，逆变器与逆变器之间，逆变器与电网之间存在着复杂的谐振耦合关系。这些有源阻尼算法将受到其他逆变器以及电网阻抗的影响，其对并联逆变器系统谐振的抑制效果以及相互间的协调控制问题仍有待进一步的研究，同时有源阻尼方法需要重新升级并网逆变器中DSP的控制算法，实现起来具有一定难度，而且改变并网逆变器的运行模式，可能会降低逆变器的正常使用寿命。The suppression of inverter parallel resonance mainly adopts active damping methods such as virtual impedance, and suppresses the system resonance peak by increasing system damping. However, the above-mentioned active damping method focuses on the resonance suppression of a single inverter, but in practice, inverters are often operated in parallel, and there are complex problems between inverters and between inverters and the grid. resonant coupling relationship. These active damping algorithms will be affected by other inverters and grid impedance, and their suppression effect on parallel inverter system resonance and mutual coordination control issues still need to be further studied. At the same time, active damping methods need to be upgraded and updated. It is difficult to implement the DSP control algorithm in the grid inverter, and changing the operation mode of the grid inverter may reduce the normal service life of the inverter.

因此，有学者提出使用外部集中式谐振抑制装置对系统谐振进行抑制。将谐振抑制装置一般同其他的逆变器一起并联安装在公共连接点(Point of Common Coupling，PCC)，这种方法无需升级原先已安装的逆变器的结构或控制算法，也不影响逆变器原有的工作模式，可提高逆变器的使用年限。按照控制方式的不同，谐振抑制装置可分为无源型和有源型。目前，有源型谐振抑制装置受容量和电压等级限制，开关频率无法提高，对高次谐波谐振的抑制效果并不理想，而无源型谐振抑制装置则会造成极大的能量损失，且对并网点电压有极大不利影响。Therefore, some scholars propose to use an external centralized resonance suppression device to suppress system resonance. The resonance suppression device is generally installed in parallel with other inverters at the Point of Common Coupling (PCC). This method does not need to upgrade the structure or control algorithm of the previously installed inverter, and does not affect the inverter. The original working mode of the inverter can increase the service life of the inverter. According to different control methods, resonance suppression devices can be divided into passive type and active type. At present, the active resonance suppression device is limited by the capacity and voltage level, the switching frequency cannot be increased, and the suppression effect on high-order harmonic resonance is not ideal, while the passive resonance suppression device will cause great energy loss, and It has a great adverse effect on the grid-connected point voltage.

因此，针对分布式逆变器集群系统的谐振问题，本发明提出了一种可调阻抗式分布式光伏发电集群谐振抑制方法。Therefore, aiming at the resonance problem of the distributed inverter cluster system, the present invention proposes a method for suppressing the resonance of the distributed photovoltaic power generation cluster with adjustable impedance.

发明内容Contents of the invention

本发明所要解决的技术问题是，提供一种简捷易于实现，对主动配电网运行工况适应性强，便于实际工程应用的可调阻抗式分布式光伏发电集群谐振抑制系统及抑制方法。The technical problem to be solved by the present invention is to provide an adjustable impedance distributed photovoltaic power generation cluster resonance suppression system and suppression method that is simple and easy to implement, has strong adaptability to the operating conditions of the active distribution network, and is convenient for practical engineering applications.

本发明所采用的技术方案是：一种可调阻抗式分布式光伏发电集群谐振抑制系统，包括有分别通过系统母线与分布式光伏发电集群并联连接在公共连接点上，并与分布式光伏发电集群共同通过配电网线路等效电感L_g并入配电网的中央控制单元、谐振抑制单元和无功调节单元，其中，所述无功调节单元的信号输出端连接中央控制单元的信号输入端用于将无功调节单元中的换流器的状态信息输出给中央控制单元，所述无功调节单元的信号输入端连接中央控制单元的信号输出端，用于接收中央控制单元的控制信号由无功调节单元中的换流器输出实际无功功率，所述谐振抑制单元的信号输入端连接中央控制单元的信号输出端，用于接收中央控制单元发出的投入电抗器的控制指令。The technical solution adopted in the present invention is: an adjustable impedance distributed photovoltaic power generation cluster resonance suppression system, which includes parallel connection with the distributed photovoltaic power generation The clusters are jointly integrated into the central control unit, resonance suppression unit and reactive power adjustment unit of the distribution network through the distribution network line equivalent inductance _Lg , wherein the signal output end of the reactive power adjustment unit is connected to the signal input of the central control unit The terminal is used to output the status information of the converter in the reactive power adjustment unit to the central control unit, and the signal input terminal of the reactive power adjustment unit is connected to the signal output terminal of the central control unit for receiving the control signal of the central control unit The actual reactive power is output by the converter in the reactive power adjustment unit, and the signal input end of the resonance suppression unit is connected to the signal output end of the central control unit for receiving the control command for inputting the reactor issued by the central control unit.

一种可调阻抗式分布式光伏发电集群谐振抑制系统的抑制方法，包括如下步骤：A suppression method for an adjustable impedance type distributed photovoltaic power generation cluster resonance suppression system, comprising the following steps:

1)当可调阻抗式谐振抑制装置检测到光伏集群发生谐振时，中央控制单元向谐振抑制单元发出投入动作指令，控制谐振抑制单元中的电抗器组从中间级4级开始投入；1) When the adjustable impedance resonance suppression device detects that the photovoltaic cluster has resonance, the central control unit sends an input action command to the resonance suppression unit, and controls the reactor group in the resonance suppression unit to start input from the middle level 4;

2)中央控制单元根据电抗器组的投入级数，计算无功补偿单元的无功输出功率参考值Q_ref；2) The central control unit calculates the reactive output power reference value Q _ref of the reactive power compensation unit according to the input stages of the reactor group;

3)使用电流互感器测得无功调节单元中的换流器的实际输出电流i，使用电压互感器测得无功调节单元中的换流器实际输出电压U和直流电压U_dc，并将实际输出电流i、实际输出电压U和直流电压U_dc送入中央控制单元，由中央控制单元计算出无功调节单元中的实际无功输出功率Q；3) Use the current transformer to measure the actual output current i of the converter in the reactive power adjustment unit, use the voltage transformer to measure the actual output voltage U and the DC voltage U _dc of the converter in the reactive power adjustment unit, and set The actual output current i, the actual output voltage U and the DC voltage U _dc are sent to the central control unit, and the central control unit calculates the actual reactive output power Q in the reactive power adjustment unit;

4)将步骤3)得到的直流电压U_dc与设定的直流电压参考值U_dcref进行比较，将两者的差值送入PI控制器得到d轴电流参考值i_dref，将步骤3)得到的实际无功输出功率Q和步骤2)得到的无功输出功率参考值Q_ref进行比较，将两者的差值送入PI控制器得到q轴电流参考值i_qref；4) Compare the DC voltage _{Udc obtained in step 3) with the set DC voltage reference value Udcref ,} send the difference between the two to the PI controller to obtain the d-axis current reference value _idref , and obtain in step 3) The actual reactive output power Q and the reactive output power reference value Q _ref obtained in step 2) are compared, and the difference between the two is sent to the PI controller to obtain the q-axis current reference value i _qref ;

5)将步骤3)得到的实际输出电流i进行dq分解，得到无功调节单元中的换流器(39)实际d轴电流i_d和实际q轴电流i_q，将实际d轴电流i_d和实际q轴电流i_q与步骤4)得到的d轴电流参考值i_dref和q轴电流参考值i_qref一起送入中央控制单元里的电流控制器中，得到脉宽调制驱动电路的输出信号U_ref，并将所述的输出信号U_ref发送给无功调节单元，控制无功调节单元中的换流器(39)实际无功输出功率Q；5) Decompose the actual output current i obtained in step 3) into dq to obtain the actual d-axis current i _d and the actual q-axis current i _q of the converter (39) in the reactive power adjustment unit, and the actual d-axis current i _d and the actual q-axis current i _q and the d-axis current reference value i _dref and q-axis current reference value i _qref obtained in step 4) are sent to the current controller in the central control unit to obtain the output signal of the pulse width modulation drive circuit U _ref , and send the output signal U _ref to the reactive power adjustment unit to control the actual reactive output power Q of the converter (39) in the reactive power adjustment unit;

6)若光伏集群谐振得到抑制，则中央控制单元停止发送投入动作指令，结束；若光伏集群谐振仍未得到抑制，则中央控制单元继续向谐振抑制单元发出投入动作指令，控制电抗器组投入级数增加一级，返回步骤2)，直至光伏集群谐振得到抑制；6) If the photovoltaic cluster resonance is suppressed, the central control unit stops sending input action commands, and ends; if the photovoltaic cluster resonance is still not suppressed, the central control unit continues to issue input action commands to the resonance suppression unit to control the input level of the reactor group increase the number by one level, and return to step 2) until the photovoltaic cluster resonance is suppressed;

步骤2)中所述的无功输出功率参考值Q_ref采用如下公式计算：The reactive output power reference value Q _ref described in step 2) is calculated using the following formula:

QQ rr ee ff == 33 Uu 22 Xx

式中，X为单相已投入电抗器的感抗值，U为可调阻抗式谐振抑制装置接入配电网的相电压。In the formula, X is the inductance value of the single-phase input reactor, and U is the phase voltage of the adjustable impedance resonance suppression device connected to the distribution network.

步骤2)中所述的电抗器组投入级数增加一级，是按照4-5-6-7-1-2-3-4的顺序循环投切。The number of input stages of the reactor group described in step 2) is increased by one level, and the switching is performed in a cycle in the order of 4-5-6-7-1-2-3-4.

本发明的可调阻抗式分布式光伏发电集群谐振抑制系统及抑制方法，利用系统低通滤波特性，通过投切电容器组改变系统阻抗，使谐振频率移向高频，在不改变原有光伏逆变器控制算法的基础上，有效实现了对分布式光伏发电集群系统谐振的抑制。同时，本发明引入了无功调节单元，可有效补偿无源设备的投入对系统基波电压造成的不利影响。本发明的方法简捷易于实现，对主动配电网运行工况适应性强，便于实际工程应用。The adjustable impedance distributed photovoltaic power generation cluster resonance suppression system and suppression method of the present invention utilizes the low-pass filter characteristics of the system, changes the system impedance by switching capacitor banks, and shifts the resonance frequency to high frequency without changing the original photovoltaic inverter Based on the inverter control algorithm, the resonance suppression of the distributed photovoltaic power generation cluster system is effectively realized. At the same time, the invention introduces a reactive power adjustment unit, which can effectively compensate the adverse effect of the input of passive equipment on the fundamental wave voltage of the system. The method of the invention is simple and easy to implement, has strong adaptability to the operating conditions of the active distribution network, and is convenient for practical engineering application.

附图说明Description of drawings

图1是本发明的可调阻抗式分布式光伏发电集群谐振抑制系统框图；Fig. 1 is a block diagram of the adjustable impedance distributed photovoltaic power generation cluster resonance suppression system of the present invention;

图2是本发明中中央控制单元构成框图；Fig. 2 is a block diagram of central control unit in the present invention;

图3是中央控制单元中电流控制器构成框图；Fig. 3 is a block diagram of the current controller in the central control unit;

图4是投入谐振抑制装置前后入网电流波形图；Figure 4 is a waveform diagram of the grid-connected current before and after the resonance suppression device is put into operation;

图5是未投入谐振抑制装置时入网电流THD图；Figure 5 is the grid current THD diagram when the resonance suppression device is not used;

图6是4级投入时入网电流THD图；Figure 6 is the grid current THD diagram when level 4 is put into operation;

图7是5级投入时入网电流THD图；Figure 7 is the grid current THD diagram when level 5 is put into operation;

图8是并网点电压变化示意图；Figure 8 is a schematic diagram of the voltage change at the grid-connected point;

图9是换流器无功输出图。Fig. 9 is a reactive power output diagram of the converter.

图中in the picture

1：谐振抑制单元 2：无功调节单元1: Resonance suppression unit 2: Reactive power adjustment unit

3：中央控制单元 4：系统母线3: Central control unit 4: System bus

5：分布式光伏发电集群 31：电流控制器5: Distributed photovoltaic power generation cluster 31: Current controller

32：脉宽调制单元 33：第一PI控制器32: Pulse width modulation unit 33: First PI controller

34：第二PI控制器 35：第一坐标变换单元34: Second PI controller 35: First coordinate transformation unit

36：第二坐标变换单元 37：第一减法器36: Second coordinate transformation unit 37: First subtractor

38：第二减法器 39：换流器38: Second subtractor 39: Inverter

40：第三PI控制器 41：第四PI控制器40: Third PI controller 41: Fourth PI controller

42：第一乘法器 43：第二乘法器42: First multiplier 43: Second multiplier

44：第三坐标变换单元 45：第三减法器44: The third coordinate transformation unit 45: The third subtractor

46：第四减法器 47：第一加减法器46: The fourth subtractor 47: The first adder and subtracter

48：第二加减法器 51：逆变器48: Second adder and subtractor 51: Inverter

52：光伏电池 L1：第一电抗器组52: Photovoltaic cell L1: First reactor group

L2：第二电抗器组 L3：第三电抗器组L2: Second reactor group L3: Third reactor group

具体实施方式detailed description

下面结合实例和附图对本发明的可调阻抗式分布式光伏发电集群谐振抑制系统及抑制方法做出详细说明。The adjustable impedance distributed photovoltaic power generation cluster resonance suppression system and suppression method of the present invention will be described in detail below in combination with examples and accompanying drawings.

如图1所示，本发明的可调阻抗式分布式光伏发电集群谐振抑制系统，包括有分别通过系统母线4与分布式光伏发电集群5并联连接在公共连接点PCC上，并与分布式光伏发电集群5共同通过配电网线路等效电感L_g并入配电网的中央控制单元3、谐振抑制单元1和无功调节单元2，其中，所述无功调节单元2的信号输出端连接中央控制单元3的信号输入端用于将无功调节单元2中的换流器39的状态信息输出给中央控制单元3，所述无功调节单元2的信号输入端连接中央控制单元3的信号输出端，用于接收中央控制单元3的控制信号由无功调节单元2中的换流器39输出实际无功功率，所述谐振抑制单元1的信号输入端连接中央控制单元3的信号输出端，用于接收中央控制单元3发出的投入电抗器的控制指令。As shown in Figure 1, the adjustable impedance distributed photovoltaic power generation cluster resonance suppression system of the present invention includes parallel connection with the distributed photovoltaic power generation cluster 5 through the system bus 4 on the common connection point PCC, and is connected with the distributed photovoltaic power generation cluster 5 in parallel. The power generation cluster 5 is jointly integrated into the central control unit 3 of the distribution network, the resonance suppression unit 1 and the reactive power adjustment unit 2 through the equivalent inductance L _g of the distribution network line, wherein the signal output terminal of the reactive power adjustment unit 2 is connected to The signal input end of the central control unit 3 is used to output the status information of the converter 39 in the reactive power adjustment unit 2 to the central control unit 3, and the signal input end of the reactive power adjustment unit 2 is connected to the signal of the central control unit 3 The output end is used to receive the control signal of the central control unit 3, and the converter 39 in the reactive power adjustment unit 2 outputs the actual reactive power, and the signal input end of the resonance suppression unit 1 is connected to the signal output end of the central control unit 3 , used to receive the control command for inputting the reactor issued by the central control unit 3 .

如图1所示，所述的谐振抑制单元1包括有第一电抗器组L1、第二电抗器组L2和第三电抗器组L3，所述第一电抗器组L1、第二电抗器组L2和第三电抗器组L3结构相同，均是由三个电感构成，所述三个电感的一端分别连接系统母线4，并通过系统母线4与分布式光伏发电集群5并联连接，所述三个电感中的每一个电感的另一端均是通过两个反向并联的晶闸管接地。晶闸管触发端接收中央控制单元的投切动作指令，控制电抗器组的投切。As shown in Figure 1, the resonance suppression unit 1 includes a first reactor group L1, a second reactor group L2 and a third reactor group L3, the first reactor group L1, the second reactor group L2 and the third reactor group L3 have the same structure, they are all composed of three inductors, one end of the three inductors is respectively connected to the system bus 4, and is connected in parallel with the distributed photovoltaic power generation cluster 5 through the system bus 4, the three The other end of each of the inductors is grounded through two antiparallel thyristors. The thyristor trigger terminal receives the switching action command from the central control unit to control the switching of the reactor group.

所述谐振抑制单元可表述为：The resonance suppression unit can be expressed as:

谐振抑制单元由三组电抗器组组成，通过晶闸管控制每组电抗器组的关断。将三组电抗器组的容量按比值4：2：1设置，共组合出容量由小到大的7级补偿级数。电抗器组投切情况与级数的关系可由下表表示。The resonance suppression unit is composed of three sets of reactor groups, and the shutdown of each reactor group is controlled by a thyristor. The capacity of the three reactor groups is set according to the ratio of 4:2:1, and a total of 7 levels of compensation series from small to large capacity are combined. The relationship between the switching condition of the reactor group and the number of stages can be expressed by the following table.

当分布式光伏发电集群系统发生谐振时，谐振抑制单元接收中央控制单元发出的投切指令，从中间级4级开始投入电抗器。当电抗器组投入后，若分布式光伏发电集群系统谐振仍未得到抑制，则电抗器组投入级数依次增加，即按照4-5-6-7-1-2-3-4的顺序依次循环投切，直至分布式光伏发电集群系统谐振得到抑制。When the distributed photovoltaic power generation cluster system resonates, the resonance suppression unit receives the switching command issued by the central control unit, and the reactors are put into operation from the middle stage 4. After the reactor group is put into operation, if the resonance of the distributed photovoltaic power generation cluster system is still not suppressed, the number of reactor group input stages will increase sequentially, that is, in the order of 4-5-6-7-1-2-3-4 Cycle switching until the resonance of the distributed photovoltaic power generation cluster system is suppressed.

如图2所示，所述的中央控制单元3可以选择德州仪器公司TMS320C24x/F24x产品。所述的中央控制单元3包括有电流控制器31，所述电流控制器31的参考电压U_ref输出端通过一个脉宽调制单元32连接无功调节单元2的输入端，所述电流控制器31的d轴电流参考值i_dref输入端连接第一PI控制器33，所述电流控制器31的q轴电流参考值i_qref输入端连接第二PI控制器34，所述电流控制器31的无功调节单元2中的换流器39实际d轴电流i_d的输入端和实际q轴电流i_q的输入端连接第一坐标变换单元35的输出端，其中，所述第一PI控制器33的输入端连接第一减法器37的输出端，所述减法器37的两个输入端分别连接无功调节单元2中的换流器39直流侧电容C_dc参考电压值U_dcref和无功调节单元2中的换流器39直流侧电容实际电压值U_dc，所述第二PI控制器34的输入端连接第二减法器38的输出端，所述第二减法器38的两个输入端分别连接无功调节单元2中的换流器39实际输出的无功功率Q和无功调节单元2中的换流器39输出的无功功率参考值Q_ref，所述第一坐标变换单元35的输入端连接无功调节单元2中的换流器39实际输出电流i的输出端，所述无功调节单元2中的换流器39实际输出电压U通过第二坐标变换单元36输出无功调节单元2中的换流器39实际d轴输出电压U_d和无功调节单元2中的换流器39实际q轴输出电压U_q连接到电流控制器31的电压输入端。As shown in FIG. 2 , the central control unit 3 can choose TMS320C24x/F24x products from Texas Instruments. The central control unit 3 includes a current controller 31, the output terminal of the reference voltage U _ref of the current controller 31 is connected to the input terminal of the reactive power adjustment unit 2 through a pulse width modulation unit 32, and the current controller 31 The d-axis current reference value i _dref input end is connected to the first PI controller 33, the q-axis current reference value i _qref input end of the current controller 31 is connected to the second PI controller 34, and the current controller 31 has no The input end of the actual _d -axis current id and the input end of the actual q-axis current _iq of the converter 39 in the power adjustment unit 2 are connected to the output end of the first coordinate transformation unit 35, wherein the first PI controller 33 The input end of the first subtractor 37 is connected to the output end of the first subtractor 37, and the two input ends of the subtractor 37 are respectively connected to the converter 39 in the reactive power adjustment unit 2. The DC side capacitor C _dc reference voltage value U _dcref and the reactive power adjustment The actual voltage value U _dc of the DC side capacitor of the converter 39 in the unit 2, the input terminal of the second PI controller 34 is connected to the output terminal of the second subtractor 38, and the two input terminals of the second subtractor 38 Respectively connect the reactive power Q actually output by the converter 39 in the reactive power adjustment unit 2 and the reactive power reference value _Qref output by the converter 39 in the reactive power adjustment unit 2, the first coordinate transformation unit 35 The input end is connected to the output end of the actual output current i of the converter 39 in the reactive power adjustment unit 2, and the actual output voltage U of the converter 39 in the reactive power adjustment unit 2 outputs reactive power through the second coordinate transformation unit 36 The actual d-axis output voltage U _d of the converter 39 in the regulating unit 2 and the actual q-axis output voltage U _q of the converter 39 in the reactive power regulating unit 2 are connected to the voltage input terminal of the current controller 31 .

所述第一坐标变换单元35和第二坐标变换单元36为abc坐标系到dq坐标系的变换。The first coordinate transformation unit 35 and the second coordinate transformation unit 36 are transformations from the abc coordinate system to the dq coordinate system.

如图3所示，所述的电流控制器31包括有：第三PI控制器40、第四PI控制器41、第一乘法器42、第二三乘法器43、第三坐标变换单元44、第三减法器45、第四减法器46、第一加减法器47和第二加减法器48，其中，所述第三减法器45的输入端分别连接第一PI控制器33的d轴电流参考值i_dref输出端和第一坐标变换单元35的实际d轴电流i_d输出端，所述第三减法器45的输出端连接第三PI控制器40，第一乘法器42的输入端连接第一坐标变换单元35的实际d轴电流i_d输出端，用于电流i_d与基波角频率w和谐振抑制单元1中电抗器实际投入电感值L相乘，所述第二乘法器43输入端连接第一坐标变换单元35的实际q轴电流i_q输出端，用于电流i_q与基波角频率w和谐振抑制单元1中电抗器实际投入电感值L相乘，所述第四PI控制器41的输入端分别连接第二PI控制器34的q轴电流参考值i_qref输出端和第一坐标变换单元35的实际q轴电流i_q输出端，所述第一加减法器47的输入端分别连接第三PI控制器40和第三乘法器43的输出端以及连接第二坐标变换单元36的电压U_d输出端，所述第二加减法器48的输入端分别连接第四PI控制器41的输出端和第一乘法器42输出端以及连接第二坐标变换单元36的电压U_q输出端，所述第一加减法器47的输出端和第二加减法器48的输出端分别连接第三坐标变换单元44的输入端，第三坐标变换单元44的输出端输出参考电压U_ref至所述脉宽调制单元32。As shown in Figure 3, the current controller 31 includes: a third PI controller 40, a fourth PI controller 41, a first multiplier 42, a second three multiplier 43, a third coordinate transformation unit 44, The third subtractor 45, the fourth subtractor 46, the first adder-subtractor 47 and the second adder-subtractor 48, wherein the input terminals of the third subtractor 45 are respectively connected to d of the first PI controller 33 axis current reference value _idref output terminal and the actual _d -axis current id output terminal of the first coordinate transformation unit 35, the output terminal of the third subtractor 45 is connected to the third PI controller 40, the input of the first multiplier 42 end connected to the actual d-axis current i _d output end of the first coordinate transformation unit 35, used for multiplying the current i _d with the fundamental angular frequency w and the actual input inductance value L of the reactor in the resonance suppression unit 1, the second multiplication The input end of the device 43 is connected to the actual q-axis current i _q output end of the first coordinate transformation unit 35, and is used for multiplying the current i _q with the fundamental angular frequency w and the actual input inductance value L of the reactor in the resonance suppression unit 1, said The input end of the fourth PI controller 41 is respectively connected to the q-axis current reference value _iqref output end of the second PI controller 34 and the actual q-axis current _iq output end of the first coordinate transformation unit 35, the first addition and subtraction The input end of the multiplier 47 is respectively connected to the output end of the third PI controller 40 and the third multiplier 43 and the output end of the voltage U _d connected to the second coordinate transformation unit 36, and the input end of the second adder-subtractor 48 The output end of the fourth PI controller 41 is connected to the output end of the first multiplier 42 and the voltage U _q output end of the second coordinate transformation unit 36 is connected, the output end of the first adder-subtractor 47 is connected to the second adder-subtractor 47 The output terminals of the subtractor 48 are respectively connected to the input terminals of the third coordinate transformation unit 44 , and the output terminals of the third coordinate transformation unit 44 output the reference voltage U _ref to the pulse width modulation unit 32 .

所述的第三坐标变换单元44为dq坐标系到abc坐标系的变换。The third coordinate transformation unit 44 is for transformation from the dq coordinate system to the abc coordinate system.

中央控制单元为谐振抑制装置的核心，当分布式光伏发电集群系统发生谐振时，首先它将向谐振抑制单元发送电抗器组投切命令，控制电抗器组的投切，同时，根据当前电抗器组投入级数，计算出投入电抗器组后消耗的无功功率。并将该无功参考值Q_ref发送给无功调节单元，作为换流器的无功输出参考值。无功参考值计算公式如下式所示，The central control unit is the core of the resonance suppression device. When the distributed photovoltaic power generation cluster system resonates, it will first send a reactor group switching command to the resonance suppression unit to control the switching of the reactor group. At the same time, according to the current reactor Group input series, calculate the reactive power consumed after the reactor group is input. And send the reactive power reference value Q _ref to the reactive power adjustment unit as the reactive power output reference value of the converter. The calculation formula of reactive power reference value is shown in the following formula,

QQ rr ee ff == 33 Uu 22 Xx

式中，X为单相已投入电抗器的感抗值，In the formula, X is the inductance value of the single-phase input reactor,

U为系统的相电压。U is the phase voltage of the system.

若系统谐振仍未得到抑制，中央控制单元继续向谐振抑制单元发送电抗器组投切命令，使电抗器组投入级数循环增加，同时将重新计算此时无功补偿单元的无功输出参考值Q_ref，并将其发送给无功调节单元。以此往复，直至系统谐振得到抑制。If the system resonance has not been suppressed, the central control unit will continue to send the reactor group switching command to the resonance suppression unit, so that the number of reactor group input cycles will increase, and at the same time, the reactive power output reference value of the reactive power compensation unit will be recalculated at this time Q _ref , and send it to the reactive power adjustment unit. Repeat this until the resonance of the system is suppressed.

本发明的可调阻抗式分布式光伏发电集群谐振抑制系统，若系统谐振仍未得到抑制，中央控制单元继续向谐振抑制单元发送电抗器组投切命令，使电抗器组投入级数循环增加，同时将重新计算此时无功补偿单元的无功输出参考值Q_ref，并将其发送给无功调节单元。以此往复，直至系统谐振得到抑制。In the adjustable-impedance distributed photovoltaic power generation cluster resonance suppression system of the present invention, if the system resonance has not been suppressed, the central control unit continues to send reactor group switching commands to the resonance suppression unit, so that the number of reactor group input stages increases cyclically, At the same time, the reactive power output reference value Q _ref of the reactive power compensation unit at this time will be recalculated and sent to the reactive power adjustment unit. Repeat this until the resonance of the system is suppressed.

无功调节单元由一电压源型PWM换流器组成。可以选择型号：XDSVG-380/100；上海思源电气/SVG100Kvar千乏；DBL-SVG100-4L-400V。当谐振抑制单元中电抗器组投入后，实际上可等效为一个感性负载，将会对并网点的基波电压造成极大影响，无功调节单元的作用为输出感性无功功率，补偿电抗器组投入后消耗的感性无功功率。The reactive power adjustment unit is composed of a voltage source PWM converter. Models can be selected: XDSVG-380/100; Shanghai Siyuan Electric/SVG100Kvar; DBL-SVG100-4L-400V. When the reactor group in the resonance suppression unit is put into use, it can actually be equivalent to an inductive load, which will have a great impact on the fundamental voltage of the grid-connected point. The role of the reactive power adjustment unit is to output inductive reactive power and compensate the reactance The inductive reactive power consumed after the generator group is put into operation.

无功调节单元的换流器将上式中由中央控制单元传输过来Q_ref作为无功参考值，向系统注入感性无功功率，实现无功功率的自给自足，即谐振抑制装置并不需要向电网吸收感性无功功率，有效弥补了电抗器组投入后基波电压产生的不利影响。The converter of the reactive power adjustment unit uses the Q _ref transmitted from the central control unit in the above formula as a reactive reference value, injects inductive reactive power into the system, and realizes self-sufficiency of reactive power, that is, the resonance suppression device does not need to supply power to the system. The grid absorbs inductive reactive power, which effectively compensates for the adverse effects of the fundamental voltage after the reactor group is put into operation.

本发明的可调阻抗式分布式光伏发电集群谐振抑制系统的抑制方法，包括如下步骤：The suppression method of the adjustable impedance distributed photovoltaic power generation cluster resonance suppression system of the present invention comprises the following steps:

1)当可调阻抗式谐振抑制装置检测到分布式光伏发电集群发生谐振时，中央控制单元向谐振抑制单元发出投入动作指令，控制谐振抑制单元中的电抗器组从中间级4级开始投入；1) When the adjustable impedance resonance suppression device detects the resonance of the distributed photovoltaic power generation cluster, the central control unit sends an input action command to the resonance suppression unit, and controls the reactor group in the resonance suppression unit to start input from the middle level 4;

2)中央控制单元根据电抗器组的投入级数，计算无功补偿单元的无功输出功率参考值Q_ref，所述的无功输出功率参考值Q_ref采用如下公式计算：2) The central control unit calculates the reactive output power reference value Q _ref of the reactive power compensation unit according to the input stages of the reactor group, and the reactive output power reference value Q _ref is calculated by the following formula:

QQ rr ee ff == 33 Uu 22 Xx

式中，X为单相已投入电抗器的感抗值，U为可调阻抗式谐振抑制装置接入配电网的相电压，In the formula, X is the inductance value of the single-phase input reactor, U is the phase voltage of the adjustable impedance resonance suppression device connected to the distribution network,

所述的电抗器组投入级数增加一级，是按照4-5-6-7-1-2-3-4的顺序循环投切；The number of input stages of the reactor group is increased by one level, which is cyclic switching in the order of 4-5-6-7-1-2-3-4;

3)使用电流互感器测得无功调节单元中的换流器的实际输出电流i，使用电压互感器测得无功调节单元中的换流器实际输出电压U和直流电压U_dc，并将实际输出电流i、实际输出电压U和直流电压U_dc送入中央控制单元，由中央控制单元计算出无功调节单元中的实际无功输出功率Q；3) Use the current transformer to measure the actual output current i of the converter in the reactive power adjustment unit, use the voltage transformer to measure the actual output voltage U and the DC voltage U _dc of the converter in the reactive power adjustment unit, and set The actual output current i, the actual output voltage U and the DC voltage U _dc are sent to the central control unit, and the central control unit calculates the actual reactive output power Q in the reactive power adjustment unit;

4)将步骤3)得到的直流电压U_dc与设定的直流电压参考值U_dcref进行比较，将两者的差值送入PI控制器得到d轴电流参考值i_dref，将步骤3)得到的实际无功输出功率Q和步骤2)得到的无功输出功率参考值Q_ref进行比较，将两者的差值送入PI控制器得到q轴电流参考值i_qref；4) Compare the DC voltage _{Udc obtained in step 3) with the set DC voltage reference value Udcref ,} send the difference between the two to the PI controller to obtain the d-axis current reference value _idref , and obtain in step 3) The actual reactive output power Q and the reactive output power reference value Q _ref obtained in step 2) are compared, and the difference between the two is sent to the PI controller to obtain the q-axis current reference value i _qref ;

5)将步骤3)得到的实际输出电流i进行dq分解，得到图1所示的无功调节单元中的换流器(39)实际d轴电流i_d和实际q轴电流i_q，将实际d轴电流i_d和实际q轴电流i_q与步骤4)得到的d轴电流参考值i_dref和q轴电流参考值i_qref一起送入图1所示的中央控制单元里的电流控制器中，得到脉宽调制驱动电路的输出信号U_ref，并将所述的输出信号U_ref发送给无功调节单元，控制无功调节单元中的换流器(39)实际无功输出功率Q；5) Decompose the actual output current i obtained in step 3) into dq, to obtain the actual d-axis current i _d and the actual q-axis current i _q of the converter (39) in the reactive power adjustment unit shown in Figure 1, and the actual The d-axis current i _d and the actual q-axis current i _q are sent to the current controller in the central control unit shown in Figure 1 together with the d-axis current reference value i _dref and the q-axis current reference value i _qref obtained in step 4) , to obtain the output signal U _ref of the pulse width modulation drive circuit, and send the output signal U _ref to the reactive power adjustment unit to control the actual reactive output power Q of the converter (39) in the reactive power adjustment unit;

6)若光伏集群谐振得到抑制，则中央控制单元停止发送投入动作指令，结束；若光伏集群谐振仍未得到抑制，则中央控制单元继续向谐振抑制单元发出投入动作指令，控制电抗器组投入级数增加一级，返回步骤2)，直至光伏集群谐振得到抑制；6) If the photovoltaic cluster resonance is suppressed, the central control unit stops sending input action commands, and ends; if the photovoltaic cluster resonance is still not suppressed, the central control unit continues to issue input action commands to the resonance suppression unit to control the input level of the reactor group increase the number by one level, and return to step 2) until the photovoltaic cluster resonance is suppressed;

为验证本发明所提方法的正确性和可行性，建立电压等级为380V(线电压)的配电网，配网中由两台逆变器组成。逆变器LCL滤波器中，L₁＝1mH，L₂＝0.1mH，C＝210uF。谐振抑制装置中，各个电抗器组的感抗值分别为0.2mH，0.1mH，0.05mH，。In order to verify the correctness and feasibility of the method proposed in the present invention, a distribution network with a voltage level of 380V (line voltage) is established, and the distribution network is composed of two inverters. In the inverter LCL filter, L ₁ =1mH, L ₂ =0.1mH, C=210uF. In the resonance suppression device, the inductance values of each reactor group are 0.2mH, 0.1mH, 0.05mH, respectively.

图4是投入谐振抑制装置前后入网电流波形图，图5是未投入谐振抑制装置时入网电流THD，图6是4级投入时入网电流THD，图7是5级投入时入网电流THD。从中可以看到，未投入谐振抑制装置时，逆变器系统系统发生了明显的谐振，谐振频率在1150Hz附近，波形畸变率达到了20％；在谐振抑制装置投入中间级第4级以后，系统的谐振得到一定的抑制，谐振频率移动至1280Hz，但入网谐波畸变率仍然大于5％，不满足入网要求；而在谐振抑制装置投入第5级以后，系统的谐振频率变为1380Hz，谐振频率处的谐波电流含量得到明显抑制，入网电流的波形畸变率仅为1.5％。Figure 4 is the grid current waveform diagram before and after the resonance suppression device is put into use. Figure 5 is the grid current THD when the resonance suppression device is not used. Figure 6 is the grid current THD when the 4th level is put into use. It can be seen that when the resonance suppression device is not used, the inverter system has obvious resonance, the resonance frequency is around 1150Hz, and the waveform distortion rate reaches 20%; after the resonance suppression device is put into the fourth stage of the intermediate stage, the system The resonance of the system has been suppressed to a certain extent, and the resonance frequency has moved to 1280Hz, but the harmonic distortion rate of network access is still greater than 5%, which does not meet the requirements of network access; and after the resonance suppression device is put into level 5, the resonance frequency of the system becomes 1380Hz, and the resonance frequency The harmonic current content at the site is significantly suppressed, and the waveform distortion rate of the incoming current is only 1.5%.

图8是并网点电压变化示意图。图9是换流器无功输出图，无功调节单元的换流器可有效补偿投入电抗器组所消耗感性无功功率，进而克服了电抗器组投入后基波电压产生的不利影响。Fig. 8 is a schematic diagram of the voltage change at the grid-connected point. Figure 9 is a diagram of the reactive power output of the converter. The converter of the reactive power adjustment unit can effectively compensate the inductive reactive power consumed by the input of the reactor group, thereby overcoming the adverse effect of the fundamental voltage after the input of the reactor group.

由仿真结果可知，应用本发明所提的方法，在不影响系统基波电压情况下，可以有效抑制分布式光伏发电系统的谐振。It can be seen from the simulation results that the method proposed in the present invention can effectively suppress the resonance of the distributed photovoltaic power generation system without affecting the fundamental wave voltage of the system.

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.