低压微网多逆变电源的综合控制策略设计

Integrated Control Strategy Design for Multi-Inverters in Low Voltage Microgrid

针对微电网通常是接入低压配电网的情况,分析了低压微电网输电线路与传统高压输电线路阻抗比的差异,对低压微网功率传输进行了理论修正.在此基础上采用不同的控制策略对低压微电网进行综合控制,联网模式下为了执行支撑本地电压和调节馈线潮流,微电源采用PQ控制策略;孤岛模式下为确保负荷能各自快速分担负载和电压频率稳定,微电源采用电压频率V/f下垂控制.为保证逆变器输出阻抗与线路阻抗相匹配,在逆变器控制策略中引入阻性虚拟阻抗,根据低压线路参数呈阻性的特点,对传统高压大电网下垂特性进行修正,通过旋转坐标正交变换矩阵,对电压频率V/f下垂控制进行了改进,使得传统的V/f下垂控制得以扩展应用于低压微网中.仿真验证分析,证明了低压微电网系统下设计的综合控制策略能够保证系统与运行的稳定性和可靠性.

This paper analyzed the power coupling problem caused by transmission line impedance of low voltage micro-grid transmission lines, which is different from traditional high-voltage transmission lines. And according to the two typical modes of microgrid, different control strategies were adopted to control the low-voltage microgrid. In grid connected mode, PQ control strategy was used with micro power sources to support the local voltage and adjust the feeder power flow of the low-voltage distribution network. In island mode, voltage/frequency （V/f） droop control was employed with micro power sources to ensure that power load can be quickly shared by each of them and hold the stability of the voltage and frequency. To match the inverter output impedance and the line impedance, resistive virtual impedance was introduced into the inverter control strategy. Based on the resistive characteristics of the low-voltage line parameters, the traditional high-voltage grid droop characteristic was amended, and through a coordinate rotating orthogonal transformation matrix, V/f droop control was improved, extending the traditional V/f droop control to low-voltage micro-grid. The simulation verification and analysis show that the integrated control strategy designed for the low-voltage micro-grid system can guarantee the stability and reliability of the system and its operation.