基于同步补偿的孤岛微电网无功均分研究

Study on Reactive Power Sharing of Island Microgrid Based on Synchronous Compensation

交流微电网孤岛运行时,由于分布式电源(DG)的等效线路阻抗存在差异,导致传统下垂控制无功均分精度较低,进而产生环流问题。为此,提出了一种基于同步补偿的改进下垂控制策略。当DG运行在无功均分模式时,同步补偿下垂特性曲线的参考电压,可以提高无功功率均分的精度。当有DG输出电压降至限定最小值时,各个DG均切换至电压恢复模式,同步恢复电压至参考电压。同时设计控制策略协调无功均分模式和电压恢复模式,使得系统稳定运行,最终实现DG输出的无功功率均分且输出电压在额定值附近。最后设计Matlab仿真和RTDS实验方案,结果验证了所设计的控制策略的有效性,且对通信带宽要求较低,具有较强的鲁棒性,仍保持了微电网各DG的"即插即用"的特点。

In the islanded AC microgrid, the line impedance between the DG units are always different, which can result in circulating current and low precision of power sharing among inverters by using the traditional droop control method. Therefore, an improved droop control strategy is proposed based on synchronous compensation for reactive power sharing in microgrid. The reference voltage of droop characteristic curve can be compensated synchronously when DG units operate at reactive power sharing mode, meanwhile the accuracy of the sharing of reactive power can also be improved. And then when the output voltage of a DG unit drops to the minimum value, each DG unit switches to the voltage recovery mode, and its voltage will recover to the reference voltage synchronously. The improved coordinated operation strategy is designed for reactive power sharing mode and voltage recovery mode, which can ensure that the accurate sharing of reactive power and the output voltage is near the rated value, and then the system can operate stably. Finally, simulations and experiments are performed in MATLAB and real-time digital simulator (RTDS) respectively to verify the validity of the proposed control strategy. It is proved that the method has low communication bandwidth requirement and strong robustness, and maintains the characteristic of "plug and play" of each DG.