统一潮流控制器并联变换器的改进型双环控制系统

分析了统一潮流控制器并联变换器在电力系统中的调节作用以及工作原理，建立了并联变换器的数学模型，提出了一种改进的双环PI解耦控制系统。采用电流前馈与PI调节共同控制变换器有功电流分量，稳定直流侧电容电压。UPFC接入端的节点电压控制采用PI调节和下垂特性组成的自动电压调整控制策略。控制系统在15 kVA的UPFC物理模型中得以实现，这种控制系统有利于加快并联变换器的动态响应，降低直流母线电压的波动，有效地控制UPFC接入端节点电压，仿真及实验结果都证明了控制系统的正确性和有效性。

Improved Double Close-Loop Control System for Shunt Inverter of UPFC

The operation principle and function of Unified Power Flow Controller (UPFC) in power system is analyzed and mathematic model of UPFC shunt inverter is established. This paper proposes an improved double close-loop decoupling control system. Outer loop of UPFC bus voltage control system adopts voltage droop control that consists of PI regulation and scaling factors of droop characteristic. A current feed-forward control is introduced into the decoupling control system of dc-link capacitor voltage regulation. The proposed control scheme is applied on a 15-kVA laboratory-scale UPFC device. Simulation and experimental results show that the proposed double close-loop decoupling control scheme can speed up the dynamic response and depress the swing of dc-link capacitor voltage and stabilize the UPFC bus voltage. They have proved the validity and efficiency of proposed control scheme.