Fuzzy Optimization for Improving Transient Synchronization Stability of VSCs in Series-Compensated System

Renewable power plants require voltage source converters (VSCs) to convert power for further utilization. The converted power needs to be transmitted to load centers that are far from the power plants. Series compensation is widely used in transmission lines to regulate system voltage and realize large amounts of power transmission. However, it has been pointed out that VSCs tend to lose transient synchronization stability when large series compensation is implemented. Although various methods have been proposed to solve the transient instability, most of them require extensive mathematical computations and have insufficient robustness, which makes them difficult for practical applications. This article proposes a hybrid fuzzy optimization controller to improve the transient synchronization stability of series-compensated system. The proposed control strategy does not rely on specific system parameters and has good robustness and adaptability. First, the synchronization instability caused by series compensation is analyzed based on the Lyapunov direct method. Then, a hybrid fuzzy controller is investigated by combining a traditional proportional-integral (PI) controller with a fuzzy PI controller. The fuzzy C-means clustering (FCM) method is proposed to help design the membership function. Finally, simulation and experiment are performed to verify the effectiveness of the proposed method.