A robust two-level coordinated static voltage security region for centrally integrated wind farms

Integration of centralized wind farms may induce cascading tripping incidents, which brings about critical challenges to secure operation of power grid. One of the major risks is the lack of coordinated voltage/reactive power control for multiple wind farms. Therefore, a robust master-slave two-level coordinated static voltage security region (VSR) is proposed in this paper, along with detailed modeling of the network topology and wind farms to achieve coordination among wind farms. The slave VSR on the wind-farm-side is designed to guarantee the operation of each wind unit within a secure range in order to protect wind units from serious over-voltage and low-voltage problems, whereas the master system-wide VSR aims to coordinate centralized wind farms to ensure security both under normal operating conditions and N - 1 contingency conditions. Furthermore, a hierarchically iterative coordination method is introduced to compute the voltage security range of each wind farm through the iteration process. A modified six-bus system with two wind farms, a real system from Northern China, and a large system with 972 wind units are studied, and results verify the effectiveness of the proposed two-level VSR and the hierarchically iterative coordination method.