Robust Voltage Control Strategy for Hybrid AC/DC Sending-side Systems to Prevent Cascading Trip Failures

Line-commutated-converter-based high-voltage direct current (LCC-HVDC) is an important and attractive method of transmitting large-scale integrated wind power. However, the contingencies induced by LCC-HVDCs and nearby areas usually lead to an overvoltage problem in hybrid AC/DC sending-side systems, which may result in severe cascading trip problems. Therefore, a robust voltage control strategy for hybrid AC/DC sending-side systems is proposed in this paper to prevent cascading trip failures and accommodate more wind power. The proposed strategies address the voltage control complexity of LCC-HVDCs and converter stations, appropriately formulate the different locally fast-response switching strategies of filter banks and different control modes of the LCC-HVDCs in the automatic voltage control system. To compute the formulated problem efficiently and quickly for online application, a method of transforming the robust optimization problem and the Benders decomposition method are introduced. Based on case studies, the computational efficiency and accuracy of the proposed method are determined using operational data for the TianShan District in the Northwest China Power Grid.