An Improved Master-Slave Control Strategy for Automatic DC Voltage Control Under the Master Station Failure in MTDC System

The master-slave (MS) control is often used in multi-terminal direct current (MTDC) system due to its stable dc voltage control and precise power regulation. However, the MS switching, which aims to maintain dc voltage control under the master station failure, relies heavily on the high-speed communication between the power dispatch center and each station. Some methods in existing works are proposed to address the high communication dependence, at the cost of steady-state control performance. In this article, an improved MS control including five-state control process is proposed to realize the automatic MS switching without communication participation. Based on logic judgment, the multilayer dc voltage clamping mechanism is created to enhance the redundancy of the dc voltage control, and a reasonable dc voltage recovery process is included to eliminate the dc voltage deviation caused by the master station failure. Furthermore, the power and dc voltage hybrid controller are developed to improve the dynamic performance of each station during the MS switching. Simulation and experimental results demonstrate the effectiveness and advantages of proposed method.