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AC/DC power electronic transformer is the core of the energy conversion device as a micro grid having a multi-port, high-capacity, high efficiency functions. Bipolar failure is one of the typical failures, causing the system does not work. This article aims to analyze the post bipolar DC microgrid faults in the AC/DC power electronic transformer is proposed to suppress over-voltage topology, analyzes the effects of lightning on the drive characteristics of a fault, and consider the safety of the system in order to run, reliability and economy, designed arrester parameters for the arrester between the valve outlet and the neutral point commutation. The energy simulation calculation of the arrester was carried out, and the effectiveness of the selection and configuration method of the arrester was verified by building a simulation platform that does not affect the normal operation. Suppressing the sub-module voltage can provide a reference for the selection of main equipment and insulation coordination.

Flexible DC transmission lines have been used in some parts of the northern China electric power system. Due to unstable centralized penetration of renewable generators, pumped storage power stations have also been established to enhance the flexibility of the power system. This paper proposes a dispatch method for AC/DC hybrid power systems with flexible DC transmission lines and pumped storage power stations. In the proposed dispatch model, the objective contains transmission cost, generation cost, and penalty cost. Constraints of flexible DC transmission lines, pumped storage power stations, as well as regular generator and system-wide dispatch constraints are considered. Case studies demonstrate that the proposed model can handle unstable power outputs of renewable generators by pumped storage power stations, eliminate renewable generator variations, and regularize the transmission power to load center.