Analysis of Islanding Permanent Magnetic Synchronous Generator Transient Voltage Characteristics with Low Frequency Transmission Power System

Low frequency AC power transmission has obvious advantages and application prospects for medium and long distance power transmission due to its high efficiency and dc flexibility. When the inverter is blocked due to the failure of the 50Hz power grid or the internal fault of the AC converter, the wind turbine side in the isolated island will have ac transient overvoltage problem, which will harm the safety of the equipment in the low-frequency network. In this paper, Permanent Magnetic Synchronous Generator (PMSG) is taken as the research object. The low-frequency transmission system based on Modular Multilevel M3C (Modular Multilevel Matrix Coverter) is designed to analyze the voltage characteristics of grid-connected ports. Through the research and analysis of the PMSG’s converter control strategy when PMSG is in the isolated after M3C blocking, the result shown that the main factor of the overvoltage problem in the isolated state of the PMSG is the transient blocking of active power, The power imbalance affects the effective modulation of the converter and the transient response of the output voltage on the PMSG’s network side. In this paper, the combined suppression method of island overvoltage with AC energy dissipation and DC unloading is proposed, PSCAD/EMTDC is used to build a low frequency system model with PMSG, and the results are analyzed and verified.