Simulation Analysis of Switching Overvoltage in 220kV/300MW Flexible Low Frequency Transmission System

Flexible low-frequency transmission, as a new type of transmission method, combines the comprehensive advantages of high-voltage AC and high-voltage DC transmission, and is of great value in the field of offshore wind power transmission. However, there are a large number of power electronic equipment in power systems, and when power system fails, the systems will have operational overvoltage, which brings impact to the equipment on both sides of converter station. Based on this, this thesis introduces offshore wind power flexible low-frequency transmission system architecture, the most important equipment in the system is modular multilevel matrix converter (M3C), and introduces M3C modeling and control strategy of the system. The 220kV/300MW offshore wind power flexible low-frequency transmission system is constructed on PSCAD/EMTDC platform, and the types of faults that can occur in the system are analyzed. Representative voltage monitoring points are selected, and the simulation calculations of switching overvoltage under different faults are carried out, so as to derive the fault condition with the highest level of the operational overvoltage, and the characterization of operational overvoltage is carried out.