Simulation Research on Offshore Flexible Low Frequency Transmission M3C Converter Station

Inhalt:
In an offshore flexible low-frequency power transmission system based on a modular multilevel matrix converter (M3C), ensuring that the module capacitor voltage follows a given value is a prerequisite for the stable operation of the system. In order to study the capacitor voltage control strategy, this paper first established the M3C mathematical model based on double alphabeta transformation, and designed the input and output dq transformation vector controllers and circulating current controllers, and then analyzed the power of the M3C bridge arm. For the frequency characteristics of the bridge arm power, the notch filter is used to separate the AC uncontrollable quantity and the DC controllable quantity, so as to obtain the expected value of the circulating current to control the circulating current. Finally, a model of the M3C converter station based on the nearest level approximation modulation is built for simulation verification. The simulation results verify the frequency characteristics of the bridge arm power, and the proposed control strategy controls the capacitor voltage within ±10% of the average value.