Joint Frequency Control Strategy for Fractional Frequency Offshore Wind Power System with Modular Multilevel Matrix Converter

In a Modular Multilevel Matrix Converter (M3C) based fractional frequency offshore wind power system, the primary equipment with strong frequency support capabilities are the wind turbines and the M3C. To fully leverage the system’s frequency regulation capabilities, this paper proposes a coordinated frequency support strategy integrating the offshore wind farm and the M3C. By coordinating the wind farm with the M3C, the system’s inertial support capability is effectively enhanced, thereby preventing secondary frequency drops. Through rationally releasing energy from storage devices, the approach compensates for energy deficits caused by DC capacitor voltage recovery in the M3C. This mechanism accelerates the restoration speed of both wind turbine rotor speeds and DC capacitor voltages of M3C, ultimately enabling the system frequency to reach a stable value more rapidly.