Asymmetric Carrier Hybrid Frequency Modulation Strategy for Inertia Flywheel ANPC Converter

With the increasing penetration of renewable energy, modern power systems exhibit low-inertia characteristics, and flywheel energy storage systems have attracted significant attention due to their capability to provide inertia support. To address the issues of high harmonic distortion and power losses in converters operating under wide frequency ranges and high-power conditions in flywheel systems, this paper proposes an asymmetric carrier hybrid-frequency modulation strategy based on a three-phase four-wire SiC-ANPC topology. By optimizing commutation paths and switching frequency distribution, the proposed method increases the equivalent output voltage frequency while reducing the switching frequency of power devices, thereby shifting harmonics to higher frequency ranges and improving loss distribution as well as thermal balance among devices. Simulation results demonstrate that the proposed strategy maintains high-quality voltage and current waveforms under sudden load variations, exhibiting strong dynamic response capability.