Research on SHEPWM Control Strategy for Replacing the DC Source in the Cascaded H‐Bridge With Capacitors

Traditional 1:1:1 cascaded H‐bridge inverters suffer from low DC‐side voltage utilization and a high rate of DC‐side failures. After replacing part of the DC‐side voltage source with floating capacitors to construct a dual‐capacitor‐cell single DC‐source inverter, traditional modulation strategies become inapplicable. Therefore, a novel modulation strategy is proposed. This strategy is based on a wide‐modulation‐depth SHEPWM, establishing four modulation modes. By sampling capacitor voltage and output current to control capacitor charging and discharging, the inverter alternates between these four modes to realize capacitor voltage regulation. Moreover, an analysis of capacitor charging and discharging conditions calculates the minimum DC capacitor value required to meet capacitor voltage ripple parameters. Simulations and experiments validate the feasibility of this strategy.