Analysis of Power Characteristics in Micro-Source Half-Bridge Converter Series Microgrids Based on VCLPD-SPWM

In half-bridge converter series microgrid (HBCS-MG) systems, output fluctuations caused by varying wind speeds and solar shading induce active power imbalances among generation modules (GMs). This imbalance increases susceptibility to overmodulation distortion and restricts the active power regulation range. To address these challenges, this paper proposes a variable carrier level phase disposition SPWM (VCLPD-SPWM) strategy to enhance the active power regulation depth of GMs at the modulation level. Assuming a stable DC-link voltage for the half-bridge converters (HCs), the power distribution characteristics and switching durations of GMs under PD-SPWM are analytically examined. Subsequently, the carrier level transition points and periods for the maximum regulation range under VCLPD-SPWM are derived, alongside the corresponding power increments and negative power characteristics of each GM. Finally, theoretical calculations, simulations, and experimental results validate the feasibility and effectiveness of the proposed strategy, demonstrating its superiority over carrier phase-shifted modulation strategies.