A common-ground switched-capacitor multilevel inverter with extended input range for renewable energy applications

• An enhanced level-shift pulse-width modulation strategy to achieve three synergistic objectives critical for renewable energy power systems: enabling wide input voltage range; precise AC output voltage regulation and reduction in capacitance requirements. • Detailed capacitance analysis demonstrates how the dc-to-ac decoupling capacitance, is repurposed within the proposed inverter to achieve multi-level output generation. • Require the smallest capacitance compared to existing common ground switched capacitor multi-level inverters. • The first single-phase quasi-Z source integrated common ground switched capacitor inverter for renewable energy applications. Multilevel inverters (MLIs) have emerged as a prominent front-end converter solution for renewable energy generation like photovoltaic (PV), fuel cell and wind turbine, owing to their low total harmonic distortion (THD) and high conversion efficiency. However, conventional MLIs face three critical limitations: (1) inability to accommodate wide input voltage fluctuations caused by renewable energy sources, such as the PV panel temperature and irradiance variations, (2) failure to mitigate inherent leakage currents in grounded systems, and (3) requiring very large capacitance. To address these challenges, this paper proposes a novel quasi-Z source (QZS)-integrated switched-capacitor multilevel inverter (SCMLI). By directly connecting the input source ground to the AC load neutral point, the topology inherently suppresses the leakage currents to less than 20 mA. Furthermore, an improved level-shift pulse-width modulation (LS-SPWM) strategy is developed to achieve three synergistic objectives required by renewable energy power systems: precise AC output voltage regulation, dynamic DC capacitor voltage stabilization under wide input variations, and reduction in capacitance requirements to improve the system’s power density through a charge-recycling cell. A 200 W, 5-level laboratory prototype validates the design, achieving a peak efficiency of 95.6 % across a wide input range. This work provides a comprehensive solution to enable MLIs with wider voltage gain regulation, reduced capacitor size and controllable input current ripple for renewable energy systems.