Unified Modeling and Control Methods for Ripple Power Decoupling Circuit Based on DC-Split Capacitor

Single-phase inverter systems inherently exhibit second-harmonic ripple power, which must be suppressed to minimize its adverse effects on the system. One effective technique for ripple power decoupling involves injecting complementary ripple voltages into dc split capacitors. By exploiting the energy differential between the split capacitors, ripple power is effectively compensated, whereas the complementary capacitor voltages maintain a stable dc bus voltage. This article presents a unified model that elucidates the internal physical mechanisms underlying power decoupling methods based on dc split capacitors. From this model, four distinct methods are derived, revealing the necessity of bidirectional power flow and explaining why certain previous methods have only achieved partial ripple power decoupling. Furthermore, the methods are compared comprehensively, taking into account capacitance requirements, semiconductor stress, and system volume to determine the optimal design. Finally, the unified model is validated using a 400-W IPOS CLLLC-fed voltage source inverter prototype. Experimental results demonstrate that all methods significantly suppress ripple power with reduced capacitance, with the differential capacitance approach, featuring an unbalanced dc operating point design, delivering the best overall performance.