DC capacitor-less inverter for single-phase power conversion with minimum voltage and current stress

Single-phase power conversion such as pulse width modulation rectifier, grid connected PV inverter system, static synchronous compensator all can be implemented by an H-bridge inverter and a large electrolytic dc capacitor to absorb the ripple power pulsating at twice the line frequency (2ω ripple power). This paper proposed a dc capacitor-less inverter for H-bridge with minimum voltage and current stress. By adding another phase leg to control an ac capacitor, the 2ω ripple power can be absorbed by the capacitor and theoretically 2ω ripples to the dc capacitor can be eliminated completely. The H-bridge and the addition phase leg can be analyzed together as an unbalanced three phase system. By adopting space-vector pulse width modulation control and choosing the optimum ac capacitance and the voltage reference, the voltage and current stress of the switches can be minimized to the same as the conventional H-bridge. The size of capacitor is reduced by ten times compared to the conventional H-bridge system. Simulation and experimental results are shown to prove the effectiveness of the proposed dc capacitor-less inverter and active power decoupling method.