Generalized active power decoupling method for H-bridge with minimum voltage and current stress

Single-phase PWM rectifier, grid connected PV inverter system, static synchronous compensator (STATCOM) 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 generalized active power decoupling method 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 SVPWM control and choosing the optimum ac capacitance and the capacitor 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 10 times compared to the conventional H-bridge system. Simulation and experimental results are shown to prove the effectiveness of the proposed active power decoupling method.