A Novel Power Decoupling Control Method to Eliminate the Double Line Frequency Ripple of Two Stage Single-Phase DC-AC Power Conversion Systems

In two-stage single-phase inverters, inherent double line frequency ripple is present at both the input and output of the front-end converter. Generally, large electrolytic capacitors are used to eliminate this double line frequency ripple. It is well known that low frequency ripple shortens the lifespan of capacitors. Hence, the system reliability can get worse. In order to eliminate the double line frequency ripple, additional hardware combined with an energy storage device is required in most of the methods developed so far. In this paper, a novel power-decoupling control method is proposed to eliminate the double line frequency ripple at the front-end converter of two-stage single phase DC/AC power conversion systems. The proposed control algorithm is composed of two loops, a ripple compensation loop and an average voltage control loop, and no extra hardware is required. Since the proposed method does not require information from the phase-locked-loop (PLL) of the inverter, it is independent of inverter control. In order to verify the validity and feasibility of the proposed algorithm a 5 kW Dual Active Bridge (DAB) DC/DC converter and a single-phase inverter are implemented. The effectiveness of the proposed method is verified through the simulation and experimental results.