Requirements for circuit components of single-phase inverter applied with power decoupling capability toward high power density

This paper discusses how to achieve high power density with high efficiency for a single-phase inverter with an active power decoupling circuit. In conventional PV inverters, bulky electrolytic capacitors are connected to DC-link in order to absorb power pulsation with twice the grid frequency. On the other hand, in the active power decoupling circuit, the small capacitor can be used. However, the additional inductors and switching devices are necessary. Thus, the power density of the active power decoupling circuit is reduced. In this paper, the Pareto optimization of power density and efficiency is used to clarify the maximum power density points of the power decoupling circuits. As a result, the maximum power density of the conventional boost type active buffer, which connects a boost chopper to DC-link, is 90% of that of electrolytic capacitor topology. In addition, this paper proposes a DC-DC converter with the power decoupling capability in order to achieve higher power density than that of the passive topology. The proposed circuit, which requires no additional inductor for the power decoupling circuit, uses discontinuous current mode (DCM) for the power decoupling capability. As a result, the maximum power density is obtained to 1.1 times higher than that of passive topology. However, the total loss of switching devices is 1.5 times higher. Thus, in order to surpass the efficiency of the passive topology by the active power decoupling, the switching device is required to reduce the total loss by 35% compared to the present products.