This disclosure generally investigates and evaluates a high density, high efficiency and long lifetime power converter which interfaces the single phase AC voltage to an energy storage device. This converter could be either unidirectional or bidirectional. In this power converter, the charging or discharging current of the energy storage device is controlled to contain a certain amount of double-line-frequency ripple which is synchronized to the AC voltage. In this way, the DC link capacitance can be reduced and high power density can be achieved. Furthermore, reduction of DC link capacitance also enables using long-lifetime capacitors. However, those charging waveforms may lead to higher converter loss. This disclosure therefore evaluates different current waveforms in terms of DC link capacitance requirement and power conversion efficiency, and reveals the optimal waveform, compared to traditional DC charging, can reduce the DC link capacitance by more than 62% while maintaining similar efficiency.