Power decoupling method comparison of isolated single-phase matrix converters using center-tapped transformer with PDM

Abstract

This paper presents an isolated type of single-phase matrix converter topology for PHV/EV on-board battery chargers. The proposed converter is comprised of a full bridge inverter, a high frequency transformer and a matrix converter. Due to the lack of DC link bus in matrix converter, in order to suppress the power fluctuation, a power decoupling method which only employs a center-tapped high frequency transformer and a small LC buffer where requires no additional switches is applied. On the other hand, the matrix converter applies PDM (Pulse Density Modulation) which achieve ZVS (zero voltage switching) in order to generate a 50Hz/60Hz sinusoidal waveform at the grid side. As a result, this converter shows promising features small size and high efficiency. In this paper, by harmonic analysis, the effectiveness of power decoupling method is evaluated in two cases: the PDM based on the PWM as a conventional method and the PDM based on the delta-sigma conversion. In the experimental results, the power decoupling method with the PDM based on the delta-sigma conversion reduces the DC bus current ripple by 84.8% comparing to the case where the power decoupling method is not applied, while the output voltage distortion is reduced by 64.1% compared with that of the PDM based on the PWM is applied.