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This study presents an active snubber recovery circuit for a dc -dc push-pull converter. Detailed waveform analysis and associated mathematical equations are presented, supported by PSpice simulations and experimentation. More importantly, unlike previous snubbers for the push -pull converter, the presented active recovery circuit remains fully functional over the complete duty cycle range. The proposed snubber technique is practically demonstrated on a 1 kW voltage-fed 48V dc /560V dc step-up push-pull converter. The experiments are conducted with a low-voltage and high-current source, typical of battery, supercapacitor, and photovoltaic source applications.

LVDC distribution networks have the potential to release larger capacity without having to upgrade the existing cables. One of the main challenges of LVDC networks is the extra customer-end DC-AC conversion stage. This paper proposes and evaluates a 5-level Si MOSFET-based MMC as a promising alternative to the conventional 2-level IGBT-based converter. This is due to the comparatively higher efficiency, power quality and reliability, and reduced EM emissions. A comprehensive analysis of a Si MOSFET 5-level MMC converter design is performed to investigate the suitability of the topology for LVDC applications. Detailed theoretical analysis of the 5-level MMC is presented, with simulated and experimental results to demonstrate circuit performance. To suppress the AC circulating current, especially the dominant 2 nd harmonics, this paper presents a double line-frequency PI with orthogonal imaginary axis control method. Comparison of simulation and experimental results with those for double line-frequency PR control shows that the proposed PI controller has better performance. In addition, it is simpler to implement and more immune to sampling/discretisation errors.