Analysis and Evaluation of 99% Efficient Step-up/down Converter based on Partial Power Processing

A step-up/and down converter based on partial power processing is proposed in this paper. With the same state equations, the step-up and step-down modes have the same small signal modelling. Therefore, a unified control strategy can be designed for both operating modes, achieving the auto-switching between two operating modes without requiring any additional control. The effect of the transformer's turn ratio on the current and voltage stresses is then analysed. The component stresses are reduced due to the decoupling of transformer. Moreover, the component stress factor method is implemented to evaluate the proposed step-up/down partial power converter. Compared with conventional step-up or step-down partial power converters, the proposed converter has the least component stress factor for a high voltage electrolysis system. In order to validate the proposed topology and modulation strategy, a 400 V prototype is implemented and experimentally evaluated. Measurement results confirm the high efficiency in the overall voltage range, and the maximum efficiency exceeds 99.5%.