Analysis and Implementation of a Hybrid DC Converter with Wide Voltage Variation

Abstract

A new hybrid DC converter is proposed and implemented to have wide voltage variation operation and bidirectional power flow capability for photovoltaic power applications. The hybrid DC converter, including a half- or full-bridge resonant circuit, is adopted to realize the bidirectional power operation and low switching losses. To overcome the wide voltage variation problem (60 V–480 V) from photovoltaic panels due to sunlight intensity, the full-bridge structure or half-bridge structure resonant circuit is used in the presented converter to implement high or low voltage gain under a low or high input voltage condition. Using a pulse frequency modulation (PFM) scheme, the voltage transfer function of the resonant circuit is controlled to regulate the load voltage. Due to the symmetric circuit structures used on the primary and the secondary sides in the proposed converter, the bidirectional power flow can be achieved with the same circuit characteristics. Therefore, the proposed converter can be applied to battery stacks to achieve charger and discharger operations. Finally, a 400 W prototype is implemented, and the performance of the proposed hybrid DC converter is confirmed by the experiments.

Keywords

• hybrid DC converter
• bidirectional power flow
• wide voltage variation
• soft switching