Research On The Current-fed-voltage-fed Half Bridge Bi-directional Dc-dc Converter

In some specific application fields which allow the power transmission between two DC sources in either direction, such as non-grid-connected wind power generation system, the bi-directional DC-DC converter can be intrduced in order to regulate the DC bus voltage and charge the battery by constant current. Comparing to two separate unidirectional DC-DC converters, the bi-directional DC-DC converter reduces weight and cost of the system.A current-fed-voltage-fed half bridge bi-directional DC-DC converter is studied in this thesis. To realize zero-voltage-switching (ZVS) of all active power devices, the converter has adoped phase-shifted control. The switching devices'voltage spikes problem is solved without any other auxiliary devices due to the capacitors'clamped fuction of half bridge. There are fewer components in this topology than those of others'current-fed isolated bi-directional DC-DC converter.The operation principle of the converter is analyzed in the paper. Based on the equivalent analysis model, the circuit characteristics are discussed. The relationship between the active power and phase-shifted angle and the condition that realizes switching devices ZVS are also induced in detail. By the analysis of current stress and the ratio of the reactive power and active power, it can be concluded that the bi-directional converter is more suitable for application fields that two DC sources have little change. The design of power stage parameters and control strategy are given. In the latter part of paper, the simulation and experimental results, which have verified the theoretical analysis and control strategy, are also presented. The converter realizes the power transmission between two DC sources in either direction.