A Novel Soft-Switching Bi-Directional DC/DC Converter

With the development of high power density, high efficiency and high frequency of the switching power supply, the bi-directional DC/DC converter has been widely used in the fields of battery energy storage systems, electric vehicle power supplies, DC uninterruptible power systems, aerospace power systems and so on.Because of the environment protection and the lack of the energy sources, the bi-directional DC/DC converter will be promoted to be applied in the applications such as the independent solar energy photovoltaic system, wind energy generation system, hybrid energy electric vehicles, mobile generation system. A high efficiency and high reliability storage energy system is needed in these applications. The storage energy system usually is a battery device, so it needs a bi-directional DC /DC converter to control the flowing of the energy. In these applications, the voltage level between the high voltage side and the low voltage side is greatly different, so it is no longer fit to use the existing bi-directional DC /DC converter.On the basis of researching the new topologies and the new control strategies of bi-directional DC /DC converter, this paper proposes a novel soft-switching bi-directional DC/DC converter by combining the cascade converter with the Push-pull/full-bridge converter. It uses phase-shifted full-bridge ZVZCS-PWM DC/DC converter when in buck mode. In boost mode, the Push-pull isolated Boost converter is used, which is cascaded by a boost converter and a push-pull converter, and is eliminated the redundancy components by a control strategy, a novel two-stage boost circuit topology is formed. Pointing to the step-up conversion, a novel method to achieve soft-switching by using a flyback coupled inductor is proposed, and the method has wide adaptability. The proposed converter is very capable of the application of bi-directional energy flowing when the voltage level between the high voltage side and the low voltage side is greatly different.This paper analyzes the operation principle of the proposed bi-directional DC/DC converter in detail and designs the control circuit. The paper researches the reasons of magnetic bias of the proposed converter and the special methods to eliminate the magnetic bias. Meanwhile, the paper does elementary study on the EMC of the converter, preparing for it is applying in the high power application. At the end, a prototype is designed, and the experiment results are in accord with the theoretical analysis.