| The bi-directional DC-DC converter has been widely used in aircraft power system, uninterrupted power supply and Hybrid Power Automobile in recent years. Bi-directional DC-DC converter is developed towards the direction of smaller volume, higher efficiency and higher power density. With the continuous improvement of the switch frequency, a larger switching loss of the power device appears, which makes much attention be paid for the soft switching of the device. In this paper, symmetric half bridge is studied, which doesn’t need any auxiliary devices to obtain the zero voltage switch of the switches with the control method of phase shift. This topology is applied to battery formation. The former stage is connected with a three-phase PWM converter, while the low voltage side with Buck-Boost bi-directional DC-DC converter to charge or discharge the battery. From the viewpoint of the actual requirement, the analysis and comparison of the bidirectional DC-DC converter topologies are performed and then the symmetric half bridge is selected as the research object. The operating principle of this bidirectional converter is described in this paper on detail and the relevant working characteristics of this converter are investigated. Also, the simulation results are given to check the validity of the analysis method. The control strategy of the symmetric half bridge bi-directional DC-DC converter is proposed and the main circuit parameters and control circuit are designed. Then, the experiments are made by a model machine. The simulated results are compared with the experimental results and a better agreement appears between them, which shows that the converter can work stably in both directions, and verify the rationality of system parameter selection and the feasibility of the design scheme. |
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