| ABSTRACT:With the wide application of batteries in the fields of electric vehicles, energy storage, micro network, communication and so on, the demand for large capacity power batteries is increasing year by year. The performance of the formation control system directly affects the technical state, service life of the Li battery, and determines the pollution degree of the power network. The structure of battery formation topology has been continuously developing. This paper analyzes and optimizes the design of the bidirectional DC/DC converter in the cascade formation system with the two level bidirectional DC/DC converters.According to design requirements of the proposed battery formation system, optimized design and analysis were done for coupled inductor Buck/Boost bidirectional DC-DC converter. First of all, operation principle of the coupled inductor Buck/Boost bidirectional DC-DC converter was analyzed, and the parameters of the circuit components was designed and selected. Then, the basic mechanism of the converter is simulated by Matlab, and the main circuit of the converter, sampling circuit, drive circuit and control circuit were designed, builded the experimental prototype.Based on power electronic modeling, we modeled small signal and large signal modeling of proposed converter and the converter considered parasitic parameters. Analysised the different of the converter power characteristics between proposed converter and the converter considered parasitic parameters. Through the analysis design a high ratio bidirectional DC-DC converter with coupled inductor had to consider appropriate range of duty ratio. Secondly, a separate analysis of the effects of different parasitic parameters in specific circuit was made, and knew that we need to choose the components with small parasitic parameters.Aiming at the problem of high switch voltage spike in coupled inductor Buck/Boost bidirectional DC-DC converter, analysised of the causes of spike,considering the actual circuit structure, and at the same time using the couple inductor leakage inductance designed active snubber circuit to achieve converter double direction zero voltage switching to reduce switching stress; and analysised the principle of the circuit with snubber circuit and the rule of switch pulses selected the specific design parameters.At the end, experiment verified the basic indexes of converter and switching converter stress after adding snubber circuit in different switching mode, respectively in Buck and Boost mode. Experimental results show that compared with single switch mode, synchronous rectifier switch mode can achieve the same ratio with smaller duty ratio, has inhibitory effect on switching spikes. Zero voltage active snubber circuit can work in the double direction, compared with passive RCD snubber circuit significantly reduced switching spikes and switch stress. Finally, experiments verify the feasibility of the selected turn ratio and snubber circuit, and the effectiveness of optimized circuit. |
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