Optimization Of A Dual Active Half Bridge Bidirectional DC-DC Converter Based On Minimum RMS Current

Due to the growing energy crisis and environmental pollution problems,the proportion of electricity generated from renewable energy sources is gradually increasing,while conventional renewable energy sources suffer from intermittency and randomness,resulting in low power quality.In order to improve the power quality,DC-DC converters are introduced in modern power systems in order to convert low quality power into high quality power.Dual active half-bridge bidirectional DC-DC converters are widely used in low and medium power levels as a key device for power conversion with the advantages of symmetrical topology,easy implementation of ZVS,and low cost.In this paper,we take the dual active half-bridge bidirectional DC-DC converter as the research object and propose a modulation strategy based on the minimum root-mean-square current to improve the transmission efficiency of the dual active half-bridge bidirectional DC-DC converter.This paper first analyzes the basic model of the dual active half-bridge bidirectional DC-DC converter,mainly including 1.Analyzing the topology of the dual active halfbridge bidirectional DC-DC converter;2.Proposing a modeling method based on the average model;3.Analyzing the losses of the dual active half-bridge bidirectional DCDC converter;4.Analyzing the Extended-Phase-Shift(EPS)strategy under the basic operating principle and operating characteristics of the dual active half-bridge bidirectional DC-DC converter are obtained by analyzing the switching modes of all switching tubes under the Extended-Phase-Shift strategy.On this basis,the average model of the dual active half-bridge bidirectional DC-DC converter under the extended phaseshift strategy is constructed,and the corresponding power transfer expression and the root mean square value of the inductor current expression are derived.Then,the conditions for zero-voltage switching(ZVS)of the dual active half-bridge bidirectional DC-DC converter are analyzed,and the corresponding constraints for inductor currents are obtained.Then,using the RMS of the inductor current as the objective function and the switch tubes achieving ZVS as the constraint,the optimal path under the extended phase shift strategy is obtained by numerical optimization.Finally,by comparing with several other modulation strategies,the Hybrid-Phase-Shift(HPS)strategy based on the minimum root-mean-square current is proposed,which minimizes the root-mean-square value of inductor current under the condition of ZVS achieved by the switching tube in the full load range,thus minimizing the conduction loss and greatly improving the transmission efficiency of the converter.Finally,a corresponding experimental platform is built for multi-angle verification,and the final results of the experiments verify the feasibility of the proposed strategy.