Research On Current-Fed Half-Bridge Based Bi-directional DC-DC Converter For Energy Storage Systems

In the distributed power supply system,the energy from the solar,wind and other new sources are random and uncertain.Therefore,there will be a power fluctuation on DC bus in the distributed power supply system,which will affect the reliability and quality of power supply system.In order to suppress the power fluctuation on the bus,the energy storage devices are usually necessary.The batteries are widely used for energy storage due to their high-energy density,high reliability and low price.To stabilize the voltage in DC bus and improve the system reliability as well as extend the service,the storage batteries are connected to the DC bus through the bi-directional dc-dc interface converters.The converters are used to control the transfer power and direction of energy,and the charge-discharge current.The performance of the bi-directional dc-dc converter affects the reliability and efficiency of the system directly.Therefore,aimed at the interface for energy storage in a distributed system,a highly reliable and efficient bi-directional dc-dc energy-storage converter that is suitable for battery storage is studied.In order to reduce the converter's size and weight,a method to realize the high frequency and the high power density is explored.This paper briefly introduces the topology of bi-directional dc-dc energy storage converter based on current-fed half-bridge,analyzes the working principle of converter,and deduces the energy transfer relation.Working states of the inductor current ripples and magnetic fluxes of the filter inductance on the battery side using different coupling ways are compared,based on which the inductor's coupling mode is chosen,and the influence of coupling coefficient on converter's soft-switching range is analyzed.This paper also proposes a control strategy of the converter.The loss model of the converter is analyzed in detail,and the calculation methods of loss in each parts are given.The coupling coefficient is chosen from the view of optimizing the converter's efficiency,and a 1.5 kW 48V/700 V prototype with 110 kHz switching frequency is designed.The corresponding results of the simulation and experiment verify the correctness of the theoretical analysis and the effectiveness of the control strategy.In order to reduce the volume and the weight of the converter,a 1kW?48V/400V?400 kHz prototype is developed.The corresponding results of the simulation and experiment verify the effectiveness of the high-frequency control method of the converter and the rationality of the hardware design,which provides a reference for further design in high frequency and high power density converter.