| In recent years, the hybrid energy storage technology is being applied in electric vehicle and renewable energy generation system, and gradually showing big advantages than traditional single energy storage technology. Hybrid energy storage system has multi-input and multi-output, and it based on the multi-port bidirectional DC/DC converters, the conventional two-port bidirectional DC/DC converters are the foundation of the multi-port bidirectional DC/DC system. The multi-port bidirectional DC/DC converter can be achieved by resembling and refactoring of the two-port bidirectional DC/DC converters, the control strategies of two-port bidirectional DC/DC converters also can be promoted to multi-port bidirectional DC/DC converters. This article study on the control strategies of two commonly used bidirectional DC/DC converter, and also doing some research on the high frequency magnetic coupled multi-port bidirectional DC/DC converter for it has compact structure, components reuse and many other advantages which is suitable for hybrid energy storage system and has great research value.When traditional phase shift control method implemented on the bidirectional DC/DC converters in the situation that the port voltage mismatching will face such problems:the soft switching area decreasing, the circulating power and the loss increasing. To overcome such problems, a novel hybrid modulation of PWM and phase shift control method is proposed based on dual active bridge converter, which obtain better work performance than traditional control method by calculating the optimal phase shift angle and duty cycle of the control pulse. By using this novel control method, the circulating power can be decreased, the soft switching area is widened and the operation characteristics when converter has a light load also being improved. The work principle is elaborated and the mathematic model is built, based on the mathematic model, comparative analysis are made with the traditional phase shift control method, the simulation model and experiment platform are construct to verify its validity and feasibility.Based on the boost half bridge-H bridge bidirectional DC/DC converter and pre-existing control method, a novel PWM plus dual phase shift control method is proposed. By adjusting duty cycle and calculating the inner phase shift angle of the control pulse to eliminate circulating power totally and improve operation characteristics of the converter. The work principle is introduced and commutation process of different operation modal is analyzed. The control strategy based on proposed control method is designed for the energy storage system of micro-grid which port voltage is changeable, and the simulation model is built to verify the validity of proposed method.Magnetic coupled multi-port bidirectional DC/DC is a new multi-port structure, which has terrific research value when it used in hybrid energy storage system. This article doing research on magnetic coupled H bridge-double half bridge three-port bidirectional DC/DC converter which applied in storage battery-ultra capacitor hybrid energy storage system. Based on the simplified model of the converter, the work principle and steady state operation characters are analyzed, the state space model and power model are built as well. Current decoupled control strategy is designed to overcome the problems of non-linear and the coupling between multi-control variables and multi-outputs of the H bridge-double half bridge three-port converter. Simulation model is built based on the control strategy, and comparative analysis are made with the strategy which without current decoupled control.The software and hardware of the experiment platform are designed in the article. A low power experiment platform is constructed according to the designed parameters, and digital control system of the dual active bridge converter is also designed. Based on this experiment platform, the close loop experiment of traditional phase shift control is accomplished, the proposed novel hybrid modulation of PWM and phase shift control method and the theoretical analysis are also verified on this platform, which provide the technical basis of the bidirectional DC/DC converter which applied in hybrid energy storage system in the further study. |
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