The Research Of Bidirectional DC-DC Converter's Control Strategy

With the shortage of fossil energy,the renewable energy like Wind power and solar energy's applications grow rapidly.However,It exists great disadvantages in stability and continuity which limit it's broad usage.In order to get over these disadvantages,the most effective way is to increase the energy storage system,keep the continuity of microgrid's power transmission.Bidirectional DC-DC converter,being as an important part of the energy storage system,It has great usage in new energy vehicle,uninterruptible power supply and new energy generation system,converter could make energy flow in Bidirectional way and the multiple usages,lessen the voltage of equipment and save the cost,have a vivid way of changing the opration mode,this article makes researches in bidirectional DC-DC converter's control strategies in such aspects.To begin with,summing-up development status of DC-DC converter,using halfbridge as mains circuit topology,analysing basic working principles of half-bridge circuit,using state space averaging method to make a small-signal model of the circuit,deducing transfer function of control amount to inductance current and inductor current to output voltage,based on current inner-loop transfer function and external voltage loop's transfer function's amplitude frequency characteristics and phase frequency characteristics,choosing the appropriate type of compensation controller,calculating the compensation circuit parameters,building a simulation model,simulating and verifying the stability of closed-loop system.Then,research on the topic of basic principle of sliding mode variable structure control strategy,combine the topology of the main circuit selected in this paper,we adopt nonsingular terminal sliding mode variable structure control strategy,based on the average state space model of DC-DC converter,deriving sliding mode variable structure control law,based on Lyapunov function judging the existence of generalized sliding mode,building simulation model by using simulation software PLECS,the PWM nonsingular terminal sliding mode variable structure control under two working modes of bidirectional DC-DC converter is simulated and verified.Finally,keeping the simulation of step change of input voltage and step change of output load current,comparing output voltage waveform between nonsingular terminal sliding mode variable structure control strategy and average current control strategy,verifying the superiority of nonsingular terminal sliding mode control strategy under various operating conditions.And combining the bidirectional DC-DC converter with the energy storage system,simulating the mode switching between charge mode and discharge mode.