Research On The Control Strategy Of Combined Power Supply Based On Hybrid Energy Storage

Since the twenty-first century, the world’s energy crisis has become more and more serious, energy saving and emission reduction technology is gradually becoming the main investment direction of the major automobile manufacturers. At present, the hybrid electric vehicle was widely accepted, electric vehicle charging technology is also constantly developing. In order to weaken the impact caused by a large number of fast charging stations, the integrated design of the charging station and the distributed power supply of the electric vehicle can be considered, they provide the energy required for charging together. The output power of wind power and photovoltaic power generation is intermittent and random, and the change of charging load is uncertain. In order to solve the above problems, energy storage devices need to be added in the distributed generation system.In order to ensure the system transient energy balance, energy storage devices need to frequently switch between charged or discharged. Frequent high power charge and discharge and deep discharge will affect the life of the battery. There is a strong complementarity between the performance characteristics of the super capacitor and the battery. If it is used in combination, the performance of the energy storage device can be greatly improved. Multiple power modules are used in parallel to meet the high power demand. It is difficult to guarantee the balance of load current of each module if it is directly connected in parallel. In order to solve this problem, the current sharing technique is adopted in the parallel charging system.Firstly, the overall scheme of the electric vehicle charging station with energy storage system is designed, the key characteristics of the battery and the super capacitor are analyzed, and several common models are analyzed.Contrast several different structure that hybrid energy storage system connect to DC bus, the battery and the super capacitor are respectively connected to DC by bidirectional DC/DC.Secondly, the inductance and capacitance in the circuit are designed separately, according to the different structure when bidirectional DC/DC connected battery or the super capacitor. The small signal model of bidirectional DC/DC converter is obtained by means of the state space averaging method. on the basis of this, the control strategy of bidirectional DC/DC converter is designed. In the Matlab/Simulink software, a simulation model of bidirectional DC/DC converter is established, and the control scheme is verified.Finally, the comparison of several common current sharing technologies is carried out, a mathematical model of the rear stage converter is established. The simulation model for the parallel current sharing plan of the post-amplifier converter is made, simulated and analyzed in Matlab/Simulink.The sharing current’s validity is verified in the parallel operation for the single-phase converter, based on the highest current sharing technique of three-loop control.