Research On Super Capacitor Charge And Discharge Control System For Micro-grid

As a small distribution network with various of distributed generation(DG)for local load,micro-grid give full play to the advantages of distributed power supply and can further improve the stability and continuity of power supply.It brings a wide range of benefits for the power users.However,there are intermittent and fluctuating characteristics of the DG output power in the micro-grid,which has a great influence on the power quality of the micro-grid.The energy storage system can be used as a kind of energy buffer link in the micro-grid which can effectively improve the quality of micro-grid power supply.In this paper,the super capacitor charge and discharge control system as the research object,its working principle,control strategy,the parameters of the closed-loop controller and the selection principle of the parameters of key devices are be in-depth researched.Firstly,the reason and characteristics of power fluctuation of microgrid are analyzed,and the overall scheme of super capacitor charge and discharge control system based on three-phase voltage source rectifier(VSR)and bidirectional DC-DCconverter is given.The small signal mathematical models of three-phase VSR and bidirectional DC-DCconverter in the two-stage power converter are established respectively.The micro-grid voltage vector feedforward decoupleing control strategy based on synchronous rotational coordinate system and phase-locked loop(PLL)technology of three-phase VSR and the double closed-loop controll strategy of the bidirectional DC-DC converter working in buck mode and boost mode are analyzed apart.The design principle of each closed-loop controller parameters is given,and the stability of the designed control system is analyzed.The coordinated control scheme of three-phase VSR and bidirectional DC-DC converter is given to achieve the overall control of the system.Secondly,according to the relevant indexes of the charge and discharge control system of super capacitor,the parameters of the key components of the system are designed to meet the requirements of the DC side ripple limitation,the harmonic current of the AC side and the dynamic response performance of the system.On the basis of the previous text,the simulation model of super capacitor charge and discharge system is established on MATLAB/Simulink simulation software.And the simulation results obtained are analyzed.The correctness of the super capacitor charge and discharge control system and its control strategy is verified.Finally,the hardware and software of the super capacitor charge and discharge control system based on DSP are designed in detail.The experimental platform is set up and the charge and discharge control system designed is verified by experiments.The experimental results show that the system designed in this paper and its control strategy is correct and feasible.