Research On Charge And Discharge Control System Of Flywheel Battery And Its Optimization

With the development of social economy and rapid expansion of global population,energy shortages and environmental pollution are increasingly serious.As an energy storage device capable of energy efficient use,flywheel energy storage battery(FESB)has characteristics of large energy storage density,high energy conversion efficiency,long service life and environmental protection,and has great engineering application value for the improvement on energy and environmental problems.Energy conversion system is the core component that controls the charge and discharge process of FESB,it can greatly affect battery's performance.This thesis focuses on the study of energy conversion system's charge and discharge process.The main research contents are as follows:(1)The hardware design of FESB's energy conversion system is completed: permanent magnet synchronous motor is selected as the integrated motor in flywheel battery;control circuit scheme of the power electronic conversion device is determined.(2)The method of charge and discharge control of FESB is studied in this thesis.In charge control system,vector control and space vector pulse width modulation(SVPWM)is used to realize fast charge process,speed-current double closed loop control and voltage feedforward compensator is built to improve system's stability and fast response.In discharge control system,variable duty cycle PWM control is used to realize the constant voltage discharge process,voltage-current double closed loop control is built to improve system's stability and anti-interference ability.(3)The working principle and limitations of PID controller is analyzed at first,then the superiority of BP neural network(BPNN)is introduced,and a method to use BPNN to optimize FESB's charge control system is proposed.BP algorithm is improved to overcome the shortage of BPNN using in PID controller,and finally the design of BPNN-PID controller is completed.(4)Simulation model of FESB's energy conversion system is built in MATLAB/Simulink.The results show that FESB's charge process is fast and stable;its output voltage is constant,and the disturbance caused by load change has little effect on output voltage.It proves the energy conversion system designed in this thesis has good charge/discharge performance.Hardware design and optimal control of FESB's energy conversion system is studied in this thesis,which provides valuable reference for intelligent control and performance improvement of FESB.