Timing Optimization And Control For Energy Equalization Of Lithium Battery Pack

With the large consumption of energy and environmental pollution has becomeincreasingly serious, the development and utilization of new energy sources is imminent.A variety of hybrid electric and pure electric vehicles, photovoltaic and wind powergeneration equipment can be utilized throughout every corner. Lithium-ion batterieswith advantages of specific energy, long cycle life, low self-discharge rate and nomemory effect,it is widely used as an energy storage device, become the current mostpromising battery. However, due to the characteristic properties of each individual cellin lithium-ion batteries series cannot be exactly the same, so there is the damage in theprocess of used because of the battery pack energy imbalance. Therefore, the batterypack needs to balance the energy to ensure consistent characteristic properties andextend battery life. At present, domestic and foreign experts have made a lot of controlstrategies for lithium-ion battery-related issues, including balanced circuit design andthe control algorithms design. However, the current research situation of control systemstill have many problems, such as balanced structural difficult to achieve, poor controlaccuracy, and low balance efficiency. For the current study, paper use a nonlinear PIDcontrol algorithm for non-dissipative equalization circuit, while for non-dissipativeequalization network structure, using dynamic programming, design an energy pathoptimization algorithm to improve the equalization efficiency, reduce the equalizationtime and the energy loss in the equalization process. Thesis’s main work as follows:①Analysis voltage and current of non-dissipative equalization circuit, accordingto the energy transfer pathways and exchange process to establish a mathematical modelof the system, for the control algorithm provides the foundation added.②Study the currently available balance control algorithm,combined with batterypack model, use nonlinear PID control algorithm to control single equalization circuit,to solve the control system control accuracy is not high, and the steady-state voltageshocks and other issues.③Using dynamic programming, paper proposes a lithium-ion battery packequalization system energy path optimization algorithm, optimize control theequalization order and energy flow of the equalization system, so that in the optimalstate, less energy loss and improve the energy efficiency of the whole system running. ④By comparing the simulation effect of fuzzy control algorithm and nonlinearPID algorithm to analyze the merits of algorithms. Build10lithium-ion battery packbalancing control system experimental platform, to verify the actual effectiveness of theproposed control algorithm, and have achieved good experimental results.In conclusion, for the shortcomings of current lithium-ion battery pack equalizationcontrol system, paper proposed a control algorithm avoid the current, voltageoscillations, improving the equilibrium speed, for controlling a single equalizationcircuit; and for network system of the whole equalization structure, use dynamicprogramming, established a lithium-ion battery pack optimal control method. Throughthe equalization path planning, to achieve equalization system optimization control,improve the efficiency and equalization time. Through simulation and experimentalshows that the algorithm can effectively solve the control and optimization issues oflithium-ion battery pack energy equalization system, to meet the applicationrequirements of the system.