Design Of Li-battery Charging Equalization And Management System

In order to solve Energy crisis and environmental pollution, many countriesincrease research investment, promoting the rapid development of electric vehicles,lithium battery is the first selection with excellent function for electric vehicles, but ahigher demand for lithium battery management system. In order to obtain high voltageand power, a large number of cells should string and parallel in connections. Due to thelimitations of the production process, the cell used in series, the initial capacity, internalresistance, voltage and other inconsistencies, causing reduced available capacity of thebattery pack, utilization fell, severe will shorten the service life of the battery pack evenproduce safety incident and serious impediment to the popularity of electric vehicles, itis the impediment for the development of electric vehicles. The lithium battery packequalizing charge and management system optimized design is conducive to promotingthe development of electric vehicles. In response to these problems, the paper mainlyhas done the following work:For its output unstable and charging efficiency, the design based on the Buckcircuit constant current constant voltage charging power; Based on the analysis oflithium batteries commonly used in connection, concluded that the first string afterparallel and first parallel after string of two connections normal conducting probabilisticmathematical model, provides a theoretical basis for the reliability of the analysis ofdifferent connection.For the equalization circuit low efficiency and high cost problems, the analysis ofthe existing several typical equalization scheme, focus on multi-winding transformercircuit that was proposed based on improved equalization circuit, the circuit has a smallsize, simple structure, low cost characteristics and has given mathematical model andsimulation to verify the feasibility of the improved circuit improved circuit; improvedbalance control decision algorithm based on statistical laws.In accordance with domestic and international state of charge (SOC state of charge)Research, analyze a variety of commonly used the SOC estimate the program for its lowestimation accuracy and difficult problem, based lithium battery Thevenin model,combined with the extended Kalman (EKF) filtering is the principle of theestablishment of a lithium battery SOC estimation algorithm, simulation analysis toverify EKF filtering algorithm can achieve estimated power lithium battery pack, can solve problems An initial value of integration method and the open-circuit voltage themethod open circuit voltage is difficult determination the difficult to achieveBased on the above-mentioned study, the completion of the lithium batterymanagement system hardware and software design, focus on the design of the FPGAcontrol circuit, the design of the detection circuit and equalized.