Research Of Li-ion Charge And Discharge System

Battery is widely applicant in every part of national economy as storage equipment. The EV bus develops rapidly nowadays, and battery is the only source of pure EV bus. The battery needs charge and discharge absolutely to enhance its performances, and tests its real capability at the same time. The charge and discharge technology is born with battery and has close relationship with it. The performance of charge and discharge system affects the technology and life-span of battery directly. It also decides the degree of pollution to the grid.Silicon-controlled rectifiers (SCR) are widely used in battery charge and discharge system at the present time. As we all know, SCR system has low power factor in grid side and causes severe harmonic pollution. However, eliminating harmonic pollution and improving power factor are a very important research task in the field of power electronics. A new solution of battery charge and discharge system base on Voltage-source PWM Rectifier (VSR) and bi-directional DC/DC converter is presented in this dissertation. The system implements bidirectional power flow, sinusoidal current control and unit power factor control in grid side as well. And it saves much energy and cause less pollution.This dissertation designs main circuit and builds up the model in MATLAB/Simulink. A full solution of hardware and software design of bi-directional DC/DC converter control system and controller base on MC9S12D64 is presented in detail in this dissertation. The charge strategy adopts combination of constant current and constant voltage. The controller communicates with battery management system (BMS) to acquire the information of each battery. And then use it as control and protect variable. The result of experiment shows that efficiency is higher than 80%, power factor is higher than 99% and THD is low than 5% in the full load. It satisfies the design requirements and it validates the feasibility of the topology.