Study On Intelligent Charging System For Electrical Vehicles

In order to solve the problem of energy crisis and enviromental pollution, the policy of energy saving and emission reduction has been proposed and publicized widely. Electrical vehicles with its low emission and high efficiency enter the horizon, and the research on them has speeded up. However, the question that how to charge the electrical vehicles fast has became their development bottleneck. Therefore the fast charging technology is one of the most important aspect in the study of the electrical vehicles, then our thesis is focus on the fast charging system of electrical vehicles.Firstly, we introduce the usual power batteries, their characteristics and the usual charging methods for these batteries. By comparing these charging methods, we choose the method of combing multi-section constant-current charging with pulse current charging, the chosen method can reduce the polarization phenomenon effectively while charging, beside it corresponds with the discipline that the acceptable maximum current is declining while charging.The charging supply with high performance is the base of fast charging system. By adopting high frequency switching mode, we can make the charger lightweight and downsized. At the same time, by using the ZVZCS technology, we can lower the switching loss and increase the efficiency of the charger. Based on the phase-shifted full-bridge converter, this paper adopts a CDD ZVZCS charging power supply by adding simple auxiliary components, consisted of two diodes and a capacitor in the secondary side of the transformer. This charging supply is composed of three-phase full-bridge rectifier, phase-shifting PWM circuit and the feedback loop of battery energy etc. By analyzing the operation principle, we develop its small signal model, design the circuit parameters and verify its validity by simulating using the PSIM software.In order to realize the intelligent control, we use the fuzzy netural network to predict the charging current at any time, then we use the fuzzy PI controller to adjust the charing current timely. By this way, we can ensure the batteries charged at the optimum rate and realize the fast charge to the batteries.Next, we design the controller based on the TI's DSP2812, including the design of power supply, voltage and current sampling circuit, IGBT drive and protection circuit. Furthermore, we design the software program of the charging system, such as phase-shifting PWM pulses subroutine, fuzzy PI subroutine, fuzzy nettural current predictor subroutine, depolarization subroutine and so on.