Research On The Battery Charger In Electric Vehicle Based On Digital Controlled Half-Bridge LLC Resonant Converter

With the increasingly serious energy and environmental problems, the electric car has becomemore and more popular. And thus, a car charger with high performance and reliability has primaryimportance. At present, the usual ways of charging are constant voltage charging, constant currentcharging, constant voltage--constant current charge, pulse current charging and so on. And amongthem, constant voltage--constant current charging is the best way to get better battery performancebecause of less possibilities of overcharging or undercharging. As a result, the battery may havelonger operation life. On the other hand, we have a lot of choice of power topology such as Forward,Buck, Boost, SRC, PRC, SPRC and so on. As LLC resonant converter can realize ZVS in the fullrange of load and input voltage, it has obvious advantages over the others. Furthermore, with the rapiddevelopment of power converter control, digital control gradually shows its advertures compared toanalog control. It is more flexible and without too many components, and can realize complicatedcontrol algorithms.In this thesis, it mainly introduces the LLC resonant converter rated at2.2kW output power, andthe digital control method is adopted to realize the close-loop control, sample and the management ofbattery charging. In this thesis, the operation principle and the frequency characteristic of thehalf-bridge LLC resonant converter are firstly introduced, and the design procedures of inductor andcapacitor are discussed. Then, the mathematical modeling on the basis of EDF is derived and verified.Based on the model, the PID compensator is designed, and the influence of digital control is alsotaken into consideration. To prove the stability, the analysis in discrete domain is also necessary. Inaddition, a simulation model and a experimental platform in Saber have been built to evaluate thetheoretical analysis.