| Traditional automobiles are facing with the problems of oil exhaustion and environmental pollution, as a effective way to solve these problems, electric vehicles have got great development all over the world. Battery system is a key technology of electric vehicle. The existing battery has the drawback of low specific power and great influence on battery service life during large capacity discharge, because of which, the dynamic property, driving range and cycle life will be affected seriously. Based on high specific power, fine low-temperature characteristics and lang cycle life of super-capacitor, this research uses lithium ion battery as the main power source witeh super-capacitor assisted, the two sources combine to a hybrid power source system by a power converter. This system can make fully use peak load shifting of super-capacitor to improve dynamic property, driving range and reduce cost.First, this paper studyed and analyzed the Working principle and basic characteristics of lithium ion battery, super-capacitor and bidirectional DC/DC transducer (three key unit of hybrid power source system) by experiment. With the help of the characteristics above, the structure design and matching parameters scheme of lithium ion battery, super-capacitor and bidirectional DC/DC transducer were determined. Base on a car of a Guangzhou Automobile Group, simulation models of lithium ion battery, super-capacitor and bidirectional DC/DC transducer were built.Second, based on the study above, this paper designed a fuzzy-logical control strategy of the hybrid power source system. Power distribution and control procedure were wrote in MATLAB to simulate the system. The result showed that the hybrid power source system could protect lithium ion battery from impact and destroy of high current and reduce its Charge and discharge current, which could increase the service life of lithium ion battery. In attition, the system could make fully use of the advantange of high charge discharge efficiency of the super-capacitor to recycle braking energy effectively, which increased the economy and driving range.In the end, based on the existing equipments, a 48V modularized experiment table of the hybrid power source system were built. The results of matching parameters and Control Strategy were verifyed. Compared the results with the single power model, it showd that the discharge current and brake energy recycle current reduced obviously, which verifyed the feasibility of matching parameters and control system of the hybrid power source system. The research increased the service life and driving range, reduced the cost of the car, and provided the theoretical basis and experimental verification for the application on electric vehicles. |
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