Modeling And Simulation Of An Ultracapacitor-Based Auxiliary Power Source System In Electric Vehicle

Electric energy is used to drive the vehicle in EV (Electric Vehicle), which makes us dispose of dependency of petrified energy. However, the travel mileage is largely limited because of the performance of battery; furthermore, the longevity of battery is also shortened sharply because of frequent acceleration and deceleration, which are common in the urban operating condition, influenced by terrain structure, traffic congestion, etc. Nowadays, balance must be taken between energy ratio and power ratio, power ratio and cycle longevity of the battery, while ultracapacitor, an assistant energy source, marks with long longevity, high efficiency, rapid charge, high power density, and the capability to restore the braking energy. The high energy ratio source and high power ratio source complement each other and are controlled coordinately in EV with an ultracapacitor-based auxiliary energy system, which lessens the need of single source, lengthens the travel mileage, all which benefit the commercial generalization and application of EV.First, battery and ultracapacitor in EV are analyzed respectively. 1. Based on the summary of request of EV to battery, the operating characteristic, such as charge and discharge, volume, temperature, were studied, and the three order battery model was established after the modification of tradition battery models, in addition, the fundamental simulation was verified, and the preferable results was obtained. 2. After generalizing the applications of ultracapacitor in EV, the mechanism and characteristic were analyzed, and the model was established with some relative experiments and mathematic analysis. 3. The structure and characteristic of hybrid power source were studied, and they were combined together with power bus and converter, finally, hybrid power source system model was established.Secondly, considering the characters of EV in urban operating conditions, the target of hybrid power source was put forward. Furthermore, the power distribution of three typical operating conditions is analyzed respectively.Finally, based on analyzing the modeling of subsystems and components in the EV simulation software ADVISOR, a model of EV with an ultracapacitor-based auxiliary energy system was established after modifying the power source model and the control strategy part of the pure EV model Focus in ADVISOR. Moreover, simulation was also validated, and comparison between them was also done. According to result, there are conspicuous improvements in acceleration performance, the efficiency of brake energy utilization, energy consumption, etc.