Browsing by Author "Cheng, Jiawei"
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Item Open Access Analytical and experimental evaluation of SiC-inverter nonlinearites for traction drives used in electric vehicles(IEEE, 2017-10-23) Ding, Xiaofeng; Du, Min; Duan, Chongwei; Guo, Hong; Xiong, Rui; Xu, Jinquan; Cheng, Jiawei; Luk, Patrick Chi-KwongThis paper investigates the inverter nonlinearities in a drive system based on silicon carbide metal-oxide-semiconductor field-effect transistor (SiC-mosfets) and compares its performance with that of an equivalent silicon insulated-gate bipolar transistor (Si-IGBT) system. Initially, a novel comprehensive analytical model of the inverter voltage distortion is developed. Not only voltage drops, dead time, and output capacitance, but also switching delay times and voltage overshoot of the power devices are taken into account in the model. Such a model yields a more accurate prediction of the inverter's output voltage distortion, and is validated by experimentation. Due to inherent shortcomings of the commonly used double pulse test, the switching characteristics of both SiC-mosfets and Si-IGBTs in the pulse width modulation inverter are tested instead, such that the actual performances of the SiC and Si devices in the motor drive system are examined. Then, the switching performance is incorporated into the physical model to quantify the distorted voltages of both the SiC-based and Si-based systems. The results show that, despite its existing nonlinearities, the SiC-based drive has lower voltage distortion compared to the conventional Si-based drive as a result of its shorter switching times and smaller voltage drop, as well as a higher efficiency. Finally, the overriding operational advantages of the SiC-based drive over its Si-based counterpart is fully demonstrated by comprehensive performance comparisons.Item Open Access An improved Thevenin model of lithium-ion battery with high accuracy for electric vehicles(Elsevier, 2019-08-07) Ding, Xiaofeng; Zhang, Donghuai; Cheng, Jiawei; Wang, Binbin; Luk, Patrick Chi-KwongThis paper proposes an improved Thevenin model of the Lithium-ion battery taking into account temperature influence on the calculation accuracy of the open circuit voltage of a battery. The calculation accuracy of the terminal voltage of a battery is improved without increasing the order of the model. Firstly, the model was proposed based on Thevenin model and the relationship between the open-circuit voltage and the state of charge. Then, based on the experimental results of the open-circuit voltage test and hybrid power pulse characteristic test, the parameters of the battery model were identified by polynomial fitting and genetic algorithm, respectively. Furthermore, the temperature effects were considered in both the open-circuit voltage and hybrid power pulse characteristic tests. Finally, the proposed model was tested and verified by experiments under the Dynamic Stress Test condition and the Urban Dynamometer Driving Schedule at different temperatures. The accuracy of the proposed model is high and the parameter identification error is less than 1%.Item Open Access A novel active equalization topology for series-connected lithium-ion battery packs(IEEE, 2020-08-11) Ding, Xiaofeng; Zhang, Donghuai; Cheng, Jiawei; Wang, Binbin; Chai, Yameng; Zhao, Zhihui; Xiong, Rui; Luk, Patrick Chi-KwongA novel nondissipative two-stage equalization circuit topology based on the traditional buck-boost circuit is proposed to achieve balancing of series-connected lithium-ion battery packs with higher efficiency and less cost, considering the background on international energy issues and the development trend of battery balancing. The proposed topology achieves high efficient balancing of lithium-ion battery packs without adding additional devices. Detailed illustration of the presented topology, the operation principles and control approaches are described with visualized figures in this article. Then, under the condition of accurate modeling of the lithium-ion battery, relying on the experimental data, the simulation block is built based on MATLAB. Furthermore, the prototype of the proposed topology was designed and manufactured. The effectiveness of the proposed topology is verified by both the simulation and experiment.