| Summary: | The brushless direct current (BLDC) machines which are preferred in light electric vehicles (LEVs) come forward as high regenerative braking capability machines due to their permanent magnet excitation and relatively simple operation. In this paper, the regenerative braking capability limits of BLDC machines and their drive circuits are examined by taking into account nonlinear circuit parameters and battery internal resistance variation. During energy recovery from mechanical port to electrical port, the inverter of BLDC machine is operated as a boost converter which enables power flow to a battery. However, the regeneration performance is also heavily dependant on the battery condition, particularly the temperature. By means of the developed detailed circuit model including the non-ideal effects of the boosting converter and the increase of the internal resistance variation which is caused by the temperature variation of the battery and ambient temperature, the specific duty cycle can be determined. The specific duty ratio is then applied in a proposed approach for various operation scenarios. The experimental tests are implemented by a 400 W BLDC machine drive system controlled via a TMS320F28335 digital signal processor. The experimental results show that the proposed comprehensive model presents a proper performance estimation of regenerative braking system under varying battery temperature.
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