Ultracapacitor based Constant Torque Regenerative Braking System for a Brushless DC Motor

In this paper a low cost and efficient ultracapacitor based constant torque regenerative braking system for a BLDC motor is proposed, which is very much suitable for electric vehicles with lead acid batteries. The proposed regenerative braking system is designed such that, the inertial energy associated with the BLDC motor at the time of braking is used to charge an ultracapacitor through a buck converter so as to get constant braking torque. By varying the charging current of the ultracapacitor any constant braking torque can be produced for the motor. Thus a characteristics similar to mechanical braking is achieved. The proposed braking system can be implemented even in sensorless bide motors since sensors are not used with this technique. To validate the dynamic performance at different load conditions the proposed system simulated and tested using MATLAB/Simulink model. The results confirm the high capability of the proposed system. Finally it is verified that the proposed technique is very much suitable for practical implementation.