Design and control of hybrid power supply for HEV

Energy storage is a major concern in today´s hybrid vehicular technology. The HEV operates with common load profile, described by relatively high peak to average power required. The complete system demands power source to be compact, lightweight and efficient with acceptable life cycle. Power source consisting of batteries which have high energy density and ultracapacitor which have high power density, specialized for the various power segments within a vehicular operating bandwidth becomes a viable solution. Ultracapacitor(UC) stored energy is directly proportional to square of terminal voltage. Under load condition terminal voltage of UC is continuously varying, so to operate DC bus with constant voltage the power electronic interface (dc-dc buck-boost converter) is needed which allows controllable power flow with better regulation of DC bus voltage. The power flow during boost mode operation is controlled by Dynamic evaluation control algorithm. This algorithm compensates all variations in the input/output voltages and load current to maintain DC bus voltage constant with a ripple of ± 2V under continuously varying load and input voltage condition. Energy saving under regeneration improves the efficiency of the complete system. The rate of transfer of energy from load to source has been controlled using hysteresis current control scheme.