Mixed Current Control Strategy for Bi-directional Boost Converter Fed BLDC Drive

Abstract

The speed of BLDC motor can be varied by applying PWM technique to inverter while the DC-link voltage is constant. Another approach is PAM technique in which the speed of motor is controlled by varying the DC-link voltage. The problem with PWM based drive is switching losses and also restriction in wide speed range operation when the drive is fed by low voltage battery. For wide speed range of operation, a high voltage battery or else a boost derived converter can be used in the front end of the inverter such that the DC-link voltages can be varied. By using boost converter, wide speed range control is possible along with the reduction of ripples in input battery current. This paper presents a mixed current control strategy which combines the inverter based (PWM) and the converter based (PAM) current controller, in addition to that the starting current is limited. The detailed mathematical analysis was derived for boost converter fed BLDC motor drive. The effect of proposed current control in the speed and starting current of motor is verified experimentally