Series IGBT Chopping Strategy to Reduce DC-Link Capacitance for Brushless DC Motor Drive System

Abstract

In this paper, a series Insulated Gate Bipolar Transistor (IGBT) chopping strategy is proposed for brushless DC motor (BLDCM) drive system with small capacitor and IGBT connected at the dc-link. When the output voltage of diode rectifier cannot satisfy the voltage required for normal operation of the BLDCM, in order to keep phase currents continuous and stable, the BLDCM is supplied by a dc-link capacitor and rectified mains supply alternately via dc-link IGBT chopping. Since energy from rectified mains supply is made best use of by dc-link IGBT chopping, energy provided by the capacitor can be reduced, and the required capacitance can be reduced accordingly. The reduction of the dc-link capacitance further reduces volume and weight of the BLDCM drive system, and improves the system reliability. The minimum required dc-link capacitance is designed from the view of energy. From another perspective, if a capacitor, whose value is larger than the minimum required one, is selected, more energy can be provided to the BLDCM due to making full use of energy from the rectified mains supply, which will make the BLDCM have a stronger ability to control currents. The correctness of the theories and the effectiveness of the proposed strategy are verified by the experimental results.