A Novel Inverter Topology for Brushless DC Motor Drive to Shorten Commutation Time

摘要

Commutations existing in a brushless dc motor (BLDCM) drive system not only aggravate the torque ripple and reduce the power factor but also cause the catastrophic failure of a sensorless drive based on the zero-crossing detection of back electromotive force when the commutation duration approaches or exceeds 30 electrical degrees. For a sensorless BLDCM drive system with a long commutation time, it is necessary to shorten the commutation time. In this paper, a technique making the commutation time significantly reduced by means of a novel inverter topology is presented. The proposed topology is based on the idea of supplying higher dc-link voltage for the freewheeling phase. First, the dc link of the backward freewheeling path is decoupled from that of the forward energy flow path. The superiority of dc-link decoupling for commutation control is analyzed. Then, in order to provide adjustable voltage higher than the dc source voltage for the dc link of the freewheeling path, a double-layer C-dump converter is proposed. Compared with the traditional unipolar C-dump converter, it not only upraises the potential of the positive rail but also lowers the potential of the negative rail. Finally, the proposed inverter topology is verified by simulation and experimental results.