Multilevel Neutral Point Clamping Double Converter for PM Synchronous motors drive

Abstract

The aim of this paper is to give a solution to unbalance problem of the input DC voltages of nine-level NPC-VSI used in high voltage and great power applications [1]. For that, one two-level PWM current rectifier-nine-level NPC VSI-PMSM cascade is presented. In the first part, we develop a knowledge model of nine-level NPC VSI and propose a space vector modulation of this converter using eight bipolar carriers. The characteristics of this strategy are studied and the performances of the drive of the PMSM fed by this inverter are presented too [2,3]. In the first case the input DC voltages of the multilevel inverter are supposed constant and equals. After that, we propose to study a new high voltage cascade two-level PWM current rectifier-nine-level NPC VSI-PMSM. This study shows particularly the problem of the stability of the DC voltages of the inverter and its consequence on the performances of the PMSM speed control. Then, we propose a solution to the problem by employed closed loop regulation using classic PI regulator mode. We add a Clamping bridge to stabilise the eight DC input voltages of nine-level NPC VSI. This cascade found applications in great power and high voltage fields as electrical traction.