Multilevel switching voltage modeling and PWM control strategies for dual two-level converters with open-end winding configuration

Abstract

Dual Two-level converters with Open-end Winding configuration (DTC-OEWs) feature several advantages over Three-level Neutral Point Clamped converters (3L-NPCs), such as even power loss distribution, no requirement of DC-link voltage balancing, fewer number of switching devices, a great number of redundant switching states. However, Pulse-width modulation strategies (PWMs) applied in Dual Two-level converters with Open-end Winding configuration (DTC-OEWs) involve complex and counter-intuitive time-shifting offset for pulse generation whereas the PWM schemes of the traditional multilevel converters, such as the carrier-based Pulse-width modulation (PWM) strategies are simple. And this renders the Pulse-width modulation (PWM) control in DTC-OEWs complex in comparison to that of the traditional multilevel converters. Therefore, multilevel switching voltage models (ML-SVMs) of the Dual Two-level converters with Open-end Winding configuration (DTC-OEWs) with isolated DC-link sources are proposed in this article, thereby enabling the Dual Two-level converters with Open-end Winding configuration (DTC-OEWs) with isolated DC sources, the three-level Neutral Point Clamped converters (3L-NPCs) and the Three-level Cascaded H-bridge converters (3L-CHBs) to be regarded as a single multilevel-converter entity. Thus, it allows a rich pool of simple and intuitive PWM strategies derived for the 3L-NPCs and the 3L-CHBs to be applied directly to the Dual Two-level converters with Open-end Winding configuration (DTC-OEWs) without any modification. Several Pulse-width modulation (PWM) strategies, which are previously utilized for the Three-level Neutral Point Clamped converters (3L-NPCs) and the Three-level Cascaded H-bridge converters (3L-CHBs), are applied to the Dual Two-level converters with Open-end Winding configuration (DTC-OEWs) by using the multilevel switching voltage models (ML-SVMs). Simulation results of several PWM strategies, including the line voltages, phase currents, and the common-mode voltages from the three-level Neutral-Point Clamped converter (3L-NPC) and the Dual Two-level converter with Open-ends Winding configuration (DTC-OEW) bear a complete resemblance, thereby indicating the correctness of the multilevel switching voltage models.