A Simple Dual Three-Level Inverter Topology With Improved Fault Tolerance

This article presents a dual three-level inverter for open-end winding motor drive applications requiring improved fault tolerance. The proposed inverter exploits the inherent properties of common-mode eliminated space vector locations to minimize the number of flying capacitors (FCs) required for single-supply operation. The inverter is fully modular and may be realized entirely using standard half-bridge blocks. The idea behind the resulting inverter structure is first explained, followed by details of other aspects such as modulation, capacitor balancing, and post-failure reconfiguration capabilities. An analysis of the power losses incurred by various sections of the inverter is also included. The proposed inverter is compared with other existing methods in terms of several parameters and is found to be capable of surviving the primary failure of any of its devices or FCs without sacrificing power capability or common-mode elimination. The functionality of the approach has been verified using practical results, obtained from an experimental induction motor drive incorporating the proposed inverter.