Open‐phase fault tolerant driving operation of dual‐inverter‐based traction drive

Abstract

A method for achieving open-phase fault tolerant operation of a dual-inverter-based traction drive with charging capability is presented. This method utilises a contactor to connect the switching nodes of the two half bridges which are normally used for AC charging in this dual inverter configuration. These half bridges are then modulated to provide a path for zero-sequence current and enhance the available voltage vector space of the drive by injecting a controllable common-mode voltage between the two inverters. A control method and five-level modulator based on zero-sequence voltage control and phase shifted carriers are introduced to accommodate this novel remedial method. Using this approach, the open-phase faulted dual inverter drive is able to operate with twice the speed range of the conventional open-phase fault tolerant approach, which is to provide a path for zero-sequence current by connecting the negative DC rails of the two inverters with a contactor. Simulation and experimental results with a prototype dual inverter drive are presented to validate the theory of the new control and modulation method. The experimental results showcase the proposed algorithms performance by dynamically responding to an open-phase fault and starting from standstill, thereby proving its validity for an electric vehicle application.