An advanced control for a PM synchronous motor drive in power degraded mode

This paper deals with a control principle designed to allow remedial strategies for Permanent Magnet Synchronous Motor (PMSM) drives. The scope of the paper is focused on three-phase machines and it aims to present a simple and easy to tune control scheme for the system while it operates in degraded mode, namely when only two out of the three phases are operational. Compared to existing control strategy dedicated to degraded mode, this work proposes an innovative one using new reference frames. Based on two innovative transformations applied respectively to the currents and the voltages of the system, the proposed control scheme allows, in degraded mode, the decoupling control of the states of the system and leads to continuous controller references during system steady states. These properties lead to a very straightforward control scheme based on independent PI controllers and to high static and dynamic performances. The parameters setting of the controller is quite simple whatever the degree of magnetic coupling between the two remaining motor phases. A laboratory test bench has been built to establish a proof of concept of the suggested remedial strategy. It is based on a three-phase open-end-winding permanent magnet machine fed with a power inverter made of three full H-bridge. This experimental setup enables to validate the main operations of the ac motor drive under degraded mode operation: torque control, speed change. Switching between healthy mode and faulty mode is also performed successfully using this setup.