۱- Introduction

۲- Innovative transformations and fictitious machine

۳- Control scheme in degraded operation mode

۴- Innovative approach proof of concept

۵- Conclusion and perspectives

References

Abstract

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.

Introduction

Electric motor drives are often used for key functionalities which are mission critical and cannot tolerate any unexpected periods of downtime due to a failure. Examples include many manufacturing processes [13,23] and transport applications [31]. For instance power-assisted steering of a ground vehicle [3,26] or the actuators of the control surfaces of a plane [33] are key examples. Some of these applications call for demanding specifications regarding high power density and high efficiency. In such cases, the best choice is often a permanent magnet synchronous machine [29]. This constraint is frequently associated with embedded systems and usually coincides with a requirement for a high level of availability and reliability.