Sensorless speed control of a five-phase induction machine under open-phase condition

Abstract

Recently, multiphase machines have been promoted as competitors to their three-phase counterparts in high-power safety-critical drive applications. Among numerous advantages of multiphase induction machine (IM) drives, self-starting and operation under open phase(s) stand as the most salient features. With open phase(s), optimal current control provides disturbance- free operation given a set of objective functions. Although hysteresis current control was merely employed in the literature as it offers a simple controller structure to control the remaining healthy phases, it is not suitable for high-power applications. In the literature, multiple synchronous reference frame (dq) control can be an alternative; however, it requires back and forth transformations with several calculations and additional sophistication. In this paper, a simple technique employing adaptive proportional resonant (PR) current controllers is presented to control a five-phase IM under open-phase conditions. Results for both volt/hertz (V/f) and field oriented control (FOC) systems are presented. Moreover, sensorless operation under fault condition is also demonstrated by estimating the machine speed using a rotor flux-based model reference adaptive system (MRAS) speed estimator. The proposed controllers are experimentally verified and compared. Although FOC provides better dynamic performance, V/f control offers a simpler control structure and a lower number of PR controllers.

Keywords

• angular velocity control
• induction motor drives
• sensorless machine control
• machine vector control
• electric current control
• model reference adaptive control systems
• sensorless speed control
• five-phase induction machine
• open-phase condition
• high-power safety-critical drive applications
• multiphase induction machine
• IM drives
• optimal current control
• objective functions
• hysteresis current control
• high switching frequency
• multiple synchronous reference frame
• adaptive proportional resonant current controllers
• PR
• field oriented control system
• FOC
• machine speed estimation
• rotor flux-based MRAS speed estimator
• prototype five-phase IM
• PR controllers
• power 1 hp