A Review about Flux-Weakening Operating Limits and Control Techniques for Synchronous Motor Drives

Ludovico Ortombina,Nicola Bianchi,Paolo Gherardo Carlet,Luca Cinti

doi:10.3390/en15051930

Abstract

This paper deals with motor design aspects and control strategies for the flux-weakening (FW) operation of synchronous motors. The theory of FW is described by taking into account different control schemes. The advantages and drawbacks of each one are discussed, as well. Moreover, some motor design considerations for achieving an effective FW operation are illustrated for permanent magnet (PM), wound rotor (WR) and reluctance (REL) synchronous machines, using the per unit approach. The distinguishing characteristic of this review provides two-fold attention on both machine design and control strategies obtained by several collaborations with industrial and commercial companies.

Highlights

In recent years, mobility is experiencing a disruptive revolution due to the worldwide diffusion of electric vehicles (EVs)
The fluxweakening (FW) mode represents the most widespread solution [6,7]. Such strategy allows for a constant deliverable maximum power and it is achieved by decreasing the motor stator current component aligned with the permanent magnet (PM) flux or by acting on the rotor windings excitation
Since high inductances are not obtained with an surface permanent magnet (SPM) motor configuration, a wide FW speed range requires the use of external inductances

Summary

Introduction

Mobility is experiencing a disruptive revolution due to the worldwide diffusion of electric vehicles (EVs). The motor control strategy can be modified, leaving the MTPA operation above the nominal speed In this condition, the fluxweakening (FW) mode represents the most widespread solution [6,7]. The fluxweakening (FW) mode represents the most widespread solution [6,7] Such strategy allows for a constant deliverable maximum power and it is achieved by decreasing the motor stator current component aligned with the PM flux or by acting on the rotor windings excitation. This solution has a limited impact on the overall system where the electric motor is mounted. The widespread feed-back, feed-forward and hybrid architectures are presented, together with other promising configurations

Motor Model and Operating Condition

Constant Maximum Available Torque Region

Flux-Weakening

Design of Electric Motors for Given FW Requirements

PM Motors

Pure Reluctance Motor

Motor with Rotor Excitation Windings

Flux-Weakening Control Strategies

Feed-Forward Schemes

Feedback Schemes

Hybrid FW Schemes

DC-Bus Voltage Use