Control of Synchronous Motors

Jean-Paul Louis

• Publisher: Wiley-ISTE
• Year: 2013
• Print ISBN: 9781848212732
• eBook ISBN: 9781118601730
• Edition: 1
• Topic: Biological Sciences
• Subtopic: System Theory
• Index: Biological Sciences

Synchronous motors are indubitably the most effective device to drive industrial production systems and robots with precision and rapidity. Their control law is thus critical for combining at the same time high productivity to reduced energy consummation. As far as possible, the control algorithms must exploit the properties of these actuators. Therefore, this work draws on well adapted models resulting from the Park's transformation, for both the most traditional machines with sinusoidal field distribution and for machines with non-sinusoidal field distribution which are more and more used in industry. Both, conventional control strategies like vector control (either in the synchronous reference frame or in the rotor frame) and advanced control theories like direct control and predictive control are thoroughly presented. In this context, a significant place is reserved to sensorless control which is an important and critical issue in tomorrow's motors.

Chapter 1

Synchronous motor controls, Problems and Modeling ¹

1.1. Introduction

The tremendous importance of rotary synchronous motors in the industrial systems control has been recalled in the general introduction of this book. There is in the professional community a very important emulation to define control structures, simple to materially implant and to design and very efficient ([BOS 86, LEO 90, VAS 90, MIL 89, LEP 90, LAC 94, LAJ 95, GRE 97, LOU 99, STU 00b, LOU 04c, LOU 09]). Nowadays, we can consider that the control structures are based on some very solid basic principles that we will present. Of course, from one designer to another, many alternatives can appear (each manufacturer wants to have their own patents), but we can consider that the basic principles exploited in practice are those that will be covered in Chapters 2 and 3 of this book, which are devoted to the torque controls. The most important key concepts will be: “self-control”, torque control in the “natural” reference frame (often known as the a-b-c reference frame); torque control in the rotor reference frame (often known as “Park reference frame” or d-q reference frame). Indeed, when the torque control is carried out, it is easy to successively implant a speed control, to obtain a device usually called an “electronic speed variator” and then if necessary, a position control. These last questions will be tackled in Chapter 4. This chapter exposes a general modeling of the synchronous motors and is particularly used as introduction to Chapters 2 to 4.

1.2. Problems on the synchronous motor control

1.2.1. The synchronous motor control, a vector control

The synchronous motor has much better performances than the direct current motor ([VAS 90, BEN 07, MUL 06]), but the counterpart has more sophisticated power electronics (an inverter instead of a rectifier or a chopper) and more complex control laws. Indeed, it is necessary to fulfill the “brush-collector” function via the converter control. This requires knowledge of the rotor flux direction. As it is interdependent with the rotor, a mechanical position sensor gives the necessary information. There are applications where we seek not to use a mechanical sensor, but this is the objective of Chapter 8 and Chapter 9. We will see that we must synchronize the currents on the position, which is the “self-control” function (see the note in section 1.4.2.2). Indeed, it is ideally necessary (here we simplify a little) to create a stator field in quadrature with the rotor field: this type of control thus completely deserves the term of “vector control”, a concept that was popularized by the induction motor‘s control [LEO 90, CAR 95, CAN 00, ROB 07]. By this strategy we seek to precisely control those as synchronous motors (and consequently in fine as direct current motors, since – as we will see – there is a very strong analogy between the axis q of the synchronous motor and the armature of the direct current motor).

These vector controls can be conceived by various approaches. Theoretically, the most satisfactory approach uses the Park model (in the rotor reference frame, known as d-q). This is discussed in Chapter 3, but historically it was not the first to be industrially used. An approach in the “natural” model (in the three-phase stator reference frame, known as a-b-c) was initially largely used, especially for the non- salient pole machines, where a “three-single-phase” model (apparently simpler) is usable: this approach leads to a “vector control”, since we always seek to impose a given direction to the stator field. This approach is covered in Chapter 2.

This gives us the chance to recall that control modeling and control design are two different activities. We can regard as “logical” the use of a three-phase model written in the natural reference frame to design an a-b-c control, since there is a s...

Table of contents

• Cover
• Title Page
• Copyright
• Introduction
• Chapter 1: Synchronous motor controls, Problems and Modeling
• Chapter 2: Optimal Supply and Synchronous Motors Torque Control: Designs in the a-b-c Reference Frame
• Chapter 3: Optimal Supplies and Synchronous Motors Torque Controls. Design in the d-q Reference Frame
• Chapter 4: Drive Controls with Synchronous Motors
• Chapter 5: Digital Implementation of Vector Control of Synchronous Motors
• Chapter 6: Direct Control of a Permanent Magnet Synchronous Machine
• Chapter 7: Synchronous Machine and Inverter Fault Tolerant Predictive Controls
• Chapter 8: Characterization of Control without a Mechanical Sensor in Permanent Magnet Synchronous Machines
• Chapter 9: Sensorless Control of Permanent Magnet Synchronous Machines: Deterministic Methods, Convergence and Robustness
• List of Authors
• Index