T14 Sensorless Control of AC machines
(Permanent magnet synchronous motors, induction motors)

Prof. Manfred Schroedl,
Vienna University of Technology, Institute of Electrical Drives and Machines, Gusshausstrasse 25/372, A-1040 WIEN
Tel. +43 (0) 1 58801 37212
Fax: ..........................37299
(Manfred.Schroedl@tuwien.ac.at

Full day (9 a.m. to 4 p.m.)
Location: Semriach
including sightseeing: Lur-Grotte or Stübing (old farming houses open air museum)

Who should attend?

Indication of level:

A systematic indroduction to vector control theory will be given, hence, it is sufficient to have a basic understanding of electrical machines. Understanding linear differential equations and complex quantities is advantageous.

Level: Advanced students and application engineers in electrical drives.

Abstract

The tutorial shows methods of speed-sensorless control of induction machines and permanent magnet synchronous machines (PMSMs, EC motors, Brushless DC motors, respectively). The presented methods offer the possibility of a relatively simple implementation in industrial drives and hence, methods with high mathematical expense will only be mentioned briefly.

EMF-based models for high speed as well as saturation-based and reluctance-based models for low speed and standstill will be discussed.

The author shows practical examples of realized drives. A practical demonstration example of a sensorless PMSM drive with high starting torque will be presented. Possible fields of applications for sensorless drives will be discussed.

Highlights: Sensorless drives for arbitrary speed including standstill, practical realizations.

Proposed schedule and title of sections

1. Introduction (planned time 15´)

Goals of the tutorial. Why "Sensorless Control"?
Discussing motivation of tutorial participants for attending the tutorial

2. Basic inverter structure for sensorless IM and PM drives (30´)

Structure with phase current measurement
Structure with DC link current measurement

3. General mathematical description of AC machines (45´)

Per unit quantities
Definition of space phasors for voltages, currents, flux linkages
Calculating a phase quantity from a space phasor quantity
Voltage equation of a coil
Voltage space phasor equation of AC stator winding system
General flux linkage equation of stator winding
Torque production based on stator current and stator flux linkage

4. The Permanent Magnet Synchronous Motor – Modelling,Control(30´)

General description

Mathematical description by means of space phasors
Flux linkage equation of PMSM
Torque production of PMSM

Control methods

PMSM control with 60° -current blocks (BLDC-mode)
PMSM control with sinusoidal currents

5. Sensorless rotor position detection of the PMSM (60´)

Sensorless position detection at high speed

Quasi-continuous detection for sinusoidal commutation
Calculating rotor position using the voltage model
Calculating rotor position using inverter short circuit state
Detecting commutation information for BLDC mode
Back EMF evaluation in the passive phase in BLDC mode

Position detection at low speed and standstill (INFORM method)

(INFORM = INdirect Flux detection by On-line Reactance Measurement)
The complex differential inductance
Reaction of the current due to a voltage step
Calculating double the value of rotor angular position
Initializing the INFORM model by shifting the magnetical set point
Examples of INFORM-measured rotor positions of some PMSMs

Improving the estimated rotor position and developing estimated speed

Simple state model of the machine (speed, position, load torque)
Measurement error feedback to improve estimated state
Examples of PMSMs with state estimator

6. The Induction Motor – Modelling and Control (30´)

General description

Mathematical description by using space phasors
Flux linkage equations of IM
Torque production of IM

Control methods

U/f-control for low dynamic properties
Field-oriented control (example for highly-dynamic operation)

7. Sensorless rotor flux angular position detection of the IM (60´)

Sensorless position detection at high speed

Voltage model for high speed operation
Current model for arbitrary speed (needs mechanical sensor)
Model using inverter short circuit state

Sensorless flux detection at low speed

Sensorless control down to flux standstill (INFORM method)
Reaction of the current due to a voltage step
Calculating double the value of rotor flux angular position
Initializing the INFORM model by magnetizing the IM
Examples of INFORM-measured rotor flux position in real drives

Improving the estimated rotor flux position

Simple state model of the machine
Measurement error feedback to improve estimated state
Examples of IMs with state estimator

8. Practical example (Demonstration) (30´)

INFORM-controlled sensorless PM drive with high starting torque
Discussion on the properties of the drive and possible applications

9. Systematic selection of appropriate sensorless control schemes (20´)

Developing a list of practical applications for sensorless control
Table with technical and economic criterias for selecting appropriate drive

10. Discussion (20´)

 

Brief Curriculum

Dipl.Ing. (1982), Dr.(1987) and habilitation degree (1992) from Vienna University of Technology.

Between 1992 and 1996: Head of the development department of ELIN Traction, Vienna, From 1996 to 1998: Head of central technical division of ATB Austria Antriebstechnik, Spielberg (Styria, Austria).

Since February, 1998: Full professor and head of Institute of Electrical Drives and Machines at Vienna University of Technology.

About 50 publications and 10 patents mainly in the field of Electrical Drives.

Actual main research field is Sensorless Control of AC machines, special electrical drives.
 

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