Analysis and Control Aspects of Brushless Induction Machines with Rotating Power Electronic Converters
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
This thesis deals with the steady-state, dynamic and control aspects of new type of brushless configuration of a doubly-fed induction machine in which the slip rings and carbon brushes are replaced by rotating power electronics and a rotating exciter. The aim is to study the stability of this novel configuration of the generator under mechanical and grid disturbances for wind power applications.
The derivation, development and analysis of the steady-state model of the brushless doubly-fed induction machine with a rotating excitor and the power electronic converters mounted on the shaft and rotating with it, is studied. The study is performed at rated power of the generator between ±20% slip range. Moreover unity power factor operation between ±20% speed range is also discussed.
Furthermore dynamic modeling and control aspects of the generator are also analyzed. The controllers were designed using Internal Model Control principles and vector control methods were used in order to control the generator in a closed-loop system. It is shown that through the use of proper feedback control, the generator behaves in a stable state both at super-synchronous and sub-synchronous speeds.
Moreover Low Voltage Ride Through of the generator during symmetrical and unsymmetrical voltage dips is also investigated. Passive Resistive Network strategy is employed for Low Voltage Ride Through of the generator during symmetrical voltage dips. On the other hand, Extended Vector Control is used in order to control the negative sequence currents during unsymmetrical voltage dips. Suppression of negative sequence currents is important as they cause extra heating in the windings and affects the lifetime of the mechanical and electrical components of the generator and system due to oscillations in power and torque.
In addition to the above studies a steady-state model of a single-fed induction machine is also developed and investigated where the rotating exciter is removed and the rotor windings are short-circuited through the two rotating power electronic converters. In this way the slip power circulates in the rotor and with the help of the two rotating electronic converters, rotor current is used to magnetize the induction machine thereby improving the power factor. The steady state model is verified through experimental results.
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , viii, 70 p.
Trita-EE, ISSN 1653-5146 ; 2012:037
Doubly-fed induction generator, extended vector control, induction machine, internal model control, Lindmark concept, low voltage ride through, passive resistive network, rotating power electronic converter, rotating exciter, symmetrical faults, synchronous machine, unity power factor, unsymmetrical faults, vector control, wind turbines.
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject Järnvägsgruppen - Elsystem
IdentifiersURN: urn:nbn:se:kth:diva-102210ISBN: 978-91-7501-466-1OAI: oai:DiVA.org:kth-102210DiVA: diva2:551539
2012-10-01, H1, Lab of Electrical Energy Conversion,, Teknikringen 33 KTH, Stockholm, 10:00 (English)
Peretti, Luca, Doctor
Sadarangani, Chandur, Professor
ProjectsBrushless Wind Generator with Rotating Power Electronic Converters
List of papers