Year

2009

Degree Name

Master of Engineering (Research)

Department

School of Electrical, Computer and Telecommunications Engineering - Faculty of Informatics

Abstract

Wind generator technologies have been widely researched and documented. Modern wind generator systems are now being implemented with an output power of up to 5 MVA. They adopt power electronic control systems which allow the system to operate with a wide range of turbine shaft speeds, as well as with Maximum Power Point Tracking (MPPT) algorithms to maximise the energy delivery to the power system.

Despite the extensive development, maximum power transfer from the total available power in the wind gusts to the grid is limited by the mechanical and electrical losses in the generation process. A Doubly-Fed Induction Generator (DFIG) uses a two stage power converter process in the rotor circuit which contributes to the electrical losses in the system. By adopting a Matrix Converter (MC), the electrical losses may be reduced as the power conversation is conducted as a single stage process. This thesis presents existing variable speed generator technologies with a focus on DFIG systems. Based on this research, an alternative design for a DFIG control system using an MC is developed and analysed.

The work begins with the presentation of existing DFIG systems using back-to-back PWM converters connected between the rotor circuit and the grid. The study examines MC technology and the application of current commutation techniques to MC systems. A non-ideal MC model and commutation controller is developed in the PSCAD / EMTDC environment. Simulation and analysis are conducted on the MC system connected to a passive load to determine its suitability for application in DFIG systems.

The MC is connected to the rotor circuit of the DFIG system in the simulation and analysis is carried out to investigate the viability of the system. From this the MC excited DFIG is extended with the development of a hybrid Maximum Power Point Tracking (MPPT) algorithm. The wind generator system is tested using pseudo-random wind speeds with varying wind gusts. The results of the simulation are presented and compared with existing MPPT technologies to assess the overall performance of the system in relation to existing technologies.

Finally, the MC excited DFIG control system is adapted to provide reactive power compensation to the power system for the regulation of voltage in distribution networks. Testing of the system using a variable load connected to a common bus bar and single transmission line is conducted. Observations from the simulation show that VAr compensation from the DFIG system does reduce voltage fluctuations in power systems.

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