Modeling and control of brushless doubly-fed bar cage induction machines

• Main Author: Hutton, Tainton
• Other Authors: Gule, Nathi, Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
• Format: Thesis
• Language: English
• Published: Stellenbosch : Stellenbosch University 2022
• Subjects: Brushless doubly-fed bar cage; UCTD; Induction Machines; Electric currents; Direct; Iceland
• Online Access: http://hdl.handle.net/10019.1/124711

Thesis (MEng)--Stellenbosch University, 2022. ENGLISH ABSTRACT: In recent years the requirement for more sustainable sources of energy has increased sig nificantly, with wind energy growing increasingly as a renewable source. Many countries are investing greatly in sustainable growth by going completely renewable. Countries like Iceland had an annual consumption of 60.8 TWh in 2019, of which 79% was produced by renewable energy sources. For this growth to be sustainable, more efficient and eco nomic sources of renewable energy will be required. The Brushless Doubly Fed Induction Generator (BDFIG) has become a focus point due to its variable speed capability and brushless technology. The direct-current-link (DC-link voltage) in the BDFIG systems’ back to back con verter allow for bidirectional power flow of the control winding’s power. Making effective control of the DC-link voltage a necessity. Due to the presence of switching elements in the back-to-back converter, there are harmonics introduced into the utility network. To mitigate this low pass filters such as inductance capacitance (LCL) and resistive inductive (RL) filters are often used. Currently, BDFIGs are not used in sizable wind farms. This is mostly due to their complexity when compared to standard doubly fed induction generators (DFIG’s) and permanent magnet synchronous generators (PMSGs). Thus far they have mostly been used in islanding applications. In this mode of operation they must be controlled to provide stable voltages at constant frequency with varying load conditions and changing wind speeds. To compete with DFIG’s which are already in the market, the BDFIG has a few disadvantages due to its slightly more complex structure, higher cost and larger dimensions. In this thesis, the power control of the grid-connected BDFIG systems in wind turbine applications are presented. Additionally the control of these machines as motors are also investigated and performed. An experimental machine consisting of a bar cage rotor is modeled in detail and ...