{'fraction_non_alphanumeric': 0.017679057116953764, 'fraction_numerical': 0.0, 'mean_word_length': 4.807894736842106, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Brushless Doubly Fed Induction Generator Based Wind Turbine Drivetrain Under Grid Fault Conditions

With growing interest in sustainable forms of energy, the wind industry is growing rapidly. The Doubly Fed Induction Generator is the most popular choice for the drivetrain because it is cost effective. However, it suffers from reliability and maintenance issues due to the slip rings and brushes it requires. The Brushless Doubly Fed Induction Generator (B-DFIG) aims to address these drawbacks. With increased wind power penetration, tripping of wind turbines during grid disturbances is no longer acceptable for the power system. Therefore, it is important to study the performance of such wind turbine drivetrain under low voltage events. This thesis studies the Low Voltage Ride Through (LVRT) characteristics of the B-DFIG for its application in wind turbines. This thesis first looks at the modelling and control of the Brushless Doubly Fed Induction Generator (B-DFIG) to be used in a wind turbine drivetrain. It develops the steady state model using circuit theory to study the steady state characteristics of the machine. The dynamic model is developed to form the basis of the study of the machine during low voltage events. Further, the controller is developed based on vector control. The second part of the thesis looks at the performance of a B-DFIG based wind turbine under symmetric low voltage dips. It compares the performance of this generator with that of the Permanent Magnet Synchronous Machine (PMSM) and Doubly Fed Induction Generator (DFIG) - two of the most prevalent generators used in wind turbine drivetrains today. The thesis also looks at protection methods for these generators. It has been seen that the issue with LVRT performance of the PMSM is the rise in the DC link voltage which is due to the mismatch in power generated by the machine and the power transferred to the grid. It has also been found that apart from offering better reliability through the exclusion of slip rings and brushes, the B-DFIG also has an improved LVRT performance when compared with the DFIG - the protection is simpler and can be built into the control algorithm of the machine controller.