Enhanced control of brushless doubly-fed reluctance generators for wind energy:A novel speed sensor-less variable speed constant frequency approach

The brushless doubly-fed reluctance generator-based wind energy conversion system presented in this study provides a dependable and affordable alternative. In comparison to traditional wind turbine generators, the brushless and cage-less rotor design eliminates the need for slip rings, reduce costs, increases efficiency, and improves reliability and durability. It consists of power winding and control winding, where the power winding connects directly to the grid, and the control winding connects via back-to-back converter. A speed sensor-less vector control scheme is proposed to overcome limitations associated with traditional speed-sensor-based vector control, such as encoder failures, cabling complexities, and maintenance issues. For the grid side converter, a grid-voltage-oriented vector control scheme is implemented to maintain a stable dc-link voltage and ensure unity power factor by reducing reactive power imbalances between the grid and the grid side converter. To maximize energy extraction under varying wind conditions, a maximum power point tracker and blade pitch angle control strategy are integrated into the machine side controller control scheme. These also helps in regulating the generated power when wind speeds exceed rated values. The system is modelled and tested in MATLAB/Simulink to evaluate performance under below-rated, rated, and above-rated wind conditions. Additionally, the control schemes are implemented and validated on a Field programmable gate array-based hardware platform. Simulation and experimental results demonstrate the effectiveness of the proposed approach, showing reduced transient oscillations and almost negligible (i.e. 0.0001 approx.) steady-state errors in response to variations in wind speed and grid voltage.