Dual-loop self-optimizing robust control of wind power generation with Doubly-Fed Induction Generator.

Area of Science:

• Renewable Energy Systems
• Control Engineering
• Electrical Engineering

Background:

• Variable speed wind turbines with Doubly-Fed Induction Generators (DFIGs) are crucial for efficient energy capture.
• Optimizing power generation in Region 2 requires precise control of generator torque and power conversion.
• Existing methods often rely on accurate wind measurements or detailed power maps, which are not always available.

Purpose of the Study:

• To develop and validate a self-optimizing robust control scheme for maximizing power generation in DFIG-based wind turbines operated in Region 2.
• To propose a dual-loop control structure that synergizes aerodynamic to rotor power conversion and rotor to electrical power conversion.
• To design a robust controller that adapts to variations in generator parameters without requiring wind speed measurements.

Main Methods:

• A dual-loop control structure featuring an outer loop Extremum Seeking Control (ESC) for generator torque regulation based on electric power feedback.
• An inner loop vector-control scheme to manage the ESC-requested torque and maximize rotor-to-grid power conversion.
• Synthesis of an H(∞) controller for performance maximization and robustness against generator parameter variations, with specifications derived from ESC-obtained rotor power spectra.

Main Results:

• The ESC effectively searches for optimal generator torque to maximize rotor power without requiring wind speed measurements or precise power map knowledge.
• The H(∞) controller ensures robust performance and maximizes power conversion efficiency under varying generator parameters.
• Simulation studies using NREL's TurbSim and FAST, Simulink, and SimPowerSystems validated the proposed control strategy's effectiveness.

Conclusions:

• The proposed self-optimizing robust control scheme successfully maximizes power generation for DFIG wind turbines in Region 2.
• The dual-loop structure and ESC-based optimization offer a practical solution for enhancing wind energy capture, even with limited system knowledge.
• The integration of H(∞) control provides robustness, ensuring reliable performance across different operating conditions and parameter uncertainties.