Nonlinear Dual-Mode Control of Variable-Speed Wind Turbines with Doubly Fed Induction Generators

TL;DR

This paper develops a nonlinear feedback/feedforward control strategy for variable-speed wind turbines with doubly fed induction generators, enabling active/reactive power control and seamless mode switching without linearization.

Contribution

It introduces a novel nonlinear control design based on original electromechanical models, employing feedback linearization, speed control, and Lyapunov-based optimization.

Findings

Controller effectively manages active and reactive power.

Seamless switching between power modes demonstrated.

Simulation results confirm robust performance.

Abstract

This paper presents a feedback/feedforward nonlinear controller for variable-speed wind turbines with doubly fed induction generators. By appropriately adjusting the rotor voltages and the blade pitch angle, the controller simultaneously enables: (a) control of the active power in both the maximum power tracking and power regulation modes, (b) seamless switching between the two modes, and (c) control of the reactive power so that a desirable power factor is maintained. Unlike many existing designs, the controller is developed based on original, nonlinear, electromechanically-coupled models of wind turbines, without attempting approximate linearization. Its development consists of three steps: (i) employ feedback linearization to exactly cancel some of the nonlinearities and perform arbitrary pole placement, (ii) design a speed controller that makes the rotor angular velocity track a desired reference whenever possible, and (iii) introduce a Lyapunov-like function and present a gradient-based approach for minimizing this function. The effectiveness of the controller is demonstrated through simulation of a wind turbine operating under several scenarios.