Direct voltage regulation of a stand‐alone DFIG system with non‐linear loads based on an improved‐extended state observer and SSM control

Abstract

This study presents a direct voltage control strategy for a stand-alone doubly fed induction generator (DFIG) subject to non-linear loads. The voltage regulator employs a super-twisting sliding mode (SSM) control to directly calculate the rotor voltage reference with the advantage of mitigating the voltage chattering and omitting the current control loops. On the basis of the harmonic-eliminating principle under non-linear loads, an improved extended state observer is proposed and applied to estimate the model-related part in the SSM control law. The advantages are that no extra sequence decomposition operations and machine parameters are required; therefore, enhancing the robustness and simplifying the structure of the controller. Finally, the proposed method is applied to a 6 kW DFIG-based hardware system under varying speed conditions. Both simulation and experiment results are given to validate the harmonic-eliminating performance of the proposed method for the stand-alone DFIG system.