Design and Hardware-in-the-Loop Experiment of Multiloop Adaptive Control for DFIG-WT

An improved perturbation observer-based mu-ltiloop adaptive control (POMAC) method is proposed for the integrated control of a doubly fed induction generator-based wind turbine (DFIG-WT). In the proposed method, the DFIG-WT is first broken down into four independent subsystems in accordance with four outputs. Meanwhile, the compensation terms used in the vector control (VC) are adopted in order to achieve the complete decoupling among the subsystems. Then, in each subsystem, a perturbation term is introduced to describe the nonlinear dynamics and uncertainties of the subsystem. Estimates of the system's states and perturbation term are obtained by a high-gain state and perturbation observer (HGSPO). Finally, the optimal output feedback control of DFIG-WT is achieved using these estimations instead of the actual values. Simulation studies are carried out using MATLAB/Simulink. Meanwhile, a hardware-in-the-loop test platform is set up using the combination of digital signal processing and control engineering and real-time digital simulator, on which the experiment is carried out to test the validity of the proposed method. Results of the simulation and experiment reveal that POMAC performs better than VC in various cases, including variable wind speed conditions, slight grid voltage dip, and severe three-phase bolted fault. Moreover, its hardware implementation illustrates that POMAC can be used in real time in practice.

I. Introduction

Over the last decade, the doubly fed induction generator-based wind turbine (DFIG-WT) has been widely utilized in the modern wind power generation systems due to its high efficiency and flexible control ability [1], [2]. Among numerous control methods of DFIG-WT, the standard vector control (VC) strategy is broadly employed in industrial application. However, applying VC for control of DFIG-WT still has the following drawbacks. In the first place, the performance of the VC highly relies on the accuracy of the model, while the definitely accurate system model is hardly available in practice [3], [4]. Moreover, the dynamic performance of the VC-controlled DFIG-WT strongly depends on the design of proportional-integral (PI) parameters. The PI parameters of VC are designed based on one operation point; however, the DFIG-WT operates at an operation envelope rather than one operation point due to time-varying wind speeds or external disturbances [5]. Furthermore, conventional VC is realized based on the assumption of a strong external power grid and the neglecting of stator resistance, which cannot be satisfied during the transient processes of grid disturbances.