Evaluating the performances of PI controller (2DOF) under linear and nonlinear operations of DFIG-based WECS: A simulation study

Belachew Desalegn; Desta Gebeyehu; Bimrew Tamrat

doi:10.1016/j.heliyon.2022.e11912

Evaluating the performances of PI controller (2DOF) under linear and nonlinear operations of DFIG-based WECS: A simulation study

Heliyon. 2022 Nov 29;8(12):e11912. doi: 10.1016/j.heliyon.2022.e11912. eCollection 2022 Dec.

Authors

Belachew Desalegn^{1

2}, Desta Gebeyehu³, Bimrew Tamrat¹

Affiliations

¹ Energy Center, Faculty of Electrical and Computer Engineering, Bahir Dar Institute of Technology, Bahir Dar University, P. O. Box 26, Bahir Dar, Ethiopia.
² Department of Physics, College of Natural and Computational Science, Wolaita Sodo University, P. O. Box 138, Wolaita Sodo, Ethiopia.
³ Department of Mechanical Engineering, Faculty of Engineering, Addis Ababa University, Addis Ababa, Ethiopia.

Abstract

Owing to different stochastic characteristics of wind energy systems, there would commonly be uncertainties in the processes of wind energy conversion that may ultimately cause to severely degrade the quality of electric power production. These uncertainties include time-varying fluctuations of mechanical & electrical parameters that can be generated during both linear, and nonlinear operating behaviors of doubly fed induction generator-based wind energy conversion system (DFIG WECS). In order to handle a wind power quality problem, the previous studies largely focused on adjustment of mechanical parameters particularly based on blade pitch angle control by proposing different control strategies, and controller models. This work proposes a rarely studied electrical parameter control method that is particularly used to implement the regulation of rotor current components & electromagnetic torque in a DFIG WECS, based on Indirect Field Oriented Control (IFOC) strategy. Accordingly, a novel Proportional Integral controller model that employs a 2-Degree-of-Freedom [PI (2DOF)] is illustrated for an enhanced control of the rotor current components (quadrature & direct currents), electromagnetic torque under a 2MW DFIG WECS, which is operationally assumed to behave both linearly & nonlinearly. Herein, nonlinear operating behavior signifies a voltage dip that was assumed to be resulting when the system's normal (linear) voltage would suddenly drop by 90%. Furthermore, the overall model of the DFIG system was simulated in MATLAB-SIMULINK environment to evaluate the performances of PI controller (2DOF) under the system's stated operating behaviors. Based on the simulation signal statistics, the quadrature current distortion levels & DC mean values were mainly considered as the criteria for evaluating the controller performances. Finally, the proposed PI controller (2DOF) model has been tested to achieve an enhanced power quality in comparison with the traditional PI controller model.

Keywords: DFIG WECS; Indirect field control strategy; Linear operating behavior; Nonlinear operating behavior; PI controller (2DOF); Voltage dip.