Disturbance rejection of the powers and DC‐link voltage of a doubly‐fed induction generator using state‐space based linear quadratic integral optimal control approach.

Summary: In this paper, an optimal linear quadratic regulator (LQR)‐based integral controller (i.e., linear quadratic integral [LQI]) has been designed with an innovative approach for the tracking problems of a wind‐driven doubly‐fed induction generator (DFIG) system. The main objective of this controller is to reject the deviations that occurred in the DFIG powers together with the DC‐link voltage due to the perturbations in the stator voltage. The purpose of the inclusion of integral action with the well‐known modern optimal controller LQR is to guarantee zero steady‐state error for disturbance rejection/set‐point tracking. Further, the genetic algorithm (GA) technique is included for the optimal design of the LQI weighting matrices, which rapidly, as well as effectively rejects the disturbances from the system by regulating the augmented state variables. Therefore, to overcome these issues we have chosen the appropriate control model, which controls as a whole, that is, a multi‐input‐multi‐output (MIMO) system. The DFIG system is a MIMO system, which has been modeled in a state‐space approach in the d‐q axes rotating frame of reference. To examine the effectiveness and robustness of the suggested control strategy, small‐signal stability has been done by eigen values and participation factors method on digital simulations in the MATLAB/Simulink environment. Furthermore, the optimal control solutions have been tested under the various larger perturbations in the stator voltage and the mechanical torque. The comparative simulation results among the different controllers show that the proposed controller greatly enhances the dynamic performances and the robustness of the DFIG‐based wind energy systems (WES). [ABSTRACT FROM AUTHOR]