Design a nonlinear auxiliary input for DFIG-based application using Lyapunov theory

In this paper, a linear optimal controller design for double-fed induction generator application has been tested in normal operating conditions. To improve conditions for voltage drop in the network, a nonlinear auxiliary input based on Lyapunov theory is designed. For this purpose, taking into account changes in the generator stator flux, a second-order transient model for electrical part and first-order model for mechanical part is considered. Furthermore, the controller of the grid side converter has been taken conventional vector control to regulate dc link. Therefore, this system is defined with three nonlinear state equations. Meanwhile, the axis d, q voltages are two inputs of it. The speed of rotor and the output voltage of the stator are controlled by using linear optimal controller and nonlinear auxiliary input. Simulation results, done by the complete simulation model for the whole system, validate designed controller based on mathematical formulation.