Nonlinear Multi Control MPC (finite control set –FCS) based Grid-Connected Doubly Fed Induction Generator

Abstract

Energy generated from fossil fuels is unable to meet exponentially increasing energy demand due to the increasing demand the world is seeking more diverse and renewable energy resources such as solar, wind, biogas, geothermally energy to meet its energy demand. In this research thesis, a focus is on energy generated from wind. The trend of wind turbine and wind farms are increasing. There are many challenges and problems in generating power from wind energy including the quality of power and stability of the system because of its irregular variable nature. In wind-based generation systems, multiple electrical machines are used to perform electromechanical energy conversion. These types of implementation have some specific advantages and disadvantages. The DFIG used in wind turbines due to its full power control capability, reduce power losses, smaller power converters cost and variable speed operation. The DFIG contains a cometer in the rotor circuit having a common DC link, the DFIG stator windings are connected directly to the grid while the DFIG rotor winding is connected to the grid via slip rings and power electronic coureter. Due to the drawbacks of the linear controller many control strategies have been proposed. One such methodology is model predictive control that is an effective solution for the control of power converters due to its high control accuracy and rapid dynamic response. In MPC present values and past values of the system are used to predict and calculate reference values of the future. This reference value comparison is done in a cost function to minimize the error and this process is repeated in every cycle of sampling time. Finite control set model predictive control (FSC-MPC) is implemented on back to back converter. The proposed work in this thesis is implemented on MATLAB/Simulink. Results of the simulation show that MPC is an effective control method to operate inverter delivering our required frequency voltages and power under multiple load conditions such as nonlinear load, linear load, and load step change. Total harmonic distortion for current and voltages is less than 3% under all mentioned load conditions. According to the simulation result, the controller has maintained the steady-state of stator-rotor current and voltages on a uniform load.