Torque Control Theories Research And Simulation For Induction Motors And Wind Turbines

The paper is subjected to induction motors (IMs) and wind turbines (WTs), implementing their control system models and simulation with Matlab/SimuLink. Aimed at drawbacks of direct torque control (DTC) for induction motors, it is considered that Space Vector Pulse Width Modulation (SVPWM) improve voltage vectors implementation, Dead-beat control strategy for reference voltage vectors and self-tuning PI controller for torque and flux ripple reduction. Then aimed at wind turbine control systems, the analysis of their structure and strategies and their influences on component mechanical loads is emphasized. We have basic simulation results for Control models and filter control theory applying on WTs.Firstly, wind energy and methods for speed control of induction motors is introduced, including DTC and wind turbine torque control typical approaches. Then IMs kinds and applications are presented. IMs dynamic model at any reference frame is obtained. Using the model, basics of DTC principle and IMs are considered. Voltage vectors influences on electronic torque and motors flux are showed. Classic DTC principle's diagram is gained. To improve classic DTC drawbacks, the paper proposes an improved Dead-beat control strategy. Voltage vectors for torque are decomposed reasonably, while one for flux is implemented simply. Two parts of it are implemented by PI controller and the product of rotor speed and stator flux respectively. The product of motor speed and stator flux magnitude is essential for keeping motor speed and flux constant. Self-tuning PI speed controller reinforced responses deeply as gradient descent optimization to adjust gains automatically online. With Matlab/Simulink tools, it is modeled including every component of IMs DTC, SVPWM and self-tunging PI controller. As the simulation of classic DTC and New dead-beat control is finished, all results obtained prove above. Systems responses such as precision of speed, flux locus, flux or torque tracking and so on is improved. The reduction of torque and flux ripples presents clearly. The paper is good for designing actual IMs DTC application based on SVPWM.Secondly, control strategies for large wind turbine is introduced, most of them are variable speed WTs'torque control. As WTs'height and flexibility increase, studies on control strategies'affects on WTs mechanical loads become more and more important, especially for variable speed. According to the relations among all subsystems of WTs, a unified control model of variable speed WTs has been built including pitch control. The drive-train torsion and tower side-side vibration are main focus. Based on classic control strategy, filters are used for reduction while the rotor are tracking for optimal speed for energy capture. With Matlab/Simulink tools, the continuous model and filter design are completed simply. The theory and simulation results prove that WTs torque control can restrain vibration successfully.