Maximum Power Point Tracking Control Of Wind Power Generation System Using Permanent Magnet Synchronous Generator

With the prominent energy shortage in the world,more and more attention has been paid to the operation efficiency of wind power generation system(WPGS).Maximum power point tracking(MPPT)technology has been a hot topic in the research of WPGS for the MPPT under low wind speed.The output characteristics of WPGS are greatly affected by the external environment,and the instability of wind energy will lead to large fluctuations in the output characteristics of wind turbines.Therefore,an effective control strategy is needed to realize the stable operation of the system and the MPPT of WPGS under the complicated environment and the uncertain model parameters.The perturb and observe(P&O)algorithm has the characteristics of simple structure,high real time and easy realization of digital controller.Based on the concept of P&O method,a nonlinear design method of robust controller with sliding mode structure is proposed.On the basis of this design method,three robust controllers are designed: P&O controller(the third chapter),MPPT controller(the fourth chapter)and speed controller(the fourth chapter),and the convergence of the three controllers is proved based on the Lyapunov theory.The control structure of the three controllers is composed of the observation process and the perturbation process.In the view of the structure of the controllers,the three controllers have the characteristics of unity;For different control purposes and application backgrounds,the three controllers introduce different control techniques and define different reference thresholds in their control structures to meet the specific control requirements of the WPGS.From the point of view of controller's function,the three controllers are independent.This paper mainly focuses on the theoretical and experimental analysis of the unified and independent features of the three controllers.Since the design of the previous three controllers are based on the integer order theory,the fractional calculus operator is introduced into the traditional sliding mode control.On the basis of the design of a fractional order,sliding mode controller is applied to realize MPPT,the genetic characteristics and the memory of the controller can use the fractional calculus operator can improve the control quality and the comprehensive performance of the system.The main contents of this paper include:1)The P&O controller(the third chapter)introduces the voltage slope detection mechanism,which can be used to detect the steep change of wind speed.The information of wind speed is transferred to the observation section of the perturb and observe controller.By this way,the problem that the traditional hill climbing searching(HCS)algorithm has the wrong searching direction is solved when the wind speed changes rapidly,and improves the wind energy capture efficiency of the WPGS.In addition,when the wind speed drops sharply,the detection mechanism can also prevent the stall problem of the WPGS.Because the perturb and observe controller designed in this paper has the characteristics of sliding mode,the controller has good robust performance,and enhances the transient stability of the system under the condition of strong disturbance.Through the MATLAB/simulink simulation to verify the validity of the voltage slope detection mechanism;In comparison with the traditional HCS algorithm,the simulation proves that the P&O has good transient performance and high wind energy capture efficiency in MPPT.2)On the basis of studying on the traditional maximum power tracking curve,a new optimal power constant(OPC)curve is derived.Different from the traditional optimal tracking curve,the OPC curve is a straight line with a fixed value.Therefore,the OPC curve simplifies the design difficulty of the MPPT control strategy and improves the stability of the system.According to the proposed optimal power constant curve,the MPPT strategy can be realized by the MPPT controller(the fourth chapter)and the speed controller(the fourth chapter).Finally,the transient performance of the designed MPPT controller and speed controller is analyzed and compared with the traditional HCS algorithm,PI controller and improved high climbing searching(IHCS)algorithm by MATLAB/simulink software.On the experimental platform of simulated PMSG,the maximum power control strategy based on robust controller is tested experimentally.3)This paper designed a fractional order sliding mode controller using the RiemannLiouville definition of fractional calculus(the fifth chapter),and the controller is proved by the Lyapunov theory.Through the construction of the two mass module model of the wind turbine drive chain considering the nonlinear gear angle,the robustness and the excellent transient performance of the fractional order sliding mode controller are verified.In the simulation part,the method of adjusting the parameters of fractional order sliding mode controller is given.And when the model parameters are uncertain,the transient performance,steady state performance,and the efficiency of capturing wind energy are studied comprehensively by the fractional order sliding mode controller and the PI controller,to illustrate the superior transient performance and robust performance of fractional order sliding mode controllers.