Research On Permanent Magnet Direct Drive Wind Power System Modeling And MPPT Control

With the rapid development of global economy,the demand for energy is increasing day by day.However,the traditional energy such as coal and petroleum has been developed because of the the continuous exploitation,while serious ecological and environmental problems have sounded the alarm to the humanity.Nowadays the exploration of new energy has become the focus of attention,wind power,as one of renewable energy which is “inexhaustible” has been rapidly developed.The paper uses permanent magnet direct drive wind power system as the research object to build model,then the control strategy and the maximum power tracking of the permanent magnet direct drive wind power system are simulated to prove the utilization rate of wind energy and realize the variable speed constant frequency power generation.Firstly,the main wind power generation system and its control technology are introduced in the paper.The basic structure of the system is analyzed and introduced.The energy conversion theory of stroke generator in wind power generation system is expounded,and the state of fan running and related parameters characteristics are analyzed and studied.In this paper,the principle,advantages and disadvantages of the three main maximum power tracking control methods are compared and analyzed.The method of speed ratio and mountain climbing is mainly studied.Aiming at the problem about the fastness and stability of the tracking control method,combine the tip speed ratio method with the variable step climbing search method to optimize and improve.Then set up the corresponding simulation modeling of optimization method.Secondly,the basic principle of permanent magnet motor and dual PWM converter is analyzed,and the mathematical model of two phase rotating coordinate system is established by transforming the three-phase coordinate system of the motor.The machine side and the grid side converter mathematical model are established,the corresponding control strategy is designed,the machine side uses zero d axis current control strategy for control loop,the outer loop adopts the closed loop PI control of active power,and the speed outer loop and MPPT control are combined to control the motor speed in theoptimum state,the double closed loop control is used in the network side,the voltage control loop used as the outer loop and the current control loop as the inner loop,and combined with SVPWM which is a new strategy to achieve the overall control of the converter,and the corresponding control strategy is modeled in.Finally,combine with the control strategy of the network side and machine side,the simulation model of the network side and machine side are combined to form the simulation model of the permanent magnet direct drive wind power generation system.The system is simulated under the step wind speed,simulation waveforms of related important parameters are obtained,the simulation results show that when the wind speed changes,all the indicators can follow the corresponding changes,and the voltage and current waveforms of the network side can work well in steady state,variable speed constant frequency power generation is realized.Then,according to the random uncertainty of the actual wind speed,the simulation operation of the system under random wind speed is also analyzed,the characteristics of each parameter can still track the rapid change of wind speed,the correctness and effectiveness of the overall control strategy are verified.