The Research on Generator-side Converter of Permanent Magnet Synchronous Generator
|School||Lanzhou University of Technology|
|Course||Control Theory and Control Engineering|
|Keywords||wind power generation permanent magnet synchronous generator SVPWM sliding model control wind energy capturing|
Nowadays, the energy crisis has become more and more prominent. So, thedevelopment of new energy resources has become the focus of attention worldwide.Compared with other new energy resources, wind power generation possesses manyadvantages such as relatively mature technology, brighter prospects for developmentand utilization. Also, the almost pollution-free superiority provokes more attention insustainable development of energy. With the development of wind power generation,the direct-drive permanent magnet synchronous generator (PMSG) has gained moreand more popularity. Possessing the advantages of low energy consumption, highreliability and precise control strategy, PMSG has become the main kind of powergenerator in large wind farms under construction. Usually, the motor speed regulationof a PMSG system can be achieved by utilizing the three-phase voltage sourceconverter. Also, it can complete the invert and rectification of the generator current.In order to solve the problems of grid connecting, the grid side converters andgenerator-side converters are necessary for energy conversion. One of the functions ofgenerator-side converters is to rectify the AC power to DC power of which the ripplecoefficient is quite low on the premise of realizing maximum wind power tracking.While implementing vector control of power generator, the precise estimation of rotorposition is needed. For PMSG, there is no enough space location to install thephotoelectric encoder which is used to detect rotor position. So, it is necessary torealize the accurate estimation of rotor position by adding some new algorithms. Inthis paper, the research is mainly focused on energy rectification, maximum powerpoint tracking, precise rotor position estimation and SVPWM modulation.The research object of this thesis is the generator-side control system ofpermanent magnet synchronous generator. Firstly, the mathematical model of PMSGand PWM converter is built. Based on the above mathematical model, the controlstrategy of generator-side converter is proposed. The PWM modulation utilizes theSVPWM modulation method. The rationality of this control strategy is verified onMATLAB/SIMULINK platform.In this thesis, the pre-positive quasi sliding model observer and the post-positionKalman filter are introduced to realize the precise estimation of rotor position. The mathematical models of quasi sliding model observer and post-position Kalman filteris presented and the reliability of them is proved. Also, the validity of control strategyand mathematical model are verified on SIMULINK simulation platform.Finally, we present the modified hill-climbing searching method by comparingoptimal tip-speed ratio method, power feedback method, three-point comparingalgorithm and traditional hill-climbing searching method. The modified hill-climbingsearching method is actually variable step-size hill-climbing searching method. Thisalgorithm is a optimal method based on the traditional hill-climbing searching and itcan realize fast response. Meanwhile, the PMSG system will be more stably by addingthe limitation of step-size. The variable step-size algorithm can be realized byprogramming S-function in MATLAB. By analyzing the simulation results underconstant wind speed and gradient wind speed disturbance, the superiority of modifiedhill-climbing searching method can be verified clearly.