Research On Modeling And Control Of Direct - Drive Permanent Magnet Synchronous Wind Turbine

Large scale exploitation and utilization of new energy become increasingly urgent with the pressing problem of environmental pollution and energy shortages. With the advantage of richness, clean and relatively perfect exploration technology, wind power resource has become a model for the exploitation and utilization of new energy. Recently, issues in term of power conversion efficiency, system stability and reliability of the control strategy, construction of the whole generation model regarding direct-drive permanent magnet synchronous generators (D-PMSG), have become the focus of research with the installed capacity increasing year by year. Therefore, it is of great significance to optimize D-PMSG’s control strategy for improving operating efficiency and the stability of the system and for further exploitation and application.In this paper, comprehensive study was carried out involving theoretical analysis, simulation, and proposal of control strategy and comparison of the findings with modeling wind turbines and studying control strategy as the main research aims. Firstly, principle of wind turbine was analyzed and an wind turbine of6kW was designed. Secondly, operating area of wind turbine was divided into two operating modes in which control strategy is proposed in terms of power conversion according to wind speed. The scheme of tracking maximum wind power by employing technique of auto-focusing optimum power point was adopted which turns out to be simple, remarkably effective and somewhat creative with good dynamic performance from the perspective of the lower power conversion rate and on the basis of wind turbines’power characteristics in low wind speed range. Additionally, the way, altering the pitch angle to reduce capability of capturing wind power, was taken to ensure constant power generator output in higher wind speed range. The method that can self-adapt fuzzy PID and reduce inertia error and eliminate signal lag to some degree was put forward because traditional PID parameters are so fixed that can hardly achieve the accuracy and real-time of pitch angle conversion. Next, PMSG mathematical model, the coordinate transformation, operating characteristics were analyzed and deduced. Considering theoretical foundation and actual situation, dual-loop vectors control strategy based on the d-axis zero current was utilized, which is simple and achieving the desired results. Finally, in order to achieve stability of DC bus voltage and operation with unity power factor, full power converter structure was analyzed and the emphasis was placed on the space vector pulse width modulation (SVPWM) control as well as grid-side voltage oriented vector control method.Control strategy of four major parts that are maximum power tracking in low wind speed range, changing pitch angle in high wind speed, generation and grid-side was accomplished respectively by means of simulating examples and building D-PMSG model. From the results we can reach a conclusion that control scheme in this paper of high feasibility and has a certain timeliness to achieve system’s stable operation. Meanwhile, D-PMSG model can provide a foundational platform for further study of this research subject.