Research On Drive Control Technologies Of High-Power Permanent Magnet Direct-Drive Wind Generation System

In recent years, inspired by national policies and energy crisis, high-power wind generation technology is developing faster and faster. Among these different wind power generation technologies, high-power permanent magnet direct-drive wind generation system becomes mainstream model due to its advantages of no gear box, high reliability, strong ability to adapt to the power grid, etc. However, the control strategies of the generator side converter of the high-power permanent magnet direct-drive wind generation system, i.e. the drive control strategies of permanent magnet synchronous generator, still have many problems, such as speed sensorless control, high performance torque control, low switching frequency model predictive control, point to point and electric control, and so on. To solve these problems, a series of studies were carried out in this thesis, and some innovative results were achieved.Firstly, this thesis systematically summarized the mathematical models of permanent magnet synchronous generator and a simplified model based on active back-electromotive force was proposed. Based on this model, medium and high speed region speed sensorless control technologies of permanent magnet synchronous generator were studied systematically in this thesis, and a full order sliding mode observer method and a full order state and sliding mode observer method, which can improve the estimation accuracy of the rotor position angle, were proposed. Besides, a detailed comparative study with the traditional second order sliding mode observer method was carried out.Secondly, in order to address the high performance torque control issues of permanent magnet synchronous generator, a full order sliding mode observer based torque closed-loop control method was proposed in this thesis. In this method, a full order sliding mode observer was adopted to observe the stator flux and torque. As a result, the influence of the non-linear changes of the generator parameters, such as inductance, was overcome, and high torque observation accuracy can be achieved under speed sensorless control mode. Therefore, the torque control performance was improved greatly.Thirdly, considering that the torque control performance of the permanent magnet synchronous generator based on vector control is deteriorating due to the decreasing of the switching frequency of the high-power wind generation system, an improved...