Research On The Control Techniques Of Variable-Speed Fixed-Ppitch Wind Power Generation System

The development and utilization of renewable energy is now considerd as an important part of sustainable development strategies both at home and abroad due to the energy crisis and environment pollution. Among various kinds of renewable energy generation techniques, wind energy is by far one of the fastest growing energy for its abundant resources and maturity of turbine techniques; and, it has become a research focus and priority all over the world. However, many key techniques of wind power generation systems (WECS) are still monopolized by several developed countries for the research on wind power generation techniques of our country is just at the beginning. Thus, much emphasis is put into the research of self-developed wind turbine techniques. Under this circumstance and supported by the Nantional Basic Program (973 Program) of China, this dissertation proposes and studies a new concept variable-speed fixed-pitch (VSFP) wind turbine and several novel full range power control strategies to optimal its performances, with which the VSFP wind turbines are hoped to have the same performance with variable-pitch variable-speed (VSVP) wind turbines.In this thesis, firstly, A WECS experimental platform, which consists of a wind turbine, a wind turbine simulator, a permanent magnetic synchronous generator, a diode rectifier, a DC/DC converter, an intelligent load simulator and a control system, is established. The system is devided into two subsystems, mechanical subsystem and electric subsystem, respectively. Then, the characteristics of the system in frequent domain of both the two subsystems are gained by mathematical analysis and model identification methods. Based on the entire system model, the operational performances of the WECS under full range wind speed and design criterion of the regulator are discussed.Secondly, the development of a wind turbine simulator (WTS), which is based on a permanent magnet synchronous generator and can simulate both the static and dynamic performance of a real turbine, makes the evaluation and improvement of the control systems for WECS in laboratory possible. In addition, some crucial techniques of WTS, such as dynamic simulation strategy, control accuracy, and simulation performance are detailedly discussed. The feasibility of the introduced strategy, correctness of the foregoing analysis, and the performance of the established WTS are verified resorting to simulation and experiment efforts.Then, after a simple illustration of the existed maximum power point tracking (MPPT) strategies, a novel power signal feedback (PSF) MPPT strategy is proposed. The operational principle of the PSF strategy is then elaboratively analyzed, during the process of which the MPPT speed of PSF strategy is experimentally proved to be much faster than that of most of the existed MPPT strategies. Fourthly, three full range power control strategies are proposed to handle the power of the wind turbine during the variation of the wind velocity. Among the three control strategies, the third strategy, developed from the PSF MPPT method, is more attractive for its simple structure and high reliability. The effective control of three operational modes and smooth transition between them are easily achieved with only two regulators. To decrease the power overloading during the fast variation of wind velocity, the soft-stall concept control strategy is further proposed and analyzed. The experimental results show that the soft-stall control strategy is superior to overcome the overloading problems while almost not decrease the turbine's annual power generation.Because the WECS has the characteristic of time-variation and non-linearity, the performance of the system can not be optimized using the traditional PID regulators. In this thesis, in order to improve the performances of the WECS, two intelligent controllers, fuzzy logic controller (FLC) and single neuron PID controller (SNC), are introduced.1) Fuzzy logic controllerThe operational principle of fuzzy logic controller and its digital realization method are firstly presented. Then, a proportional factor self-adaptation PI-like FLC is propsed, by the control of which the static and dynamic performances of the wind turbine are considerably improved. Experimental comparations among traditional PID control, conventional PI-like FLC and self-adaptation PI-like FLC are also carried out.2) Single neuron PID controllerA fuzzy SNC (FSNC) is used to regulate the turbine speed of WECS. The output proportional factor of the FSNC is regulated on-line with a fuzzy controller. The experimental results show that the performance of FSNC can be obviously meliorated.Lastly, the wind tunnel experiments are done to test the aerodynamic characteristic of the wind turbine, especially in the deep stall regime, and to verify the correctness and effectiveness of the WTS system, full range power control and soft-stall control strategies.