Study On A Simulative Test-bed For Doubly-fed Wind Power Generation System

The wind power generation is an effective renewable energy source that is receiving more and more attention in recent years. With large-scale development and utilization of wind power the study on wind power generation system as well as the mutual influence between it and the grid is imminent. Because of the complexity of the wind power generation system especially the generator-converter subsystem, it is not sufficient to verify the feasibility and reliability of the hardware, software and control strategy etc. merely by computer simulation. But it is also not economic and realistic by mounting the prototype to real installation for the verification of a single function or performance index. Furthermore, even the in-situ environment could not willingfully provide all the test conditions as the designer wished. It is a natural conclusion that some simulative facility might be constructed with real hardware, aiming at the verification of the system components. As described in this thesis, a simulative testbed is developed for the verification of the doubly-fed generator-converter subsystem that is part of a complete wind power generation system.Within the simulative testbed the generator-convereter subsystem with its controller is a real prototype to be tested and the wind turbine is a simulated one that is the key of the testbed design. Most of the existing wind turbine simulator designs are based on steady-state output characteristics of wind turbine with wind turbine simulation programs developed, but the driver does not fully reflect the real characteristics of the wind turbine, thus is not suitable to be a substitute for actual wind turbine for the complete research of wind power generation system. To remedy the drawbacks of existing wind turbine simulator, a novel dynamic torque compensation scheme that takes wind shear effect, tower shadow effect and big inertia of the actual wind turbine into account is developed in the thesis. It makes the dynamic response of the wind turbine simulator closer to actual ones and can be used as a substitute for actual wind turbine in experiment. With the other components of the wind wind power generation system mathematically modeled, an entire double-fed wind power generation system simulative testbed was eventually constructed.Based on such a simulative testbed, the influence of the dynamic characteristics of wind turbine, especially the third harmonic torque caused by wind shear and tower shadow on system performance is studied in detail. The affection of the mechanical transmission's parameters on system transient performance is also studied and a selection principle of the optimal mechanical parameters is obtained. Study is also carried out on the stability of doubly-fed generator with stator voltage oriented vector control, as well as the the influence of the electrical parameters on the system transient performance. The above studies provide a useful reference to the parameter design and system analysis.In preparation of the thesis, a simulative testbed with a 15kW asynchronous motor driving an 11kW doubly-fed generator was constructed and debugged. Based on this facility, the correctness of the dynamic wind turbine algorithm was verified, the doubly-fed generator operating characteristics in different conditions was examined, and the dynamic response of the whole system was tested. Both the simulation and experimental results confirmed the correctness and effectiveness of the wind turbine simulation program and system control strategy.