Analysis And Research Of Doubly-Fed Wind Power Generator Operation Characteristics And Its Thermal Performance

Nowadays the conventional scare energy becomes increasingly rare and the environmental problem becomes increasingly serious. As a representative of the new energy power generation technologies, wind power generation is developing at a ever fast speed. According to the operational features of the generator, wind power generation can be divided into two types:constant speed constant frequency(CSCF) and variable speed constant frequency(VSCF), among which the variable speed constant frequency doubly-fed generator (DFIG) has the advantages as the variable speed generation, flexible rotor ac excitation, small capacity of converter and good ability of power regulation, becoming one of the most widely used type of wind turbines.The paper chooses the doubly-fed wind power generator as the main research object, the research thesis cover the operation principle, control strategy research, and focus on the main component, the doubly-fed generator, studies its thermal performance analysis, fault characteristics and lifetime prediction research, etc. Main contents include as follows:Firstly introduces the operation principle of the the doubly-fed wind power generator, followed by which the mathematical model of doubly-fed wind power system components is derived detailedly and also established. Based on the stator flux oriented vector control technology, the doubly-fed wind power generator vector control system is established, which implementing the maximum power point tracking, the decouple of active power and reactive power and also the independent control between them. Then the simulation model is established on Matlab/Simulink platform, studies the operation characteristics under different wind speed. the simulation results show that the established model has good dynamic response characteristics, and it can correctly reflect the wind power system internal relations of each variable. Secondly analyzes the doubly-fed generator internal power loss principle and the mechanism of temperature rise, combined with the heat transfer theory, based on the similarity theory and circuit theory, then a lumped parameter thermal network model of the DFIG is built, which is embedded into the doubly-fed wind power generator dynamic simulation model. Continuely the generator components of heating and cooling mechanism is researched, and the dynamic and steady state thermal analysis of the generator stator winding is studied under the condition of the changed wind speed. Then the mechanism of generator cooling system failure and voltage unbalance fault is studied respectively. Based on the established model above, the temperature rise characteristics of the generator and its fault features of the two failure modes is obtained. And the characteristics are compared to the SCADA data collected in wind farms. The results show the established thermal network model and the mechanism analysis reasonable and correct. Finally, the generator lifetime prediction theory is studied, and analyzes the variation of generator life under normal operation and the two failure modes.The researches done by this paper provide a certain theory basis and reference for further study of the doubly-fed wind turbine operation characteristics and thermal characteristic, the generator structure optimization design, and the development of the novel fault diagnosis algorithm used in wind turbines.