Analysis Of Relationship Between Distortion Of DFIG Air Gap Flux Density And Multi-source Signs

With the fossil fuel consumption and the deterioration of environmental problems, new energy power generation industry is being paid more and more attention. From a global perspective, wind power industry has been of great development, the cost of wind power has been declining and even becomes the lowest-cost power generation mode in many parts of the world, which in turn will greatly push forward the development of wind power industry. In recent years, a lot of promotion of Variable speed constant frequency(VSCF) technology makes the installed capacity of double fed induction generator(DFIG) in the proportion of the total capacity of the assembly machine continue to increase. The poor environment which wind turbines work and the state of three-phase voltage imbalance of the grid will have a bad effect on the stable operation of wind turbines, and even lead to failure, eventually lead to significant economic losses and affect security and stability operation. So it is essential to do a simulation inside the generator the generator of electromagnetic field in different conditions to achieve early warning of generator fault diagnosis.In this paper, based on the finite element theory, 2D electromagnetic field model of DFIG is established in the finite element software Ansoft. First of all, in the Circuit Editor(Maxwell Circuit Editor) of Ansoft software Circuit model is respectively established to simulate three kinds of working conditions, such as normal condition, mutation of wind speed condition and three-phase voltage imbalance of the grid condition, and then in the motor design software RMxprt DFIG 2D electromagnetic field model is established and imported into Maxwell 2d for subsequent solution. Get the generator field lines and air-gap flux density in normal condition and the Model has been proved to be correct. By defining a path in the air gap for solving the change of the air-gap flux density curve in three conditions, the curve was observed and analyzed to characterization of its change. In this paper, we study three kinds of air gap flux density distortion characterization, temperature, vibration and current, respectively, and define the characteristic factor among three characterizations in the form of energy. That is, under different working conditions, we choice the characterization which is of the biggest change as the characteristic factor to determine the relationship between the distortion of air-gap flux density and characterizations. The simulation results show that, compared with normal working condition, the change of the air gap flux density curve in wind speed generator does not change and this accords with the principle of variable speed constant frequency in doubly-fed generator; the air gap flux density curve is distorted of three-phase voltage imbalance condition. By quantitative calculation in vibration, temperature, and current, the change of stator current is the largest and it is chosen as the characteristic factor of air gap flux density distortion. By detecting the stator current, the change of air-gap magnetic field in condition of three-phase voltage unbalance can be found.Through the above analysis, Ansoft software can accurately get the electromagnetic field distribution inside the doubly-fed generator, through the simulation, problems related to electromagnetic fields can be solved and analyzed. Performance characterization factor of air gap flux density distortion can be chosen by quantitative calculation. The research of this paper is expected to provide theoretical support to improve the early fault diagnosis of DFIG.