| As the most mature and commercial method of renewable power generation,wind power technology is growing fast these years.In particular,doubly fed induction generator(DFIG)has the highest market share among all the generator types with its great control effect and generating efficiency.DFIG is the core component of wind turbines,whose condition has a serious influence on operating safety.Therefore,it'svery important to carry out an on-line condition monitoring and fault diagnosis plan to DFIG.In this paper,the causes and harms of several common faults are explained in the first place such as stator inter turn faults,rotor inter turn faults and rotor eccentricity.Based on electromagnetic knowledge,a complete mathematical analysis of these faults is presented,and the fault characteristics in torque,speed and stator currents are deducted.Considering the large range of generator speed,the traditional diagnosis methods of induction machine have several disadvantages.For example,all the fault-related frequencies are changing with the rotor speed,besides,they could be very close to the fundamental component and could be easily drown.To solve these problems effectively,several diagnosis methods are analysed in this paper such as envelope spectrum,instantaneous power spectrum,symmetrical components method,and axis orbit.Induction machine models under these fault conditions are established in Ansoft Maxwell 2D software using finite element analysis method.All the fault characteristics are evidenced,and the diagnosis methods presented are proved to be effective.Besides,several parameters such as instantaneous speed are found to be doable to diagnose machine faults.In the end,a complete condition monitoring and fault diagnosis platform for DFIG is established in Labview.This platform is able to monitor important parameters immediately and analyse historical data on line based on the electrical data and vibration data acquired.The software interface is beautiful and easy to operate. |
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