Analysis Of Asynchronous Extra-high Synchronous Generator Under Loss Of Excitation

The stator winding of asynchronous extra-high synchronous generator adopts crosslinked polyethylene cable.The asynchronous power generation technology is employed,the step-up transformer is cancelled,and it can be directly connected to power grid.Though the separate regulation of active power,reactive power and rotational speed,variable speed constant frequency power generation is attained.The excitation-loss fault of synchronous could induce local overheating and system component over current.In some cases,the power system may even be collapsed,and it seriously threatens the safe operation of larger-capacity generating set.The structure and operational characteristics of asynchronous extra high voltage synchronous generator is different from the traditional generator.During the operation of motor,there are often short circuit faults at the ends or converters and corresponding lines of rotor windings,which is very easy to cause loss of excitation for motors.Therefore,the investigation about its excitation-loss fault is very essential.Based on motor basic principles,this paper firstly builds the mathematical model of asynchronous extra high voltage synchronous generator and its excitation-loss fault.Moreover,the theoretical analysis concentrating on two-phase short-circuit excitation-loss and three-phase short-circuit excitation-loss in asynchronous extra high voltage synchronous generator is employed.Then the law of the electrical quantity after excitation-loss and converting into asynchronous operation its discussed in the transient process.Afterwards,the field model of asynchronous extra high voltage synchronous generator and its excitation-loss fault system model are established as well.Considering the effect of core saturation,slot effect and core eddy current in asynchronous extra high voltage synchronous generator after faults,the field-circuit coupled finite element method is applied to analyze two-phase short-circuit excitation-loss fault and three-phase short-circuit excitation-loss fault to achieve the law of the stator and rotor current,magnetic field line distribution,flux density distribution,air gap radial magnetic density distribution and magnetic field harmonic content,when slip ratio is 0 and-0.2.