Research For Rotor Variables Detection Of AC Inductive Brushless Excitation System

Brushless excitation technology has many advantages,and it can not only improve the stability and reliability of excitation system,but also can reduce the maintenance.AC frequency induction brushless excitation system is a new excitation system,and it has high couping relationship bewteen stator and rator variable and has high dynamic performance, and its excitation power is without of speed limits and advantages of small size.It can supplement the existing shortages of brushless excitation system, so it has good prospects and research value.This paper will deeply research for brushless excitation system for the detection with AC induction exciter stator and rotor tightly coupled relationship, and it can solve the brushless excitation system current detection and fault judgment for rectifier with sensorless which has been plagued for long time.AC frequency induction brushless excitation system whitch includes rotor current of AC frequency induction exciter, excitation current,rotating rectifier fault detection and judgment. Firstly, This paper establishes the model of AC frequency exciter with different coordinate systems and rotating rectifier model,and then it analysises the relationship between rectified voltage Ud and the rectified current Id and calculates the corresponding angles.This paper proposes a further modified voltage model method of rotor flux observer because the method of improved the voltage model flux observer is not accurate in dynamic operation problem.That is to use the actual field current to compensate flux amplitude and phase error for the first-order inertia rotor flux integral element to,and its detection performance is better.For the problems of rotor counter electromotive force in the actual system after one-order approximate integration link, this paper uses online calibration method based on the counter electromotive force times low pass filter. This method needs less parameters and easily digital realization, etc.Then it establishes MATLAB simulation model of a brushless excitation system variable detection to detecte the flux value,the rotor current value, rotating rectifier failure simulation analysis.It analysis rotor flux and current when the parameters changed.It analysis the normal operation of therectifier, single / dual open run, rotor current single / double-barreled short circuit running for FFT harmonic analysis.It can determine rectifier failue through each characteristic of parameter values fundamental amplitude, DC integrated component,the second harmonic amplitude and total harmonic distortion(THD).Finally, the hardware and software for AC induction brushless excitation system rotor variable detecting is designed, and the rotor variable detection software is writtend.It builds a test platform for the core hardware control panel based on TMS320F2808 DSP chip.then it uses the the platform to perfrom the detection system for rotor current and field current steady-state test.The results show that the accuracy of detection of the rotor flux and rotor current detection and excitation current detection theory methods.