The Discrete Frequency Conversion Technology And Harmonic Performance Testing Of The Permanent Magnet Synchronous Motors

Aiming at the intense torque fluctuation and large in-rushing current of the line-start Permanent Magnet Synchronous Motor (PMSM), a soft-start method based on the discrete frequency conversion was presented, and the systematic analysis on the phase sequence of discrete bands, band selection and band switching principle were carried out.The main tasks are as follows.Taking a5.5kW PM motor as an example, the general math model, with abc and dqO coordinate system, are established by means of the Matlab/Simulink software, respectively. Further, with the S-function, a quarter frequency starter model based on thyristor switch are also established. Combining the motor model in dqO coordinate system and quarter frequency starter model, the starting process simulation of the5.5kW PM motor is realized under the condition of the quarter frequency.In addition, through amorous time-stepping finite analysis and experimental research in permanent magnet motor, it is found that the comparison of the test and simulation results on dynamic performance of the PM motor will be affected significantly, when the line impedance is large or the power supply contains a certain quantity of harmonic component during the experiment process, however, the ideal sine voltage waveform is used in simulation analysis. In order to eliminate the influence of line impedance and harmonic component on the motor performance test. The auxiliary testing device which is composed of three-phase capacitor and single-phase adjustable reactor parallel-series is designed and developed, then the corresponding experiments are made, the tests result shows the obvious filtering effect.The research results in this paper lay a theoretical foundation for further studying on the soft starting of a PM motor with the discrete frequency conversion technology considering the saturation and complex non-linear condition. Meanwhile, it also provides the necessary technical support for avoiding the harmonic and line impedance influence on the PM motor performance test.