Research Of Asynchronous Machine Drive System Supplied By Double-Frequency Inverter

AC drive is as good as DC drive with the control theory is more perfect and the control system is developed. When we use converter to drive machine, another problem appears. In order to improve the output performance of the inverter, high frequency has become the develop direction of power electronic technology. But when the switch frequency is higher, the switch loss is also higher, then the efficiency of the inverter drops, therefore it limits the work frequency's increasing, the improving of performance and the expending in all fields of the inverter. Inverter can only work on low frequency because of switch limit in high power drive field, so there are many low frequency waveforms which will bring additional loss and electric torque change of the machine, and the efficiency of the all system drops.In this paper, double-frequency converter theory which is proposed by power electronic department of electrical engineering college, chongqing university is applied. In order to improve the performance and the efficiency of the high-power inverter, double-frequency inverter based on one-cycle control and hysteresis control is adopted in asynchronous machine drive. The low frequency switch shares the current of the high frequency switch and transfers the most power. The high frequency switchs transfer the small power and improve the dynamic response of the system. In the paper, a appropriate control means of the asynchronous machine drive system supplied by double-frequency inverter by studying asynchronous machine vector control, thus it can make the all system have good dynamic and static performance.Simulation results have proved that the asynchronous machine drive system supplied by double-frequency inverter has huge advantage than the system supplied by single-frequency inverter. Compares with the drive system supplied by single high frequency, the double-frequency drive system has the similar low stator current harmonic and low electric torque change, but its high frequency switch current is only 19% of the switch current of normal single-frequency inverter. Compare with the drive system supplied by single low frequency, the stator current harmonic and is only 12% of the later and the torque change is only 10% of the latter, thus the additional loss and quiver of the machine all decrease.In order to study the feasibility of asynchronous machine drive system supplied by double-frequency inverter, a hardware circuit of the half bridge inverter with double-frequency is designed and experimental analysis is also done. The dual integrator ACF2101 is adopted to achieve one-cycle control in the high frequency part of this circuit, and it solves the problem that it brings whose reset time is too long of the integrator. In the low frequency part, the current sensors are adopted to convert current signal to voltage signal, then hysteresis control is got.By theory analysis, simulation and some experiment, it is proved that inverter with double-frequency can be used to improve efficiency of the inverter and it has value in use in high-power AC drive.