Simulation Research On Cascade Speed Control System Of Inner-feedback Motor Controlled By PWM Inverter

With the development of power electronics technology and computer control technology, the cascade speed regulation slip power recovery technology of 3 phase motor renewed attention, in recent years, chopper circuit used in cascade speed regulation technology of inner-feedback motor with its good performance and high precision control shows good prospects for energy conservation in the high voltage & large power motor.At present, the chopper cascade speed regulation technology of inner-feedback motor adopts commonly SCR thyristor inverter to feedback the slip power of the motor to grid, although the use of chopper control technology has greatly improved the power factor, there are still many disadvantages:the voltage waveform of grid is distort, the power factor is reduced in lower speed and the inverter subversion can be happened some cases because the use of thyristor inverter.For lack of above, in this paper, using three-phase voltage-type PWM inverter instead of the traditional thyristor inverter, with it't advantages:Three-phase voltage-type PWM inverter power factor and the Controlled DC current, from the structure, it breaks the limitations of traditional SCR cascade control technology can not be further enhanced the system power factor as the circuit limitin this paper, the cascade speed control technology of inner-feedback motor based on thyristor inverter has been researched, and the electromagnetic relations within the inner-feedback motor has been analysed, which provide a theoretical basis for the establishment of simulation models of the inner-feedback motor; By analyzing the direct current loop of the chopping cascade control system of the inner-feedback motor, the principle of the chopping cascade control system has been revealed. The power factor and the system harmonics have been analyzed, and the way of improving power factor and reducing harmonics has been given. The three-phase PWM inverter technology has been used in the cascade control system, and the new system maintain all the merits of the original chopping cascade control system, and combinating the characteristics of the three-phase PWM inverter, the power factor of the cascade speed control system will be improved by increasing the inverter power factor, and the harmonics pollution will be reduced by controlling the inverter AC side current waveforms.As there are less the PWM inverter applied in the cascade control system, and it even still at the stage of theoretical research. So, in this paper the simulation model of the cascade speed control system of inner-feedback motor based on the three-phase voltage-type PWM inverter is rebuild and it has been proved accurate by the theoretical analysis and simulation results, which provide the convenients for the PWM inverter applications in engineering; because the power factor of the cascade speed control system decreases with the speed dropped, the feasible solution had been designed by controlling the PWM inverter reactive current to produce capacitive reactive current compensation for speed device by inductive power, so the system can maintain high power factor in a low speed. The characterisics and the potential proplems in peration has analyzed by the simulation experiments systematically, which provide a more reliable theorical basis for the engineering application.