Study On Dual- Pwm Variable Frequency Adjustable Speed System

The background of the paper is the project——"development of energy feedback type low-voltage inverter"which is cooperated betwen Henan University of Science and Technology and CITIC Heavy Industries Automation Engineering CO., LTD, in the paper, aim at the mine hoist which requests high-transmission performance, the theory and basic testing of dual-PWM variable frequency adjustable speed system are studied.The rectifier of traditional inverter adopts non-controlled rectifier that is composed by diodes, so when the inverter is running in four quadrants, the energy can't be return. the PWM rectifier is instead of non-controlled rectifier, it is composed by IGBT and diodes, the network side power factor can be 1 (rectification state) or -1 (energy feedback state).The mathematical model of three-phase voltage-type PWM rectifier based on d ? qcoordinates is deduced, the voltage, current double closed-loop control structure is designed, the double closed-loop control system of PWM rectifier is established.In the direct touqer control, because the integrator of traditional U ? Istator flux observer which can't restraint DC drift error, so the Low-pass filter is instead of it, the amplitude and phase of the observed value of Stator flux are compensated.The traditional direct touqer control is improvement with DSVM (discrete space vector modulation), in this theory, the voltage vector is inceased, and the switching tables is established according to different speed,the large torque ripple is avoided. Because the vector control is opposite mature, based on it is analysed, the digtal equipment of vector control is tried to realize, the hardware circuit is built and the bottom software is drawn up,the test equipment of SVPWM(space vector PWM ) variable frequency adjustable speed system is established.The simulation system of the PWM rectifier, vector control, and direct touqer control are established. The simulation results proved that PWM rectifier can achieve two-way flow of energy, the vector control has a stable performance, and the torque ripple of direct torque control is reduced by the theory of DSVM, the DC drift error is restrainted by the stator flux observer which is improved.finally, the test is run by the test equipment of SVPWM variable frequency adjustable speed system, the motor is controlled well in 20HZ.