The Research Of The Low-speed Performance Of The Inverter Dead Time Compensation

With the development of Power Electronic and Computer Control technology，AC SpeedRegulation technique is obtaining a more and more extensive application. While among theapplications，most control system are based on V/F and the rest adopt SPWM AC-DC-ACinvertor. The use of power electronics device overcomes a lot of problems in the AC SpeedRegulation，improving the performance of AC Speed Regulation. However，the performanceof Frequency Transformer control system is not ideal running in the low speed，such as poorstarting performance，small torque at low speed，week loading capacity，low speed torqueripple and instable rotation. In order to improve the low speed performance of V/F control ofthe asynchronous motor，I opt the dead zone of inverter，affecting the system performance atlow speed and system stability，to analysis and research.Firstly，in order to improve the low speed motor startup performance，I did the analysisof the mathematical model of asynchronous motor， considering the stator voltagecompensation.Secondly，I analysis the motor open-loop control system to solve the low speed torqueripple while the motor rotation is not smooth. The reasons for the unsteady voltage outputwaveform distortion is the waveform distortion jitter of frequency conversion device in theposition of the motor.Thirdly，in order to solve the waveform distortion，basing on the working principle ofinvertor，I analyses the mechanism of dead zone and the influence of dead zone of inverteroutput. To eliminate the dead zone effect on the output current and output voltage，I designeda method based on "four zero" the pulse of dead zone compensation. The technical difficultyof Dead zone compensation is the judgment of the polarity of the stator current. Through thecombination of software，hardware and the use of high performance Hall current closed-loopsensor solved current polarity detection problems. Finally，I applied the designed compensation solution to the SC400VA series inverter andthrough the actual testing，debugging results conclude that the compensation methodimproves torque output，current waveform，stability of rotation at low frequency quite well.