Compensation Of Dead-Time Effects Based On Adaptive Harmonic Filtering In The Vector-Controlled AC Motor Drives

The vector control theory combines the unified theory of electrical, electricalenergy conversion and coordinate transformation theory.Induction motor statorcurrent vector will be decomposed into two DC components by rotor fieldorientation to achieve decoupling. The induction motor is equivalent to a DCmotor.When the switching frequency is high or very low, the output voltagewaveform of the inverter distortion occurs significantly due to the dead-time effects,thereby causing current distortion. At the same time, additional losses and torquereduce the control performance. Therefore, the compensation of the vector controlsystem’s dead-time is of great significance to improve the quality of the control ofmotor.This paper analyzes the principle of the vector control, harmonic effects, thecommon method of dead time compensation, the effects of the output voltage and thecurrent waveforms of the inverter due to the dead-time effects. This paper presents anew PWM dead-time compensation method, which is called the compensation ofdead-time effects based on the Second order lattice Gray–Markel filter and based onharmonic analysis and distortion filter technology within the dead-time. Tocompensate the harmonic distortion, the harmonic compensator with all-pass-basedadaptive band-pass filter is proposed and is built up the feedback loop with currentcontrollers in order to minimize the distortions due to dead-time effects. The methodonly compensates the fundamental and sixth harmonic component of theinverter-output distortions in synchronous reference frame.The fundamentalcomponent is compensated by feed-forward adding a predetermined compensationsignal to the voltage reference of ac motor drive. The method is software intensiveand independent of the polarity of the phase currents and nonlinear-switchingcharacteristics varied with operating conditions of the inverter. It has a good effect toimprove the performance of the vector control system.At different frequencies, the dead-time compensator based on the adaptive filterhas different effects on the output current waveform, and the effect of harmoniccompensation is also different. On the basis of the above studies, the newcompensation method will be used in the vector control theory of the ACasynchronous motor using DSP to control, and then build simulation model in MATLAB to complete the verification. Simulation results show that the proposed method canimprove the distortions of the output voltage and the current waveforms and reducethe harmonic components significantly. The sixth-harmonic and the fundamentalharmonic are well compensated. This design meets the desired design effect.In orderto verify the actual compensation effects of the proposed method; I also did somepreparatory work for the test in this paper.