PWM-synchronised flux position estimator for sensorless motor drive with IM based on FPGA

This article presents a PWM-synchronised flux position estimator implemented with use of FPGA applied to sensorless motor drive with IM. Combining PWM modulator with synchronised analog to digital converters allows for precise current measurement without the glitch effect. The direct information about voltage vectors timing, together with right current and DC-voltage measurements during switching sequence allow for precise current derivative determination with reduced noise and converter nonlinearities. This way the EMF calculation is more precise. The unit has three main tasks: I: generating the PWM signals, II: synchronised measurement of the voltages and currents in the machine and converter during each switching sequence, and III: rotor flux position estimation using zero and active PWM periods (essential in field oriented control of AC motor drive). The measurement and estimation scheme allows for the sensorless speed control and flux estimation algorithms which are further developed to relieve the processor from much of its processing load