A novel line synchronisation method for PWM rectifiers-theory and application

A control method has been described that allows a standard AC motor drive to be used as a PWM rectifier without additional hardware. By using the PWM modulator output voltage to give indirect supply voltage sensing, phase information is available at every sample. When used with a PLL, this gives robust line synchronisation as has been demonstrated. Pre-start tests, required to pre-load various parts of the control system when starting, have been described and proven to give excellent supply synchronisation. Field experience with systems up to 1 MW has shown the method to be very reliable.