The analysis of AC/DC converter harmonics in transient state

Voltage and current network harmonics generated during operation of a DC motor drive supplied by AC/DC power converters are analyzed. Two kinds of current controlled AC/DC power converters are considered: (1) line-commutated; and (2) force commutated (PWM rectifiers). The full regulation loop is included. Transient states harmonics during speed and torque change are considered and compared with ones in steady-state. Results show their significant increase, specially during starting of DC drives. They exceed both short-term and long-term limits defined by existing standards or recommendations. Therefore harmonics in transient states must be taken into account when AC side filter is designed, particularly in cases of large size DC drives, where transient intervals are significant.