On-line filtering reactance identification in voltage-source three-phase active-front-end rectifiers

PWM voltage-source three-phase active-front-end rectifiers are a well established alternative in adjustable speed drives. They allow near sinusoidal input currents and thus near unity power factor while providing the active power required by the load. Moreover, recently introduced control strategies allow these topologies compensate reactive power while controlling the active power. The performance of the topology depends upon the appropriate operation of the line inductances that are required as ac filters by the topology. Such line inductors are under severe working conditions as PWM type of voltage waveforms are applied across it. This will eventually lead to deviation of the nominal inductance values and hence control strategies will not longer operate as designed. Particularly, the presence of non characteristics harmonics is produced. This paper presents an alternative to on-line identification of the ac inductors values that can be used for diagnosis purposes of the ac filter status and by the control strategy in order to compensate their negative effects.