Controlled AC drives with ride-through capability at power interruption

General-purpose PWM (pulse width modulated) inverter drives are equipped with an undervoltage protection mechanism, causing the system to shut down within a few milliseconds after a power interruption in the mains. This may entail loss or damage of material in such critical applications as the production of textile fibers on paper, or with extruder drives. The proposed solution to this problem is to recover some of the mechanical energy stored in the rotating masses. When a power interruption occurs, a sequence of fast feedforwarded commands is applied to force an immediate transition into the regeneration mode. During the interrupt interval, the drive system continues to operate at almost zero torque, just regenerating a minor amount of power to cover the electrical losses in the inverter. The method is implemented in an additional software package to be used with general-purpose inverter drives of limited dynamic performance. Experimental results are presented