Digital control of three-phase PWM inverters for UPSs using dead-beat observer

The authors describe a digital control method operated by a digital signal processor (DSP) of a three-phase PWM inverter with an inductor-capacitor (L-C) filter for uninterruptible power supplies (UPSs) in the inverter output. The inverter output voltage control system has a minor loop of the filter capacitor current. In the loop, a full-order observer operating at dead-beat estimation compensates a lag-time caused by the DSP and disturbances. The observer estimates the capacitor current and the disturbances. Controllers for the current and the voltage control system consist of a dead-beat controller and a proportional compensator respectively. Experimental results showed output voltage distortion of 0.84% at a 10 kVa capacitor input rectifier load and voltage regulation under 0.5%.<<ETX>>