Instantaneous feedback control of a single-phase PWM inverter with nonlinear loads by sine wave tracking

The authors propose a novel method for the instantaneous digital control of a PWM (pulse-width modulated) inverter used in an uninterruptible power supply. The output voltage is compared to a sinusoidal reference at each sampling instant to compute in real time through a digital controller the pulse width of the same interval. The closed-loop digital feedback eliminates the steady-state error of the output voltage with a very short computation time. This strategy is verified through computer simulations and provides a very fast compensation of disturbances caused by nonlinear loads, such as rectifiers and triac loads, with low total harmonic distortion and fundamental control. >