An optimized control of PWM-rectifiers with predicted variable duty-cycles

An optimized control of PWM voltage source rectifiers (VSR) is presented. First, in a multi-input look-up table the different converter voltage-vectors are ordered with respect to their aptitude to increase (or decrease) the active power, depending on the angular position of the input voltage vector. A simple procedure allows the quick selection of the most suitable converter-voltage which ensures the correct slope sign of both active and reactive power, in order to satisfy the respective reference values. A predictive procedure evaluates the application time of the selected voltage vector within the actual sampling interval, in order to keep the instantaneous active power inside prefixed hysteresis bands. The proposed algorithm quickly evaluates also the voltage vector to be applied in the remaining part of the sampling interval. Numerical investigations in some heavy operating conditions are carried out at a fixed average value of the switching frequency, especially with reference to current distortion and asymmetry.