Comparison of a active harmonic compensator with PWM and delta modulation under distorted voltage conditions

摘要

This paper, presents three phase shunt active filter under distorted voltage condition, the active power filter control is based on the use of self tuning filter (STF) for reference current generation and on a modulated hysteresis current controller for generation of pulses, classical extraction technique such as instantaneous p-q theory for reference current generation and with delta modulation for generation of pulses. The dc capacitor voltage is controlled by fuzzy logic controller. The diode rectifier feed RL load is taken as a nonlinear load. Comparisons made between the use of Self Tuning Filter based extraction technique of the 3 level inverter with that of classical extraction technique with Delta Modulation. The self tuning filter allows extracting directly the voltage and current fundamental components in the axis without phase locked loop (PLL) under distorted voltage condition. The comparative analysis is made based on working under distorted voltage condition, and the total harmonic distortion of source current after compensation. Self tuning filter based extraction technique is good under distorted voltage conditions. The total harmonic distortion (THD) of source current is fully reduced and inverter switching is 3–4 times fast in delta modulation based active filter, but it produces poor result under distorted voltage condition. The effectiveness of the two methods is theoretically studied and verified by computer simulation.