Control of single phase power factor pre-regulator for an on-line uninterruptible power supply using fuzzy logic inference

A fuzzy logic inference control scheme is proposed and applied in control of a power factor corrected (PFC) pre-regulator used in a high performance online uninterruptible power supply (UPS). Since the performance of a fuzzy logic controller only depends on the selection of membership functions and the inference of fuzzy rules, and fuzzy set theory, in nature, is capable of working with nonlinear systems, the fuzzy logic controllers have an advantage in coping with the time varying nonlinearity of switches in PFC pre-regulator, and it does not require an accurate mathematical model of the PFC pre-regulator when the controller is designed. This fuzzy logic controller used for PFC pre-regulator has been realized by using a 16 bit digital signal processor (DSP). Experimental verifications have been carried out on a 3 kVA UPS. The experiment results show that the fuzzy logic inference based controller can achieve both good dynamic response and low total harmonic distortion (THD) under large load disturbance and plant uncertainties