Cascaded Proportional Control with Algebraic Estimators for PFC AC/DC Converters

Abstract

Conventionally, a proportional-integral (PI)-based dual-loop control strategy, in which both the dc-bus voltage and the inductor current are regulated, is utilized to control ac/dc converters with power factor correction (PFC). Due to the characteristics of the PI controller, converters experience poor control performance such as current distortion and slow dynamic response. This paper proposes a novel cascaded proportional control in conjunction with algebraic estimation method for PFC ac/dc converters. Different from the conventional control system, the average dc-bus energy and the instantaneous input power of the converter are regulated. Moreover, system nonlinearity, load power and uncertainties are estimated by incorporating algebraic estimators. A holistic design of controller parameters and stability analysis are presented based on the z-domain transfer functions. A 1 kW PFC ac/dc prototype is designed and experimental results demonstrate the effectiveness of the proposed control scheme.