Stability Analysis of PFC Converters Under Different Source Impedances and Its Consequences on Zero-Crossing Distortion

Abstract

In the presence of multiple power converters in a power system the total current may exhibit zero-crossing distortion in the form of recurrent damped oscillations with high magnitude. These oscillations are synchronized with the power system frequency. This paper presents a comprehensive analysis of the input current of single-phase ac-dc converters fitted with power factor correction (PFC) controllers. Emphasis is given on the impacts of the source impedance, and on how the number of converters connected to a common coupling point (PCC) impacts the PFC controller’s performance. A system model is developed followed by simulation and measurements in a real installation with electronic ballasts used to drive fluorescent lighting tubes. Results show that the recurrent damped oscillations originating from PFC controllers are close to the harmonic range and with a very low level of cancellation between devices. The magnitude therefore increases proportionally with the number of devices. As the source impedance increases, instability may occur. Possible explanations for these observations are discussed.