Quasi-active Power Factor Correction: The Role of Variable Inductance

Werner Wölfle, Prof. W. G. Hurley

The mains current in an AC/DC converter contains periodic current pulses, due to the action of the rectifier and the output buffer capacitor. The high current peaks cause harmonic distortion of the supply current and low power factor. The level of harmonics can be reduced by introducing active power factor correction in the form of a DC/DC converter with almost sinusoidal input current. The design parameters for such a pre-regulator are investigated in principle in this project. Passive power factor correction in the form of an input filter inductor is less expensive but as a 50Hz component it is bulky and must be sized to handle the full power range of a standard power supply. This project investigates the use of variable inductance (the inductance varies with current), which provides adequate harmonic reduction. Three types of inductors are analysed and investigated: an inductor with a fixed air-gap operating with a saturated core, a swinging inductor which has a stepped gap and a novel inductor construction with a sloped air-gap. Results are presented for 200W power supply and it is shown that the sloped air-gap inductor has the best performance in terms of harmonic response and size.

Start date: 1st of September 1998. This project has been completed.

Project collaborators: Convertec Ltd

Project Publications

Journal
L. Zhang, W. G. Hurley, W. H. Wölfle, “A New Approach to Achieve Maximum Power Point Tracking for PV System with a Variable Inductor”, IEEE Trans. on Power Electronics (Special Issue on Microgrids), vol.  26, no. 4, pp. 1031-1037, April 2011.
W. G. Hurley, W. Wölfle, "Quasi-Active Power Factor Correction with a Variable Inductive Filter: Theory, Design and Practice", IEEE Trans. on Power Electronics, vol. 18, no. 1, pp. 248-255, January 2003.

Conference
L. Zhang, W. G. Hurley, W. H. Wölfle, “A New Approach to Achieve Maximum Power Point Tracking for PV System with a Variable Inductor”, 2nd International Symposium on Power Electronics for Distributed Generation Systems, PEDG 2010, Hefei, China, pp. 948-952, June 2010.
W. Wölfle, W. G. Hurley, "Power Factor Correction and Harmonic Filtering for AC/DC Converters", Proceedings of the 28th IEEE Industrial Electronics Conference, IECON'02, Seville, Spain, pp. 3238-3243, (Invited paper), November 2002.
U. Reghelin, W. G. Hurley, W. Wölfle, "Quasi-Active Power Factor Correction with a Variable Inductive Filter: Finite Element Analysis", Proceedings of the 37th Universities Power Engineering Conference, UPEC2002, Staffordshire University, pp. 431-435, September 2002.
W. Wölfle, W. G. Hurley, S. Lambert, "Quasi-active Power Factor Correction: the Role of Variable Inductance", Proceedings of the IEEE Power Electronics Specialists Conference, PESC'01, Vancouver, Canada, vol. 4, pp. 2078-2083, June 2001.
W. Wölfle, W. G. Hurley, S. Arnold, "Power Factor Correction for AC-DC Converters with Cost Effective Inductive Filtering", Proceedings of the IEEE Power Electronics Specialists Conference, PESC'00, Galway, Ireland, pp. 332-337, June 2000.

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