1412 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 38, NO. 5, SEPTEMBER/OCTOBER 2002 A Unity-Power-Factor Buck-Type PWM Rectifier for Medium/High-Power DC Motor Drive Applications Hazım Faruk Bilgin, Member, IEEE, K. Nadir Köse, Gürkan Zenginobuz, Muammer Ermis ¸, Member, IEEE, Erbil Nalçacı, Is ¸ık Çadırcı, Member, IEEE, and Hasan Köse Abstract—This paper describes the application of a single-stage unity-power-factor buck-type pulsewidth modulation (PWM) rec- tifier to medium- and high-power variable-speed dc motor drives. The advantages of the developed system are low harmonic dis- tortion in ac supply currents (complying with IEEE Std. 519 and IEC 555), nearly unity power factor over a wide oper- ating shaft speed range, and nearly level armature current and voltage waveforms. These properties of output voltage and current quantities of the converter eliminate entirely any failure risk in current commutation even for oldest motor designs, and further motor problems such as accelerated aging in motor insulation, and mechanical failure due to circulating bearing currents. The design criteria and operating features and characteristics of the buck-type PWM rectifier employed in a unity-power-factor dc motor drive are discussed in the paper. The performance of the resulting system has been tested on 25–65-kW 100–150-A 10–20-kHz dc motor drives, used in various processes of an iron and steel plant. Index Terms—DC motor drives, power quality, pulsewidth modulation, rectifiers. I. INTRODUCTION I N RECENT YEARS, increasing emphasis on power quality has directed researchers toward proposing and developing inherently clean new power converter topologies. These con- verters operate at nearly unity power factor (PF), inject very low harmonic content into the supply, and work at relatively high converter efficiencies. Several unity-PF rectifier topologies such as the buck, boost, and buck–boost-derived topologies with or without isolation have been proposed to date. Their performances have been reported in the literature [1]–[12]. Among these, the unity-PF buck-type pulsewidth modulation (PWM) rectifier is one of the most common topologies studied in detail over the past ten years [2], [4]–[11]. These studies deal only with the Paper IPCSD 02–037, presented at the 2001 Industry Applications Society Annual Meeting, Chicago, IL, September 30–October 5, and approved for pub- lication in the IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS by the Indus- trial Power Converter Committee of the IEEE Industry Applications Society. Manuscript submitted for review August 1, 2001 and released for publication June 7, 2002. H. F. Bilgin, M. Ermis ¸, E. Nalçacı, and I. Çadırcı are with the TÜB ˙ ITAK-METU Information Technologies and Electronics Research Institute, TR06531 Ankara, Turkey, and also with the Electrical and Elec- tronics Engineering Department, Middle East Technical University, TR06531 Ankara, Turkey (e-mail: faruk.bilgin@bilten.metu.edu.tr; ermis@metu.edu.tr; aenal@rorqual.cc.metu.edu.tr; cadirci@bilten.metu.edu.tr). K. N. Köse and G. Zenginobuz are with the TÜB ˙ ITAK-METU Information Technologies and Electronics Research Institute, TR06531 Ankara, Turkey. H. Köse is with the ISKENDERUN Iron and Steel Plant, TR31319 Hatay, Turkey. Publisher Item Identifier 10.1109/TIA.2002.803005. application of unity-PF buck-type PWM rectifier to passive loads [2], [4]–[6], [8]–[10] except [11], which investigates the converter–dc motor combination. Unfortunately, there are limited publications on the use of this converter in practical applications [7]. Many high-frequency PWM techniques, such as the modified sinusoidal PWM [2], space-vector modulation [4], and delta modulation [10] techniques have been proposed, and imple- mented for the single-stage three-phase buck-type PWM recti- fier. The operating principles and design criteria for buck-type PWM rectifier using modified sinusoidal PWM technique are given in [2]. A modified sinusoidal PWM-technique-based algorithm which is employing a separate control loop for compensation of input current displacement factor in steady state and output voltage regulation has been developed in [5]. The PWM technique using a space-vector modulation has been developed and implemented for buck-type PWM rectifiers in [4]. Isolated buck-type PWM rectifiers have been investigated in [6] and [8], and zero-voltage switching for these types has been realized in [6]. Buck-type PWM rectifier offers a good solution for direct conversion of ac to dc at high power densities to meet the strict PF penalty limits imposed by electricity authorities and input line current harmonic distortion limits dictated by various har- monic standards such as IEEE Std. 519, IEC 555, etc. One inter- esting application of this converter may be the upgrading work that can be conducted on dc motor drives still working in in- dustry to comply with present power quality regulations. This converter also offers superior output characteristics, especially for old dc motor designs when combined with a simple and, hence, cheap high-frequency output filter. This paper deals with the design and implementation of a three-phase buck-type PWM rectifier for medium/high-power dc motor drive applications. Design criteria, important features of the resulting dc motor drives, and operating characteristics of the buck-type PWM rectifier in variable-speed dc motor ap- plications are given in the paper. Successful performance fig- ures for the resulting dc motor drives have been obtained in the field. This upgrading work has been applied to various pro- cesses of the Iskenderun Iron and Steel Plant, Hatay, Turkey, resulting in minimized downtimes, reduced periodic inspection and maintenance work, and increased conversion efficiencies since mid-2000. II. PROBLEM DEFINITION In this paper, the three-phase unity-PF buck-type PWM rectifier has been applied to medium-power adjustable-speed 0093-9994/02$17.00 © 2002 IEEE