Lecturer：Dr. Akshay K. Rathore
Topic：Low Switching Frequency Control of Medium Voltage Multilevel Inverters for High Power Industrial AC Drives
To ensure high efficiency for high power applications, it is better to raise voltage level than current level to reduce conduction losses. For this reason, medium voltage level (>4kV) has gained importance over low voltage (690 V) level for industrial applications including manufacturing and marine. However, owing to limitation on blocking voltage of available devices, multilevel inverter topologies have been introduced. To limit the switching losses of semiconductor devices in multilevel inverters at medium voltage high power, low device witching frequency modulation is desired. Low device switching frequency modulation results into higher total harmonic distortion of inverter output/machine current that requires large filter size. A novel Synchronous Optimal Pulsewidth (SOP) modulation technique is developed and implemented to reduce the device switching frequency down to 20% without compromising on harmonic distortion and filter requirements. It limits switching losses of semiconductor devices and reduces thermal and cooling requirements. Even 0.2% saving is significant at MW power level as it drastically reduces thermal and cooling requirements as well as energy saving over time is huge and can feed the most of the auxiliary load. It is a patented software based offline technique commercialized by WEG, Brazil in their products. A generalized analysis and mathematical model of the SOP technique is developed to implement it for any voltage levels of multilevel inverters. Recently, 50Hz device switching frequency for seven level inverters has been implemented and experimentally demonstrated.
Dr. Akshay K. Rathore Info：
Dr. Akshay Kumar Rathore received the M.Tech. degree from the Indian Institute of Technology (BHU), Varanasi, India, in 2003. He received the Ph.D. degree from the University of Victoria, Victoria, BC, Canada, in 2008. He had two subsequent Postdoctoral Research Appointments with the University of Wuppertal, Germany, and University of Illinois at Chicago, IL, USA. From November 2010 to February 2016, he was an Assistant Professor in the Department of Electrical and Computer Engineering, National University of Singapore, Singapore. He is currently an Associate Professor at the Department of Electrical and Computer Engineering, Concordia University, Montreal, QC, Canada. He has published more than 170 research papers in international journals and conferences including 58 IEEE Transactions. His research is mainly focused on current-fed converters and multilevel inverters. He is leading the area of current-fed power electronics and contributed to analysis, design, and development of new classes of such converters.