Dr. Akshay K. Rathore (Senior Member, IEEE) is an Associate Professor at Department of Electrical and Computer Engineering, Concordia University, Montreal, Canada since 2016. He was an Assistant Professor at National University of Singapore (NUS), Singapore from 2011-2015. He received his Masters degree in Electrical Machines and Drives from Indian Institute of Technology, BHU, Varanasi, India in 2003 and was awarded Gold Medal for securing highest standing among all electrical engineering specializations. He received his PhD degree in Power Electronics from University of Victoria, BC, Canada in 2008. He was a recipient of NSERC Research Assistantship, Univesity PhD full Fellowship, and Thouvenelle Graduate Scholarship. From Sept 2008Oct. 2010, he had two subsequent postdoctoral appointments with University of Wuppertal, Germany, and University of Illinois at Chicago, USA. He was a Visiting Professor at University of Technoology at BelfortMontbelliard (UTBM), France in 2015. Dr. Rathore has been working on analysis, design, and development of high-density soft-switching power electronics systems, in particular, current-fed topologies and novel pulsewidth modulation (PWM) techniques for low voltage high current aplications including renewables, distributed generation, microgrid, and electric transportation applications. He has successfully designed and developed several current-fed topologies in his lab and has demonstrated high performance. Presently, he invented a novel and innovative modulation technique to achieve snubberless zero current commutation and natural device voltage clamping of current-fed converters (songle-phase and three-phase topologies) solving their traditional problem of turn-off voltag spike and opening its market for industries. Recently, he designed and developed other class Impulse Commutated Current-fed Converters (single-phase and three-phase) with soft-switching or semiconductor devices and solving classical turn-off device voltage overshoort probem. In additon, he contributed to development of synchronous optimal PWM (SOP) techniques for low switching frequency of medium voltage multielevl inverter topologies for high power industrial ac drives and common mode elimination. He has 1 patent, commercialized by WEG Brazil. At NUS Singapore, he was the coordinator of NUS-IIT Bombay joint PhD program. At NUS Singapore, he was responsible for teaching and course revamp on Smart Grids, Modeling and Control of Advanced Power Conveters, and Modeling and Control of Electric Drives. He developed a lab manual for undergraduate course Solar Photovoltaic Energy Systems. He is currently the leader on current-fed research area. He secured above 3M$ research funding at Singapore through various industries and government agencies. He has supervised over 20 PhDs, postdoctoral fellows, research engineers, and graduate students. His two undergraduate students received Power Engineering Gold Medal for their projects. Dr. Rathore is a recipient of 2013 IEEE IAS Andrew W. Smith Outstanding Young Member Award (first working in Asia to receive this award) and 2014 Isao Takahashi Power Electronics Award. He has been listed in Marquis Who's Who in Science and Engineering in 2006, Who's Who in the World, and Who's Who in America in 2008. He was a consultant to WEG, Brazil, Crenergy Systems Pte Ltd, Singapore and Robert Bosch (SEA) Pte Ltd, Singapore. He has published over 130 research papers in reputed journals including 45 IEEE Transactions and IEEE international conferences, has 1 patent, and contributed to one book chpater. He delivered tutorials in IEEE International Conferences in Japan, India, China, and Nepal. He delivered technical guest lectures at various industries including ABB Baden, Switzerland, ABB Chennai, India, GE Bangalore, India, Schneider Electric Vancouver, Canada, and Delta-Q Burnaby, Canada. He has made sevral industry visits including Nextek Power Systems, USA, Princeton Power Systems, USA, Enphase Energy, USA, and KocoSolar, Germany. He has been a Technical Program Committee member for IAS Annual Meeting, ECCE, APEC, ECCE-Asia, and PEDES. He is a Member of IAS Industrial Power Converters Committee, Industrial Drives Committee, Industrial Automation and Control Committee, Transportation Systems Committee, and Renewable and Sustainable Energy Conversion Systems Committee. Dr. Rathore is Vice-Chair of IAS Industrial Automation and Control Committee (IACC), and Secretary of IAS Renewable and Sustainable Energy Conversion Systems Committee for 2016-17. He was IACC Awards SubCommittee Chair for 2014-15. He is Paper Review Chair (TCPRC) of Industrial Automation and Control Committee, IEEE Transactions on Industry Applications for 2016-17. He is an Associate Editor of IEEE Transactions on Industry Applications, IEEE Transactions on Industrial Electronics, IEEE Transactions on Transportaion Electrification, IEEE Transactions on Sustainable Energy, IEEE Journal of Emerging Selected Topics in Power Electronics, and IET Power Electronics. He has edited 3 special issues on Transportation Electrification on various IEEE Journals. He established and is mentoring IEEE IAS SB at Indian Institute of Technology (IIT), BHU, Varanasi, Uttar Pradesh Section, India (established Jan 2016). He was elected Secretary (2013-14) and Committee member (2011-12) for IEEE IAS Singapore Chapter. He is award committee member for IEEE IAS Andrew W Smith Outstanding Young member Achievement Award, 2015‐16. He was IAS nominated Academia Interface Committee Chair and IAS YPP Event Organizer and Moderator at ITEC‐India 2015, Chennai, India. He was a panelist at YPP event at APEC 2015, Charlotte, USA. Contact information: Concordia University, Montreal, Canada e-mail: [email protected] Lecture Topics 1. Snubberless Naturally Clamped Soft-switching Bidirectional Current-fed Converters Bidirectional dc/dc converters are required for energy storage and dc microgrid applications. Current-fed converters offer inherent voltage gain, short circuit protection and current limiting features, and are suitable for such applications. However traditional drawback of voltage spike at turn-off across the semiconductor devices has limited the use the current-fed topologies. Conventionally, dissipative/passive snubbers or active-clamping circuits have been adopted to address this problem. However, such circuits introduce complexity, reduce efficiency, and compromise on original boost capacity of the converters. Low peak and circulating current through the devices are limited than conventional current-fed and voltagefed PWM and resonant converters. It, therefore, delivers higher efficiency. Snubberless Naturally Clamped Current-fed Converters refer to a new class of converters with a newly developed modulation scheme that solves this traditional problem without any additional snubber or auxiliary clamp circuit while preserving the boost capacity and circuit originality. This newly invented modulation technique has been implemented on single-phase, threephase, and interleaved topologies and demonstrated the attributes of natural voltage clamping and zero current commutation of semiconductor devices along with soft-switching. This class of converters will open scope for current-fed converters in industries. It is a fixed frequency duty cycle modulation and only a series inductance value between source and load needs to be designed. 2. Impulse Commutated Frequency Modulated Soft-switching Current-fed Converters Impulse Commutated Current-fed Converters is mainly ‘Unidirectional’ class of current-fed converters attaining soft-switching, zero current commutation and voltage clamping of semiconductor devices through a high-frequency resonant tank. It is a simple, easy, and cost effective way of solving the traditional turn-off voltage spike across the devices. The important point to note is that this is not a resonant converter because the design is done such that the resonance takes place during a short period, i.e., overlap period of devices when turnoff procedure of a pair of devices is about to start. Therefore, it offers benefits of peak and circulating current limitations as compared to the conventional resonant converters. Device rms and average currents also reduce with load current and therefore, do not compromise on partial load efficiency. These converters are suitable for solar photovoltaic and fuel cell application or in general mainly low voltage high current applications. Voltage gain characteristic is immune to load variation. However, voltage regulation against source voltage variation is attained through frequency modulation. A detailed and systematic analysis and design procedure is developed to design the resonant tank to achieve the desired attributes. This new class opens scope for renewable industries. 3. 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. 4. Common Mode Voltage Elimination in Dual Inverter Fed Open End Winding Induction Machines Common mode voltage is a major concern in open-end winding machines operated from common dc link inverters. Common dc link inverters eliminate the need of multi-winding transformer but require a bulky common mode inductor to suppress the common mode currents in machine developed due to common mode voltage. Several techniques have been proposed to reduce the common mode voltage and so the size of the common mode inductor. A modified Synchronous Optimal Pulsewidth (SOP) modulation technique is developed and implemented to completely eliminate the common mode current and eliminate the need of bulky and costly common mode inductor. A simple off-line method limits the device switching losses, total harmonic distortion as well as set common mode current to zero. It is quite applied to industrial applications requires 6 cables to go in the field away from the inverters. Simple off-line determination of optimal switching points of the one inverter devices over a switching cycle and 120o phase-shifted for other inverter devices achieves the said objectives. The algorithm has been implemented and experimentally demonstrated for five-level and modular multilevel inverters. 5. Single Reference Six Pulse Modulation (SRSPM) for High-Frequency Pulsating DC Link Three-Phase Inverters Sinusoidal Pulse Width Modulation (SPWM) technique has been a powerful method to generate sine waveform at inverter output from a fixed dc link input. Similarly, space vector modulation (SVM) and carrier based three-reference three-phase sine modulation have been widely adopted for three-phase sine AC output from a fixed dc link. These two modulation techniques are implemented on 3-phase 3-leg (6 switches) six-step inverter topology if the dc link voltage is much higher than desired three-phase rms output. However, if the source/dc link voltage is lower or much lower than ac rms output, then frond-end dc/dc converters becomes necessary. To implement existing SVM or carrier based modulation, traditionally large number of devices (three dc/dc bridges), three-phase magnetics, and large costly unreliable electrolytic capacitor are employed to develop a high voltage dc link at inverter input. Novel Single-reference-Six-Pulse Modulation (SRSPM) reduces the need of threephase dc/dc system, three-phase magnetics to single-bridge Single-phase magnetics and completely eliminates the dc link electrolytic capacitor allowing pulsating dc link voltage waveform at the inverter input. It significantly reduces the cost, size, and weight and improves reliability of the system. The control complexity is much simplified because of reduced reference signals generation and gate driving requirements due to reduced number of devices. This novel SRSPM is simple and results in saving of 87% switching losses. The concept has been experimentally implemented and demonstrated with closed loop control to achieve 97% efficiency at low voltage high current specifications. 6. High-Frequency Soft-Switching PWM and Resonant DC/DC Converter Topologies for Solar/Fuel Cell Applications High-frequency operation is desired to realize a low cost, light weight and compact power electronics system. However, efficiency is major concern owing to hard-switching of the semiconductor devices at high device switching frequency. To mitigate the switching losses and achieve high efficiency, soft-switching is necessary. Soft-switching can be implemented in several ways, (1) Modulation technique, (2) Resonant tank leading to development of resonant converters, and (3) Auxiliary Transition Circuit. These types have their own merits and demerits based on the applications and specifications. Still, major challenge is to maintain soft-switching with variations in source voltage and load current. To maintain softswitching and high efficiency over such large various without compromise on circuit complexity and rated load performance (circulating currents and components’ ratings) is a real challenge. A classification of specifications has been done to determine the suitability of a particular converter from variety of converters, i.e., voltage-fed and current-fed converters, PWM and resonant converters, and circuit topology. Detailed analysis and results justify how to select and choose a type of soft-switching converter and topology for given source/load profiles and specifications.