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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.