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Nikita joined Dyson Institute as a Lecturer in Electronics in Sept 2020. Before that, she was a Schlumberger Post-Doctoral Fellow at the Department of Engineering Sciences, University of Oxford (2019-20) with a Doctorate in Electrical Engineering from University of Cambridge (2013-18). She was a gold medallist and university topper for both undergraduate (BTech) and master’s degree (MTech) in Engineering. She undertook her PhD research in Electrical Engineering from the Department of Engineering, University of Cambridge as a Churchill College member. She was awarded scholarships from Cambridge University Nehru Trust, Federation for Women Graduates and Google Europe to pursue her multidisciplinary research in Gallium Nitride (GaN) power electronics. Her doctoral research investigated introducing Machine Learning to bridge the gap between the laboratory and commercial application space in GaN power electronics. Nikita's current multi-disciplinary research interests range from Machine learning for Power Electronics, GaN Power Electronics, AI Policy to Disruptive Technology Innovations in Engineering and its Impact on Developing Economies & Socio-Cultural Identities. Listed in the ‘Top 50 Women in Engineering in UK' in 2017(Women’s Engineering Society), she is a Global Ambassador for the Queen Elizabeth Prize for Engineering and a TEDx Speaker. Beyond an educator, Nikita is a EdTech Entrepreneur and a champion for women in STEM aspiring to engineer society for good.
This paper begins with a comprehensive review into the existing GaN device models. Secondly, it identifies the need for a more accurate GaN switching model. A simple practical process based on radio frequency techniques using vector network analyser is introduced in this paper as an original contribution. It was applied to extract the impedances of the GaN device to develop an efficient behavioural model. The switching behaviour of the model was validated using both simulation and real time double pulse test experiments at 500 V, 15 A conditions. The proposed model is much easier for power designers to handle, without the need for knowledge about the physics or geometry of the device. The proposed model for Transphorm GaN HEMT was found to be 95.2% more accurate when compared to the existing LT-spice manufacturer model. This work additionally highlights the need to adopt established RF techniques into power electronics to reduce the learning curve while dealing with these novel high-speed switching devices.
Nikita Hari; Sridhar Ramasamy; Mominul Ahsan; Julfikar Haider; Eduardo M. G. Rodrigues. An RF Approach to Modelling Gallium Nitride Power Devices Using Parasitic Extraction. Electronics 2020, 9, 2007 .
AMA StyleNikita Hari, Sridhar Ramasamy, Mominul Ahsan, Julfikar Haider, Eduardo M. G. Rodrigues. An RF Approach to Modelling Gallium Nitride Power Devices Using Parasitic Extraction. Electronics. 2020; 9 (12):2007.
Chicago/Turabian StyleNikita Hari; Sridhar Ramasamy; Mominul Ahsan; Julfikar Haider; Eduardo M. G. Rodrigues. 2020. "An RF Approach to Modelling Gallium Nitride Power Devices Using Parasitic Extraction." Electronics 9, no. 12: 2007.
Nikita Hari; Mominul Ahsan; Sridhar Ramasamy; Padmanaban Sanjeevikumar; Alhussein Albarbar; Frede Blaabjerg. Gallium Nitride Power Electronic Devices Modeling Using Machine Learning. IEEE Access 2020, 8, 119654 -119667.
AMA StyleNikita Hari, Mominul Ahsan, Sridhar Ramasamy, Padmanaban Sanjeevikumar, Alhussein Albarbar, Frede Blaabjerg. Gallium Nitride Power Electronic Devices Modeling Using Machine Learning. IEEE Access. 2020; 8 ():119654-119667.
Chicago/Turabian StyleNikita Hari; Mominul Ahsan; Sridhar Ramasamy; Padmanaban Sanjeevikumar; Alhussein Albarbar; Frede Blaabjerg. 2020. "Gallium Nitride Power Electronic Devices Modeling Using Machine Learning." IEEE Access 8, no. : 119654-119667.
In recent trends, the use of electric vehicles is taking a sudden hike as they seem to be a much more friendly for the environment as compared to the conventional vehicles that run on combustion engines for a mode of transportation. With the increasing popularity of electric vehicles, the demand on the utility grid is also increasing. To overcome this problem, other alternative sources of energy need to be considered. Photovoltaic energy as the solution is finding its place in the EV charging systems. However, the total amount of energy that can be generated from the PV system is constrained, based on many parameters such as solar radiation, availability of space for Solar power plant development, maintenance of the system, etc. Hence, to maintain the continuity of the system, it needs to be integrated with the grid as well. This offers a smooth charging operation for the electric vehicles. In this paper, a new method is introduced for the integration between the solar inverter system and the utility transmission grid. Quasi-Z-source topology is proposed for the system integration. This topology facilitates a bidirectional flow of power between the PV source, the storage unit and the utility grid. The greatest advantage of this topology is its flexibility with different voltage levels of the solar inverter DC connection and the storage battery which requires no circuit alteration for charging batteries of different ratings. The hardware for the system is also fabricated. The results demonstrate that the proposed topology fits the generalized requirements.
D Sattianadan; K Saravanan; S. Murugan; Nikita Hari; P. Venkadesh. Implementation of quasi-z source inverter for grid connected PV based charging station of electric vehicle. International Journal of Power Electronics and Drive Systems (IJPEDS) 2019, 10, 366 -373.
AMA StyleD Sattianadan, K Saravanan, S. Murugan, Nikita Hari, P. Venkadesh. Implementation of quasi-z source inverter for grid connected PV based charging station of electric vehicle. International Journal of Power Electronics and Drive Systems (IJPEDS). 2019; 10 (1):366-373.
Chicago/Turabian StyleD Sattianadan; K Saravanan; S. Murugan; Nikita Hari; P. Venkadesh. 2019. "Implementation of quasi-z source inverter for grid connected PV based charging station of electric vehicle." International Journal of Power Electronics and Drive Systems (IJPEDS) 10, no. 1: 366-373.
A novel approach to modelling Gallium Nitride (GaN) power devices using Machine Learning (ML) is presented in this paper. To make it easier for the power designers to use GaN devices, this work proposes deep feed forward GaN ML device models which are highly accurate and can predict the switching behaviour of the device without having to delve into the physics and geometry of the device. The strategy in this research work is to use deep learning techniques to build a GaN based regression model using stochastic gradient algorithm by back propagation. Among the different neural network architectures trained and tested, a deep feed forward neural network with 5 hidden layers and 30 neurons, was found to be the best for prediction and optimization. The possibility of employing ML techniques for GaN can help open doors for faster commercialization of GaN power electronics.
Nikita Hari; Soham Chatterjee; Archana Iyer. Gallium Nitride Power Device Modeling using Deep Feed Forward Neural Networks. 2018 1st Workshop on Wide Bandgap Power Devices and Applications in Asia (WiPDA Asia) 2018, 164 -168.
AMA StyleNikita Hari, Soham Chatterjee, Archana Iyer. Gallium Nitride Power Device Modeling using Deep Feed Forward Neural Networks. 2018 1st Workshop on Wide Bandgap Power Devices and Applications in Asia (WiPDA Asia). 2018; ():164-168.
Chicago/Turabian StyleNikita Hari; Soham Chatterjee; Archana Iyer. 2018. "Gallium Nitride Power Device Modeling using Deep Feed Forward Neural Networks." 2018 1st Workshop on Wide Bandgap Power Devices and Applications in Asia (WiPDA Asia) , no. : 164-168.
Wide Band Gap power semiconductor switching devices offer superior performance compared to an equivalent Si power device. SiC MOSFETs can be competitive when compared to Si IGBTs of the same voltage class, whilst offering greater benefits at high switching frequencies. Operating SiC MOSFETs at high switching frequencies imposes significant challenges, including: Ringing and voltage overshoot issues, making accurate high bandwidth measurements, and the requirement for a high-performance gate drive circuit. This paper presents a prototype low inductance PCB design for a SiC MOSFET switching circuit. In addition, a linear current gate-drive circuit and a high bandwidth on-board measurement system have been developed and the designs for these are presented. The measurement system showed good agreement with the external probe measurements and superior bandwidth. Hard-switching tests with a 900V SiC MOSFET showed that the dVDS/dt becomes largely invariant to changes in load current when using a current source gate drive. The measured dVDS/dt slew rates are compared with the dVDS/dt slew rates estimated from the parameter values given in the SiC MOSFET datasheet, and the two sets of results show good agreement. In this paper, the performance of an optimised circuit is successfully demonstrated and the benefits are discussed.
Edward Shelton; Xueqiang Zhang; Tianqi Zhang; Nikita Hari; Patrick Palmer. Low inductance switching for SiC MOSFET based power circuit. 2017 IEEE Energy Conversion Congress and Exposition (ECCE) 2017, 5093 -5100.
AMA StyleEdward Shelton, Xueqiang Zhang, Tianqi Zhang, Nikita Hari, Patrick Palmer. Low inductance switching for SiC MOSFET based power circuit. 2017 IEEE Energy Conversion Congress and Exposition (ECCE). 2017; ():5093-5100.
Chicago/Turabian StyleEdward Shelton; Xueqiang Zhang; Tianqi Zhang; Nikita Hari; Patrick Palmer. 2017. "Low inductance switching for SiC MOSFET based power circuit." 2017 IEEE Energy Conversion Congress and Exposition (ECCE) , no. : 5093-5100.
Ed Shelton; Nikita Hari; Xueqiang Zhang; Tianqi Zhang; Jin Zhang; Patrick Palmer. Design and measurement considerations for WBG switching circuits. 2017 19th European Conference on Power Electronics and Applications (EPE'17 ECCE Europe) 2017, 1 .
AMA StyleEd Shelton, Nikita Hari, Xueqiang Zhang, Tianqi Zhang, Jin Zhang, Patrick Palmer. Design and measurement considerations for WBG switching circuits. 2017 19th European Conference on Power Electronics and Applications (EPE'17 ECCE Europe). 2017; ():1.
Chicago/Turabian StyleEd Shelton; Nikita Hari; Xueqiang Zhang; Tianqi Zhang; Jin Zhang; Patrick Palmer. 2017. "Design and measurement considerations for WBG switching circuits." 2017 19th European Conference on Power Electronics and Applications (EPE'17 ECCE Europe) , no. : 1.
Nikita Hari; Teng Long; Edward Shelton. Investigation of gate drive strategies for high voltage GaN HEMTs. Energy Procedia 2017, 117, 1152 -1159.
AMA StyleNikita Hari, Teng Long, Edward Shelton. Investigation of gate drive strategies for high voltage GaN HEMTs. Energy Procedia. 2017; 117 ():1152-1159.
Chicago/Turabian StyleNikita Hari; Teng Long; Edward Shelton. 2017. "Investigation of gate drive strategies for high voltage GaN HEMTs." Energy Procedia 117, no. : 1152-1159.
Presently, most of the commercial and industrial sectors are using PV system because of its advantages towards clean and green energy. Subsequently, it is not an ideal power source as it solely depends upon sun light. In the recent past, a lot of research and development has been carried out to enhance the reliability, efficiency and cost effectiveness of power electronics converters in order to increase the conversion efficiency from the PV cells. Thus, this paper presents a modified interleaved Flyback inverter for standalone PV applications. The proposed system is developed by interleaving of three Fly-back cells along with one PV source. The effectiveness of the design have been validated by PV based Fly-back converter simulation model. Also, a real time prototype of the proposed system is built and evaluated under realistic conditions.
Somashree Pathy; R Sridhar; Nikita Hari; Subhranshu Sekhar Dash; C. Subramani. A modified module integrated — Interleaved boost converter for standalone photovoltaic (PV) application. 2016 IEEE International Conference on Renewable Energy Research and Applications (ICRERA) 2016, 989 -994.
AMA StyleSomashree Pathy, R Sridhar, Nikita Hari, Subhranshu Sekhar Dash, C. Subramani. A modified module integrated — Interleaved boost converter for standalone photovoltaic (PV) application. 2016 IEEE International Conference on Renewable Energy Research and Applications (ICRERA). 2016; ():989-994.
Chicago/Turabian StyleSomashree Pathy; R Sridhar; Nikita Hari; Subhranshu Sekhar Dash; C. Subramani. 2016. "A modified module integrated — Interleaved boost converter for standalone photovoltaic (PV) application." 2016 IEEE International Conference on Renewable Energy Research and Applications (ICRERA) , no. : 989-994.
Nikita Hari; T. Logan; R. McMahon. Design considerations for 600 V GaN cascode based half-bridge converter systems for utility based applications. 8th IET International Conference on Power Electronics, Machines and Drives (PEMD 2016) 2016, 1 .
AMA StyleNikita Hari, T. Logan, R. McMahon. Design considerations for 600 V GaN cascode based half-bridge converter systems for utility based applications. 8th IET International Conference on Power Electronics, Machines and Drives (PEMD 2016). 2016; ():1.
Chicago/Turabian StyleNikita Hari; T. Logan; R. McMahon. 2016. "Design considerations for 600 V GaN cascode based half-bridge converter systems for utility based applications." 8th IET International Conference on Power Electronics, Machines and Drives (PEMD 2016) , no. : 1.
The proliferation of power electronics based equipment has produced a significant impact on the quality of electric power supply. Conventional power quality mitigation equipment is proving to be inadequate for an increasing number of applications, and this fact has attracted the attention of power engineers to develop dynamic and adjustable solutions to power quality problems. This has led to development of Custom Power Devices (CPD). One modern and very promising CPD that deals with both load current and supply voltage imperfections is the Unified Power Quality Conditioner (UPQC). This paper investigated the development of UPQC control schemes and algorithms for power quality improvement and implementation of a versatile control strategy to enhance the performance of UPQC. The proposed control scheme gives better steady-state and dynamic response. The validity of the proposed control method is verified by means of MATLAB/SIMULINK.
Nikita Hari; K. Vijayakumar; Subhranshu Sekhar Dash. A versatile control scheme for UPQC for Power Quality Improvement. 2011 International Conference on Emerging Trends in Electrical and Computer Technology 2011, 453 -458.
AMA StyleNikita Hari, K. Vijayakumar, Subhranshu Sekhar Dash. A versatile control scheme for UPQC for Power Quality Improvement. 2011 International Conference on Emerging Trends in Electrical and Computer Technology. 2011; ():453-458.
Chicago/Turabian StyleNikita Hari; K. Vijayakumar; Subhranshu Sekhar Dash. 2011. "A versatile control scheme for UPQC for Power Quality Improvement." 2011 International Conference on Emerging Trends in Electrical and Computer Technology , no. : 453-458.