@article{kim_lee_bhattacharya_2022, title={Improved EEMF-Based Position Sensorless Control for Non-sinusoidal Back-EMF PMSMs}, volume={1}, ISSN={["2093-7423"]}, DOI={10.1007/s42835-021-00985-1}, journal={JOURNAL OF ELECTRICAL ENGINEERING & TECHNOLOGY}, author={Kim, Heonyoung and Lee, Kibok and Bhattacharya, Subhashish}, year={2022}, month={Jan} }
 @article{lee_kim_lukic_2020, title={A Rotating Restart Method for Scalar (v/f) Controlled Synchronous Reluctance Machine Drives Using a Single DC-Link Current Sensor}, volume={8}, ISSN={["2169-3536"]}, DOI={10.1109/ACCESS.2020.3000220}, abstractNote={This paper presents a rotating restart method for $v/f$ scalar controlled Synchronous Reluctance Machines (SynRMs) using a single DC-link current sensor. In such a case, the initial rotor position and speed are required to restart the machine due to the absence of a position sensor. The method proposes to inject three active voltage vectors in the stationary reference frame to induce the phase currents required for estimating the rotor position and speed. In addition, the phase current reconstruction method is proposed to reduce the distortion of the measured phase currents caused by adopting a single DC-link current sensor and to consequently enhance the rotor position estimation accuracy. With the proposed method, the appropriate voltage vector can be applied to the machine, thus minimizing the inrush current during the restart. Furthermore, the proposed method only requires the machine parameters on the nameplate, and it does not require any additional machine-specific tuning processes. This paper proposes a simple restart method suitable for scalar-controlled SynRM drives with a single DC-link current sensor. The effectiveness of the proposed restart scheme is validated through the simulation and experimental results.}, journal={IEEE ACCESS}, author={Lee, Kibok and Kim, Heonyoung and Lukic, Srdjan M.}, year={2020}, pages={106629–106638} }
 @article{kim_han_lee_bhattacharya_2020, title={A Sinusoidal Current Control Strategy Based on Harmonic Voltage Injection for Harmonic Loss Reduction of PMSMs With Non-Sinusoidal Back-EMF}, volume={56}, ISSN={["1939-9367"]}, url={https://doi.org/10.1109/TIA.2020.3016210}, DOI={10.1109/TIA.2020.3016210}, abstractNote={In permanent magnet synchronous machine design, a limited number of stator and rotor slots distorts the air-gap flux distribution and its effective length. It causes machine parameters to vary with the rotor position. The rotor flux linkage harmonics introduce nonsinusoidal back-EMF, which causes current harmonics when conventional PI current controller is adopted. Those machines suffer from high-frequency torque ripple due to air-gap flux harmonics in low-speed region. However, in high-speed region, where the torque ripple is filtered out by the mechanical system, the torque ripple may be disregarded. In this case, torque-ripple suppression methods and the associated harmonic current components generate losses. Therefore, a sinusoidal current control is required to reduce the undesired harmonic losses. In this manner, this article focuses on the sinusoidal current control strategy based on harmonic voltage injection, which requires knowledge of rotor magnet flux linkage harmonics. This article also proposes both off- and on-line schemes for the identification of rotor magnet flux linkage harmonics. These methods do not require any proprietary machine design details such as the shape of stator or rotor for finite element analysis. Commonly used PI plus resonant controller is also designed and its disadvantages in terms of speed-dependent gain and stability, in comparison to the proposed scheme, are highlighted. Finally, experimental results are presented to compare the proposed scheme with the conventional method at different operating conditions.}, number={6}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Kim, Heonyoung and Han, Yongsu and Lee, Kibok and Bhattacharya, Subhashish}, year={2020}, month={Nov}, pages={7032–7043} }
 @article{lee_ahmed_lukic_2019, title={Restart Strategy for Scalar (V/f) Controlled Synchronous Reluctance Machine Driving a High-Inertia Load}, volume={55}, ISSN={["1939-9367"]}, DOI={10.1109/TIA.2019.2914880}, abstractNote={Momentary power disruptions commonly occur in many industrial settings, and can trip large electric machines, which must then be brought to zero speed before the machine can be restarted. The resulting frequent interruptions in industrial processes can have negative effects on productivity. A restart algorithm brings the machine back to the original speed as soon as power is restored, without waiting for the machine to reach zero speed. This paper proposes an approach for implementing a restart algorithm for synchronous reluctance machines (SynRMs) that use a simple identification algorithm to determine the speed and position of the machine so that the appropriate voltage vector can be applied, thus minimizing the inrush current during the restart. The proposed method only requires nameplate machine parameters and needs no machine-specific tuning, making the approach suitable for implementation with both high-inertia vector and scalar-controlled SynRM.}, number={4}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Lee, Kibok and Ahmed, Sara and Lukic, Srdjan M.}, year={2019}, pages={3834–3841} }
 @article{lee_ahmed_lukic_2017, title={Universal Restart Strategy for Scalar (V/f) Controlled Induction Machines}, volume={53}, ISSN={["1939-9367"]}, DOI={10.1109/tia.2017.2733497}, abstractNote={This paper presents a universal flying restart strategy for scalar (V/f) controlled induction machines. The proposed method performs a frequency search to estimate the rotor speed, and applies the correct frequency and voltage to minimize the inrush current during the restart. This method uses the measured phase current and the motor nameplate parameters, thus making the approach ideal for scalar-controlled motor drives. In addition, the restart algorithm provides controllable restart dynamics, independent of the motor parameters. The main advantages of this method include simple and cost effective implementation without the need for additional sensors, and controllable restart dynamics independent of the motor parameters. Beyond the development of the algorithm, we consider implementation issues to provide a general guideline for the application of the developed algorithm.}, number={6}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Lee, Kibok and Ahmed, Sara and Lukic, Srdjan M.}, year={2017}, pages={5489–5495} }
 @inproceedings{lee_lukic_ahmed_2016, title={A universal restart strategy for induction machines}, DOI={10.1109/ecce.2016.7854802}, abstractNote={This paper presents an approach to implement the universal flying restart for an induction machine using a frequency search algorithm that determines the rotor speed so that the correct frequency and voltage can be applied to minimize the inrush current during the restart. This method only uses the measured phase current and the motor nameplate parameters, thus making it ideal for use with scalar-controlled motor drives. An additional benefit of the proposed approach is that the time to estimate the rotor speed is independent of the motor parameters, and is defined by the restart algorithm itself. Beyond the development of the algorithm, implementation issues will be considered to provide general guideline for the application of the developed algorithm.}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Lee, K. and Lukic, S. and Ahmed, S.}, year={2016} }
 @article{lee_ahmed_lukic_2016, title={Universal Restart Strategy for High-Inertia Scalar-Controlled PMSM Drives}, volume={52}, ISSN={["1939-9367"]}, DOI={10.1109/tia.2016.2581764}, abstractNote={In many industrial settings, momentary power disruptions commonly occur, resulting in tripping of large electric machines, which then have to be brought to zero speed before the machine can be restarted. This can result in frequent interruptions in an industrial process, which can have negative effects on productivity. A more practical approach would restart the machine back to the original speed as soon as power is restored, not having to wait for the machine to be at a standstill. This concept is known as flying restart. In this paper, we propose an approach to implement the flying restart for permanent magnet synchronous machines (PMSM) by using an identification algorithm that determines the speed and position of the machine back-electromotive force so that the correct voltage vector can be applied, thus minimizing the inrush current during the restart. The novelty of the proposed method is that its implementation only requires nameplate machine parameters and needs no machine-specific tuning, making the approach suitable for implementation with both vector- and scalar-controlled PMSM.}, number={5}, journal={IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS}, author={Lee, Kibok and Ahmed, Sara and Lukic, Srdjan M.}, year={2016}, pages={4001–4009} }
 @inproceedings{lee_lukic_ahmed_2015, title={A universal restart strategy for permanent magnet synchronous machines}, DOI={10.1109/ecce.2015.7309712}, abstractNote={In many industrial settings, momentary power disruptions commonly occur, resulting in tripping of large electric machines, which then have to be brought to zero speed before the machine can be restarted. This approach can result in frequent interruptions in an industrial process, which can have negative effects on productivity. A more practical control implementation would restart the machine back to the original speed as soon as power is restored, not having to wait for the machine to be at a standstill. This concept is known as flying restart. In this paper we propose an approach to implement the universal restart for PMSM through a simple identification algorithm which determines the speed and position of the machine back-emf so that the correct voltage vector can be applied and thus minimize the inrush current during the restart. Beyond the development of the basic algorithm, implementation issues will be considered to provide general guideline for the application of the developed algorithm.}, booktitle={2015 ieee energy conversion congress and exposition (ecce)}, author={Lee, K. and Lukic, S. and Ahmed, S.}, year={2015}, pages={373–380} }
 @article{pantic_lee_lukic_2015, title={Receivers for Multifrequency Wireless Power Transfer: Design for Minimum Interference}, volume={3}, ISSN={["2168-6785"]}, DOI={10.1109/jestpe.2014.2356853}, abstractNote={Inductive (or wireless) power transfer is proving to be an effective way to deliver power over short distances in a wide range of applications. Frequently, there is a need to deliver power from a single transmitter to multiple mutually coupled receivers. In this paper, we quantify how the power delivered to each receiver is affected due to the resonant frequency shift resulting from receiver mutual coupling. We show that the effect on power delivered is quite severe, especially in high-quality-factor systems. We develop the mathematical framework and demonstrate experimentally that the problem disappears if each receiver is tuned at one of the frequencies emitted by a single transmitter. We adopt the concept of frequency traps as a method to completely decouple the receivers.}, number={1}, journal={IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS}, author={Pantic, Zeljko and Lee, Kibok and Lukic, Srdjan M.}, year={2015}, month={Mar}, pages={234–241} }
 @article{pantic_lee_lukic_2014, title={Multifrequency Inductive Power Transfer}, volume={29}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2014.2298213}, abstractNote={This paper presents a generalized analysis of an inductive power transfer system where multiple frequencies are used to transfer power through the magnetic link. Specifically, we consider a system that amplifies both the fundamental and the third harmonic generated by a full-bridge inverter in order to transfer power to a receiver at both frequencies. The system is analyzed in a generalized manner, by looking at the transconductance function at the transmitter and the receiver for each of the harmonics. Using this approach, the emitted field strength, inverter losses, combined transmitter and receiver coil conduction losses, and VA ratings are compared to a reference single-frequency system. The analysis shows that the dual-frequency system can outperform the single-frequency equivalent for all metrics considered; however, in practice, a tradeoff between the performance criteria is necessary, since the optimal operation points for each criterion cannot be attained with a single design.}, number={11}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Pantic, Zeljko and Lee, Kibok and Lukic, Srdjan M.}, year={2014}, month={Nov}, pages={5995–6005} }
 @article{lee_pantic_lukic_2014, title={Reflexive Field Containment in Dynamic Inductive Power Transfer Systems}, volume={29}, ISSN={["1941-0107"]}, DOI={10.1109/tpel.2013.2287262}, abstractNote={We present a new topology appropriate for “dynamic” wireless charging. Possible applications include charging of electric vehicles or robots moving in a large, predesignated area. We propose a system with a transmitter made from multiple coils commensurable with the moving receiver(s), and powered by a single inverter. The proposed system uses the reactance reflected by the receiver to automatically increase the field strength in coupled portions of the transmitter-receiver system, thus allowing efficient power transfer and adherence to electromagnetic field emission standards without complex shielding circuits, switches, electronics, and communication. The power transfer is at its peak when the transmitting and receiving coils approach their maximum coupling (as defined by the geometrical constraints of the system), resulting in improved system-level efficiency. The presented analysis is supported with simulations and experiments.}, number={9}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Lee, Kibok and Pantic, Zeljko and Lukic, Srdjan M.}, year={2014}, month={Sep}, pages={4592–4602} }
 @inproceedings{lee_pantic_lukic_2013, title={Field containment in dynamic wireless charging systems through source-reciever interaction}, DOI={10.1109/ecce.2013.6647183}, abstractNote={This paper presents a new topology appropriate for dynamic wireless charging of electric vehicles. We propose a source coil made from multiple lumped coils powered by a single inverter, with the receiver coil mounted on the vehicle. The proposed system uses the reflected reactance from the receiver to automatically limit the field strength in uncoupled portions of the source-receiver system, thus allowing the system to more easily meet the electromagnetic field emission standards without complex shielding circuits, switches, electronics and communication systems. The power transfer is at its peak when the source-receiver coils pair is strongly coupled resulting in improved system-level efficiency. The analysis is supported by simulation and experiments.}, booktitle={2013 ieee energy conversion congress and exposition (ecce)}, author={Lee, K. and Pantic, Z. and Lukic, S.}, year={2013}, pages={3658–3663} }
 @inproceedings{pantic_lee_lukic_2013, title={Inductive power transfer by means of multiple frequencies in the magnetic link}, DOI={10.1109/ecce.2013.6647080}, abstractNote={In this paper we explore the concept of transmitting and receiving power wirelessly at multiple frequencies. This proposed frequency multiplex is achieved by using multi-resonant tanks at the transmitter and receiver to amplify and extract power at multiple frequencies. Frequency multiplexed IPT system is a new concept that has numerous advantages over the state of the art: (1) low switching frequency converters can be used to drive high-frequency IPT systems, (2) emission standards may become easier to meet by spreading the power transfer over a spectrum of frequencies, (3) single-frequency receivers tuned to different frequencies can be charged simultaneously even though their coils are at close proximity and mutually coupled, etc. In this paper we develop the theory of source and receiver resonant tank design, and present the complete methodology for determining the system quality factor, effective resistance and power transfer at each frequency. We present a case study of a system that transfers equal amounts of power at 25 kHz and 75 kHz through simulations and experiments.}, booktitle={2013 ieee energy conversion congress and exposition (ecce)}, author={Pantic, Z. and Lee, K. and Lukic, S.}, year={2013}, pages={2912–2919} }