Sheldon S. Williamson

Concordia University Montreal, Montréal, Quebec, Canada

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Publications (156)

  • abhijit choudhury · Pragasen Pillay · Sheldon Williamson
    [Show abstract] [Hide abstract] ABSTRACT: This paper presents a performance comparison study between the space-vector and carrier-based PWM techniques used for neutral point clamped (NPC) 3-level inverter. A reduced switching loss based modulation technique is used for the SVPWM scheme and a third harmonic injected PWM technique is used for the carrier-based PWM scheme. A 110 kW surface-PMSM is used with the NPC inverter, as generally being used for electric vehicle propulsion applications. Detailed simulation studies are carried out to show the performance comparison between the two modulation techniques for the total harmonic distortion, torque ripple, total inverter losses, conduction and switching losses for each power switches, their anti parallel diodes, and for the two NPC diodes. Simulation studies are carried out in MATLAB/ SIMULINK platform and the power switches are modeled in PLACES. A scaled down laboratory prototype with a 6.0 kW SPMSM and a 3-level NPC inverter is built to show the performance of the system with both control strategies.
    Conference Paper · Dec 2016
  • Abhijit Choudhury · Pragasen Pillay · Sheldon S. Williamson
    [Show abstract] [Hide abstract] ABSTRACT: A modified virtual space vector (MVSV) based DC-link voltage balancing strategy is proposed in this paper for a three-level inverter. In the proposed strategy, the summation of the three phase currents for virtual vector needs not to be zero and it also keeps the two capacitor voltages balanced with wider range of load variations. The duty cycles for all the power switches are also derived in this paper using a nearest three-voltage vector scheme. Due to the reduced use of the medium voltage vectors, the proposed control strategy can considerably decrease the neutral point voltage fluctuation for lower power factor based loads as well. Detailed simulation and experimental studies are also carried out to show the effectiveness of the proposed system with a DC-link voltage balancing strategy with permanent magnet synchronous machine. Voltage and current harmonic distortions are also presented with change in modulation index. A Dspace® based real time operating system is used for real time implementation with a 6.0 kW surface PMSM.
    Article · Dec 2016 · IEEE Transactions on Industry Applications
  • Abhijit Choudhury · Pragasen Pillay · Sheldon S. Williamson
    [Show abstract] [Hide abstract] ABSTRACT: A performance comparison study between lower switching loss-based space-vector pulsewidth modulation (PWM) strategy for a three-level neutral-point-clamped inverter and a proposed modified-carrier-based PWM strategy is carried out for an electric vehicle propulsion application. The proposed carrier-based strategy uses single carrier and reduces the switching losses compared with the conventional carrier-based strategies by eliminating the common modulation interval between the upper and lower modulating signals. The inverter switching and conduction losses, total inverter loss, and voltage and current harmonic distortions are also compared with both the control strategies. PLECS is used to simulate the inverter losses with a 54-kW surface permanent magnet synchronous machine (SPMSM). Detailed simulation and experimental performances with the proposed carrier-based strategy and the dc-link voltage balancing during the change in speed and torque variations are carried out on a scaled-down prototype of 6-kW SPMSM. Dspace is used for hardware verification. Results show that, with the proposed carrier-based strategy, the dc-link capacitors are balanced even during the change in speed and torque.
    Article · Sep 2016 · IEEE Journal of Emerging and Selected Topics in Power Electronics
  • Abhijit Choudhury · Pragasen Pillay · Sheldon S. Williamson
    [Show abstract] [Hide abstract] ABSTRACT: This paper presents a hybrid pulse width modulation-based discontinuous modulation (D-HPWM) strategy with dc-link voltage balancing for a three-level neutral-point-clamped (NPC) traction inverter drive. The results are then compared with continuous-hybrid-PWM (C-HPWM) to check the performance improvement. The HPWM strategy uses both the advantages of carrier- and space-vector-based PWM strategies. The duty cycles are generated using the carrier-based strategy to reduce the computational time and complexity of the system and redundant vector states are used to keep the two dc-link capacitor voltages balanced. As discontinuous PWM (DPWM) reduces the switching losses considerably compared to the continuous PWM, the DPWM strategy is developed in this paper for the HPWM-based strategy. Detailed comparison studies are then carried out in MATLAB/Simulink and PLECS to show the conduction and switching loss distribution with change in modulation index for different power switches. A 54.0-kW surface permanent magnet synchronous machine (PMSM) is used for this simulation studies. Moreover, the total inverter loss and losses in each insulated gate bipolar transistor (IGBT) are also compared. Detailed experimental performance analysis is also carried out with a scaled down prototype of a 6.0-kW surface PMSM, NPC inverter, and real-time emulator DSpace, to show the capacitor voltage deviation with both control strategies.
    Article · Aug 2016 · IEEE Transactions on Industry Applications
  • Conference Paper · Jun 2016
  • Deepak Rozario · Najath Abdul Azeez · Sheldon S. Williamson
    Conference Paper · Jun 2016
  • Deepak Rozario · Najath Abdul Azeez · Sheldon S. Williamson
    Conference Paper · Jun 2016
  • Source
    Sumit Pramanick · Mathews Boby · Najath Abdul Azeez · [...] · Sheldon Williamson
    [Show abstract] [Hide abstract] ABSTRACT: This paper presents a harmonic elimination technique based on a 3-level dodecagonal space vector structure for open-end winding IM drives with a single DC supply. Advantages of dodecagonal space vector switching and multilevel inverters are achieved with a single DC supply. A DC-supply fed 3-level flying capacitor(FC) inverter feeds active power to one end of the IM winding terminals and H-bridge connected capacitors eliminate 5th and 7th order harmonics from the other end. A PWM technique is developed to switch the 3-level dodecagonal space vectors and simultaneously control the H-bridge capacitors at 0.1445V DC. The 5th and 7th order harmonics are eliminated for the full modulation range of the 3-level FC inverter, including the extreme six-step operation. An increase in the linear modulation range has been achieved, resulting in improved DC bus utilization. Harmonic elimination is achieved by increasing switching frequency of the low voltage capacitor connected H-bridge inverter, thus switching frequency for the high voltage DC supply fed FC inverter is not increased. Using the proposed scheme the instantaneous phase voltage never exceeds 2 3 V DC (maximum phase voltage applied for hexagonal space vector structure) for which the machine windings are rated. Additionally, the proposed inverter has also been shown to operate for field oriented control of the open-end winding IM drive.
    Full-text Article · Mar 2016 · IEEE Transactions on Industrial Electronics
  • Amandeep Singh · Najath Abdul Azeez · Sheldon S. Williamson
    Conference Paper · Mar 2016
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: This paper proposes a novel harmonic suppression scheme for 2-level inverter fed 3-terminal induction motor drives using switched capacitive filter. Capacitor fed H-bridges used as filters are cascaded to conventional 2-level inverter to eliminate 5th and 7th order harmonics for the full modulation range including six-step operation. For the first time 2-level dodecagonal voltage space vector is implemented with single DC supply for 3-terminal induction motor drive. Enabling the switched capacitive filtering at low voltage domain and shifting the high frequency switching to the switched capacitive filter is shown. An uniform PWM technique is shown which charges and maintains the capacitor voltages while eliminating the 5th and 7th order harmonics for the full speed range.
    Full-text Article · Jan 2016 · IEEE Transactions on Power Electronics
  • Abhijit Choudhury · Pragasen Pillay · Sheldon Williamson
    [Show abstract] [Hide abstract] ABSTRACT: This paper presents an improved DC-link voltage balancing algorithm for a three-level neutral point clamped inverter by considering phase current direction. Detailed studies on the effects of change in load current direction on the DC-link capacitor voltages are presented. A maximum value of power factor is numerically derived, above which it affects the capacitor voltage balancing capability. Compared to the previously presented research work, the inputs to the space-vector pulse width modulation (SV-PWM) block are the three phase currents and the difference between the two capacitor voltages. Depending on the states of the two DC-link capacitor voltages and phase current direction, redundant voltage vectors sequences are selected. The selected vectors keep the capacitor voltage deviations within 5% of the total DC-link voltage. Two zero switching vectors (PPP, NNN) are also removed from all sub sectors of the earlier proposed strategy, which one used to produce higher common mode voltages (CMV). Detailed simulation and experimental results are presented in this paper for a 6.0 kW surface permanent magnet synchronous machine (SPMSM). Both the simulation and experimental results show the required performance of the proposed system.
    Article · Jan 2016 · IEEE Transactions on Industry Applications
  • Source
    Kunwar Aditya · mohamed youssef · Sheldon S. williamson
    [Show abstract] [Hide abstract] ABSTRACT: It is fairly well-known in circuit theory that the product of magnetic coupling coefficient and system quality factor is the single most important figure of merit (FOM) for optimizing the design of series-series-compensated resonant inductive coupling coils. Coils with high value of FOM can operate efficiently under misalignment conditions, such as poor coupling systems. This would be the case in transit systems with on-road/in-motion charging systems using inductive power transfer (IPT). Archimedean spiral coils are widely used for stationary charging of electric vehicles (EVs). This is due to ease of manufacturing, lower material cost, symmetric coupling profile, ease of experimental characterization, and very well-known magnetic characteristics. In this paper, a comprehensive analysis of Archimedean spiral coil structure has been presented, with the aim of establishing key design parameters, leading to high FOM. Knowing the key parameters in order to adjust the coupling coefficient and system quality factor gives a designer abundant options to design coils that can handle misalignment, and at the same time, minimize losses. For this purpose, 2D analysis of a range of coils with difference geometric parameters have been performed. Finite element analysis (FEA) has been used to establish key coil design parameters, in order to obtain a high value of FOM. Results of this design and analytical work will lead to efficient IPT coil design methodologies, which in turn will lead to considerable cost and energy savings. Due to their scalable and modular nature, this work is also applicable to any lumped system specifically utilizing Archimedean spiral coils
    Full-text Conference Paper · Nov 2015
  • Source
    Kunwar Aditya · mohamed youssef · sheldon S. williamson
    [Show abstract] [Hide abstract] ABSTRACT: In this paper thorough analysis of Series-Parallel resonant inductive coupling (SPRIC) has been presented using two-port network theory. Characteristic of SPRIC has been derived and plotted against load variation and frequency variation in MATLAB. Concept of forced resonance and natural resonance has been discussed. Important expressions such as current transfer ratio, voltage transfer ratio, maximum efficiency etc. has been derived and presented. To study the circuit behavior of the SPRIC a prototype has been built in the lab. Experimental results along with simulation results has been presented to verify the derived expression and characteristics of series-parallel topology.
    Full-text Conference Paper · Nov 2015
  • Vamsi Krishna Pathipati · Najath Abdul Azeez · Sheldon S. Williamson
    Conference Paper · Nov 2015
  • Lesedi Masisi · Pragasen Pillay · Sheldon Williamson
    [Show abstract] [Hide abstract] ABSTRACT: This paper is concerned with the use of a three-level inverter for a synchronous reluctance machine (SynRM). The SynRM suffers from a poor power factor due to poor machine saliency. This makes it harder to operate the three-level neutral-point-clamped inverter due to a strict requirement to have the two dc-link capacitor voltages balanced. This paper proposes a new nearest three vector modulation algorithm which can balance the two dc-link capacitors even at poor machine saliency ratio (poor power factor). In this paper, a method of sizing the two dc-link capacitors based on the machine power is also proposed. A comparison between two- and three-level inverters was conducted. The SynRM registered lower d-axis current ripple with a three-level inverter, indicating lower core losses in the machine.
    Article · Nov 2015 · IEEE Transactions on Industry Applications
  • Siddhatha A. Singh · Najath A. Azeez · Sheldon S. Williamson
    Conference Paper · Nov 2015
  • Kunwar Aditya · Bernardo Peschiera · Sheldon S. Williamson
    [Show abstract] [Hide abstract] ABSTRACT: The main objective of this paper is to study and analyze the power supply stage of a series-series (SS) fixed-frequency inductive power transfer (IPT) system, in order to suggest effective soft switching techniques to improve its performance. Because of the characteristics of the system, zero voltage switching (ZVS) operation was used and three control strategies were compared: phase-shift (PS) control, asymmetrical duty cycle (ADC) control and optimal asymmetrical voltage cancellation (o AVC) control. The o AVC control is found to be more efficient for this application. Additionally, this paper presents an inductive power transfer transformer (IPTT) prototype that was built in the laboratory, which helped validate the theoretical analysis and simulation results with practical tests. The plots and circuit simulations were obtained from MATLAB and SIMULINK respectively.
    Conference Paper · Oct 2015
  • Abhijit Choudhury · Pragasen Pillay · Sheldon S. Williamson
    [Show abstract] [Hide abstract] ABSTRACT: A modified virtual space vector based DC-link voltage balancing strategy is proposed in this paper. The summation of the three phase currents for the virtual vector needs not to be zero and it also keeps the two capacitor voltages balanced over a wider range of load variations. The duty cycles for all the power switches are also derived in this paper. Due to the reduced use of medium voltage vectors the proposed control strategy can considerably decrease the neutral point voltage fluctuation for lower power factor based loads as well. Detailed simulation and experimental studies are also carried out to show the effectiveness of the proposed system with a DC-link voltage balancing strategy. Voltage and current harmonic distortions are also presented with change in modulation index. A Dspace® based real time operating system is used experimental validation with a 6.0 kW surface PMSM.
    Conference Paper · Sep 2015
  • Abhijit Choudhury · Pragasen Pillay · Sheldon S. Williamson
    [Show abstract] [Hide abstract] ABSTRACT: A reduced common mode voltage (CMV) based DC-link voltage balancing strategy is proposed for a neutral point clamped (NPC) three-level inverter with permanent magnet synchronous machine. Compared to the earlier proposed strategy, it completely eliminates the Vdc/2 corresponding CMV by eliminating the two zero voltage vectors (PPP, NNN) from the space vector switching sequences. Hence, it uses only one zero voltage (OOO) vector with the other redundant voltage vectors to produce the reference vector in inner subsectors. Detailed simulation and experimental studies are also carried out to show the effectiveness of the proposed system with DC-link voltage balancing ability. Harmonic distortions are also compared with the previously proposed scheme. Dspace® based real time operating system is used for real time implementation with 6.0 kW surface PMSM.
    Conference Paper · Sep 2015
  • [Show abstract] [Hide abstract] ABSTRACT: Plug-in hybrid electric vehicles (PHEVs) are seen to be a step forward in transportation electrification, to replace internal combustion engine (ICE)-based conventional vehicles. However, to consider the vehicle-to-home (V2H) and home-to-vehicle (H2V) capabilities, new energy control strategy has to be developed to avoid new peaks consumption. This paper presents a novel controller based on fuzzy logic, which integrates an objective state-of-charge (SoC) for V2H application. The V2H capability is used when the PHEV is connected to the home to help the grid to meet the household loads during peak period. The SoC objective is the minimum SoC that the PHEV has to have when the driver connects the PHEV to the home. The proposed controller is applied on fourth different scenario.
    Article · Aug 2015

Publication Stats

2k Citations

Institutions

  • 2007-2015
    • Concordia University Montreal
      • Department of Electrical and Computer Engineering
      Montréal, Quebec, Canada
  • 2004-2005
    • Illinois Institute of Technology
      • Department of Electrical & Computer Engineering
      Chicago, Illinois, United States