S.S. Williamson

Concordia University Montreal, Montréal, Quebec, Canada

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Publications (86)61.34 Total impact

  • Kunwar Aditya, Bernardo Peschiera, Sheldon S. Williamson
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    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.
    IECON 2014 - 40th Annual Conference of the IEEE Industrial Electronics Society, Dallas, TX, USA; 10/2015
  • Abhijit Choudhury, Pragasen Pillay, Sheldon S. Williamson
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    ABSTRACT: This paper presents an extensive comparative study between a two- and three-level inverter for electric vehicle traction applications. An advanced control strategy for balancing the two dc-link capacitors is also proposed. In this paper, the main focus is on the total voltage harmonic distortion (%THDv), the analytical derivation of the three-level capacitor currents, and the voltage balancing of two capacitor voltages. For generating the gate signals, space vector pulse width modulation (SV-PWM) is used. The developed voltage-balancing scheme helps to reduce the number of converter switching sequences, compared with the conventional SV-PWM strategy, and keeps the voltage difference between the two dc-link capacitors at the desired voltage level. The developed test-bench is used for a permanent magnet synchronous machine drive for electric vehicle (EV) applications. Detailed simulation studies are performed using MATLAB/Simulink block set and experimental verification is achieved using dSpace based real-time simulator. Both the simulation and experimental results show a significant improvement in reduction of total harmonic distortion (%THD (_{textit{v}}) ) for the three-level inverter.
    Emerging and Selected Topics in Power Electronics, IEEE Journal of. 09/2014; 2(3):529-540.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Vehicle electrification is a step forward to reduce CO2 emissions. However, using Plug-in Hybrid Electric Vehicles (PHEVs) and Electric Vehicles (EV.) efficiently, battery has to be charged during night to decrease the usage of the Internal Combustion Engine (ICE). There are two methods to charge PHEV battery. Either plugs directly the battery with the electric outlet or using wireless method which uses Inductive Power Transfer (IPT) technology. The aim of this paper is to compare the two methods of PHEV battery charging. The comparison will hold on the energy cost which takes into account the household loads, the solar production, the PHEV driving cycle and the probability that the driver forgets to ping the battery charger. The study will use real data collected at ÉcoTerra house located in Eastman (Québec, Canada).
    IEEE Transportation Electrification Conference, Michigan, USA; 06/2014
  • Kunwar Aditya, sheldon williamson
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    ABSTRACT: Loosely coupled inductive power transfer (IPT) systems have recently gained worldwide attention for electric vehicle (EV) battery charging. EV batteries have mainly two charging stages: constant voltage charging and constant current charging stage. Numerous published papers suggest that the secondary of loosely coupled IPT systems, if series compensated, can act as constant-voltage source; and, if parallel compensated, it can act as constant-current source. In this paper the authors have shown that both series as well as parallel compensated secondary can act as constant-current source as well as a constant-voltage source, depending on the nature of power supply. Hence, same topology can be utilized efficiently for EV charging in all the stages. Moreover a detailed comparison of series-series and series- parallel topology has been presented with intention of showing that Series-Series topology represents the best choice for IPT system among the two.
    IEEE Transportation Electrification Conference and Expo (ITEC'14); 06/2014
  • Kunwar Aditya, sheldon williamson
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    ABSTRACT: Recently loosely coupled inductive power transfer (IPT) has gained worldwide attention for battery charging applications for electric vehicles (EVs). Since a high frequency operation is a must for transferring power inductively over a large air gap with reasonable efficiency, a careful design is needed. This paper reviews the basic design considerations for designing such a system. Critical design parameters, such as skin effect, proximity effect (at high frequency), and field-shaping techniques, to reduce leakage flux, has been demonstrated using Finite Element Analysis (FEA). In addition, different compensation technique and control strategies for IPT system has been discussed.
    IEEE Transportation Electrification Conference and Expo (ITEC'14); 06/2014
  • Abhijit Choudhury, Pragasen Pillay, Sheldon S. Williamson
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    ABSTRACT: This paper presents an advanced switching sequence for space-vector pulsewidth modulation (SV-PWM)-based three level neutral-point clamped inverter. The developed scheme helps to reduce the number of converter switching sequences, compared with the conventional SV-PWM strategy, and keeps the voltage difference between the two dc-link capacitors at the desired voltage level. The developed test bench is utilized for a permanent magnet synchronous machine (PMSM) drive for electric vehicle applications. The proposed strategy is compared with the performance of a PI controller-based voltage balancing strategy. The proposed control strategy is based on the nearest three-vector (N3V) scheme, with a hysteresis control of the dc-link capacitor voltage difference. Conventional N3V scheme uses a higher number of switching sequences, which makes the switching losses higher. In addition, these switching sequences are not same for all subsectors. This makes the switching frequency to vary extensively. In the proposed control strategy, a reduced number of switching sequences are used, and they are same for all subsectors. This makes the system operate with constant switching frequency. Detailed simulation studies are performed to verify the performance of the proposed control strategy. The performance-based test results are then compared with those of a PI controller-based strategy. Experimental test results show significant improvement in the performance of the PMSM with respect to dc-link capacitor voltage variation as well as wide speed and torque range of machine operation.
    Emerging and Selected Topics in Power Electronics, IEEE Journal of. 06/2014; 2(2):296-307.
  • Kunwar Aditya, Sheldon Williamson
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    ABSTRACT: Loosely coupled inductive power transfer (IPT) systems have recently gained enormous attention for electric vehicle (EV) battery charging. For EV battery charging, a constant-current source is required. Numerous published papers suggest that the secondary of loosely coupled IPT systems, if series compensated, can act as constant-voltage source; and, if parallel compensated, it can act as constant-current source. In this paper, the authors prove that both series as well as parallel compensated secondary can act as constant-current source as well as a constant-voltage source, depending on the nature of power supply. Hence, either of the topological options can be utilized efficiently for EV charging. The authors intend to present the work for the case where primary is in the form of a long track, such as in a mono-rail or electric traction metro system. Hence, the primary is always considered to be series compensated.
    IEEE 23rd International Symposium on Industrial Electronics (ISIE), 2014; 06/2014
  • Abhijit Choudhury, Pragasen Pillay, M. Amar, Sheldon S. Williamson
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    ABSTRACT: A performance comparison study for a two- and three-level inverter based permanent magnet synchronous machine (PMSM) drive has been carried out. A novel space-vector pulse width modulation (SV-PWM) based DC-link voltage balancing algorithm is also presented, to drive the machine from three-level inverter. The proposed algorithm keeps the two DC-link capacitor voltages at their specific voltage tolerance level. Two-level inverter is also feed by space-vector based pulse width modulation (SV-PWM) technique. Total voltage harmonic distortion (THD), capacitor RMS current ripple (Icap), Conduction and switching losses for IGBT and diodes, torque ripple (Trpp) and DC-link capacitor voltage ripple (Vcaprip) are considered to perform the comparison study for both the inverters. Switching losses are calculated in PLECS environment using data sheet parameters from Infineon and control logics are developed in MATLAB/ Sim power system (SPS) tool box. For this study a 110.0 kW surface-PMSM is considered, which are mainly used for electric vehicle propulsion applications. A scaled down prototype is built in laboratory for both the inverters and tested with a 6.0 kW surface-PMSM. Both the simulation and experimental results show satisfactory performance of the proposed system.
    2014 IEEE Transportation Electrification Conference and Expo (ITEC); 06/2014
  • Ebrahim Saeidi Dehaghani, Behzad Asaei, Sheldon S. Williamson
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    ABSTRACT: Battery electric vehicles (BEVs) and plug-in hybrid electric vehicles (PHEVs) are becoming more popular in recent years. Apart from charging vehicles from grid, it has been proposed that electric vehicles (EVs) can help grid with variety of services such as ancillary service, regulation and pick shaving, with reverse power flow. While application of EVs to sustain grid in high demand time will not be a smart idea of the field, helping local distribution grid in the event of power outage in an emergency situation such as floods or storms to improve security and reliability of the grid, may use as a lucrative idea.
    2014 IEEE Transportation Electrification Conference and Expo (ITEC); 06/2014
  • Siddhartha Anirban Singh, Sheldon S. Williamson
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    ABSTRACT: In recent years, there has been great interest in the research and development of electric vehicles (EVs). In the past 5 years, numerous EVs and plug-in hybrid electric vehicles (PHEVs) have been introduced in the market by auto manufacturers. However, with the increase in demand of EVs/PHEVs comes the need to provide charging facilities at convenient locations, for recharging of the on-board batteries. Fast charging is also a necessity for consumer convenience. Therefore, off-board charging infrastructures have to be looked at closely. This need for fast charging is creating a shift in EV charger development work to focus on DC charging facilities. This paper provides an overview of various power converter topologies used for a photovoltaic (PV) and grid connected DC charging infrastructures. Specific focus is placed on Z-source converters that can be used for a single-stage connection of PV, grid, and EV. PWM control techniques for off-board converters are also reviewed in this paper.
    2014 IEEE Transportation Electrification Conference and Expo (ITEC); 06/2014
  • Zahra Amjadi, Sheldon S. Williamson
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    ABSTRACT: This paper presents the analysis and novel controller design for a hybrid switched-capacitor (SC) bidirectional DC/DC converter, applicable for electric and plug-in hybrid electric vehicles (HEV/PHEV) energy storage system (ESS) applications, based on power of traction motor and battery current gradient. Features of voltage step-down, voltage step-up, and bi-directional power flow are integrated into a single circuit. The developed novel control strategy enables simpler dynamics compared to a standard buck converter with input filter. Experimental results show, the proposed converter topology enables good regulation capability, low EMI, lower source current ripple, ease of control, and continuous input current waveform in both buck as well as boost modes of operation.
    IEEE Transactions on Smart Grid 01/2014; 5(1):158-166. · 4.33 Impact Factor
  • Bernardo Peschiera, Sheldon S. Williamson
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    ABSTRACT: For the last two decades, significant improvements in charging technologies have been made. Moreover, novel applications have been proposed and tested, obtaining important and promising results. Inductive charging for electric vehicles (EV) and hybrid electric vehicles (HEV) is one of them. Because of the positive impact that this technology represents, it is important to understand the general characteristics of this novel application. This paper aims to give a general understanding of inductive charging systems for EV and HEV. The explanation of what is an inductive power transfer (IPT) transformer and how electrical power is transferred through air is presented. The review of the electrical characteristics of an IPT transformer is shown: derivation of equations and presentation of the equivalent circuit. The analysis and comparison of two different circuit topologies is also covered (series-series and parallel-parallel). Also, to validate the theoretical concepts, an IPT transformer setup with 5cm of air gap is simulated. The plots and circuit simulations where obtained in MATLAB and SIMULINK respectively.
    2013 IEEE Transportation Electrification Conference and Expo (ITEC); 06/2013
  • L. Sejpal, L.A.C. Lopes, M. Amar, S.S. Williamson
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    ABSTRACT: This paper concentrates on the application of a three-level Neutral-Point Clamped (NPC) inverter in a Permanent Magnet Synchronous Motor (PMSM) driven electric vehicle. Carrier-Based Space Vector Modulation (CB-SVM) strategy allows a simple technique for inverter switching. A split-capacitor dc bus voltage balancing strategy using a simple PI controller has been presented for the entire speed range of operation of the PMSM. For the same current Total Harmonic Distortion (THD), three-level NPC inverter provides a 65% reduction in switching frequency when compared to a conventional two-level inverter while driving the PMSM with the same parameters. Torque and speed dual loop controllers have been developed using the Field-oriented Control technique to have a wider range of operation beyond the base speed of the PMSM.
    Transportation Electrification Conference and Expo (ITEC), 2013 IEEE; 01/2013
  • D. Miskovski, S.S. Williamson
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    ABSTRACT: Environmental concerns and rising oil prices have contributed of development and commercialization of electric (EV) and hybrid electric vehicles (HEV). They are emerging the market with rapid pace and very soon the supporting equipment will be necessary. As a part of that, the EV charging stations are maybe the most important ring in the chain of complete transportation system's replacement. The EV PV public charging station is conceived as a contactless power transfer post that will be located in the parking areas of large shopping centers, touristic sites, sports venues, airports, etc. With its most important difference from on-road high-power charging station, this type of system will provide only partial charging of the EV's energy storage system (ESS), for example, 30% of the battery capacity during one to two hours period. The station will be equipped with energy storage system consisting of serial-parallel bank of Li-Ion batteries. It will be supplied by PV system and a grid interface. The power transfer from the station to the EV will be conducted through Inductive Power Transfer (IPT) system, consisting of resonant converter and air-core transformer (ACT). The IPT may be the most convenient way for EV charging. It has many advantages, including the convenience of being cordless and the safety during the charging. Most of the problems connected to plugging the charging plug are eliminated (possible sparking and mechanical damage of the electrical contacts). However, the IPT must be designed as high efficient system where several important issues must be considered: large air gap, good tolerance to misalignment, safe electromagnetic radiation and system's compactness. The project will be basic (generic) approach how the EV public charging stations should be designed. The assessment of the system elements according to the pre-determined parameters will be confirmed by its layout design and simulation. They will be the source for determining the system effi- iency and cost during standard conditions of exploitation.
    Transportation Electrification Conference and Expo (ITEC), 2013 IEEE; 01/2013
  • L. Masisi, A. Choudhury, P. Pillay, S. Williamson
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    ABSTRACT: This paper investigates the performance of a two level and a three level inverter drives for a permanent magnet synchronous machine (PMSM) under different switching frequencies. The experiments were conducted via a real time based system called Opal-RT. The inverters were operated at 1 kHz and 5 kHz switching frequencies. The torque was varied between 2 N.m and 4 N.m at a constant speed of 800 rpm. However the torque ripples and the copper losses between the two inverter drives were similar and the copper losses were independant of the swicthing frequency. At 5 kHz inverter switching frequency the two level inverter performed better at 4 N.m with a total current harmonic distortion of 2.55% and a torque ripple of 10%. However overall the three level inverter had low voltage and current harmonic distortion which translates to lower iron losses. Swicthing at 5 kHz frequency showed to have lower overall harmonic distortion than at 1 kHz for both inverters. The greater the capcitor voltage error the more the torque ripples even though the machine registered lower current total harmonic distortion for the three level inverter.
    Industrial Electronics Society, IECON 2013 - 39th Annual Conference of the IEEE; 01/2013
  • Bernardo Peschiera, Sheldon S. Williamson
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    ABSTRACT: For the last two decades, significant improvements in charging technologies have been made. Moreover, novel applications have been proposed and tested, obtaining important and promising results. Inductive charging for electric vehicles (EV) and hybrid electric vehicles (HEV) is one of them. Because of the positive impact that this technology represents, it is important to understand the general characteristics of this novel application. This paper aims to give a general understanding of inductive charging systems for EV and plug-in HEV. The explanation of what is an inductive power transfer (IPT) transformer and how electrical power is transferred through air is also presented. The review of the electrical characteristics of an IPT transformer is shown: derivation of equations and presentation of the equivalent circuit. The analysis of the series-series (SS) compensation topology is covered. Additionally, to validate the theoretical concepts, an IPT transformer setup with a 5cm air gap is simulated. The simulation results where as expected from the theory. The power transfer capability of the system was increased from 0.05 W, with no capacitive compensation, to 87.6 W, with capacitive compensation. The plots and circuit simulations where obtained in MATLAB and SIMULINK respectively.
    Industrial Electronics Society, IECON 2013 - 39th Annual Conference of the IEEE; 01/2013
  • A. Choudhury, P. Pillay, S.S. Williamson
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    ABSTRACT: This paper presents a modified DC bus voltage balancing algorithm for a neutral-point clamped (NPC) three-level inverter based motor drives for permanent magnet synchronous machines (PMSM) used in electric vehicle applications. The topology used for DC bus voltage balancing is based on nearest three vectors (N3V) with a space vector pulse width modulation scheme (SV-PWM). In this scheme, the voltage space vectors are rearranged based on the four redundant small voltage vectors, to keep the two DC link capacitor voltages in their specific tolerance bands, even during fast transient conditions of the machine. This topology provides high stability and lower switching loss compared to the conventional N3V scheme. The performance of the proposed scheme is verified by simulation and hardware experimental tests.
    Industrial Electronics Society, IECON 2013 - 39th Annual Conference of the IEEE; 01/2013
  • A. Choudhury, P. Pillay, S.S. Williamson
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    ABSTRACT: A online rotor position error minimization technique for Hall sensor based permanent magnet synchronous machine has been presented in this paper. Generally the Hall sensor and rotor magnets are not perfectly synchronised, which leads to a phase difference in actual rotor position and Hall sensor output. This phase shift leads to increase in d-axis current and total machine current, which may affect the closed loop speed or torque control of machine. Simulation studies have been carried out in Matlab Simulink platform and hardware implementation has been done with Opel-RT based real-time system. Both the simulation and hardware results show satisfactory performance of the proposed system.
    Applied Power Electronics Conference and Exposition (APEC), 2013 Twenty-Eighth Annual IEEE; 01/2013
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    ABSTRACT: Plug-in Hybrid Electric Vehicles (PHEVs) are seen to be a step forward in vehicle electrification, to replace ICE based conventional vehicles. Using a PHEV implies that part of the vehicle energy comes from the grid or other sources, such as renewable energy, to charge the battery. However, renewable energy sources being intermittent sources, these new needs would only shift the problem by increasing the number of nuclear and coal power plants, and will not permit solving the problem of pollution or fossil fuel depletion. There is a need to optimize the way, in which the available resources are utilized, in order to reduce dependency on nuclear and coal power plants. This will achieve the overall goal of minimizing pollution, reducing the depletion rate of fossil fuels, as well as reduce the overall cost. This paper proposes a hybrid power system for house energy needs by utilization of renewable energy sources, grid, as well as the PHEV battery source. Emphasis of paper is on optimization of the overall cost of the system, by selecting the most cost effective and feasible option among the available options; namely, renewable energy sources, the grid and the battery of the PHEV. As a prerequisite to the implementation of this scheme, it is desirable to work out an approximate amount of available energy. For this, the efficiencies of the various power converters involved must be determined and taken into account to reduce the energy losses.
    Transportation Electrification Conference and Expo (ITEC), 2013 IEEE; 01/2013
  • Seyoung Kim, S.S. Williamson
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    ABSTRACT: In this paper, a new multiple-input DC/DC integrated converter is proposed for a fuel cell/battery/ultracapacitor electric vehicle. The power density increases in the order of fuel cell, battery, and ultracapacitor and the energy density is reverse of the order. The proposed converter combines interleaved type boost converters and two parallel-connected bidirectional DC/DC converters. The advantages of the proposed converter topology are improved power density, due to the fact that a heavy power transformer is not used, and the state of charge of battery as well as that of the ultracapacitor can be controlled easily.
    Transportation Electrification Conference and Expo (ITEC), 2013 IEEE; 01/2013