S.S. Williamson

Concordia University Montreal, Montréal, Quebec, Canada

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Publications (36)12.39 Total impact

  • Z. Amjadi, S.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.
  • A. Shafiei, A. Momeni, S.S. Williamson
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    ABSTRACT: This paper proposes a novel MPPT algorithm mainly for battery charging applications which are considered constant voltage type loads. This is achieved mainly with output current maximization. This technique benefits from advantages such as very simple current controller and also circuit topology independency. This provides high efficiency for energy conversion with low cost for low power, low cost applications. A new hybrid PV model is introduced for simulation purposes. Finally, simulation results will be provided confirming the validity of the algorithm.
    Electrical & Computer Engineering (CCECE), 2012 25th IEEE Canadian Conference on; 01/2012
  • Zahra Amjadi, Sheldon S. Williamson
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    ABSTRACT: This paper presents the modeling, design, and novel control strategy development for a hybrid switched-capacitor bidirectional dc/dc converter, applicable for a hybrid electric vehicle energy storage system. The proposed control strategy is based on the power profile of the traction motor and the gradient of battery current. Features of voltage step-down, voltage step-up, and bidirectional power flow are integrated into a single circuit, and are verified on an experimental prototype. The developed control strategy enables simpler dynamics, compared to a standard buck converter with input filter, good regulation capability, low EMI, lower source current ripple, ease of control, and continuous input current waveform in both buck and boost modes of operation.
    IEEE Transactions on Smart Grid 01/2012; 3:332-340.
  • Z. Amjadi, S.S. Williamson
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    ABSTRACT: This paper presents the analysis and novel controller design for a hybrid switched-capacitor bidirectional dc/dc converter that is applicable for hybrid electric vehicle (HEV)/plug-in HEV energy-storage system (ESS) applications, based on the power of the traction motor and the gradient of the battery current. Features of voltage step-down, voltage step-up, and bidirectional power flow are integrated into a single circuit. The novel control strategy enables simpler dynamics, compared with a standard buck converter, with input filter, good regulation capability, low electromagnetic interference, lower source current ripple, ease of control, and continuous input current waveform in both modes of operation (buck and boost modes).
    IEEE Transactions on Vehicular Technology 02/2011; · 2.06 Impact Factor
  • Z. Amjadi, S.S. Williamson
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    ABSTRACT: This paper presents the performance comparison and transfer efficiency modeling and analysis of a 2-quadrant switched capacitor converter (2-Q SCC), a 4-Q SC Luo converter and interleaved SCC, applicable for hybrid electric and plug-in hybrid electric vehicles (PHEV) Energy storage system (ESS) applications. SCCs offer essential features of voltage step-down, voltage step-up, and bidirectional power flow, associated with two or more HEV energy storage devices.
    IECON 2010 - 36th Annual Conference on IEEE Industrial Electronics Society; 12/2010
  • C. Desai, S.S. Williamson
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    ABSTRACT: It has been proven in literature that both the drivetrain as well as control strategy parameters have significant effects on the performance of hybrid electric vehicles (HEVs). A global optimization methodology based on particle swarm optimization (PSO) is presented in this paper for the parameter optimization of parallel hybrid electric drivetrain and control strategy simultaneously. The developed methodology aims at improvement in terms of fuel economy, without compromising driving performance. Simulation results show an improvement in the fuel economy, emissions, and overall drivetrain efficiency, which prove the potential of the optimization technique.
    Energy Conversion Congress and Exposition (ECCE), 2010 IEEE; 10/2010
  • Z. Amjadi, S.S. Williamson
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    ABSTRACT: This paper presents the analysis and novel controller design for a hybrid 4-quadrant (4-Q) switched-capacitor (SC) Luo and a conventional buck-boost bidirectional DC/DC converters, for HEV/PHEV energy storage system 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 novel hybrid controller strategy enables simpler dynamics compared to a standard buck converter, with input filter, good regulation capability, low EMI, lower source current ripple, ease of control, and continuous input current waveform in both modes of operation (buck and boost modes).
    Vehicle Power and Propulsion Conference (VPPC), 2010 IEEE; 10/2010
  • A. Shafiei, S.S. Williamson
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    ABSTRACT: There has been an increasing attraction towards plug-in hybrid electric vehicles (PHEVs) within the auto industry. However, high battery prices and short life spans have led to growing interest in development of advanced charging techniques and algorithms. In this paper, the characteristics of batteries used in PHEVs, which include Pb-acid, Ni-Cd, Ni-MH, Li-ion, and Li-polymer are reviewed, and different charging methods such as constant voltage, constant current, pulsed charging and burp charging are investigated. Termination methods such as time, voltage, voltage drop (dv/dt), current, and temperature are also discussed. Suitable charging algorithms for these battery types will be reviewed and evaluated. Battery charging issues such as cell equalization, state of charge estimation and thermal management will be discussed. Finally, future research trends of charging of PHEVs are described.
    Vehicle Power and Propulsion Conference (VPPC), 2010 IEEE; 10/2010
  • C. Desai, F. Berthold, S.S. Williamson
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    ABSTRACT: Plug-in Hybrid Electric Vehicles (PHEVs) can significantly reduce petroleum consumption and the only difference from hybrid electric vehicles (HEVs) is the ability of PHEVs to use off-board electricity generation to recharge their energy storage system. The fuel economy of PHEV is highly dependent on All-Electric-Range (AER), drivetrain component size and control strategy parameter. In this study we consider PHEV version of parallel hybrid NOVA transit bus model developed with the Powertrain System Analysis Toolkit (PSAT). A genetic based derivative free algorithm called Multi-Objective Genetic Algorithm (MOGA) is used to optimize conflicting drivetrain and control strategy parameters. The AER, fuel economy, emissions and main performance constraints of the PHEVs will be compared for the initial design and final optimal design.
    Electric Power and Energy Conference (EPEC), 2010 IEEE; 09/2010
  • Z. Amjadi, S.S. Williamson
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    ABSTRACT: A novel power electronics energy management system for hybrid electric and plug-in hybrid electric vehicles (PHEV) is designed using a bidirectional switched capacitor (SC) DC/DC Luo converter. The controller uses the voltage-lift technique and presents a low output ripple, high power density, high efficiency, high voltage gain, and simple structure. A detailed efficiency modeling and analysis is also presented to support the claims.
    Electrical and Computer Engineering (CCECE), 2010 23rd Canadian Conference on; 06/2010
  • Z. Amjadi, S.S. Williamson
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents the analysis and novel controller design for a hybrid switched-capacitor bidirectional dc/dc converter. Features of voltage step-down, step-up, and bidirectional power flow are integrated into a single circuit. The novel control strategy enables simpler dynamics compared to a standard buck converter with an input filter, good regulation capability, low electromagnetic interference, lower source current ripple, ease of control, and continuous input current waveform in both modes of operation (buck and boost modes).
    IEEE Transactions on Industrial Electronics 04/2010; · 5.17 Impact Factor
  • Source
    Z. Amjadi, S.S. Williamson
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    ABSTRACT: Batteries, ultracapacitors (UCs), and fuel cells are widely being proposed for electric vehicles (EVs) and plug-in hybrid EVs (PHEVs) as an electric power source or an energy storage unit. In general, the design of an intelligent control strategy for coordinated power distribution is a critical issue for UC-supported PHEV power systems. Implementation of several control methods has been presented in the past, with the goal of improving battery life and overall vehicle efficiency. It is clear that the control objectives vary with respect to vehicle velocity, power demand, and state of charge of both the batteries and UCs. Hence, an optimal control strategy design is the most critical aspect of an all-electric/plug-in hybrid electric vehicle operational characteristic. Although much effort has been made to improve the life of PHEV energy storage systems (ESSs), including research on energy storage device chemistries, this paper, on the contrary, highlights the fact that the fundamental problem lies within the design of power-electronics-based energy-management converters and the development of smarter control algorithms. This paper initially discusses battery and UC characteristics and then goes on to provide a detailed comparison of various proposed control strategies and proposes the use of precise power electronic converter topologies. Finally, this paper summarizes the benefits of the various techniques and suggests the most viable solutions for on-board power management, more specific to PHEVs with multiple/hybrid ESSs.
    IEEE Transactions on Industrial Electronics 03/2010; · 5.17 Impact Factor
  • Z. Amjadi, S. S. Williamson
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    ABSTRACT: This paper presents the detailed analysis and novel hybrid controller design for bidirectional energy management solutions, using smart power electronic DC/DC converter solutions. More specifically, an intelligently designed novel digital control technique is presented for 4-quadrant (4Q) switched-capacitor (SC) Luo DC/DC converters, based on power of traction motor and gradient of battery current. Features of voltage step-down, step-up, and bi-directional power flow are integrated into a single circuit. The novel hybrid control system enables simpler dynamics compared to a standard buck converter with input filter, superior regulation capability, lower source current ripple, ease of control, and continuous input current waveform in buck and boost modes of operation.
    01/2010;
  • Zahra Amjadi, Sheldon S. Williamson
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    ABSTRACT: This paper presents the performance comparison and transfer efficiency modeling and analysis of a 4-quadrant switched capacitor Luo (4-Q SC Luo) converter and 2-Q SCC, applicable for hybrid electric and plug-in hybrid electric vehicles (PHEV) Energy storage system (ESS) applications. Features of voltage step-down, voltage step-up, and bi-directional power flow are integrated into a single circuit. The SCC enables simpler dynamics compared to a standard buck converter, with input filter, good regulation capability, low EMI, lower source current ripple, ease of control, and continuous input current waveform in both modes of operation (buck and boost modes).
    01/2010;
  • M. Jain, C. Desai, N. Kharma, S.S. Williamson
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    ABSTRACT: Considerable efforts have been made recently to develop a completely zero-emission and highly fuel efficient vehicle. Due to clean and efficient power generation, the hydrogen fed fuel cell vehicle (FCVs) has received considerable attention. However, major obstacles such as cost of the hydrogen infrastructure, driving range, and cost of the fuel cell greatly influence FCV development. At the same time, proper utilization of grid power, along with a modified electrical system infrastructure, would encourage automakers to envisage plug-in versions of fuel cell vehicles. This paper presents the optimal powertrain component sizing of a fuel cell plug-in hybrid electric (FC-PHEV) vehicle, comprised of a fuel cell with electrolyser, Ni-MH battery as secondary energy storage, and a propulsion motor. Such a PHEV architecture provides an additional degree of freedom, as the grid power can be used to recharge batteries, or for the electrolysis of water, to generate hydrogen and oxygen, which increases the driving range of vehicle as well as the overall powertrain efficiency. Hence, the overall performance and efficiency are much superior when compared to ordinary PHEV or FC-HEV powertrains. This paper uses a small vehicle power train for modelling and simulation purposes. Optimal sizing of the power train components using multi-objective genetic algorithm will be presented. Moreover, overall vehicle performance and fuel economy for different driving loads will also be analysed. Finally, an overall cost analysis will also be presented.
    Industrial Electronics, 2009. IECON '09. 35th Annual Conference of IEEE; 12/2009
  • Z. Amjadi, S.S. Williamson
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    ABSTRACT: A novel controller for a switched capacitor (SC) bidirectional DC/DC converter is proposed for plug-in hybrid electric vehicle energy storage systems, with simultaneous step-up and step-down output voltages. The novel control strategy enables simpler dynamics compared to a standard buck converter with input filter, good regulation capability, lower source current ripple, ease of control, and continuous input current waveform in both modes of operation (buck and boost modes). A detailed efficiency modeling and analysis is also presented to support the claims.
    Industrial Electronics, 2009. IECON '09. 35th Annual Conference of IEEE; 12/2009
  • A.G. Siraki, N. Curry, P. Pillay, S.S. Williamson
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    ABSTRACT: In recent years, renewable energy resources have attracted a lot of effort and attention, due to issues related to utilization of traditional fossil fuels. Global warming, major energy crises, and unsecure energy supply has motivated developed countries to speed-up the process of installing renewable technologies. On the other hand, deregulation of power systems, with the aim of more competitive and efficient power generation, creates new opportunities for use of renewable technologies at the distribution level. Residential and commercial buildings consume a great portion of generated power in most countries. Therefore, there exists a need for reduction of power consumption, by using efficient generation technologies, using local renewable energy generation. This paper comprehensively reviews potential and available renewable energy technologies, to be embedded in new or existing urban buildings, and investigates a few novel building power system arrangements.
    Industrial Electronics, 2009. IECON '09. 35th Annual Conference of IEEE; 12/2009
  • M. Jain, S.S. Williamson
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    ABSTRACT: In most conventional EV applications, a central high speed electric motor is mechanically coupled to the wheels by a single speed reduction gearbox and a mechanical differential. An innovative alternative utilizes low speed, high torque, gearless, electric motors, mounted completely inside the rim of the wheels, to provide instantaneous torque and eliminate driveline transmission losses. These in-wheel motors have many advantages, including no mechanical linkages and independent and precise torque control of each wheel. Furthermore, advanced control functions like Antilock Braking System (ABS), Anti Slip Regulation (ASR), Electronic Stability Program (ESP), and steering assistance can be easily integrated. In this paper, various motors and control strategies for such in-wheel motor drives for 2-wheel and 4-wheel drive vehicles have been presented.
    Electrical Power & Energy Conference (EPEC), 2009 IEEE; 11/2009
  • C. Desai, S.S. Williamson
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    ABSTRACT: Stimulated by the urgent need for clean energy generation, improvised energy management strategies/control strategies for hybrid electric vehicles, plug-in hybrid electric vehicles, and all-electric vehicles are attracting much research interest. This paper presents the classification and study of various control strategies used in hybrid electric vehicles. Comparison of different control strategies with their advantages and disadvantages are also summarized, which provide novel directions for further developments.
    Electrical Power & Energy Conference (EPEC), 2009 IEEE; 11/2009
  • Z. Amjadi, S.S. Williamson
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    ABSTRACT: Batteries, ultra capacitors, and fuel cells are widely being proposed for electric and plug-in hybrid electric vehicles (EVs/PHEVs) as an electric power source or an energy storage unit. Implementation of several control methods have been presented in the past, with the goal of improving battery life and overall vehicle efficiency. It is clear that the control objectives vary with respect to vehicle velocity, power demand, and state-of-charge of both the batteries and ultra-capacitors. Hence, an optimal control strategy design is the most critical aspect of an all-electric/plug-in hybrid electric vehicle operational characteristic. This paper initially discusses energy storage characteristics, and then describes types of hybrid electric vehicle energy storage systems (ESS), energy source models, and type of DC/DC converters.
    Electrical Power & Energy Conference (EPEC), 2009 IEEE; 11/2009