Shaahin Filizadeh

Profile of Charging Load on the Grid Due to Plug-in Vehicles

The paper presents a study of the profile of the load imposed on a power system by grid-charging of the onboard battery pack of electric and plug-in hybrid vehicles. The study uses a large database of field-recorded driving cycles stamped with parking times and locations to predict realistic driving habits of drivers in an urban setting. A fuzzy-logic inference system is designed to emulate the decision-making process of a driver when deciding to charge the vehicles battery. The charging load is then estimated on an hourly basis for a number of electric and plug-in hybrid vehicles with different storage capacities. Level-1 and level-2 charging regimes as well as two scenarios for charging, namely charging at home and charging at home and work, are considered. The load profile is presented as an hourly probability of charging for each vehicle type. The results demonstrate how penetration of plug-in hybrid and electric vehicles affects the load on a utility network.

An Optimized Space Vector Modulation Sequence for Improved Harmonic Performance

This paper proposes a method for optimization of the harmonic performance of converters under space vector modulation (SVM) control. It is shown that SVM provides a number of degrees of freedom, which make it suitable for optimization, subject to desired constraints. An objective function is defined, which seeks to minimize the most significant harmonic components of the generated waveform while keeping other harmonic components within the acceptable range outlined in the available standards. Since the formulation of the problem involves both real and integer variables, specialized optimization methods capable of handling mixed-integer variables need to be employed, and hence, a genetic algorithm optimizer is used to solve the optimization problem. Optimized SVM sequences obtained for various operating points under different sampling frequencies are shown to result in significant reduction of dominant harmonics while maintaining the waveform quality within prescribed limits.

Optimization-enabled electromagnetic transient simulation

Electromagnetic transient simulation programs (EMTP-type programs) are powerful tools for the study of a wide range of power system transient problems. This paper introduces a novel tool in which an emtp-type program becomes the objective function evaluator for a nonlinear optimization algorithm. In this approach, the nonlinear optimization program is given control to perform several consecutive runs with a view to minimize (or maximize) the desired objective function, which is computed from the results of each simulation run. Since the optimization algorithm strategically selects the parameters for the emtp run, the overall design process is orders of magnitude faster than that possible from sequential or random (Monte-Carlo-type) multiple-runs of the EMTP-type program. The paper discusses the mechanics of the interface as well as design of objective functions. The power of the proposed method is demonstrated through two examples for the design of power-electronic converters.

Battery Storage Sizing in a Retrofitted Plug-in Hybrid Electric Vehicle

This paper develops a simulation-based framework for optimal sizing of the additional energy storage required to retrofit a hybrid electric vehicle (HEV) to a plug-in hybrid electric vehicle (PHEV). Simulations are conducted on a vehicular model developed for a midsize sedan (Toyota Prius) using a new weekly vehicle-usage profile constructed for average driving and most probable parking times based on the data collected in the city of Winnipeg (Canada). Three battery technologies that are commercially available for electric vehicle propulsion are used in the simulations to determine the optimal sizing of the battery storage, given the constraints on the volume of the battery pack for lowest cost. Overnight-charging and opportunity-charging scenarios are also implemented in the simulation, and their impact on the optimal sizing is discussed.

Dynamic Average Modeling of Front-End Diode Rectifier Loads Considering Discontinuous Conduction Mode and Unbalanced Operation

Electric power distribution systems of many commercial and industrial sites often employ variable frequency drives and other loads that internally utilize dc. Such loads are often based on front-end line-commutated rectifiers. The detailed switch-level models of such rectifier systems can be readily implemented using a number of widely available digital programs and transient simulation tools, including the Electromagnetic Transient (EMT)-based programs and Matlab/Simulink. To improve the simulation efficiency for the system-level transient studies with a large number of such subsystems, the so-called dynamic average models have been utilized. This paper presents the average-value modeling methodologies for the conventional three-phase (six-pulse) front-end rectifier loads. We demonstrate the system operation and the dynamic performance of the developed average models in discontinuous and continuous modes, as well as under balanced and unbalanced operation.

An Optimization-Enabled Electromagnetic Transient Simulation-Based Methodology for HVDC Controller Design

This paper introduces a procedure for using optimization-enabled electromagnetic transient simulation (OE-EMTS) for the design of HVDC system controls. The OE-EMTS method conducts a sequence of simulation runs of the network, guided by a nonlinear optimization algorithm. The controller parameters in each subsequent run are refined with the aim of achieving a desired performance measure, mathematically represented by an objective function (OF). The paper demonstrates a design procedure, in which the selection of the OF follows an evolutionary path. The system is first designed with an initial OF, which often results in some unforeseen negative system behavior. In the next stage, a new OF is selected, which has the potential for mitigating this negative behavior. This cycle is terminated when a high-quality design is achieved. The procedure is exemplified with the controller design for a 200-MW back-to-back dc scheme to operate within a range of inverter short circuit ratios. The optimality measure considers dynamic changes in controller set-points as well as recovery from faults.

On Conversion of Hybrid Electric Vehicles to Plug-In

The retrofit conversion of currently available hybrid electric vehicles (HEVs) to plug-in HEVs (PHEVs) is studied in this paper through experiments and simulations using the powertrain system analysis toolkit (PSAT). First, a rule-based fuzzy controller of the battery energy-management unit is developed to simulate different energy-management policies. Second, by modifying the energy-control strategy, the model of the conversion PHEV (C-PHEV) is verified with experiments. Finally, the C-PHEV model is used to simulate different battery energy-management control strategies. The results show improvement in fuel economy, whereas the energy-management controller discharges the power through the plug-in battery pack only when the state of charge of the base vehicle battery is close to its minimum value. This method keeps the advantage of driving in electric mode using a combination of two batteries and optimizing the use of regenerative braking capabilities, which is the main advantage of HEVs. It is also found that increasing the power threshold of the internal combustion engine (ICE) improves the performance of C-PHEV. Increasing the ICE power threshold increases the engine efficiency by running the engine in its efficient points. It also drives the vehicle in electric mode in higher power demands.

Modeling of LCC-HVDC Systems Using Dynamic Phasors

This paper presents an average-value model of a line commutated converter-based HVDC system using dynamic phasors. The model represents the low-frequency dynamics of the converter and its ac and dc systems, and has lower computational requirements than a conventional electromagnetic transient (EMT) switching model. The developed dynamic-phasor model is verified against an EMT model of the CIGRE HVDC Benchmark. Simulation results confirm the validity and accuracy of the average-value model in predicting the low-frequency dynamics of both the ac and dc side quantities. Merits and applicability limitations of the average model are highlighted.

Techniques for Interfacing Electromagnetic Transient Simulation Programs With General Mathematical Tools IEEE Taskforce on Interfacing Techniques for Simulation Tools

This paper describes methods and issues related to interfacing electromagnetic transient simulation programs with general mathematical algorithms, which are either custom-developed by the user or are available through other mathematical analysis platforms. Various interfacing types and techniques are described along with potential areas of application. Implementation methods are detailed for each type of interface as well. This paper presents several interfacing examples from a wide variety of applications, including advanced switching schemes for power converters and controller implementation.

Inclusion of robustness into design using optimization-enabled transient simulation

This paper presents an approach to the design of robust power-electronic systems (i.e., those which have optimal operation over a range of operating configurations). Designing nonlinear systems, such as power-electronic converters, to be robust is a challenging task as settings that may be optimal for a given operating configuration may be inadequate for another. This paper extends the method of combining nonlinear optimization with electromagnetic transient simulation, which has previously been successfully applied to the design of optimal systems at only one operating point; to an approach which simultaneously considers a range of operating points. The method is exemplified using two examples. In the first example, a dc power supply is designed to operate optimally over a range of current order settings. The second is the case of an HVdc system, which is optimized to work well with a range of possible ac system configurations.