Serkan Dusmez

Comprehensive Topological Analysis of Conductive and Inductive Charging Solutions for Plug-In Electric Vehicles

The impending global energy crisis has opened up new opportunities for the automotive industry to meet the ever-increasing demand for cleaner and fuel-efficient vehicles. This has necessitated the development of drivetrains that are either fully or partially electrified in the form of electric and plug-in hybrid electric vehicles (EVs and HEVs), respectively, which are collectively addressed as plug-in EVs (PEVs). PEVs in general are equipped with larger on-board storage and power electronics for charging or discharging the battery, in comparison with HEVs. The extent to which PEVs are adopted significantly depends on the nature of the charging solution utilized. In this paper, a comprehensive topological survey of the currently available PEV charging solutions is presented. PEV chargers based on the nature of charging (conductive or inductive), stages of conversion (integrated single stage or two stages), power level (level 1, 2, or 3), and type of semiconductor devices utilized (silicon, silicon carbide, or gallium nitride) are thoroughly reviewed in this paper.

Optimization of Sizing and Battery Cycle Life in Battery/Ultracapacitor Hybrid Energy Storage Systems for Electric Vehicle Applications

Electric vehicle (EV) batteries tend to have accelerated degradation due to high peak power and harsh charging/ discharging cycles during acceleration and deceleration periods, particularly in Urban driving conditions. Oversized energy storage system (ESS) meets the high power demand; however, in tradeoff with increased ESS size, volume, and cost. In order to reduce overall ESS size and extend battery cycle life, battery/ultracapacitor (UC) hybrid ESS (HESS) has been considered as a solution in which UCs act as a power buffer to charging/discharging peak power. In this paper, a multiobjective optimization problem is formulated to minimize the overall ESS size, while maximizing the battery cycle life according to the assigned penalty functions. An integrated framework for HESS sizing and battery cycle life optimization applied in a midsize EV, using an Autonomie simulation model, is described and illustrated in this paper. This multidimensional optimization is realized by a sample-based global search oriented DIviding RECTangles (DIRECT) algorithm. The optimization results under Urban Dynamometer Driving Schedule (UDDS) are compared with the battery-only ESS results, which demonstrate significant battery cycle life extension of 76% achieved by the optimized HESS with 72 UC cells.

Design and Analysis of a Full-Bridge LLC-Based PEV Charger Optimized for Wide Battery Voltage Range

In this paper, a two-stage onboard battery charger is analyzed for plug-in electric vehicles (PEVs). An interleaved boost topology is employed in the first stage for power factor correction (PFC) and to reduce total harmonic distortion (THD). In the second stage, a full-bridge LLC-based multiresonant converter is adopted for galvanic isolation and dc/dc conversion. Design considerations are discussed, focusing on reducing the charger volume and optimizing the conversion efficiency over the wide battery-pack voltage range. A detailed design procedure is provided for a 1-kW prototype, charging the battery with an output voltage range of 320-420 V from 110-V 60-Hz single-phase grid. Experimental results show that the first-stage PFC converter achieves THD of less than 4% and a power factor higher than 0.99, and the second-stage LLC converter operates with 95.4% peak efficiency and good overall efficiency over wide output voltage ranges.

Maximum Efficiency Point Tracking Technique for

In this paper, a variable dc link technique is proposed to track the maximum efficiency point of the LLC converter for plug-in electric vehicle battery-charging applications over a wide battery state-of-charge (SOC) range. With the proposed variable dc link control approach, the dc link voltage follows the battery pack voltage. The operating point of the LLC converter is always constrained to the proximity of the primary resonant frequency so that the circulating current in the magnetizing inductor and the turning-off currents of MOSFETs are minimized. In comparison with conventional approaches, the proposed variable dc link voltage methodology demonstrates efficiency improvement across the wide SOC range. Efficiency improvements of 2.1% at the heaviest load condition and 9.1% at the lightest load condition are demonstrated.

LLC

Electrification of performance vehicles brings several challenges, such as the necessity of high-power sources, which can satisfy the power requirements during acceleration and efficiently retrieve energy during deceleration without performance and life cycle deterioration of such sources. In addition, the limited space under the hood for these vehicles eliminates the possibility of utilizing large volume high-power propulsion machines. This paper proposes a fuzzy logic supervisory wavelet-transform frequency decoupling-based energy management strategy implemented on a new powertrain deploying two propulsion machines rated at different powers with a hybrid battery/ultracapacitor (UC) energy storage system (ESS). The proposed control and energy management strategy guarantees that battery and UC provide the base and transient-free powers, respectively, while state of charge (SOC) of UC is maintained at an optimal value. The torque demand is split among the propulsion machines by solving the formulated unconstrained optimization problem. With the proposed hybrid ESS and energy/power decoupling strategy, power density of the ESS can be increased, vehicle performance can be improved, and battery lifetime can be prolonged.

-Based PEV Chargers Through Variable DC Link Control

The basic power electronic interfaces rendering volume and weight of electric and plug-in hybrid electric vehicles are an inverter, an on-board charger, and a bidirectional dc/dc converter. This paper proposes an innovative integrated bidirectional converter with a single-stage on-board charger to reduce the number of switches, size, and weight of the power electronic interfaces. The analyses show that 266 cm 3 and 1.1 kg can be saved due to the elimination of the inductor core used for power factor correction in charging mode, in addition to the reduction achieved through removal of inductor winding, power switches, diodes, and additional heat sink of the conventional structures. A proof-of-concept prototype with power limits of 8.4 kW in charging and 20 kW in propulsion modes has been designed and validated at various power levels. The peak efficiencies for propulsion and regenerative braking operations are measured as 96.6% and 94.1%, respectively. The power factor is recorded as 0.995 at 1.8 kW charging power, where crest factor and peak efficiency are recorded as 1.49 and 91.6%, respectively.

A Supervisory Power-Splitting Approach for a New Ultracapacitor–Battery Vehicle Deploying Two Propulsion Machines

Level 1 and level 2 EV/PHEV charging methods tend to require excess time to reach a full charge, preventing a seemless transition from conventional gasoline vehicles to battery-powered vehicles. The level 3 off-board charging infrastructure will alleviate the down-time required for vehicle charging, and provide an option for quick refueling. It is necessary to choose suitable power electronic interfaces for these chargers to prevent any potential damage to the grid, and optimize system efficiency. This paper introduces level 3 charging along with compatible battery chemistries, and analyzes some high power quality converters based on two different power conversion architectures. In particular, the paper focuses on several isolated and non-isolated DC-DC power converter topologies, and provides a detailed comparison in terms of component size and efficiency.

A Compact and Integrated Multifunctional Power Electronic Interface for Plug-in Electric Vehicles

In battery/ultracapacitor electric vehicles, a bidirectional dc/dc converter is employed to process the power according to the power references obtained from the energy management controller. The selection of this converter is of critical importance for the overall system efficiency and size. This study proposes using a three-level dc/dc converter and provides a comprehensive comparison with the conventional two-level and interleaved bidirectional buck/boost converters in terms of magnetic component size/weight and overall efficiency. Unlike the comparative studies presented in the literature, where the efficiency comparison of converters is conducted based on given fixed input and output parameters, power references obtained from a wavelet-transform-based energy management strategy with varying energy source voltages and traction power are considered in this paper. The results of the analyses show that a three-level converter exhibits higher overall efficiency and has smaller size inductor. A 1-kW bidirectional three-level dc/dc converter is designed as a proof of concept, which exhibits 93.2% peak efficiency at 200-kHz switching frequency.

Comprehensive analysis of high quality power converters for level 3 off-board chargers

A three-level (TL) bidirectional dc/dc converter is a suitable choice for power electronic systems with a high-voltage dc link, as the voltage stress on the switches is half and inductor current ripple frequency is twice the converters switching frequency. This study proposes a zero-voltage transition (ZVT) TL dc/dc converter to enable operation with higher switching frequency in order to achieve higher power density and enhance efficiency. Two identical ZVT cells, each one composed of two resonant inductors, a capacitor, and an auxiliary switch, are integrated with the conventional TL topology to enable soft switching in all four switches in both buck and boost operation modes. In addition, a variable dead-time control is proposed to increase the effective duty ratio at heavy loads. The proposed soft-switching feature has been demonstrated under different loading conditions. A 650-W prototype is designed and fabricated, which exhibits 95.5% at full load.

Comparative Analysis of Bidirectional Three-Level DC–DC Converter for Automotive Applications

The current research trend to increase the power density of power electronics interfaces in automotive applications is the cost-effective integration of power converters. This paper proposes a reduced-part integrated power electronics interface that is capable of charging the battery and adjusting the voltage levels of a battery and a dc link during propulsion and regenerative braking. In the proposed topology, one inductor is shared between a dc/dc converter and a charger, eliminating the need for an additional magnetic component for the charging stage. A charge nonlinear-carrier control (NLC) method, which reduces the feedback circuitry, is adopted, and different nonlinear reference voltage waveforms are generated for each half-cycle of the grid to ensure a unity power factor and stable operation. To verify the concept, a 750-W prototype has been built and tested for each operation mode.