B. Vural

A dynamic lithium-ion battery model considering the effects of temperature and capacity fading

Battery models capture the characteristics of real-life batteries, and can be used to predict their behavior under various operating conditions. In this paper, a dynamic model of lithium-ion battery has been developed with MATLAB/Simulink® in order to investigate the output characteristics of lithium-ion batteries. Dynamic simulations are carried out, including the observation of the changes in battery terminal output voltage under different charging/discharging, temperature and cycling conditions, and the simulation results are compared with the results obtained from several recent studies. The simulation studies are presented for manifesting that the model is effective and operational.

A Bidirectional Nonisolated Multi-Input DC–DC Converter for Hybrid Energy Storage Systems in Electric Vehicles

To process the power in hybrid energy systems using a reduced part count, researchers have proposed several multiinput dc-dc power converter topologies to transfer power from different input voltage sources to the output. This paper proposes a novel bidirectional nonisolated multi-input converter (MIC) topology for hybrid systems to be used in electric vehicles composed of energy storage systems (ESSs) with different electrical characteristics. The proposed converter has the ability to control the power of ESSs by allowing active power sharing. The voltage levels of utilized ESSs can be higher or lower than the output voltage. The inductors of the converter are connected to a single switch; therefore, the converter requires only one extra active switch for each input, unlike its counterparts, hence resulting in reduced element count. The proposed MIC topology is compared with its counterparts concerning various parameters. It is analyzed in detail, and then, this analysis is validated by simulation and through a 1-kW prototype based on a battery/ultracapacitor hybrid ESS.

Fuel Consumption Comparison of Different Battery/Ultracapacitor Hybridization Topologies for Fuel-Cell Vehicles on a Test Bench

The power train of fuel-cell vehicles (FCVs) can be composed of onboard hybrid energy sources to reduce fuel consumption, extend driving range through regenerative braking energy recovery, and possibly increase the specific power density. One of the main issues significantly affecting the FCV performance is the chosen hybrid system topology along with system components, which requires research to find the best hybrid structure for the lowest fuel consumption. Although several hybridization topologies have been studied separately in the literature, an overall investigation and fuel consumption comparison of the most promising fuel-cell (FC) power-train topologies along with the experimental verification should be realized. In this regard, this paper demonstrates a detailed comparison of four different hybrid FC power-train configurations with feasible battery and ultracapacitor (UC) combinations, on a test bench using normalized ECE-15 drive cycle. The results demonstrate that the lowest equivalent fuel consumption can be achieved with FC/battery/UC hybrid combination.

A dynamic ultra-Capacitor model for vehicular applications

Ultra-capacitor (UC) models capture the characteristics of real-life UCs, and can be used to predict their behavior under various operating conditions. In this paper, a dynamic model of UC that can be useful for vehicular applications has been developed using MATLAB/Simulink®. Dynamic simulations are carried out to obtain the changes in UC terminal output voltage under different charge/discharge rates and temperature conditions. Then, the simulation results are verified compared with the results obtained from experimental studies. Comparisons show that the model is effective and operational.

An Energy Management Strategy for a Concept Battery/Ultracapacitor Electric Vehicle With Improved Battery Life

Using multi-input converters (MICs) in hybrid energy storage systems (HESSs) presents several advantages, such as low component count, control simplicity, and fully control of source energies. The power levels of sources in these systems need to be determined wisely by an energy management strategy (EMS). This paper presents an EMS for a battery/ultracapacitor (UC) HESS including a bidirectional MIC for electric vehicles (EVs). Thanks to the fact that energy flow between battery and UC is free in this MIC, the proposed EMS not only regulates the state-of-charge of UC but also smooths the battery power profile by using a fuzzy logic controller and a rate limiter. Therefore, it results in a sustainable HESS with longer battery life. Through a simulation study and an experimental setup including a real EV, the performance of the proposed system is evaluated comprehensively. Then, based on experimental results, battery cycle-life improvement due to the battery/UC hybridization is explored.

A wavelet-ADALINE network based load sharing and control algorithm for a FC/UC hybrid vehicular power system

The most attractive features of fuel cell technologies are the environment friendly operation and fuel economy. Instead of using only a FC system for vehicle propulsion, hybridizing FC system with an energy storage system provides many advantages. Fuel cell (FC) and ultra-capacitor (UC) based hybrid power systems appear to be very promising for satisfying high energy and high power requirements for vehicular applications. In this study, an adaptive linear neuron (ADALINE) network and wavelet transform based energy management strategy developed for a FC/UC hybrid vehicle system is proposed. While wavelet transforms are suitable for analyzing and evaluating the dynamic load demand profile of a hybrid electric vehicle (HEV), the use of adaline network controller is appropriate for the hybrid system control. The mathematical and electrical models of the system are developed in detail and simulated using Matlab®, Simulink® and SimPowerSystems® environments.

Battery/UC hybridization for electric vehicles via a novel double input DC/DC power converter

In this work, for electric vehicles (EVs), a novel double input DC-DC power converter, that enables utilization of a battery and ultra-capacitor (UC) in parallel while increasing the overall performance of electric vehicles and recovering regenerative breaking energy, is introduced. Since UCs have higher power density when compared to batteries, by the use of a UC as a power input, DC bus voltage regulation at transients and peak loads is achieved easily, thus the life of the battery and efficiency of the system are increased. The average value model of the proposed converter is created in MATLAB®, Simulink® and SimPowerSystems® environment, then its dynamic performance is tested under the load determined from the ECE-15 drive cycle.

Implementation of a reliable load sharing strategy between battery and ultra-capacitor on a prototype electric vehicle

In this study, a battery and ultra-capacitor (UC) hybrid electric vehicular system is proposed. The battery supplies the long term energy requirements of the vehicle while UC is employed for picking up the transient load variations that can seriously damage the electrochemical structure of the battery. An experimental assessment of the constructed vehicle prototype of such hybrid structure is realized under a real time drive cycle. The proposed system provides the advantages of eliminating of the supervisory control system necessity as well as realizing a more reliable local control approach based on voltage regulation compared to current based control approaches.

Current ripple minimization of a PEM fuel cell via an interleaved converter to prolong the stack life

This paper focuses on to prolong the Proton Exchange Membrane (PEM) fuel cell stack life via an interleaved double switch buck-boost converter. PEM fuel cells are environmental friendly energy sources, and widely used in several applications such as electrical vehicles, power plants, back-up power units, thanks to their fast start-up ability, portability, and efficient operation. In the steady-state, the fuel cell current ripple may result in damage to the fuel cell chemical structure, so it is required to extract its power via a power converter that can overcome this issue. Therefore, in this work, a power converter topology and a control method are proposed in order to reduce the converter input current ripple in both buck and boost operation modes with the help of its two input inductors. In addition to that, sharing input current via these inductors decreases input capacitance voltage stresses and average current flowing through the interleaved inductors thus smaller input capacitance and inductors also increase the cost effectiveness of proposed converter. The simulation results indicate that the proposed interleaved buck-boost topology reduces the input current ripple, and leads less settling time hence better dynamic response owing to its interleaved structure.

Small scale test bench based performance analysis of a fuel cell/ultra-capacitor hybrid vehicular power system with an improved power conditioning unit

For vehicular systems, fuel cells (FCs) are considered as a potential long term alternative to replace conventional combustion engines. However, high cost and slow dynamic response of FC are still the main challenges for wider applications. To overcome this problem, an auxiliary power system with adequate power capacity has to be incorporated. Ultra-capacitors (UCs) can provide an applicable solution in this aspect. Thus, a test bench of FC/UC hybrid configuration that can be suitable for vehicular systems is presented in this paper. In addition, an improved power conditioning unit (PCU) that can enhance fuel economy compared to conventional converter topologies is provided. Two different hybridization topologies are examined from different aspects. A test bench performance verification of a fuzzy logic based energy management strategy that was discussed in earlier simulation-based studies of the authors is investigated. Experimental results with small-scale devices, namely, a PEMFC (1200 W, 46 A) manufactured by the Ballard Power System Company, and four UC modules (58 F, 15 V) manufactured by the Maxwell Technologies Company, illustrate the performance analysis of both the applied PCUs and employed energy-management scheme during load cycles.