Search

Ultracapacitors have been attracting interest to apply as energy storage devices with advantages of fast charging capability, high power density, and long lifecycle. As a storage device, accurate monitoring is required to ensure and operate safely during the charge/discharge process. Therefore, high accuracy estimation of the state of charge (SOC) is needed to keep the Ultracapacitor working properly. This paper proposed SOC estimation using the Adaptive Neuro-Fuzzy Inference System (ANFIS). The ANFIS is tested by comparing it to true SOC based on an equivalent circuit model. To find the best method, the ANFIS is modified and tested with various membership functions of triangular, trapezoidal, and gaussian. The results show that triangular membership is the best method due to its high accuracy. An experimental test is also conducted to verify simulation results. As an overall result, the triangular membership shows the best estimation. Simulation results show SOC estimation mean absolute percentage error (MAPE) is 0.70 % for charging and 0.83 % for discharging. Furthermore, experimental results show that MAPE of SOC estimation is 0.76 % for random current. The results of simulations and experimental tests show that ANFIS with a triangular membership function has the most reliable ability with a minimum error value in estimating the state of charge on the Ultracapacitor even under conditions of indeterminate random current.

The growing penetration of converter-interfaced distributed renewable energy sources (CI-DRES) has posed several challenges into the electric power systems, e.g., the instability caused by the intermittent nature of the primary sources, power quality issues, etc. Several algorithms have been proposed to mitigate the CI-DRES power fluctuations and reduce high active power ramp-rates (RRs) at the point of common coupling (PCC) with the grid using energy storage systems (ESS). However, these algorithms present some drawbacks. In this article, a new ramp-rate limitation (RRL) control method is proposed to address existing gaps in the technical literature. This algorithm is performed considering the connection of a supercapacitor (SC) at the dc-link of a DRES converter. The relationship between the SC voltage and the degree to which the RRL is achieved is established, aiming to reduce the SC voltage fluctuations and increase the SC life time. The RRL control is validated in a real experimental testbed and compared to state-of-the-art approaches. This control is also modeled in Matlab/Simulink in order to perform techno-economic investigations on the influence that several parameters (SC size, SC charging/discharging cycles, cost, etc.) have on the achieved RRL at the DRES PCC. [ABSTRACT FROM AUTHOR]

Choice of hybrid electric vehicles (HEVs) in transportation systems is becoming more prominent for optimized energy consumption. HEVs are attaining tremendous appreciation due to their eco-friendly performance and assistance in smart grid notion. The variation of energy storage systems in HEV (such as batteries, supercapacitors or ultracapacitors, fuel cells, and so on) with numerous control strategies create variation in HEV types. Therefore, choosing an appropriate control strategy for HEV applications becomes complicated. This paper reflects a comprehensive review of the imperative information of energy storage systems related to HEVs and procurable optimization topologies based on various control strategies and vehicle technologies. The research work classifies different control strategies considering four configurations: fuel cell-battery, battery-ultracapacitor, fuel cell-ultracapacitor, and battery-fuel cell- ultracapacitor. Relative analysis among different control techniques is carried out based on the control aspects and operating conditions to illustrate these techniques’ pros and cons. A parametric comparison and a cross-comparison are provided for different hybrid configurations to present a comparative study based on dynamic performance, battery lifetime, energy efficiency, fuel consumption, emission, robustness, and so on. The study also analyzes the experimental platform, the amelioration of driving cycles, mathematical models of each control technique to demonstrate the reliability in practical applications. The presented recapitulation is believed to be a reliable base for the researchers, policymakers, and influencers who continuously develop HEVs with energy-efficient control strategies.

Utilization of an ultracapacitor (UC)-based energy storage device can provide one of the most efficient solutions for short-term operational challenges in grid-connected photovoltaic (PV) systems. This paper proposes an algorithm for coordinated control of PV and ultracapacitor-based energy storage system to minimize the effects of sudden changes in solar irradiance and the presence of low voltages at the point of common coupling. In addition, this work proposes an improved multi-mode operational scheme for control of an ultracapacitor-based energy storage system that takes into consideration various associated limits during charging and discharging modes. The effectiveness of the proposed algorithm in mitigating the impacts of low voltages and short term changes in irradiance is demonstrated using simulation analysis carried out on the modified Consortium for Electric Reliability Technology Solutions (CERTS) microgrid testbed.

The piezoelectricity allows the generation of electric power taking advantage of the movement of vehicles and pedestrians. Many prototypes have been made with piezoelectric generators, but at present, their commercialization and use have not been popularized due to their low power generation and energy losses. A design of an experimental prototype of an energy harvester with piezoelectric materials that reduces these losses and generates more energy thanks to the resonance with the beams is proposed in this article. An equilateral triangular tile is designed such it will not deform when a force acts on it. The tile has four-cantilever beams, and it is designed to resonate with the natural frequency of the piezoelectric material. This is coupled to the piezoelectric device. The vibration generated on the beam, by a mechanical load, is used to generate more energy when it resonates. The piezoelectric is a ceramic material and generates a nominal power of 75 mW before placing it on the beam, and 375 mW after being placed on the beam. However, the energy collection circuit has losses due to its own consumption, the transmission of energy to the storage system, and in the mechanical system.

To overcome the failure of power electronic transformer in resisting input voltage interruption in power grid, a combination between energy storage link and PET(power electronic transformer) is utilized. The energy storage link consists of an ultracapacitors and a bidirectional DC/DC converter. When input voltage interruption occurs, PET with energy storage link can maintain PET′s low DC voltage to be stable. The main parameters of energy storage link are analyzed, the control strategy of the link is designed, and the simulation experiment is built in the MATLAB/Simulink. The simulation experiment results verify the ability of a diagram of PET with energy storage link can resist input voltage interruption in power grid, making the safe and stable operation of equipment in power grid.

Ultracapacitors has now become an integral part of the contemporary energy storage systems. Their uniqueness in optimal power delivery, charge storage capabilities and long cyclic stability (˃105) are what make them attractive to the energy storage industries. Basically, Ultracapacitor consists of two separated electrodes impregnated with an electrolyte. Its performance is largely a function of the chosen electrode-electrolyte materials. The choice of the materials depends on the prevailing conditions at hand and is always at a tradeoff between certain merits and demerits. In this communication, we reviewed two contemporary materials namely; Transition Metal Oxides and Conducting Polymers with emphasis on the challenges associated with each. This will create an avenue in determining the direction and future perspective of Ultracpacitors materials. [ABSTRACT FROM AUTHOR]

As energy storage device of hybrid electric vehicles (HEVs), ultracapacitors feature the advantages of higher power density and longer life cycle compared with batteries. However, when ultracapacitors of the same power level are used instead of batteries, fuel consumption becomes more sensitive to changes in control parameters as ultracapacitors store much less energy, and the state of charge (SOC) is power-sensitive. In this paper, optimization of control parameters for a power-split HEV with ultracapacitors is addressed to achieve better fuel economy. First, a power-split HEV model and a corresponding control strategy are established under the MATLAB script environment for convenient analysis and application of an optimization algorithm. Second, focusing on the power-sensitive characteristic of the SOC, three key control parameters are determined, and their effects on fuel consumption are analyzed. Third, an improved particle swarm optimization (IPSO) algorithm is proposed to overcome the disadvantage of the PSO trapping into “local optimum” and improve optimization efficiency. To fully exploit the fuel-saving capability of the HEV, driving cycle segmentation is also considered. The IPSO is used to optimize three key control parameters under the segmented adapted world transient vehicle cycle. Finally, the optimal results are applied to hardware-in-the-loop test to verify the effectiveness of the proposed optimization method. Compared with the fuel consumption before optimization, the fuel saving rate reaches 9.20% in the urban section, 6.40% in the roadway section, and 5.40% in freeway section.

Copyright of Revista Facultad de Ingeniería Universidad de Antioquia is the property of Universidad de Antioquia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The rough and porous structure of the electrode and electrolyte interface in ultracapacitors results in hysteresis between the excitation current and corresponding terminal voltage. The hysteretic behavior causes an increment in terminal voltage even after the removal of input excitation current, referred to as remnant voltage. The design and operation of any ultracapacitor-based energy system should necessarily take into account the hysteretic behavior and the associated remnant voltage for optimal utilization of ultracapacitor as a storage device. Proper modeling of hysteresis allows for determining the optimal excitation profile for charging the ultracapacitor, such that proper balance between the load demand and energy storage is achieved. Motivated by the effectiveness of fractional calculus in representing the long-term memory effect and charge diffusion phenomena in ultracapacitors, this article proposes a fractional calculus-based approach for modeling the hysteresis and estimating the related remnant voltage and associated energy availability after the completion of periodic charging excitations. Analytical expressions for ultracapacitor voltage and energy storage have been formulated for different hysteresis levels using fractional calculus. The formulation helps in quantifying the hysteresis as a function of the excitation magnitude/duration and ultracapacitor model parameters, thus providing a platform for improving the energy efficiency of the ultracapacitor-based energy management applications by optimal charging. The derived expressions have been experimentally validated for varying dynamics of current excitation. [ABSTRACT FROM AUTHOR]

This article explores hybrid energy storage devices in which an individual electrode is composed of a mixture of the active materials used in lithium-ion batteries and ultracapacitors, allowing them to exhibit characteristics of both device types. In order to explore the breadth of options between a pure battery electrode and a pure ultracapacitor electrode, seven different electrode compositions containing mixtures of lithium iron phosphate (LiFePO4) and activated carbon have been investigated. The hybrid electrodes have been implemented in an aqueous lithium sulfate electrolyte with single-electrode measurements using a reference electrode. The hybrid pulse power characterization (HPPC) test profile has been employed to characterize the energy and power capability of each electrode composition. An approach for converting single-electrode cycling results to full cell predictions suitable for the HPPC analysis procedure is presented. By executing this procedure, battery scale factors representing estimates of the quantity of active material required to achieve a set of energy storage target requirements have been calculated. Models of full 18650-format hybrid cells are developed to extend results to optimize a tailored energy storage system on the basis of total cell mass and volume. These results show that the required amount of active materials, total mass, or total volume of an energy storage system can be minimized for a given application by using a hybrid electrode and adjusting the constituent fraction of battery and ultracapacitor materials. [ABSTRACT FROM AUTHOR]

A novel dynamic average-value model (AVM) of energy storage systems (ESS) integration in power grid for long-term control is developed and validated. It is expected to greatly improve the computational speed of power system dynamics in a long-term simulation. To end this, the development of the dynamic AVM of ESS integration including ultracapacitor, DC–DC converter, and voltage source converter is elaborated upon. A new control strategy which uses digital logic circuit is proposed to keep the ultracapacitors from overcharging without significantly increasing the charging time. To validate the proposed dynamic AVM and control strategy, case studies are carried out to perform the dynamics as affected by sudden changing of charging/discharging of ESS. The accuracy of the proposed model and controller is verified by the simulation results with that obtained from the detailed model implemented in MATLAB/Simulink. Moreover, the time-step size is enlarged greatly without sacrificing the accuracy, therefore the computational speed is improved significantly.

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2.Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

The use of electric vehicles and their various configurations is seen as a major alternative in efforts towards reducing pollutant emissions from motor vehicles that continue to use fossil fuels. Electric transport technology presents more efficient means of energy conversion in vehicles: electric (EV), hybrid (VH), and hybrid electric (HEV) vehicles. For example, the energy storage system in the latter can be made up of ultracapacitors (UCs), batteries (Bs), and fuel cells. This work focuses on HEVs powered by batteries and ultracapacitors. In particular, the multiple converter configuration (C-CM) for the HEV powertrain system is analyzed using electric models of the vehicle powertrain components. To analyze the multiple converter configuration, parameters of a vehicle taken from the literature and the electrical model of the configuration were developed. With the above, the proposed configuration was evaluated before driving cycles (CITY II and ECE) and the configuration performance was compared with respect to other configurations. In the C-CM model, limitations in the choice of the number of Bs and UCs were observed in the powertrain depending on the maximum power of both energy sources and vehicle load demand. The results show that more energy is extracted from the batteries in the ECE cycle than in the CITY taking into account that the batteries are used as the main power source. C-CM results compared to other configurations show that energy extracted from batteries in the CITY is the same across all configurations. While energy consumption is lower in the ECE, C-CM results were not very significant compared to other configurations. However, the C-MC has the advantage of having better power flow control due to having two converters, thus improving HEV safety. [ABSTRACT FROM AUTHOR]

Porous graphitic activated carbon made from biodegradable starch-based packing peanuts contain metallic impurities, such as sodium and potassium impurities. The metallic impurities are not only eliminated in the activation process and revelation. These carbon sheets appear to form an ultrathin graphitic layer on the surface of the disordered carbon framework of the packed peanut-derived activated carbon. The shell-like graphitic structure can be explained by potassium penetration into the carbon structure during chemical activation and subsequent catalytic graphitization by the metallic impurities. These graphitic structures produce high-power density properties. As sodium impurities are present in the depth of the PP-C, it is possible to synergize the effects of potassium. The combination of these structural properties enables the carbon sheets to provide a harmonious electrochemical environment for the full realization of fast ion transport and high capacitance. Image 1 • The shell-like graphitic structure was derived from biodegradable starch-based packing peanuts. • These carbon sheets seem to form an ultrathin graphitic layer on the surface of the disordered carbon framework. • The shell-like graphitic structure is capable of creating a structure that combines the high surface area of micro/mesopores. • The shell-like graphitic structure exhibited excellent electrochemical performance. • These results should encourage the establishment of a new economic platform for advanced porous graphitic carbon. [ABSTRACT FROM AUTHOR]

Ultracapacitor (UC) based dc–dc power supplies are widely used for addressing surge power demands and to provide energy backup to critical loads. The conventional control techniques, such as unified control strategy, though ensure seamless mode transition, do not offer complete flexibility in charging and discharging controls which is crucial in UC-based backup systems. On the other hand, controls, such as independent switch control, though allow great flexibility in control, do not ensure seamless mode transition without appropriate mode-switch logic. This paper proposes a time-varying virtual resistance based mode transition control for independent switch control which not only ensures smooth, seamless transition between charging and discharging control modes but also ensures complete control over the mode transition durations. The proposed control is found to be robust to error mode identification as compared to introducing dead band between control modes. The proposed control is verified on a proof of concept experimental setup at a power level of $P_o=65$ W, voltage level of $V_g=26$ V with the dc–dc converter switching at $f_{\text{sw}}=100$ kHz. The performance comparison with PWM blocking method is also evaluated where the proposed control is found to work well. [ABSTRACT FROM AUTHOR]

A novel dynamic average-value model (AVM) of energy storage systems (ESS) integration in power grid for long-term control is developed and validated. It is expected to greatly improve the computational speed of power system dynamics in a long-term simulation. To end this, the development of the dynamic AVM of ESS integration including ultracapacitor, DC–DC converter, and voltage source converter is elaborated upon. A new control strategy which uses digital logic circuit is proposed to keep the ultracapacitors from overcharging without significantly increasing the charging time. To validate the proposed dynamic AVM and control strategy, case studies are carried out to perform the dynamics as affected by sudden changing of charging/discharging of ESS. The accuracy of the proposed model and controller is verified by the simulation results with that obtained from the detailed model implemented in MATLAB/Simulink. Moreover, the time-step size is enlarged greatly without sacrificing the accuracy, therefore the computational speed is improved significantly. [ABSTRACT FROM AUTHOR]

In this paper, a lifetime prediction model, including an equivalent circuit model, a thermal model and an aging model is developed for the prediction of the state of charge (SOC), temperature and state of health (SOH) of the ultracapacitor. The aging model is developed based on the evolution of impedance parameters in the accelerated aging tests conducted at various voltages and temperatures. Based on the fitting results of various aging models for capacitance fade and conductance loss, a power function of the equivalent aging time is chosen for better prediction of the nonlinear aging process including the burning phase and slow aging phase. The consistency and accuracy of the power function aging model allow straightforward implementation in the lifetime prediction model as the equivalent aging time and thus the capacitance, resistance and SOH can be updated with the voltage and temperature of the ultracapacitor at each time step. The experimental results show that the lifetime prediction model is capable of predicting SOC, temperature and SOH of test cells of various aging conditions under three types of charge/discharge current profiles. In the future, the lifetime prediction model can be utilized for the development of predictive estimators and energy management of ultracapacitors. • Lifetime prediction model includes equivalent circuit, thermal and aging models. • Different aging models for ultracapacitors and Lithium-ion batteries are compared. • Power function model predicts better the fast burning and slow aging phases. • The aging model achieves accurate prediction and high computation efficiency. • Model validated against data from cells of various aging conditions. [ABSTRACT FROM AUTHOR]

In order to enhance the electrochemical efficiency of supercapacitors, novel active electrode materials are being developed. This study provides a unique method to synthesize an integrated structure consisting of a nickel-cobalt metal-organic framework (NiCo-MOF) on functionalized carbon nanofiber (f-CNF) utilizing a single-step solvothermal method. Physicochemical characterization confirmed the successful synthesis of the integrated system of NiCo-MOF@f-CNF. This novel structure has the potential to significantly improve the electrochemical properties of the initially prepared material for use in supercapacitors. The synthesized electrode has a higher specific capacitance/capacity value of 788 F g−1 (315.2 C g−1) at 1 A g−1 and high cycling stability. The developed hybrid device exhibited a promising specific energy of 8.6 Wh kg−1 and a high specific power of 1147 W kg−1, demonstrating potential for practical applications. The current study suggests that the proposed material can be a viable electrode for high-efficiency supercapacitors. • An integrated structure of NiCo-MOF@f-CNF nanocomposite was prepared and used as an efficient electrode in supercapacitors. • Electrical conductivity, mechanical properties, and surface accessibility were enhanced when f-CNF joined NiCo-MOF. • NiCo-MOF@f-CNF hierarchical structure exhibits a specific capacitance of 788 F g−1 at a current density of 1 A g−1. • NiCo-MOF@f-CNF//AC hybrid supercapacitor shows a specific energy of 8.6 Wh kg−1 at a specific power of 1.147 kW kg−1. [ABSTRACT FROM AUTHOR]

With the purpose of designing the electric powertrain of a high performance electric vehicle capable of running a quarter mile in 10 seconds, firstly it is necessary to calculate the required energy, torque, and power in order to size and select the suitable storage components and electric motors. Secondly, an assessment of the powertrain arrangement is needed to choose the best internal configuration of the vehicle and guarantee the highest efficiency possible. Finally, a design of the power conversion stages, specifically the DC-DC converter that interfaces the storage unit with the electric motors, is required as well. This paper shows the energy calculation procedure based on a longitudinal dynamic model of the vehicle and the selection method of the storage components and motors needed for this application, as well as the design of two 100kW interleaved boost converters with coupled inductors. In addition, a novel operation of the interleaved boost converter is proposed in order to increase the efficiency of the converter. As a result, the designed converter achieved a power density of 24,2kW/kg with an efficiency of 98 %, which was validated by experimental tests of a low power prototype.

This paper introduces a modular testbed to simulate AC/DC microgrids. The testbed is implemented in Matlab Simulink and is based on the energetic macroscopic representation (EMR) formalism. It is designed to be a tool to evaluate energy management strategies in AC/DC microgrids. The microgrid simulation model includes a photovoltaic generator, a fuel cell system, ultracapacitors, and batteries on the DC side. It includes voltage source converters (VSC) to couple the DC side with the AC side of the microgrid, which includes a variable AC load and a synchronous generator. Two case studies illustrate the use of the testbed. The model is implemented in Matlab Simulink and made openly available for the scientific community. Using this model, researchers can develop and evaluate energy management strategies in AC/DC microgrids.

The objective proposed by the EU to drastically reduce vehicular CO2 emission for the years up to 2030 requires an increase of propulsion systems’ efficiency, and accordingly, the improvement their technology. Hybrid electric vehicles could have a chance of achieving this, by recovering energy during braking phases, running in pure electric mode and allowing the internal combustion engine to operate under better efficiency conditions, while maintaining traditionally expected vehicle performances (mileage, weight, available on-board volume, etc.). The energy storage systems for hybrid electric vehicles (HEVs) have different requirements than those designed for Battery Electric Vehicles (BEVs); high specific power is normally the most critical issue. Using Li-ion Batteries (LiBs) in the designing of on-board Energy Storage Systems (ESS) based only on power specifications gives an ESS with an energy capacity which is sufficient for vehicle requirements. The highest specific power LiBs are therefore chosen among those technologically available. All this leads to an ESS design that is strongly stressed over time, because current output is very high and very rapidly varies, during both traction and regeneration phases. The resulting efficiency of the ESS is correspondingly lowered, and LiBs lifetime can be relevantly affected. Such a problem can be overcome by adopting hybrid storage systems, coupling LiBs and UltraCapacitors (UCs); by properly dimensioning and controlling the ESS’ components, in fact, the current output of the batteries can be reduced and smoothed, using UCs during transients. In this paper, a simulation model, calibrated and validated on an engine testbed, has been used to evaluate the performances of a hybrid storage HEV microcar under different operative conditions (driving cycles, environment temperature and ESS State of Charge). Results show that the hybridization of the powertrain may reduce fuel consumption by up to 27%, while LiBs lifetime may be more than doubled.

This study highlights an attempt of comparing the performance of several energy storage (ES) devices like battery ES, flywheel ES, capacitive ES, superconducting magnetic ES, ultra‐capacitors and redox flow battery (RFB) in automatic generation control under bilateral deregulated scenario. The considered system comprises gas and thermal generations wherein a geothermal power plant (GTPP) is also incorporated. Gas and thermal systems are provided with appropriate generation rate constraints. A new fractional order (FO) cascade controller named as FO proportional‐integral–FO proportional‐derivative (FOPI–FOPD) is proposed as secondary controller and its performance is compared with commonly used classical controllers. A novel stochastic algorithm, sine cosine algorithm, has been used to optimise controller gains and other parameters. Analyses of dynamic responses reveal the superiority of FOPI–FOPD over others in terms of settling time, peak deviation and magnitude of oscillation. The effect due to GTPP introduction has been examined and the responses disclose that the integration of GTPP leads to better dynamics. Performances of various ES devices in the presence of FOPI–FOPD controller are also compared and dynamic responses of RFB found superior to others. For a more realistic scenario, analysis is done considering time delay and some practical plants of Nevada, USA. [ABSTRACT FROM AUTHOR]

This work carries out a comparison of non-isolated topologies for power electronic converters applied to Hybrid Energy Storage Systems. At the considered application, several options for three-port circuits are evaluated when interfacing a DC link with two distinct electrical energy storage units. This work demonstrates how the proposed structure, referred to as Series-Parallel Connection, performs as a simple, compact and reliable approach, based on a modification of the H-bridge configuration. The main advantage of this solution is that an effective large voltage gain at one of the ports is attained by means of a simple topology, preventing the use of multilevel or galvanic-isolated power stages. The resulting structure is thoroughly compared against the most significant direct alternatives. The analysis carried out on the switching and conduction losses in the power switches of the target solution states the design constraints at which this solution shows a performance improvement. The experimental validations carried out on a 10 kW prototype demonstrate the feasibility of the proposed scheme, stating its benefits as well as its main limitations. As a conclusion, the Series-Parallel Connection shows a better performance in terms of efficiency, reliability and controllability in the target application of compensating grid or load variations in Non-Isolated Hybrid Storage Systems, with large mismatch in the storage device voltage ratings. [ABSTRACT FROM AUTHOR]

The use of electric vehicles and their various configurations is seen as a major alternative in efforts towards reducing pollutant emissions from motor vehicles that continue to use fossil fuels. Electric transport technology presents more efficient means of energy conversion in vehicles: electric (EV), hybrid (VH), and hybrid electric (HEV) vehicles. For example, the energy storage system in the latter can be made up of ultracapacitors (UCs), batteries (Bs), and fuel cells. This work focuses on HEVs powered by batteries and ultracapacitors. In particular, the multiple converter configuration (C-CM) for the HEV powertrain system is analyzed using electric models of the vehicle powertrain components. To analyze the multiple converter configuration, parameters of a vehicle taken from the literature and the electrical model of the configuration were developed. With the above, the proposed configuration was evaluated before driving cycles (CITY II and ECE) and the configuration performance was compared with respect to other configurations. In the C-CM model, limitations in the choice of the number of Bs and UCs were observed in the powertrain depending on the maximum power of both energy sources and vehicle load demand. The results show that more energy is extracted from the batteries in the ECE cycle than in the CITY taking into account that the batteries are used as the main power source. C-CM results compared to other configurations show that energy extracted from batteries in the CITY is the same across all configurations. While energy consumption is lower in the ECE, C-CM results were not very significant compared to other configurations. However, the C-MC has the advantage of having better power flow control due to having two converters, thus improving HEV safety.

Ultracapacitors (UCs), with their features of high power density and high current charge-discharge, have become the best choice for dynamic power compensation to improve the stability of microgrids and are increasingly being applied in microgrids. This paper presents the control of an energy storage system (ESS) based on ultracapacitors in the context of grid-connected microgrids. The ESS is composed of DC/AC and DC/DC converters tied by a dc link. An improved dynamic model for the ESS is proposed. Based on the proposed model a Proportional-Integral-Resonant (PIR) DC link voltage controller is proposed to maintain the DC link voltage through the charging-discharging control of ultracapacitors, capable of working properly under all operating conditions. An extra double frequency component is injected into the UC current by a R controller to dynamically compensate for DC instantaneous power and double frequency AC instantaneous power due to unbalanced grid conditions and disturbances. This feature maintains the DC link voltage constant under unbalanced conditions and increases the degrees of freedom of the DC/AC converter and thus facilitates the application of UCs in microgrids. Simulation and experimental results verify the effectiveness of the proposed control strategy.

Ultracapacitors (UCs) are the focus of increasing attention in electric vehicle and renewable energy system applications due to their excellent performance in terms of power density, efficiency, and lifespan. Modeling and parameterization of UCs play an important role in model-based regulation and management for a reliable and safe operation. In this paper, an equivalent circuit model template composed of a bulk capacitor, a second-order capacitance-resistance network, and a series resistance, is employed to represent the dynamics of UCs. The extended Kalman Filter is then used to recursively estimate the model parameters in the Dynamic Stress Test (DST) on a specially established test rig. The DST loading profile is able to emulate the practical power sinking and sourcing of UCs in electric vehicles. In order to examine the accuracy of the identified model, a Hybrid Pulse Power Characterization test is carried out. The validation result demonstrates that the recursively calibrated model can precisely delineate the dynamic voltage behavior of UCs under the discrepant loading condition, and the online identification approach is thus capable of extracting the model parameters in a credible and robust manner.

A new generation high field spherical tokamak, ST40, is currently under construction at Tokamak Energy Ltd (TE). The main parameters of ST40 are: R 0 = 0.4–0.6 m, A = 1.7–2.0, I pl = 2 MA, B t = 3 T, κ = 2.5. It will have power supplies based on ultracapacitors, liquid nitrogen-cooled copper magnets, up to 2 MW of neutral beam injected (NBI) power, and a pulse length of ∼3 s when operating at full power. To stabilize the highly elongated plasma, in addition to active vertical control, liquid nitrogen-cooled passive plates will be installed. ST40 is aimed at demonstrating burning plasma condition parameters ( nTτ E ) and may also be suitable for DT operations in future. The main physics and engineering challenges are caused by the high toroidal field, relatively high plasma current, and wall and divertor power loads. [ABSTRACT FROM AUTHOR]

This contribution outlines the design of electric vehicle direct-current (DC) bus control system supplied by a battery/ultracapacitor hybrid energy storage system, and its coordination with the fully electrified vehicle driveline control system. The control strategy features an upper-level DC bus voltage feedback controller and a direct load compensator for stiff tracking of variable (speed-dependent) voltage target. The inner control level, comprising dedicated battery and ultracapacitor current controllers, is commanded by an intermediate-level control scheme which dynamically distributes the upper-level current command between the ultracapacitor and the battery energy storage systems. The feedback control system is designed and analytical expressions for feedback controller parameters are obtained by using the damping optimum criterion. The proposed methodology is verified by means of simulations and experimentally for different realistic operating regimes, including electric vehicle DC bus load step change, hybrid energy storage system charging/discharging, and electric vehicle driveline subject to New European Driving Cycle (NEDC), Urban Driving Dynamometer Schedule (UDDS), New York Certification Cycle (NYCC) and California Unified Cycle (LA92), as well as for abrupt acceleration/deceleration regimes.

The global need to solve pollution problems has conducted automotive engineers to promote the development and the use of electric vehicle technologies. This paper focuses on the fuel cell hybrid electric vehicle which uses a proton exchange membrane fuel cell as a main source associated to hybrid storage device: lithium ion battery and ultracapacitors. A common interest in such technology is to spread out the energy flow between its different sources in order to satisfy the power demand for any requested mission. However, the challenging task stills the optimization of this split to reduce hydrogen consumption and respect, at the same time, the system limitations such as admissible limits of storage system capacities and battery current variation. An adaptive filtering-based energy management strategy is proposed in this paper to ensure an optimum distribution of the energy between the sources taking into account dynamic and energetic constraints of each device. For more performance, a fuzzy logic system is used to adapt the frequency of separation with the system state evolution. A sliding mode control is applied to control electric characteristics (voltage and currents) in the considered hybrid power supply. Simulation results, obtained under MATLAB®/SimPowerSystems® for four driving cycles are presented. The proposed strategy achieved good performances by respecting the ultracapacitors state of charge while preserving the battery lifetime under various driving missions.

Copyright of Visión Electrónica is the property of Fondo de Universidad Distrital Francisco Jose de Caldas and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Compared to Li-ion batteries, supercapacitors (SCs) boast longer lifespan, higher power density, and wider operational temperature range. Nevertheless, SCs are expensive (almost 40 times more expensive per watthour than Li-ion batteries). SCs aging is critical. Two types of aging tests are usually performed. Floating aging tests apply constant constraints (voltage and temperature), and cycling aging tests apply multiple charges and discharges. We focus our study on floating aging [corresponding for instance to parking mode for electrical vehicles (95% of the time) or uninterruptible power supplies (UPSs) when they are not solicited (quite all the time)]. All results in the literature conclude that voltage level is an acceleration factor for SC aging. According to the literature, it would be interesting to totally discharge the SCs when they are not in active use (i.e., when the UPSs or vehicles are turned off) to improve their lifespan. Contrary to the literature forecasts (i.e., lower voltage increases lifespan of SC), the results obtained in this paper by alternating voltage resets (0 V, 60 °C) and floating aging (2.8 V, 60 °C) show that discharging even very few times the SCs shortens their lifespan drastically. Physical interpretations are presented to explain aging increase with voltage resets. [ABSTRACT FROM AUTHOR]

This paper proposes a multi-agent control strategy to coordinate power sharing between heterogeneous energy storage devices distributed throughout a DC microgrid. Without requiring a central controller, the proposed control strategy extends the benefits offered by hybrid energy storage systems to DC microgrids with batteries and ultracapacitors spatially distributed at different levels of the power distribution hierarchy. The proposed control strategy has the following advantages. 1) The high frequency microgrid load is provided by the ultracapacitors. 2) The low frequency load is provided by batteries used for bulk energy storage during islanded mode, and the main grid during grid connected operation. 3) The ultracapacitor voltages are regulated at a desired reference. 4) State of charge balancing is provided between the batteries. 5) The energy storage systems cooperate based on neighbor-to-neighbor output feedback over a sparse communication network. The only communication requirement is a spanning tree from the ultracapacitor leaders and battery leaders to their respective followers. Simulations are presented demonstrating the performance of the proposed control strategy for a 380 VDC datacenter during grid connected and islanded operation. [ABSTRACT FROM PUBLISHER]

Ultracapacitors (UCs) have been widely recognized as an enabling energy storage technology in various industrial applications. They hold several advantages including high power density and exceptionally long lifespan over the well-adopted battery technology. Accurate modeling and State-of-Charge (SOC) estimation of UCs are essential for reliability, resilience, and safety in UC-powered system operations. In this paper, a novel fractional-order model composed of a series resistor, a constant-phase-element (CPE), and a Walburg-like element, is proposed to emulate the UC dynamics. The Grünald-Letnikov derivative (GLD) is then employed to discretize the continuous-time fractional-order model. The model parameters are optimally extracted using genetic algorithm (GA), based on the time-domain data acquired through the Federal Urban Driving Schedule (FUDS) test. By means of this fractional-order model, a fractional Kalman filter is synthesized to recursively estimate the UC SOC. Validation results prove that the proposed fractional-order modeling and state estimation scheme is accurate and outperforms current practice based on integer-order techniques. [ABSTRACT FROM AUTHOR]

Herein, synthesis and characterization of amorphous MnO 2 and application in asymmetric aqueous ultracapacitors are reported. Different amorphous manganese oxide (MnO 2 ) materials were synthesized from the reduction of KMnO 4 in different media such as ethanol (EtOH) or dimethylformamide (DMF). The electrochemical behavior of amorphous MnO 2 , labeled MnO 2 -Et and MnO 2 -DMF, were studied by using cyclic voltammetry, impedance spectroscopy, and galvanostatic cycling in aqueous electrolyte. XRD, BET, TEM, and SEM characterizations highlighted the amorphous nature and the nanostructuration of these MnO 2 materials. BET measurement established that these amorphous MnO 2 are mesoporous. In addition, MnO 2 -Et exhibits a larger specific surface area (168 m 2 g −1 ), a narrower pore diameters distribution with lower diameters compared to MnO 2 -DMF. These results are in agreement with the electrochemical results. Indeed, MnO 2 -Et shows a higher specific capacitance and lower impedance in aqueous K 2 SO 4 electrolyte. Furthermore, aqueous asymmetric ultracapacitors were assembled and studied using amorphous MnO 2 as positive electrode and reduced graphene oxide (rGO) as negative electrode. These asymmetric systems exhibit an electrochemical stability for more than 20,000 galvanostatic cycles at current density of 1 A g −1 with an operating voltage of 2 V. [ABSTRACT FROM AUTHOR]

Supercapacitors (SCs) impedance modeling represents one important key to get information for SCs health monitoring and simulation. As a matter of fact, SCs behavior is dependent on various parameters such as pore size distribution of electrodes, electrolyte state, temperature, aging, etc. We propose in this study to model SC taking into account physical considerations. Basing on the theory on homogenous structure impedance, we first define the single pore model using the uniform size of pores distribution. In the second step, we attempt to generalize this circuit model considering an electrode with different pores sizes or different penetrabilities of the pores. This model called multipore (MP) model (or multipenetrability model) has been developed by our laboratories. This model allows analyzing the behavior of SC by modeling each group of electrode pores as a branch of an electrical equivalent circuit. This paper is the first in the literature to give a simple and reproducible method for MP model parameters identification. The validity of the identification method will also be verified at different SC aging rates thanks to experimental aging tests. [ABSTRACT FROM AUTHOR]