A review of fractional-order techniques applied to lithium-ion batteries, lead-acid batteries, and supercapacitors

Electrochemical energy storage systems play an important role in diverse applications, such as electrified transportation and integration of renewable energy with the electrical grid. To facilitate model-based management for extracting full system potentials, proper mathematical models are imperative. Due to extra degrees of freedom brought by differentiation derivatives, fractional-order models may be able to better describe the dynamic behaviors of electrochemical systems. This paper provides a critical overview of fractional-order techniques for managing lithium-ion batteries, lead-acid batteries, and supercapacitors. Starting with the basic concepts and technical tools from fractional-order calculus, the modeling principles for these energy systems are presented by identifying disperse dynamic processes and using electrochemical impedance spectroscopy. Available battery/supercapacitor models are comprehensively reviewed, and the advantages of fractional types are discussed. Two case studies demonstrate the accuracy and computational efficiency of fractional-order models. These models offer 15–30% higher accuracy than their integer-order analogues, but have reasonable complexity. Consequently, fractional-order models can be good candidates for the development of advanced b attery/supercapacitor management systems. Finally, the main technical challenges facing electrochemical energy storage system modeling, state estimation, and control in the fractional-order domain, as well as future research directions, are highlighted

Development of a Power Factor Corrected High Current Supercapacitor Charger for a Surge Resistant UPS

The Uninterrupted Power Supplies (UPSs) provide short term power back up to electrical loads when the mains power fail. Usually UPSs employ battery packs as the energy storage device. However the limitations of battery packs can affect the UPS performance. As an alternative energy storage device, the supercapacitor (SC) technology is well developed over the past 30 years. Due to recent developments, single cell commercial supercapacitors are available up to about 5000 farads. Over the past 10 years, supercapacitor direct current (DC) voltage ratings have gradually increased to about 2.7 V/cell. New lithium based supercapacitor families have DC ratings up to 3.5 V/cell. For the high current applications, the supercapacitors have some advantages over batteries, which are the low effective series resistance (ESR), high power densities and high surge withstand capability. This thesis is a continuation of the work begun by Kozhiparambil, P. K. on Surge Resistant Uninterrupted Power Supply (SRUPS). The reason for this continual research is due to identify weaknesses in original of SRUPS work with regard to the design of the charger. To reduce the components contain, also achieve common mode transient rejection capability, a flayback mode high current charger with power factor correction has been developed for charging the SC banks. The prototype circuit includes multiple SC banks to transfer the energy from the 240 V, 50 Hz power line to the load maintaining high isolation level. The loads receive continuous and surge free power from the SC banks, and has electrical isolation from the main power line. An IGBT is used as a switch for the flyback charger, which has the advantage of high current capability. The experimental results show the design was valid for the SRUPS and it demonstrated the capability to transfer the energy through a flyback charger with power factor correction

Online Parameter Estimation for Supercapacitor State-of-Energy and State-of-Health Determination in Vehicular Applications

WOS:000536291000079Online accurate estimation of supercapacitor state-of-health (SoH) and state-of-energy (SoE) is essential to achieve efficient energy management and real-time condition monitoring in electric vehicle (EV) applications. In this article, for the first time, unscented Kalman filter (UKF) is used for online parameter and state estimation of the supercapacitor. In the proposed method, a nonlinear state-space model of the supercapacitor is developed, which takes the capacitance variation and self-discharge effects into account. The observability of the considered model is analytically confirmed using a graphical approach. The SoH and SoE are then estimated based on the supercapacitor online identified model with the designed UKF. The proposed method provides better estimation accuracy over Kalman filter (KF) and extended KF algorithms since the linearization errors during the filtering process are avoided. The effectiveness of the proposed approach is demonstrated through several experiments on a laboratory testbed. An overall estimation error below 0.5% is achieved with the proposed method. In addition, hardware-in-the-loop experiments are conducted and real-time feasibility of the proposed method is guaranteed

Batteries and Supercapacitors for Electric Vehicles

International audienceDue to increasing gas prices and environmental concerns, battery propelled electric vehicles (BEVs) and hybrid electric vehicles (HEVs) have recently drawn more attention. In BEV and HEV configurations, the rechargeable energy storage system (RESS) is a key design issue [1–3]. Thus, the system should be able to have good performances in terms of energy density and power capabilities during acceleration and braking phases. However, the thermal stability, charge capabilities, life cycle and cost can be considered also as essential assessment parameters for RESS systems.Presently batteries are used as energy storage devices in most applications. These batteries should be sized to meet the energy and power requirements of the vehicle. Furthermore, the battery should have good life cycle performances. However, in many BEV applications the required power is the key factor for battery sizing, resulting in an over-dimensioned battery pack [4,5] and less optimal use of energy [4]. These shortcomings could be solved by combination of battery system with supercapacitors [6–8]. In [9], it is documented that such hybridization topologies can result into enhancing the battery performances by increasing its life cycle, rated capacity, reducing the energy losses and limiting the temperature rising inside the battery. Omar et al. concluded that these beneficial properties are due to the averaging of the power provided by the battery system [4,6,9]. However, the implementation of supercapacitors requires a bidirectional DC–DC converter, which is still expensive. Furthermore, such topologies need a well-defined energy flow controller (EFC). Price, volume and low rated voltage (2.5–3 V) hamper the combination of battery with supercapacitors [6,10]. In order to overcome these difficulties, Cooper et al. introduced the Ultra-Battery, which is a combination of lead-acid and supercapacitor in the same cell [11]. The new system encompasses a part asymmetric and part conventional negative plate. The proposed system allows to deliver and to absorb energy at very high current rates. The Ultra-Batteries have been tested successfully in the Honda Insight. However, this technology is still under development. In the last decade, a number of new lithium-ion battery chemistries have been proposed for vehicular applications. In [12–15], it is reported that the most relevant lithium-ion chemistries in vehicle applications are limited to lithium iron phosphate (LFP), lithium nickel manganese cobalt oxide (NMC), lithium nickel cobalt aluminum oxide (NCA), lithium manganese spinel in the positive electrode and lithium titanate oxide (LTO) in the negative electrode. In this chapter, the performance and characteristics of various lithium-ion based batteries and supercapacitor will be evaluated and discussed. The evaluation will be mainly based on the electrical behavior. Then the characteristics of these RESS systems will be investigated based on the electrical and thermal models

Failure prediction of ultra capacitor stack using fuzzy inference system

The failure of the ultracapacitor was significantly accelerated by elevated temperature or increased voltage. Because of the capacitance difference between the capacitor cells, after a number of deep charging/discharging cycles, the voltage difference between cells will be enlarged. This will accelerate the aging of the weak ultracapacitors and affect the output power. So, to improve stack reliability, a correct and timely failure prediction is essential. Based on diverse faults, a fuzzy rule-based inference system, which could approximate human reasoning, was considered. With this method we can reduce uncertainty, inconvenience and inefficiency resulting from the inherent factors. The simulate results under industrial application conditions are given to verify the method

Feasibility study of an electrical energy storage in a marine vessel

In this Master’s thesis, energy storage solutions were designed for two vessels with long route of operation. The aim was to achieve fuel savings and reduce emissions. The fuel savings resulted from three sources. Firstly, the capacity effect of the battery enables shore power to be utilized at sea. The second factor is peak shaving, where engine runtime and load are optimized in order to have lower specific fuel consumption. The third effect comes from shutting down the engines and providing the hotel load with shore connection when the ship is berthed at port. In the theoretical part of the thesis, energy storage solutions were presented and a battery was selected as the energy storage for the inspection. Furthermore, varying battery capacities were introduced, and battery usage was briefly reviewed from the point of view of safety, legislation and installation structure. In the case study, two battery types, NMC/LFP and LTO, were selected for closer inspection regarding their application in the vessels from economic and fuel saving perspectives. Two alternative battery capacities were considered. The capacity options were intended for similar kind of use but with differences in engine profile and resulting battery demand. Battery use between different capacities was optimized so that the cycle count would result in 10 year cycle-life for NMC/LFP and 20 year cycle-life for LTO battery. The results showed that among the options, the smaller capacity NMC/LFP battery was the most economically feasible while still achieving good emission savings. Higher capacity battery would be better for drivability and engines as well as for fuel savings, but at the expense of economic feasibility. Sensitivity analysis showed that for the first vessel, the chosen battery solution would likely be feasible with the fuel price of 1000 €/t when the electricity price is below 15 c/kWh. For the second vessel, the economic feasibility would be more challenging to achieve. With fuel price of 1000 €/t, the electricity price would need to be below 7 c/kWh. Increase in fuel price would improve the economic feasibility, whereas the increase in electricity price and investment cost would impair it

Energy storages in high-power STATCOM applications

Renewable energy sources are connected to the electric grid at an increasing pace. Previously synchronous generators have been the basis of stable grid operation, but nowadays and in the future, synchronous generators are being replaced by renewable energy sources that are grid connected using power electronics converters. Replacement of synchronous machines can cause for example decrease of inertia which can make the power grid more vulnerable to stability issues. To avoid such problems, new control methods have been developed to maintain stable grid operation in a situation where synchronous machines are not present. Grid-forming control method is being applied to a static synchronous compensator (STATCOM) compensation device that is traditionally used just for reactive power compensation, but for inertial response also active power injection and absorption are required. STATCOM can provide active power response if the device has sufficiently large energy storage for active power injection and absorption. Previously capacitors have been used as the capacitors have a long lifetime of well over 10 years, fast response time and can tolerate high voltages. In reactive power compensation the capacitors have been used to provide voltage for the modular multilevel converter in order to be able to inject or absorb reactive power. Nowadays transmission system operators have showed interest in STATCOM devices that are capable of active power injection and absorption. However, the energy density of capacitors is quite low, so more cost and size effective solutions need to be investigated which presents the main objective of this thesis. The new energy storage should be safe, capable of producing high power output and have larger stored energy than previously. In addition, the size, complexity and cost should be minimal. Supercapacitors, Li-ion batteries, superconducting magnetic energy storages, flywheels and Li-ion capacitors were identified as possible energy storage options. Based on characteristics of each energy storage option, supercapacitors and Li-ion batteries are seen as the best options. Closer analysis of the supercapacitors and Li-ion batteries has been made using commonly used simulation models. Especially different supercapacitor models can have significant differences that will affect the sizing and ratings. Battery sizing was done using LTO cell parameters while supercapacitor sizing was done based on 3200 F cell. Simulating the behavior of the energy storage as a part of STATCOM model showed that the voltage change during the start of discharge and charge can be significantly large. Based on the decreasing voltage characteristics of batteries and supercapacitors during discharge, it is seen that a DC-DC converter should be used as it will also have a significant effect on the overall costs. Major difference between batteries and supercapacitors is that the equivalent series resistance of batteries is much larger. Charging and discharging rate of batteries is lower than with supercapacitors which means that many more parallel battery strings are needed to limit the current experienced by one cell in common DC-link implementation. Benefit of using batteries is that the voltage during discharge and charge is very linear with a small slope unlike with supercapacitors. Voltage change for batteries during short charging and discharging is small because the batteries are oversized in terms of energy for the given power requirement. Based on simple calculations, the initial investment to buy the energy storage is smaller with batteries than with supercapacitors

Hourly Dispatching Wind-Solar Hybrid Power System with Battery-Supercapacitor Hybrid Energy Storage

This dissertation demonstrates a dispatching scheme of wind-solar hybrid power system (WSHPS) for a specific dispatching horizon for an entire day utilizing a hybrid energy storage system (HESS) configured by batteries and supercapacitors. Here, wind speed and solar irradiance are predicted one hour ahead of time using a multilayer perceptron Artificial Neural Network (ANN), which exhibits satisfactory performance with good convergence mapping between input and target output data. Furthermore, multiple state of charge (SOC) controllers as a function of energy storage system (ESS) SOC are developed to accurately estimate the grid reference power (PGrid,ref) for each dispatching period. A low pass filter (LPF) is employed to decouple the power between a battery and a supercapacitor (SC), and the cost optimization of the HESS is computed based on the time constant of the LPF through extensive simulations. Besides, the optimum value of depth of discharge for ESS considering both cycling and calendar expenses has been investigated to optimize the life cycle cost of the ESS, which is vital for minimizing the cost of a dispatchable wind-solar power scheme. Finally, the proposed ESS control algorithm is verified by conducting control hardware-in-the loop (CHIL) experiments in a real-time digital simulator (RTDS) platform

Control of Energy Storage

Energy storage can provide numerous beneficial services and cost savings within the electricity grid, especially when facing future challenges like renewable and electric vehicle (EV) integration. Public bodies, private companies and individuals are deploying storage facilities for several purposes, including arbitrage, grid support, renewable generation, and demand-side management. Storage deployment can therefore yield benefits like reduced frequency fluctuation, better asset utilisation and more predictable power profiles. Such uses of energy storage can reduce the cost of energy, reduce the strain on the grid, reduce the environmental impact of energy use, and prepare the network for future challenges. This Special Issue of Energies explore the latest developments in the control of energy storage in support of the wider energy network, and focus on the control of storage rather than the storage technology itself