Synergetic Control of a Hybrid Battery-Ultracapacitor Energy Storage System

This chapter presents a synergy-based cascade control scheme for a hybrid battery-ultracapacitor (UC) energy storage system. The purpose is to improve the dynamic response of the battery-based energy storage system using an ultracapacitor module as an auxiliary energy storage unit. A bidirectional DC-DC converter is designed to interface between the ultracapacitor module and the main DC-bus. The control scheme is based on a fast inner current control loop using sliding mode control and an outer loop for DC-bus voltage regulation using synergy-based control. The improvement in performance is demonstrated through simulation and experiments. The results show that the DC-bus voltage is well regulated under external load disturbances with fast dynamic transients. The ultracapacitor module is able to absorb the sudden load variations and limit the battery power requirements by maintaining an optimal power balance between the two embedded storage units. The performance of the proposed synergy-based controller is compared with the standard PI controller, and its ability to achieve optimal transient performance is verified

A Modular Multi-level Converter for Energy Management of Hybrid Energy-Storage Systems in Electric Vehicles

Electric vehicles (EVs) are substantial applications of clean energy. Their effectiveness for mainstream transportation is predicated on the efficient use of stored energy within the vehicles’ power pack. Among rechargeable storage solutions, lithium-ion (Li-ion) battery cells have high energy density making them suitable to supply the EVs’ average power. However, the peak power requirements of the vehicles exert stress on the Li-ion cells due to their low pulsating power capabilities. Ultracapacitors can be used instead as the power-pulsating storage elements given their superior power density. Incorporating the two cell types for energy storage signifies a hybrid configuration that leads to challenging tasks in managing the energy between cells due to varying cell dynamics. Therefore, this study investigated the design of an end-to-end hybrid energy-storage and management system. The limitations of existing power electronics and control schemes were identified based on comparative analysis, both on a cell level and on a system level. Subsequently, an energy system was developed that utilized modular multi-level converters to manage the energy between the different cell types. The formulated control strategy accounted for various power modes and added immense flexibility in charge sharing through diverse switching states. Furthermore, the proposed configuration eliminated the conventional need for a system level drive inverter feeding the EV motor. Electro-mechanical modeling results and physical design merits verified the proposed configuration’s effectiveness in improving EV efficiency

A system analysis and modeling of a HEV based on ultracapacitor battery

© 2017 IEEE. There is a clear shift toward the implementation of electrified vehicles in the market, influenced by the introduction of stricter mandatory regulations on fuel economy improvement and emissions reduction. Of these vehicles, the penetration of hybrid vehicles in the market has much potential for growth in the next few years. The adoption of these vehicles has been limited by the high cost of HEV's, which have less uptake in developing regions. Considering this point, developing countries would see the greatest benefit in adopting HEV technology. A mild hybrid system has an observable advantage in these markets due to its maximum benefit/cost ratio when compared to a full hybrid, plug-in hybrid or electric vehicles. This paper discusses the development of a mild hybrid system for such markets with a focus on improving drive performance and efficiency. To achieve this, high power density ultracapacitors are used based on their fast charging and discharging characteristics, together with intelligent drivetrain control taking advantage of the ultracapacitors' characteristics to deliver smooth torque delivery during gear change (torque-filling). A comparison and analysis is undertaken, of both conventional powertrain and an otherwise identical powertrain but for the incorporation of components required for the mild hybrid system. Software models simulated the powertrains in specific driving conditions, with observations made of the advantages of MHEV over conventional drivetrains. The model demonstrated increased fuel efficiency and performance

Hybrid fuel cell-based energy system with metal hydride hydrogen storage for small mobile applications

This paper describes the general architecture of a hybrid energy system, whose main components are a proton exchange membrane fuel cell, a battery pack and an ultracapacitor pack as power sources, and metal hydride canisters as energy storage devices, suitable for supplying power to small mobile non-automotive devices in a flexible and variable way. The first experimental results carried out on a system prototype are described, showing that the extra components, required in order to manage the hybrid system, do not remarkably affect the overall system efficiency, which is always higher than 36% in all the test configurations examined. in fact, the system allows the fuel cell to work most often at quasi-optimal conditions, near its maximum efficiency (i.e. at low/medium loads), because high external loads are met by the combined effort of the fuel cell and the ultracapacitors. For the same reason, the metal hydride storage system can be used also under highly dynamic operating conditions, notwithstanding its usually poor kinetic performance. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved

Urban and extra-urban hybrid vehicles: a technological review

Pollution derived from transportation systems is a worldwide, timelier issue than ever. The abatement actions of harmful substances in the air are on the agenda and they are necessary today to safeguard our welfare and that of the planet. Environmental pollution in large cities is approximately 20% due to the transportation system. In addition, private traffic contributes greatly to city pollution. Further, “vehicle operating life” is most often exceeded and vehicle emissions do not comply with European antipollution standards. It becomes mandatory to find a solution that respects the environment and, realize an appropriate transportation service to the customers. New technologies related to hybrid –electric engines are making great strides in reducing emissions, and the funds allocated by public authorities should be addressed. In addition, the use (implementation) of new technologies is also convenient from an economic point of view. In fact, by implementing the use of hybrid vehicles, fuel consumption can be reduced. The different hybrid configurations presented refer to such a series architecture, developed by the researchers and Research and Development groups. Regarding energy flows, different strategy logic or vehicle management units have been illustrated. Various configurations and vehicles were studied by simulating different driving cycles, both European approval and homologation and customer ones (typically municipal and university). The simulations have provided guidance on the optimal proposed configuration and information on the component to be used

Energy Management of a Battery-Ultracapacitor Hybrid Energy Storage System in Electric Vehicles

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. An oversized energy storage system (ESS) can meet the high power demands; however, it suffers from increased size, volume and cost. In order to reduce the overall ESS size and extend battery cycle life, a battery-ultracapacitor (UC) hybrid energy storage system (HESS) has been considered as an alternative solution. In this work, we investigate the optimized configuration, design, and energy management of a battery-UC HESS. One of the major challenges in a HESS is to design an energy management controller for real-time implementation that can yield good power split performance. We present the methodologies and solutions to this problem in a battery-UC HESS with a DC-DC converter interfacing with the UC and the battery. In particular, a multi-objective optimization problem is formulated to optimize the power split in order to prolong the battery lifetime and to reduce the HESS power losses. This optimization problem is numerically solved for standard drive cycle datasets using Dynamic Programming (DP). Trained using the DP optimal results, an effective real-time implementation of the optimal power split is realized based on Neural Network (NN). This proposed online energy management controller is applied to a midsize EV model with a 360V/34kWh battery pack and a 270V/203Wh UC pack. The proposed online energy management controller effectively splits the load demand with high power efficiency and also effectively reduces the battery peak current. More importantly, a 38V-385Wh battery and a 16V-2.06Wh UC HESS hardware prototype and a real-time experiment platform has been developed. The real-time experiment results have successfully validated the real-time implementation feasibility and effectiveness of the real-time controller design for the battery-UC HESS. A battery State-of-Health (SoH) estimation model is developed as a performance metric to evaluate the battery cycle life extension effect. It is estimated that the proposed online energy management controller can extend the battery cycle life by over 60%

Ultracapacitor Heavy Hybrid Vehicle: Model Predictive Control Using Future Information to Improve Fuel Consumption

This research is concerned with the improvement in the fuel economy of heavy transport vehicles through the use of high power ultracapacitors in a mild hybrid electric vehicle platform. Previous work has shown the potential for up to 15% improvement on a hybrid SUV platform, but preliminary simulations have shown the potential improvement for larger vehicles is much higher. Based on vehicle modeling information from the high fidelity, forward-looking modeling and simulation program Powertrain Systems Analysis Toolkit (PSAT), a mild parallel heavy ultracapacitor hybrid electric vehicle model is developed and validated to known vehicle performance measures. The vehicle is hybridized using a 75kW motor and small energy storage ultracapacitor pack of 56 Farads at 145 Volts. Among all hybridizing energy storage technologies, ultracapacitors pack extraordinary power capability, cycle lifetime, and ruggedness and as such are well suited to reducing the large power transients of a heavy vehicle. The control challenge is to effectively manage the very small energy buffer (a few hundred Watt-hours) the ultracapacitors provide to maximize the potential fuel economy. The optimal control technique of Dynamic Programming is first used on the vehicle model to obtain the \u27best possible\u27 fuel economy for the vehicle over the driving cycles. A variety of energy storage parameters are investigated to aid in determining the best ultracapacitor system characteristics and the resulting effects this has on the fuel economy. On a real vehicle, the Dynamic Programming method is not very useful since it is computationally demanding and requires predetermined vehicle torque demands to carry out the optimization. The Model Predictive Control (MPC) method is an optimization-based receding horizon control strategy which has shown potential as a powertrain control strategy in hybrid vehicles. An MPC strategy is developed for the hybrid vehicle based on an exponential decay torque prediction method which can achieve near-optimal fuel consumption even for very short prediction horizon lengths of a few seconds. A critical part of the MPC method which can greatly affect the overall control performance is that of the prediction model. The use of telematic based \u27future information\u27 to aid in the MPC prediction method is also investigated. Three types of future information currently obtainable from vehicle telematic technologies are speed limits, traffic conditions, and traffic signals, all of which have been incorporated to improve the vehicle fuel economy

Advancing the development of hybrid electric vehicles in motorsport : innovation report

Club motorsport, a low cost, amateur form of motorsport, forms a significant part of the motorsport industry in the United Kingdom. If efforts are not made to move towards more environmentally friendly technologies, then this form of motorsport is at risk of becoming irrelevant. One approach taken by other motorsport sectors has been to implement hybrid electric vehicle technology, which can result in improved vehicle performance on the race track. However, the companies that operate in the club motorsport sector do not typically have the resources and experience necessary to develop these technologies. An innovative process was used to guide the design of a new hybrid electric vehicle drivetrain for use in club motorsport. This process made use of the ability for vehicle manufacturers to set the vehicle specifications in club motorsport. A conjoint analysis of customer requirements was carried out, a first for the industry, and led to the development of a market simulation tool. A vehicle simulation tool was then developed to assist in the evaluation of the hybrid electric drivetrain design options. The result of following this process was a new and innovative hybrid electric drivetrain installed in a Westfield Sportscars Sport Turbo, reducing 0-60mph acceleration time from 5.4 seconds to 3.8 seconds. An innovative type of system control was implemented, by where the driver is given a finite amount of boost energy for use throughout the race. The drivetrain can also be easily transferred to other vehicle platforms, as the first shelf engineered hybrid drivetrain for motorsport, allowing its use by multiple manufacturers across the club motorsport and niche vehicle sectors. This project has shown that it is possible to implement environmentally friendly technologies, such as hybrid electric vehicle technology, into club motorsport and be able to meet customer, technical and cost requirements. The process that has been developed enables innovation in hybrid electric race car design. This has been shown in the development of a hybrid electric vehicle suitable for use, and sale, in the club motorsport industry

Analysis, modeling, and control of half-bridge current-source converter for energy management of supercapacitor modules in traction applications

In this work, an in-depth investigation was performed on the properties of the half-bridge current-source (HBCS) bidirectional direct current (DC)-to-DC converter, used to interface two DC-link voltage sources with a high-voltage-rating mismatch. The intended implementation is particularly suitable for the interfacing of a supercapacitor (SC) module and a battery stack in a hybrid storage system(HSS) for automotive applications. It is demonstrated that the use of a synchronous rectification (SR) modulation scheme benefits both the power-stage performance (in terms of efficiency and reliability) and the control-stage performance (in terms of simplicity and versatility). Furthermore, an average model of the converter, valid for every operating condition, is derived and utilized as a tool for the design of the control system. This model includes the effects of parasitic elements (mainly the leakage inductance of the transformer) and of the converter snubbers. A 3 kW prototype of the converter was used for experimental validation of the converter modeling, design, and performance. Finally, a discussion on the control strategy of the converter operation is included