An innovative control strategy for a hybrid energy storage system (HESS)

© 2017 IEEE. Electric Vehicles (EVs) adopting both batteries and supercapacitors have attracted a significant amount of attention in research communities due to its unique power sharing capabilities. A Hybrid Energy Storage System (HESS) can effectively reduce power stress that would otherwise be applied to batteries alone, and whose weight and size is still a common concern when competing against conventional ICE-powered cars. In this paper, a high-level control strategy is developed to adaptively split the load between two sources for an electric vehicle adopting HESS under real-life load fluctuations. A converter - Supercapacitor Pack (SP) coupled HESS upon which such an algorithm is deployed on, is proposed to divert excess power into the SP via a smart Power Converter (PC) which is located in between in order to regulate both behaviors. Such a power split strategy (PSS) is designed in such a way to track real-time load profiles and determines one important variable - the cut-off frequency. A simplified HESS model is first developed. The power split algorithm is coded in Matlab and then applied to this HESS model. Finally, the overall system is tested comprehensively over 4 EPA driving cycles. Simulation results prove its effectiveness in coping with even the harshest driving scenarios in real life

A multi-criteria performance study of an integrated demand/supply energy system for low and zero carbon technologies within domestic building design

When low carbon and renewable energy (RE) systems are adopted in a building, matching the outputs from RE systems (e.g. photovoltaic, solar collectors, small scale wind turbines and heat pumps) to demand has to be taken into account to fully realise the potential of the hybrid energy system. Considering the varying demand profiles due to different building design options (e.g. orientation, construction types etc), it is necessary to evaluate key technology elements in an integrated context and establish appropriate strategies for simultaneously meeting heating and electricity loads as well as matching demand and supply. This paper presents a new approach to evaluate the interactive effects of low carbon technologies and demand reduction measures in the early design stage of a new building. A case study of a sustainable domestic building project (PLUS 50), was implemented on the basis of the proposed design approach

Hybrid Energy Storage Systems Based on Redox-Flow Batteries: Recent Developments, Challenges, and Future Perspectives

Recently, the appeal of Hybrid Energy Storage Systems (HESSs) has been growing in multiple application fields, such as charging stations, grid services, and microgrids. HESSs consist of an integration of two or more single Energy Storage Systems (ESSs) to combine the benefits of each ESS and improve the overall system performance, e.g., efficiency and lifespan. Most recent studies on HESS mainly focus on power management and coupling between the different ESSs without a particular interest in a specific type of ESS. Over the last decades, Redox-Flow Batteries (RFBs) have received significant attention due to their attractive features, especially for stationary storage applications, and hybridization can improve certain characteristics with respect to short-term duration and peak power availability. Presented in this paper is a comprehensive overview of the main concepts of HESSs based on RFBs. Starting with a brief description and a specification of the Key Performance Indicators (KPIs) of common electrochemical storage technologies suitable for hybridization with RFBs, HESS are classified based on battery-oriented and application-oriented KPIs. Furthermore, an optimal coupling architecture of HESS comprising the combination of an RFB and a Supercapacitor (SC) is proposed and evaluated via numerical simulation. Finally, an in-depth study of Energy Management Systems (EMS) is conducted. The general structure of an EMS as well as possible application scenarios are provided to identify commonly used control and optimization parameters. Therefore, the differentiation in system-oriented and application-oriented parameters is applied to literature data. Afterwards, state-of-the-art EMS optimization techniques are discussed. As an optimal EMS is characterized by the prediction of the system’s future behavior and the use of the suitable control technique, a detailed analysis of the previous implemented EMS prediction algorithms and control techniques is carried out. The study summarizes the key aspects and challenges of the electrical hybridization of RFBs and thus gives future perspectives on newly needed optimization and control algorithms for management systems

Challenges for the Goal of 100% Renewable Energy Sources to Fit the Green Transition

The increasing penetration of Renewable Energy (RE) into the electrical market is desirable in terms of sustainability. Nevertheless, it is a challenge that all the interested actors shall address from both the technical and economical points of view. This paper provides an overview of the main challenges and solutions towards the technological transition to an electrical system with 100% renewable energy sources in terms of innovations and operative limits of the traditional systems. These innovative paradigms will also address the social impact and government policies

Integration, control and optimization of the solar photovoltaic-battery system in microgrids

This document composes the work realised and the research results developed within the scope of electric energy storage at the Renewable Energy Chair of the University of Évora. The current legal and technological framework of electrochemical energy storage technologies is reported, and its framework is demonstrated in the Portuguese and European contexts. Next, the experimental microgrid that comprises several electric energy storage technologies is described. The lithium-ion and vanadium redox flow technologies were tested and characterized for later validation of the electrical models that describe their performance. A state-of-the-art review allowed the experimentation of energy management strategies that fit the technologies studied, allowing smarter management in residential and services sectors. In this thesis, management algorithms, battery models, and an indication of technical, economic and energy parameters were combined in a tool to study the simulation of the operation of these technologies, allowing to define different operating objectives, fine-tune parameters and even join the operation of different technologies. This work was accompanied by national and international projects, attempting to respond to existing problems in the operation of real systems and gaps identified in the design phase, such as a robust dimensioning tool, with the integration of different battery managing methods; Integração, controlo e otimização do sistema solar fotovoltaico-bateria em microrredes Resumo: Este documento compõe o trabalho realizado e respetivos resultados da investigação desenvolvida no âmbito do armazenamento de energia elétrica na Cátedra Energias Renováveis da Universidade de Évora. Os atuais enquadramentos legais e tecnológicos das tecnologias eletroquímicas de armazenamento de energia são relatados, nos contextos português e europeu. Seguidamente, uma microrrede experimental que inclui diversas tecnologias de armazenamento de energia elétrica é descrita. As tecnologias de fluxo redox de vanádio e de iões de lítio foram objeto de ensaio e caracterização, para posterior validação dos correspondentes modelos que descrevem a sua performance elétrica. A revisão do estado da arte permitiu a experimentação de estratégias de gestão de energia que se adequam às tecnologias estudadas, que permitam a sua gestão inteligente, no contexto residencial e de serviços. Nesta tese, os algoritmos de gestão, os modelos das baterias, a indicação de parâmetros técnicos, económicos e energéticos foram combinados numa ferramenta para estudo da simulação da operação destas tecnologias permitindo definir diferente objetivos, afinar parâmetros e até operar conjuntamente diferentes tecnologias. Este trabalho foi acompanhado pelo paralelismo de projetos nacionais e internacionais, tentado dar resposta a problemas existentes na operação de sistemas reais, e lacunas identificadas na fase de projeto, tal como uma ferramenta de dimensionamento robusto, com a integração de diferentes formas de gerir baterias

Sizing and control of a Hybrid hydro-battery-flywheel storage system for frequency regulation services

Energy security and environmental challenges are some of the drivers for increasing the electricity generation from non-programmable Renewable Energy Source (RES), adding pressure to the grid, especially if located in weakly connected (or isolated) islands, like Sardinia. Variable-speed Pumped Storage Hydro Power (PSHP) can offer a high degree of flex ibility in providing ancillary services (namely primary and secondary regulations), but due to the hydromechanical nature of the equipment, sudden variations in the power output cause wear and tear. Other energy storage devices can not compete with PSHP in terms of energy and power availability. This work aims to assess the potential benefits derived from the hybridization of a PSHP with Battery Energy Storage System (BESS) and Flywheel Energy Storage System (FESS) in providing frequency regulation services to the grid of the Sardinia Island (Italy). The focus of the study tries to cross both the plant owner point of view, whose aim is to have a smooth PSHP operation and the economic incentive to hybridize the plant, and the Transmission System Operator’s, whose aim is to have a fast reacting plant that better stabilizes the grid frequency. This is done by simulations of a detailed dynamic model of the PSHP, whose hydraulic machine has been characterized from real experimental data, the BESS and the FESS. Moreover, two power management strategies are presented, based on different criteria, to effectively coordinate the devices making up the Hybrid Energy Storage System (HESS). First the simulations are performed open-loop, to assess the impact of various combinations of installed BESS and FESS powers over the wear and tear of the equipment. Later the model is used in an optimization procedure to find the combination of installed BESS and FESS powers and the respective controlparameters that would guarantee the maximum economic return at the end of the investment life. Last, the model is included into a Sardinian power system model and simulated in a future scenario with high RES penetration, assessing the plant capabilities to effectively contain and restore the frequency. Results show that there is not a catch-all solution in terms of hybridization and that a trade-off must be made between the plant owner’s urge to smoothly operate the plant in order to reduce the equipment degradation, and the TSO’s objective to have fast responsive plants providing high quality frequency regulation services. If on one hand open-loop simulations show that the hybridization reduce the main wear and tear indicators, on the other the optimal hybrid system limits the plant ability to contain the frequency excursions in closed-loop simulations, as the optimization problem was formulated over the plant owner’s interests. The results show that there much potential for frequency stabilization and wear and tear reduction, but more techno-economic data is required to fully investigate the benefits of this configuration.Energy security and environmental challenges are some of the drivers for increasing the electricity generation from non-programmable Renewable Energy Source (RES), adding pressure to the grid, especially if located in weakly connected (or isolated) islands, like Sardinia. Variable-speed Pumped Storage Hydro Power (PSHP) can offer a high degree of flex ibility in providing ancillary services (namely primary and secondary regulations), but due to the hydromechanical nature of the equipment, sudden variations in the power output cause wear and tear. Other energy storage devices can not compete with PSHP in terms of energy and power availability. This work aims to assess the potential benefits derived from the hybridization of a PSHP with Battery Energy Storage System (BESS) and Flywheel Energy Storage System (FESS) in providing frequency regulation services to the grid of the Sardinia Island (Italy). The focus of the study tries to cross both the plant owner point of view, whose aim is to have a smooth PSHP operation and the economic incentive to hybridize the plant, and the Transmission System Operator’s, whose aim is to have a fast reacting plant that better stabilizes the grid frequency. This is done by simulations of a detailed dynamic model of the PSHP, whose hydraulic machine has been characterized from real experimental data, the BESS and the FESS. Moreover, two power management strategies are presented, based on different criteria, to effectively coordinate the devices making up the Hybrid Energy Storage System (HESS). First the simulations are performed open-loop, to assess the impact of various combinations of installed BESS and FESS powers over the wear and tear of the equipment. Later the model is used in an optimization procedure to find the combination of installed BESS and FESS powers and the respective controlparameters that would guarantee the maximum economic return at the end of the investment life. Last, the model is included into a Sardinian power system model and simulated in a future scenario with high RES penetration, assessing the plant capabilities to effectively contain and restore the frequency. Results show that there is not a catch-all solution in terms of hybridization and that a trade-off must be made between the plant owner’s urge to smoothly operate the plant in order to reduce the equipment degradation, and the TSO’s objective to have fast responsive plants providing high quality frequency regulation services. If on one hand open-loop simulations show that the hybridization reduce the main wear and tear indicators, on the other the optimal hybrid system limits the plant ability to contain the frequency excursions in closed-loop simulations, as the optimization problem was formulated over the plant owner’s interests. The results show that there much potential for frequency stabilization and wear and tear reduction, but more techno-economic data is required to fully investigate the benefits of this configuration

A Hybrid Energy Storage System for a Coaxial Power-Split Hybrid Powertrain

A hybrid energy storage system (HESS) consisting of batteries and supercapacitors can be used to reduce battery stress and recover braking energy efficiently. In this paper, the performance of a novel coaxial power-split hybrid transit bus with an HESS is studied. The coaxial power-split hybrid powertrain consists of a diesel engine, a generator, a clutch, and a motor, whose axles are arranged in a line. A mathematical model of the coaxial power-split hybrid powertrain with an HESS is established and the parameters are configured using experimental data. Subsequently, to estimate the system performance, a program is designed based on Matlab and Advisor. A rule-based control strategy is designed and finely tuned for the coaxial power-split hybrid powertrain. Then, using the Chinese Transit Bus City Driving Cycle (CTBCDC), the system characteristics and energy efficiencies of the designed coaxial power-split hybrid powertrain with an HESS are analysed. The results indicate that the proposed coaxial power-split hybrid powertrain with an HESS can fulfil the drivability requirement of transit bus and enhance the energy efficiency significantly compared with a conventional powertrain bus as well as reduce the battery stress simultaneously. Using an HESS is a good solution for the coaxial power-split hybrid transit bus

Development of a Control Strategy for the Hybrid Energy Storage Systems in Standalone Microgrid

The intermediate energy storage system is very necessary for the standalone multi-source renewable energy system to increase stability, reliability of supply, and power quality. Among the most practical energy storage solutions is combining supercapacitors and chemical batteries. However, the major problem in this kind of application is the design of the power management, as well as the control scheme of hybrid energy storage systems. The focal purpose of this paper is to develop a novel approach to control DC bus voltage based on the reference power\u27s frequency decomposition. This paper uses a storage system combined of batteries and supercapacitors. These later are integrated in the multi-source renewable energy system to supply an AC load. This technique uses the low-pass filters\u27 properties to control the DC bus voltage by balancing the generated green power and the fluctuating load. The hybrid storage system regulates power fluctuations by absorbing surplus power and providing required power. The results show good performances of the proposed control scheme, such as low battery current charge/discharge rates, lower current stress level on batteries, voltage control improvements, which lead to increase the battery life

Optimized Off-Grid Energy Systems Using Climate-Based Energy Demand for Soft-Walled Facilities

Remote contingency military operations often require the use of temporary facilities powered by inefficient diesel generators that are expensive to operate and maintain. Site planners can reduce operating costs by augmenting generators with hybrid energy systems, but they must select the optimal design configuration based on the region’s climate to meet the power demand at the lowest cost. To assist planners, this paper proposes two innovative, climate-optimized, hybrid energy system selection models. The first model is capable of selecting the facility insulation type, solar array size, and battery backup system to minimize the annual operating cost. The Hybrid Energy Renewable Delivery System (HERDS) model builds on this model by minimizing the entire system’s net present cost, and accounts for the transportation costs of airlifting the system to an operational site. To demonstrate the first model’s capability in various climates, model performance was evaluated for applications in southwest Asia and the Caribbean. An additional case study was performed on Clark Air Base, Philippines to highlight the HERDS model’s capabilities. The capability of both models is expected to support planners of remote sites in their ongoing effort to minimize fuel requirements, lower annual operating costs and increase site resiliency