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

Energy Storage Systems for Traction and Renewable Energy Applications

Energy storage systems are the set of technologies used to store various forms of energy, and by necessity, can be discharged. Energy storage technologies have a wide range of characteristics and specifications. Like any other technology, each type of energy storage has its pros and cons. Depending on the application, it is crucial to perform a tradeoff study between the various energy storage options to choose the optimal solution based on the key performance objectives and various aspects of those technologies. The purpose of this thesis is to present a thorough literature review of the various energy storage options highlighting the key tradeoffs involved. This thesis focuses on evaluating energy storage options for traction and renewable energy applicationsHybrid Electric Vehicles (HEVs) is one key application space driving breakthroughs in energy storage technologies. The focus though has been typically on using one type of energy storage systems. This thesis investigates the impact of combining several types of batteries with ultracapacitor. A case study of integrating two energy storage systems in a series-parallel hybrid electric vehicle is simulated by using MATLAB-SIMULINK software.The other key application space is renewable energy especially wind and solar. Due to the intermittent nature of renewable energy sources, energy storage is a must to achieve the required power quality. Therefore, this thesis aims to investigate different cases of combining different types of energy storage with wind and solar. Hybrid Optimization Model for Electric Renewables (HOMER) software is utilized to study the economic and sizing aspects in each case

Erinevate energia salvestustehnoloogiate uudsed rakenduspõhimõtted liginullenergiahoonetes

A Thesis for applying for the degree of Doctor of Philosophy in Technical Sciences.In this thesis the renewable energy storage options in residential buildings are under investigation. This is to store cheap electricity due to the temporary overproduction of large wind farms and also on-site solar and wind farms. In an electric system, there should be a balance at all times between energy production and consumption: as much as is produced should also be consumed. Deviating significantly from this balance can damage electrical equipment or cause serious network failures and even blackouts. Unfortunately, both solar and wind energy generation possibilities are associated with (rapid) changes in production. The simplest examples are wind gusts for wind turbines and intermittent cloud cover for solar panels where the electric output power changes in seconds. In order to smooth out the rapid changes in electricity production, the work proposes the possibility to add ultracapacitors to the battery bank for temporary energy storage, which would act as a buffer and are able to temporarily store the produced electricity. So far, the sale of green energy to the electricity grid has been supported at the state level. However, this paper examines the next step in how to support the storage capacity of the produced energy in order to increase self-consumption. To this, a state subsidy measure for battery banks is proposed. Due to short-term overproduction of electricity, there are more and more situations where electricity is sold at zero or even negative prices on the power exchange. The reason is simple - it is more practical for producers to temporarily pay to consumers for electricity consumption than to stop production for a while. This work also proposes a method for storing energy in heat carriers under favorable conditions for the consumer in order to ensure a balance between the production and consumption of the electricity network.Antud doktoritöö käsitleb taastuvenergia salvestusvõimaluste kasutamist elumajades. Seda nii kohapealsete päikeseparkide ja tuulegeneraatorite kui ka suurte tuuleparkide aeg-ajalisest energia ületootmisest tingitud odava elektrienergia salvestamiseks. Energia tootmise ja tarbimise puhul peaks valitsema igas hetkes tasakaal: sama palju kui toodetakse tuleb ka tarbida. Kui sellest tasakaalust väga kõrvale kalduda, võib see elektrilisi seadmed kahjustada või esineb tõsiseid võrgurikkeid ja isegi katkestusi. Paraku on aga nii päikese- kui ka tuuleenergia tootmine seotud (kiirete) muutustega toodangus. Lihtsaimad näited selleks on tuulepuhangud tuulegeneraatorite puhul ning vahelduv pilvisus päikesepaneelide puhul mil elektriline väljundvõimsus muutub sekunditega. Tasandamaks kiireid muutusi elektritootmisel, pakutakse töös välja võimalus lisada akupangale energia ajutiseks salvestamiseks ülikondensaatorid, mis käituks puhvrina ning on võimelised toodetud elektrienergiat ajutiselt salvestama. Senini on riiklikul tasandil toetatud roheenergia müüki elektrivõrku. Antud töös uuritakse aga järgmist etappi, kuidas toetada toodetud energia salvestusvõimalusi eesmärgiga suurendada omatarbimist. Selleks pakutakse välja riiklik akupankade subsideerimise meede. Elektrienergia lühiajalisest ületootmisest tulenevalt esineb üha rohkem olukordi, mil elektribörsil müüakse elektrit null või isegi negatiivse hinnaga. Põhjus on lihtne – tootjatel on otstarbekam ajutiselt elektritarbimisele peale maksta, kui tootmine korraks seisma panna. Antud töös pakutakse samuti välja meetod, kuidas tarbijale soodsatel tingimustel energiat soojuskandjatesse salvestada, tagamaks elektrivõrgu tootmise ja tarbimise tasakaalu.Publication of this theisis is supported by the Estonian University of Life Sciences; and the Doctoral School of Energy and Geotechnology III, (Estonian University of Life Sciences ASTRA project “Valuechain based bio-economy”); and the Estonian Centre of Excellence in Zero Energy and Resource Efficient Smart Buildings and Districts, ZEBE, grant 2014-2020.4.01.15-0016 funded by the European Regional Development Fund

Bi-level Optimization of Sizing and Control Strategy of Hybrid Energy Storage System in Urban Rail Transit Considering Substation Operation Stability

The hybrid energy storage system (HESS) which consists of battery and ultracapacitor can efficiently reduce the substation energy cost from grid and achieve the peak shaving function, due to its characteristics of high-power density and high-energy density. The sizing of HESS affects the operation cost of whole system. Besides, operation stability (like substation peak power and voltage fluctuations) is rarely considered in urban rail transit (URT) when sizing optimization of HESS is considered. Thus, this research proposes a sizing and control strategy optimization of HESS in URT. First, the mathematic model of URT with HESS is established, which is used to simulate URT and HESS operation state by power flow analysis method. Then, based on the proposed HESS control principle, a bi-level optimization of HESS in URT is proposed. The master level aims to optimize the rated capacity and power of HESS, reducing total operational cost. Then, the HESS control strategy is optimized at slave level, reducing substation peak power and voltage fluctuations of URT. The case study is conducted based on the data of Merseyrail line in Liverpool. A comparison is also conducted, which shows that the proposed method can reduce daily operation cost by 12.68% of the substation, while the grid energy cost is decreased by 57.26%

Feasibility Study of Energy Storage Technologies for Remote Microgrid’s Energy Management System

Energy storage systems (ESSs) play a significant role in remote microgrids energy management system (EMS) with the large penetration rate of renewable energy which is intermittent in nature. Energy storage improves system reliability and efficiency in remote microgrids by optimizing the power demand and generation to reduce operational costs. Moreover, it increases the dispatch ability of the energy sources in remote microgrid systems. Lead acid battery (PbA) can be used as an energy storage device in remote microgrids due to its low cost; however, the response rate, short life cycle, and depth of discharge (DoD) lead to high operational costs. Ultracapacitor has a considerably longer life cycle, its energy density is low, and the initial cost is very high. Lithium-ion (Li-ion) and hybrid ion batteries may have comparatively better economical prospects in terms of DoD, life cycle, and operational cost. In this thesis, different energy storage technologies are considered for remote microgrids energy management systems. In addition, the Schiffer weighted Ah throughput model introduces two weight factors to describe that a battery degrades faster in real time operation than the standard test conditions due to different stress factors. These weight factors virtually increase the battery throughput, and accelerate the degradation. To mitigate this problem, different periodical and auto cycling strategies were investigated in this thesis. However, the results demonstrated that frequent full charging prevents the battery from over degradation. Auto cycling strategy was found more cost effective than the periodical cycling. Applying this cycling strategy, the yearly total operational cost of a microgrid system with a 142 kWh PbA battery bank was reduced by 0.62% ($826). Results also showed that the wear cost is an important factor to consider while designing the energy management system. Li-ion and hybrid-ion batteries had lower wear costs and showed great potentiality, although the EMS with a Li-ion battery was found to be 2.55% more cost effective and 1.5% more fuel efficient than hybrid ion batteries. The reduction in operational cost ensures the access to low cost electricity for the people in remote areas. It will accelerate the development of industries, communications, technologies, and the standard of living including the remote health clinics in those areas. Furthermore, the reduction in generators fuel consumption will reduce CO2 emission which will lower the global warming and the greenhouse effect. In this thesis, one of the objectives was to prolong the battery lifetime by preventing the degradation, that may lower the number of yearly battery disposals which are hazardous to the human health and the environment

PEMFC Optimization Strategy with Auxiliary Power Source in Fuel Cell Hybrid Vehicle

one of the present-day implementation of fuel cell is acting as main power source in Fuel Cell Hybrid Vehicle (FCHV). This paper proposes some strategies to optimize the performance of Polymer Electrolyte Membrane Fuel Cell (PEMFC) implanted with auxiliary power source to construct a proper FCHV hybridization. The strategies consist of the most updated optimization method determined from three point of view i.e. Energy Storage System (ESS), hybridization topology and control system analysis. The goal of these strategies is to achieve an optimum hybridization with long lifetime, low cost, high efficiency, and hydrogen consumption rate improvement. The energy storage system strategy considers battery, supercapacitor, and high-speed flywheel as the most promising alternative auxiliary power source. The hybridization topology strategy analyzes the using of multiple storage devices injected with electronic components to bear a higher fuel economy and cost saving. The control system strategy employs nonlinear control system to optimize the ripple factor of the voltage and the current and using the AOC-EMS system to improve the hydrogen consumption rate. ECMS and BERS strategy based on Time-Triggered Controller Area Network (TTCAN) also promoted to optimize hydrogen consumption rate from recovered kinetic energy while in braking regeneration mode

Addressing Instability Issues in Microgrids Caused By Constant Power Loads Using Energy Storage Systems

Renewable energy sources, the most reasonable fuel-shift taken over the naturally limited conventional fuels, necessarily deal with the self-functional microgrid system rather than the traditional grid distribution system. The study shows that the microgrid system, a comparatively low-powered system, experiences the challenge of instability due to the constant power load (CPL) from many electronic devices such as inverter-based systems. In this dissertation, as a methodical approach to mitigate the instability complication, AC microgrid stability is thoroughly investigated for each and every considerable parameter of the system. Furthermore, a specific loading limit is depicted by evaluating the stability margin from the small signal analysis of the microgrid scheme. After demonstrating all cases regarding the instability problem, the storage-based virtual impedance power compensation method is introduced to restore the system stability and literally extend the loading limit of the microgrid system. Here, a PID controller is implemented to maintain the constant terminal voltage of CPL via current injection method from storage. Since the system is highly nonlinear by nature, advanced nonlinear control techniques, such as Sliding Mode Control and Lyapunov Redesign Control technique, are implemented to control the entire nonlinear system. Robustness, noise rejection, and frequency variation are scrutinized rigorously in a virtual platform such as Matlab/Simulink with appreciable aftermaths. After that, a comparative analysis is presented between SMC and LRC controller robustness by varying CPL power. From this analysis, it is evident that Lyapunov redesign controller performs better than the previous one in retaining microgrid stability for dense CPL-loaded conditions. Finally, to ensure a robust storage system, Hybrid Energy Storage System is introduced and its advantages are discussed as extended research work