Fuzzy logic in battery energy storage system (BESS)

The battery energy storage system (BESS) is a portable device that consists of batteries, controllers, sensors, relays, and other elements that are vital for battery charging and electricity supply operations. A BESS can be used in on or off grid applications to supply electricity as the main source or a back-up source of energy, and to eliminate power factor surcharge by utility companies. This research seeks to design, apply, and validate the use of fuzzy logic controller as a battery management system to regulate the simultaneous charging and discharging processes of batteries. In this project, BESS hardware is constructed to include two 24V battery sets, an electrical load, proper electrical connections, switches, relays, current sensors, voltage measurements, LED indicators, and a microcontroller. Fuzzy logic controllers, one for each battery set, are designed, simulated, and analyzed in MATLAB before implemented in the actual BESS hardware. The experiment involves repeatedly running the BESS for several hours, through a number of charging and discharging cycles, and analyzing current and voltage measurements. By comparing the performances of the fuzzy logic controllers and that of a conventional sequential algorithm, it can be concluded that the fuzzy logic controller can be applied as a safe and efficient battery management system and may improve the battery life in a BESS

Comparative Study of Online Open Circuit Voltage Estimation Techniques for State of Charge Estimation of Lithium-Ion Batteries

Online estimation techniques are extensively used to determine the parameters of various uncertain dynamic systems. In this paper, online estimation of the open-circuit voltage (OCV) of lithium-ion batteries is proposed by two different adaptive filtering methods (i.e., recursive least square, RLS, and least mean square, LMS), along with an adaptive observer. The proposed techniques use the battery’s terminal voltage and current to estimate the OCV, which is correlated to the state of charge (SOC). Experimental results highlight the effectiveness of the proposed methods in online estimation at different charge/discharge conditions and temperatures. The comparative study illustrates the advantages and limitations of each online estimation method

Online Hybrid Intelligent Tracking Control for Uncertain Nonlinear Dynamical Systems

[[abstract]]A novel online hybrid direct/indirect adaptive Petri fuzzy neural network (PFNN) controller with stare observer for a class of multi-input multi-output (MIMO) uncertain nonlinear systems is developed in the paper. By using the Lyapunov synthesis approach, the online observer-based tracking control law and the weight-update law of the adaptive hybrid intelligent controller are derived. According to the importance and viability of plant knowledge and control knowledge, a weighting factor is utilized to sum together the direct and indirect adaptive PFNN controllers. In this paper, we prove that the proposed online observer-based hybrid PFNN controller can guarantee that all signals involved are bounded and that the system outputs of the closed-loop system can track asymptotically the desired output trajectories. An example including four cases is illustrated to show the effectiveness of this approach.[[conferencetype]]國際[[conferencedate]]20120918~20120922[[booktype]]電子版[[iscallforpapers]]Y[[conferencelocation]]Tokyo, Japa

Modeling, Analysis, and Design of a PV-Based Grid-Tied Plug-In Hybrid Electric Vehicle Battery Pack Charger

Ever-increasing fossil fuels consumption in recent decades has emitted tremendous amounts of greenhouse gases, a big part of which cannot be absorbed by natural processes happening in nature. These gases have increased earth temperature by absorbing extra radiations from sunlight and turning them into heat. Global warming has had terrible effects for all creatures around the world and can threat life on Earth in future. Utilization of green or renewable energies during the recent years is getting more popular and can be a solution to this serious problem. A big source of these pollutants is transportation sector. Electrification of transportation can noticeably reduce greenhouse gasses if the electricity is obtained using renewable energy sources. Otherwise, it will just shift the problem from streets to fossil fuel power plants. Electric vehicles (EVs) were introduced around one century ago; however, they were replaced by internal combustion engine cars over time. Nevertheless, recently they are getting more interest because of their superior performance and clean operation. Solar electricity which can be obtained using photovoltaic panels is one of the easiest ways as long as sun is available. They can be easily mounted on the roofs of buildings or roof tops of parking slots generating electric power to charge the battery pack of the EVs while providing shade for the cars. Since solar energy is intermittent and variable, power grid should be involved to ensure enough power is available. Conventional solar chargers inject power to the grid and use grid as the main source because of its reliability and being infinite. Hence, they use grid as a kind of energy storage system. This approach can lead to problems for grid stability if solar panels are utilized in large scales and comparable to the grid. In this work, a solar powered grid-tied EV/PHEV charger is introduced which uses all the available power from PV panels as the main energy source and drains only the remaining required power from the grid. The proposed configuration provides great flexibility and supports all the possible power flows. To design an efficient system the load should be known well enough first. A comprehensive study has been done about behavior, characteristics and different models of different chemistries of batteries. Specific phenomena happening in battery packs are outlined. A novel maximum power point tracking (MPPT) technique has been proposed specifically for battery charging applications. A specific configuration involving DC link coupling technique has been proposed to connect different parts of the system. Different possible topologies for different parts of the proposed configuration have been considered and the suitable ones have been selected. Dual active bridge topology is the heart of this configuration which acts as the bidirectional charger. A detailed state space modeling process has been followed for the power converters and various small signal transfer functions have been derived. Controllers have been designed for different power converters using SISO design tool of Matlab/Simulink. Different modes of operation for the charger including constant current mode (CCM) and constant voltage mode (CVM) have been analyzed and appropriate cascade controllers have been designed based on required time domain and frequency domain characteristics. Finally, simulation tests have been conducted and test results have been graphed and analyzed for different modes of operation, all possible power flows and various voltage and current set points

A multi-modular second life hybrid battery energy storage system for utility grid applications

The modern grid system or the smart grid is likely to be populated with multiple distributed energy sources, e.g. wind power, PV power, Plug-in Electric Vehicle (PEV). It will also include a variety of linear and nonlinear loads. The intermittent nature of renewable energies like PV, wind turbine and increased penetration of Electric Vehicle (EV) makes the stable operation of utility grid system challenging. In order to ensure a stable operation of the utility grid system and to support smart grid functionalities such as, fault ride-through, frequency response, reactive power support, and mitigation of power quality issues, an energy storage system (ESS) could play an important role. A fast acting bidirectional energy storage system which can rapidly provide and absorb power and/or VARs for a sufficient time is a potentially valuable tool to support this functionality. Battery energy storage systems (BESS) are one of a range suitable energy storage system because it can provide and absorb power for sufficient time as well as able to respond reasonably fast. Conventional BESS already exist on the grid system are made up primarily of new batteries. The cost of these batteries can be high which makes most BESS an expensive solution. In order to assist moving towards a low carbon economy and to reduce battery cost this work aims to research the opportunities for the re-use of batteries after their primary use in low and ultra-low carbon vehicles (EV/HEV) on the electricity grid system. This research aims to develop a new generation of second life battery energy storage systems (SLBESS) which could interface to the low/medium voltage network to provide necessary grid support in a reliable and in cost-effective manner. The reliability/performance of these batteries is not clear, but is almost certainly worse than a new battery. Manufacturers indicate that a mixture of gradual degradation and sudden failure are both possible and failure mechanisms are likely to be related to how hard the batteries were driven inside the vehicle. There are several figures from a number of sources including the DECC (Department of Energy and Climate Control) and Arup and Cenex reports indicate anything from 70,000 to 2.6 million electric and hybrid vehicles on the road by 2020. Once the vehicle battery has degraded to around 70-80% of its capacity it is considered to be at the end of its first life application. This leaves capacity available for a second life at a much cheaper cost than a new BESS Assuming a battery capability of around 5-18kWhr (MHEV 5kWh - BEV 18kWh battery) and approximate 10 year life span, this equates to a projection of battery storage capability available for second life of >1GWhrs by 2025. Moreover, each vehicle manufacturer has different specifications for battery chemistry, number and arrangement of battery cells, capacity, voltage, size etc. To enable research and investment in this area and to maximize the remaining life of these batteries, one of the design challenges is to combine these hybrid batteries into a grid-tie converter where their different performance characteristics, and parameter variation can be catered for and a hot swapping mechanism is available so that as a battery ends it second life, it can be replaced without affecting the overall system operation. This integration of either single types of batteries with vastly different performance capability or a hybrid battery system to a grid-tie 3 energy storage system is different to currently existing work on battery energy storage systems (BESS) which deals with a single type of battery with common characteristics. This thesis addresses and solves the power electronic design challenges in integrating second life hybrid batteries into a grid-tie energy storage unit for the first time. This study details a suitable multi-modular power electronic converter and its various switching strategies which can integrate widely different batteries to a grid-tie inverter irrespective of their characteristics, voltage levels and reliability. The proposed converter provides a high efficiency, enhanced control flexibility and has the capability to operate in different operational modes from the input to output. Designing an appropriate control system for this kind of hybrid battery storage system is also important because of the variation of battery types, differences in characteristics and different levels of degradations. This thesis proposes a generalised distributed power sharing strategy based on weighting function aims to optimally use a set of hybrid batteries according to their relative characteristics while providing the necessary grid support by distributing the power between the batteries. The strategy is adaptive in nature and varies as the individual battery characteristics change in real time as a result of degradation for example. A suitable bidirectional distributed control strategy or a module independent control technique has been developed corresponding to each mode of operation of the proposed modular converter. Stability is an important consideration in control of all power converters and as such this thesis investigates the control stability of the multi-modular converter in detailed. Many controllers use PI/PID based techniques with fixed control parameters. However, this is not found to be suitable from a stability point-of-view. Issues of control stability using this controller type under one of the operating modes has led to the development of an alternative adaptive and nonlinear Lyapunov based control for the modular power converter. Finally, a detailed simulation and experimental validation of the proposed power converter operation, power sharing strategy, proposed control structures and control stability issue have been undertaken using a grid connected laboratory based multi-modular hybrid battery energy storage system prototype. The experimental validation has demonstrated the feasibility of this new energy storage system operation for use in future grid applications

Design of control tools for use in microgrid simulations

2018 Summer.Includes bibliographical references.New technologies are transforming the way electricity is delivered and consumed. In the past two decades, a large amount of research has been done on smart grids and microgrids. This can be attributed to two factors. First is the poliferation of internet. Internet today is as ubiquitous as electricity. This has spawned a new area of technology called the internet of things (IoT). It gives us the ability to connect almost any device to the internet and harness the data. IoT finds use in smart grids that allow utiliy companies to deliver electricity efficiently. The other factor is the advancement in renewable sources of electricty and high power semiconductors coupled with their decreasing cost. These new sources disrupt the traditional way of electicity production and delivery, putting an increased focus on distributed power generation and microgrids. A microgrid is different from a utility grid. The difference is in the size of the grid, power level, a variety of possible sources and the way these are tied together. These characteristics lead to some unique control challenges. Today's appliances and consumer goods are powered using a standardized AC power. Thus a microrid must deliver uninterrupted and high quality power while at the same time taking into account the vastly different nature of the microsurces that produce the power. This work describes control system tools for different power converters that will be used in simulating microgrids.\ Simulations are important tool for any researcher. It allows researchers to test their research and theories at a greatly reduced cost. The process of design, testing and verification is an iterative process. Simulations allow a cost effective method of doing research, substituting the actual process of building experimental systems. This greatly reduces the amount of manpower and capital investment. A microgrid consists of several building blocks. These building blocks can be categorized into microsources, energy stores, converters and the loads. Microsources are devices that produce electric power. For example, a photovoltaic panel is a mirosource that produces DC power. Converters act as an interface between microsources and the grid. The constituent chapters in the document describe microsources and converters. The chapters describe the underlying control system and the simulation model of the system designed in Simulink. Some of the tools described are derived from the MATLAB/Simulink Examples library. Original authors of the simulation models and systems have been duly credited. Colorado State University has a vibrant research community. The tools described in this thesis are geared to be used for research into microgrids. The tools are developed in a simulation software called Simulink. The tools would allow future researchers to rapidly build microgrid simulations and test new control system implementations etc. The research described in the thesis builds upon the research by Han on natural gas engine based microgrid. The control tools described here are used to construct a microgrid simulation. The microgrid is built around a natural gas engine. Due to the transport lag in delivering fuel, a natural gas engine exhibits significant deviation in the AC grid frequency when subjected to step load. The microgrid setup along with the control system described here, minimizes the frequency deviation, thus stabilizing the microgrid. Simulation results verify the working of the tools