PERFORMANCE CHARACTERIZATION OF A MOBILE MICROGRID

With a rising global emphasis on the use of renewable energy and the reduction of fossil fuels, the Department of Defense is incorporating microgrid technology into energy management systems at forward-deployed and domestic installations. Understanding the nature of the connection between a microgrid and the local utility grid is critical in determining if sensitive loads will be adequately supported. IEEE Standard 1547-2018 applies to this interconnection and specifies the technical requirements and limitations for normal and abnormal operation and expectations for interrupting events. A commercial-off-the-shelf (COTS) microgrid is tested for its compliance to this standard and also for characteristics, such as efficiency, that help define its operational capability. The microgrid can operate in a grid-connected state or an islanded state, disconnected from the utility grid, if the grid is unavailable or if the power quality is unable to support military operations. A microgrid testbed was set up that included the individual COTS components, a centralized control system and several measurement instruments connected that read voltages and currents continuously throughout the experiments. By observing the microgrid functionality, this thesis created an objective characterization template that can be used to assess the capabilities of other COTS microgrids to determine whether they are capable of supporting sensitive loads on forward-deployed or domestic military installations.Captain, United States Marine CorpsApproved for public release. Distribution is unlimited

Electric Power System Studies for a Multi-MW PV Farm and Large Rural Community with Net Zero Energy and Microgrid Capabilities

Solar photovoltaic (PV) systems are currently being deployed at an accelerated rate because of their cost-competitiveness and environmental benefits, which make them a prime candidate for local renewable energy generation in communities. Microgrids can help accommodate for the problems that accompany PV systems, such as intermittency due to weather, by coordinating different distributed energy resources (DERs), while islanded or by drawing power from the utility while in grid-connected mode. An islanding option is also important for resilience and grid fault mitigation, even if other DERs are not present within the system. This paper studies the potential benefits that a multi-MW utility-scale PV farm may yield for a large rural community when installed within a grid-connected microgrid structure. The PV system was optimally sized based on net present cost (NPC) with a net zero energy (NZE) goal. With local solar PV generation and a connection to the grid to transmit overgeneration through, the community can be NZE by having a PV farm power rating that is much greater than the peak load demand. This may lead to cases of increased transient severity during mode transitions and may require substantial curtailment of PV. A control scheme is proposed to smooth system transients that result from the switching between the two modes of operation in order to avoid system damage or unreliable load service

Microgrid

A microgrid has a group of electrical generation and various types of loads operated as single controllable power system. Microgrid is a best option for configuration of recent model power grids. Microgrids are capable of work in parallel with the existing grid as well as off grid as isolated mode. The microgrid enables the grid connection as either AC grid or DC grid and it provides connections of variable AC and DC sources with loads. Microgrid has modeled such a way that it avoids multiple reverse connections. Power electronic devices such as converters and inverters are ensures safe operation and control of the microgrid. The proper modeling and simulation results ensure the successful implementation of microgrid. The challenges involved in implementation and the modeling of AC/DC and hybrid grid in the tied mode have been discussed. The simulation modeling of the microgrid in MATLAB/SIMULINK platform is explained with neat circuit diagram. This chapter provides the readers complete and comprehensive overview about microgrids and their different modes of operations

PSCAD Modeling and Stability Analysis of a Microgrid

As power systems are evolving, engineers are facing, and will continue to face, new challenges with respect to maintaining the system in terms of stable operation. Many different forms of generation are becoming prevalent, including; small synchronous generators, photovoltaic generation, and energy storage techniques in the form of battery and ultracapacitor systems. One of the evolutions occurring in the power system is the emergence of microgrids, small power systems capable of isolating from the major power grid in the form of islands. Microgrids use distributed generation to provide power to small communities, and they come with several advantages and disadvantages. This thesis shows the design process employed to model a microgrid, which contains a variety of distributed resources, in PSCAD, as well as investigate the transient instability of the microgrid when transitioning to islanded operation. Modeling techniques for both grid-connected and islanded operation of the microgrid are considered in this study. In addition to modeling techniques, the effectiveness of proper control of energy storage assets in a microgrid is demonstrated through the implementation and comparison between real & reactive power regulation and voltage & frequency regulation

Investigations of AC Microgrid Energy Management Systems Using Distributed Energy Resources and Plug-in Electric Vehicles

The world has witnessed a rapid transformation in the field of electrical generation, transmission and distribution. We have been constantly developing and upgrading our technology to make the system more economically efficient. Currently, the industry faces an acute shortage of energy resources due to overconsumption by industries worldwide. This has compelled experts to look for alternatives to fossil fuels and other conventional sources of energy to produce energy in a more sustainable manner. The microgrid concept has gained popularity over the years and has become a common sight all over the world because of the ability of a microgrid to provide power to a localized section without being dependent on conventional resources. This paper focuses on development of such an AC hybrid microgrid, which receives power from distributed energy resources (DERs) such as a PV array alongside a battery storage system, and also uses an emergency diesel generator system and an online uninterruptible power supply (UPS) system to provide power to predefined loads under different conditions. This paper also addresses on the power flow to the loads under two main modes of operation—on grid and off grid—and investigates the microgrid in different states and sub-states. The final objective is to design an efficient microgrid model such that it can sustain the multiple loads simultaneously under all operating conditions

Transition between stand-alone and grid connected solar photovoltaic microgrids

1 online resource (viii, 59 pages) : charts (some colour)Includes abstract.Includes bibliographical references (pages 52-59).In this study, conversion of Solar Photovoltaic (PV) energy to increase sustainable energy and increase system efficiency is being studied. During the process, both stand-alone mode and grid connected mode microgrid with energy storage system (ESS) have been tested in a simulation environment. Their transition from one mode to another have been discussed for research purpose. Solar photovoltaic PV modules, energy storage devices (Battery), power electronics converters are used to validate the desired results. The study of stand-alone to grid-connected systems will be analyzed and tuned for a stable system performance. During the tuning, the voltage and the frequency are the key driving parameters to be controlled and evaluated. Also, the study of grid connected configurations will be conducted and then both systems will be compiled together using a switching property. The aim is to work on control system for creating the transition in the systems. The study is tested with MATLAB/Simulink platform-based simulations. The major focus will be on the control mechanism of the inverters in both modes, specifically for this study

Real-time modeling and simulation of distribution feeder and distributed resources

Includes bibliographical references.2015 Fall.The analysis of the electrical system dates back to the days when analog network analyzers were used. With the advent of digital computers, many programs were written for power-flow and short circuit analysis for the improvement of the electrical system. Real-time computer simulations can answer many what-if scenarios in the existing or the proposed power system. In this thesis, the standard IEEE 13-Node distribution feeder is developed and validated on a real-time platform OPAL-RT™. The concept and the challenges of the real-time simulation are studied and addressed. Distributed energy resources include some of the commonly used distributed generation and storage devices like diesel engine, solar photovoltaic array, and battery storage system are modeled and simulated on a real-time platform. A microgrid encompasses a portion of an electric power distribution which is located downstream of the distribution substation. Normally, the microgrid operates in paralleled mode with the grid; however, scheduled or forced isolation can take place. In such conditions, the microgrid must have the ability to operate stably and autonomously. The microgrid can operate in grid connected and islanded mode, both the operating modes are studied in the last chapter. Towards the end, a simple microgrid controller modeled and simulated on the real-time platform is developed for energy management and protection for the microgrid

Evolution of microgrids with converter-interfaced generations: Challenges and opportunities

© 2019 Elsevier Ltd Although microgrids facilitate the increased penetration of distributed generations (DGs) and improve the security of power supplies, they have some issues that need to be better understood and addressed before realising the full potential of microgrids. This paper presents a comprehensive list of challenges and opportunities supported by a literature review on the evolution of converter-based microgrids. The discussion in this paper presented with a view to establishing microgrids as distinct from the existing distribution systems. This is accomplished by, firstly, describing the challenges and benefits of using DG units in a distribution network and then those of microgrid ones. Also, the definitions, classifications and characteristics of microgrids are summarised to provide a sound basis for novice researchers to undertake ongoing research on microgrids

Energy storage sizing for low-inertia microgrids, and lessons learned from a potential microgrid

The coordinated control of multiple distributed generators in a microgrid and the preservation of adequate system inertia in real-time operations are some of the principal technical challenges for stable microgrid operation. One issue in particular pertains to grid-tied inverters, which, as mandated by present standards, are only permitted to operate at unity power factor, thereby requiring the microgrid’s synchronous generators to operate at a low power factor. This behavior accordingly introduces ramifications by limiting the generator’s active power output, which would compromise frequency and voltage stability margins. Consideration is also given to the effect of line impedances, since interconnecting microgrid lines can be described by a variety of X/R ratios that affect the control and flow of active and reactive power. Moreover, the absence of a stiff grid presents control challenges for grid-tied inverters due to the inverters’ tendency to regulate the voltage at the point of common coupling. These same inverters also jeopardize microgrid stability due to their low equivalent inertia as traditional forms of generation (i.e., spinning sources) become displaced by inertia-less inverters. Because of this low microgrid inertia, fluctuations in the output power of renewable energy sources or changes in local load levels may lead to power quality or frequency/voltage stability concerns. Therefore, energy storage sizing is investigated in this dissertation, as it is closely related to the stability analysis of microgrids. Furthermore, an existing residential community (in Austin, TX) described by a moderate penetration of photovoltaic sources and electric vehicle charging is considered, and the implications of said community being retrofitted to a microgrid are examined.Electrical and Computer Engineerin