Integrity Protection of the DC Microgrid

The direct current (DC) microgrid has attracted great attention in the recent years due to its significant advantages over the alternating current (AC) microgrid. These advantages include elimination of unnecessary AC/DC power converters, lower investment cost, lower losses, higher reliability, and resilience to utility-side disturbances. A practical DC microgrid requires an effective control strategy to regulate the DC bus voltages, enable power sharing between the distributed energy resources (DERs), and provide acceptable dynamic response to disturbances. Furthermore, when the power demand of the loads is higher than the power generation of the DERs in the DC microgrid, the power balance cannot be maintained by control actions and the DERs fail to regulate the DC bus voltages. Under such conditions, it is necessary to shed some of the non-critical loads in order to protect the integrity of the DC microgrid. Thus, the DC microgrid also requires an effective load shedding scheme. This thesis is focused on developing advanced control and load shedding strategies for integrity protection of the DC microgrid. The studies reported in this thesis include developing (i) a versatile DC bus signaling control strategy to achieve coordinated decentralized control of the DERs and loads in the DC microgrid without utilizing costly high-bandwidth communication systems, (ii) an improved mode-adaptive droop control strategy to enable desirable and reliable control mode switching by the DERs under various operating conditions, and (iii) adaptive non-communication based load shedding schemes to enable the DC microgrid to ride through the disturbances that cause large power deficit and voltage sags. The performances of the proposed integrity protection schemes are investigated under various generation and load disturbances in both grid-connected and islanded operation modes of the DC microgrid. Comprehensive time-domain simulation studies are conducted on a detailed DC microgrid study system using the PSCAD/EMTDC software. The study results indicate that the proposed control strategies: (i) improve power sharing between the DERs, (ii) effectively regulate the DC bus voltages under various operating conditions, (iii) improve the DC microgrid stability and its dynamic response to large disturbances, (iv) do not require an excessively large grid-tie converter or energy storage systems, and (v) enhance the DC microgrid reliability, flexibility, modularity, and expandability. The study results also indicate that the proposed adaptive load shedding schemes (i) effectively maintain the power balance in the DC microgrid through fast and coordinated shedding of non-critical loads, (ii) prevent the bus voltages in the microgrid from falling below predetermined lower limits, (iii) ensure that the critical loads do not experience excessive steady-state voltage deviations, (iv) minimize the magnitudes and durations of temporary voltage sags caused by sudden disturbances, and (v) increase the reliability of the power supplied to the loads, by preventing over-shedding

Automation, Annunciation, and Emergency Safety Shutdown of a Laboratory Microgrid Using a Real-Time Automation Controller (RTAC)

Over the last decade, microgrid deployments throughout the world have increased. In 2019, a record number of 546 microgrids were installed in the United States [1]. This trend continues upward to combat extreme weather conditions and power shortages throughout the country. To better equip students with the necessary skillsets and knowledge to advance in the microgrid field, Cal Poly San Luis Obispo\u27s Electrical Engineering Department and the Power Energy Institute have invested resources to develop a laboratory microgrid. This thesis sets to improve the laboratory microgrid\u27s existing automation using the Schweitzer Engineering Laboratory SEL-3530 Real-time Automation Controller (RTAC). The improved automation features a new load-shedding scheme, LCD annunciator and meter panel, and emergency safety shutdown system. The load shedding scheme aims to enhance the grid\u27s frequency stability when the inverter-based power output declines. The LCD annunciator and meter panels provide real-time oversight of the microgrid operating conditions via the RTAC Human Machine Interface (HMI). The emergency safety shutdown enables prompt de-energization and complete isolation of the laboratory microgrid in hazardous conditions such as earthquake, fire, arcing, and equipment malfunction and activates an audible siren to alert help. This safety system provides safety and peace of mind for students and faculties who operate the Microgrid. Lastly, this thesis provides an operating procedure for ease of operation and experiment

A CFD simulation study on pressure drop and velocity across single flow microchannel heat sink

This paper presents a numerical simulation of flow in a microchannel heat sink. The channel was defined as a dimension with less than 1.0milimeter and greater than 100.0micrometer. The ANSYS CFX 2015 was used to predict the flow in the microchannel. Besides, simulations were undertaken to determine the flow of the fluid within the microchannel in three different models. Therefore, three different models were employed for this study. The first model was a square-shaped channel with 0.5mm width and 0.5mm height constructed along 28.0mm channel length. The second and the third models were in rectangular shape. The differences between these models were their width and height of channel. The dimension for the second model was 0.75mm height and 0.5mm width (rectangular A), while the dimension for the third model was 0.5mm height and 0.75mm width (rectangular B). All the microchannel heat sink models had been simulated and showed results for pressure, temperature, and velocity inside the microchannel. The results were compared for each model and the data had been validated from published data. In addition, the initial velocity was set in a range between 0.1m/s and 0.5m/s. The highest pressure drop was recorded for the square microchannel. It was 58.12% higher than the pressure drop found in the rectangular microchannel with 0.75mm width, while 0.02% closer with the 0.75mm-height rectangular microchannel. Furthermore, there was a 33.34% of temperature difference, which had been higher for the square microchannel. Nevertheless, the highest velocity of 0.57m/s was recorded at the outlet of the microchannel. These had been consistent with other published data

Wide-Area Time-Synchronized Closed-Loop Control of Power Systems And Decentralized Active Distribution Networks

The rapidly expanding power system grid infrastructure and the need to reduce the occurrence of major blackouts and prevention or hardening of systems against cyber-attacks, have led to increased interest in the improved resilience of the electrical grid. Distributed and decentralized control have been widely applied to computer science research. However, for power system applications, the real-time application of decentralized and distributed control algorithms introduce several challenges. In this dissertation, new algorithms and methods for decentralized control, protection and energy management of Wide Area Monitoring, Protection and Control (WAMPAC) and the Active Distribution Network (ADN) are developed to improve the resiliency of the power system. To evaluate the findings of this dissertation, a laboratory-scale integrated Wide WAMPAC and ADN control platform was designed and implemented. The developed platform consists of phasor measurement units (PMU), intelligent electronic devices (IED) and programmable logic controllers (PLC). On top of the designed hardware control platform, a multi-agent cyber-physical interoperability viii framework was developed for real-time verification of the developed decentralized and distributed algorithms using local wireless and Internet-based cloud communication. A novel real-time multiagent system interoperability testbed was developed to enable utility independent private microgrids standardized interoperability framework and define behavioral models for expandability and plug-and-play operation. The state-of-theart power system multiagent framework is improved by providing specific attributes and a deliberative behavior modeling capability. The proposed multi-agent framework is validated in a laboratory based testbed involving developed intelligent electronic device prototypes and actual microgrid setups. Experimental results are demonstrated for both decentralized and distributed control approaches. A new adaptive real-time protection and remedial action scheme (RAS) method using agent-based distributed communication was developed for autonomous hybrid AC/DC microgrids to increase resiliency and continuous operability after fault conditions. Unlike the conventional consecutive time delay-based overcurrent protection schemes, the developed technique defines a selectivity mechanism considering the RAS of the microgrid after fault instant based on feeder characteristics and the location of the IEDs. The experimental results showed a significant improvement in terms of resiliency of microgrids through protection using agent-based distributed communication

Identification and development of microgrids emergency control procedures

Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 200

Power flow stabilization and control of microgrid with wind generation by superconducting magnetic energy storage

High penetration of renewable energy sources such as wind generation in microgrids (MGs) causes fluctuations of power flow and significantly affects the power system (PS) operation. This can lead to severe problems, such as system frequency oscillations, and/or violations of power lines capability. With the proper control, superconducting magnetic energy storage (SMES) is able to significantly enhance the dynamic security of the PS. In an SMES system, the power conditioning system (PCS) is the crucial component that directly influences the validity of the SMES in the dynamic control of the PS. This paper proposes the use of an improved SMES controller for the stabilization and control of the power flow of wind-hybrid MGs. In this sense, the design and implementation of a novel high-performance PCS scheme of the SMES is described. Moreover, a detailed model of the SMES unit is derived and a novel three-level control scheme is designed, comprising a full decoupled current control strategy in the d-q reference frame and an enhanced PS frequency controller. The dynamic performance of the proposed systems is fully validated by computer simulation.Fil: Molina, Marcelo Gustavo. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Mercado, Pedro Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Stabilization and control of tie-line power flow of microgrid including wind generation by distributed energy storage

High penetration of wind generation in electrical microgrids causes fluctuations of tie-line power flow and significantly affects the power system operation. This can lead to severe problems, such as system frequency oscillations, and/or violations of power lines capability. With proper control, a distribution static synchronous compensator (DSTATCOM) integrated with superconducting magnetic energy storage (SMES) is able to significantly enhance the dynamic security of the power system. This paper proposes the use of a SMES system in combination with a DSTATCOM as effective distributed energy storage (DES) for stabilization and control of the tie-line power flow of microgrids incorporating wind generation. A new detailed model of the integrated DSTATCOM-SMES device is derived and a novel three-level control scheme is designed. The dynamic performance of the proposed control schemes is fully validated using MATLAB/Simulink. © 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.Fil: Molina, Marcelo Gustavo. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Mercado, Pedro Enrique. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentin

Security of electric power systems : cascading outage analysis, interdiction model and resilience to natural disasters

textSecure electric power system operation is key to social warfare. However, recent years have seen numerous natural disasters and terrorist attacks that threat the grid security. This dissertation summarizes the efforts to develop a model to analyze cascading outages, an interdiction model to analyze worst-case attacks on power grids, and research on grid resilience to natural disasters. The developed cascading outage analysis model uses outage checkers to systematically simulate the system behavior after an initial disturbance, and calculate the potential cascading outage path and electric load shedding. The new interdiction model combines the previously developed medium-term attack-defense model with the short-term cascading outage analysis model to find worst-case terrorist attack. The dissertation also reviews the research on power grid resilience to natural disaster, and develops a framework to simulate the impacts of hurricanes.Electrical and Computer Engineerin

ICT-Enabled Control and Energy Management of Community Microgrids for Resilient Smart Grid Operation

Our research has focused on developing novel controllers and algorithms to enhance the resilience of the power grid and increase its readiness level against major disturbances. The U.S. power grid currently encounters two main challenges: (1) the massive and extended blackouts caused by natural disasters, such as hurricane Sandy. These blackouts have raised a national call to explore innovative approaches for enhanced grid resiliency. Scrutinizing how previous blackouts initiated and propagated throughout the power grid, the major reasons are lack of situational awareness, lack of real-time monitoring and control, underdeveloped controllers at both the transmission and distribution levels, and lack of preparation for major emergencies; and (2) the projected high penetration of renewable energy resources (RES) into the electric grid, which is mainly driven by federal and state regulatory actions to reduce GHG emissions from new and existing power plants, and to encourage Non Wire Solutions (NWS). RESs are intermittent by nature imposing a challenge to forecast load and maintain generation/demand balance. The conceived vision of the smart grid is a cyber-physical system that amalgamates high processing power and increased dependence on communication networks to enable real-time monitoring and control. This will allow for, among other objectives, the realization of increased resilience and self-healing capabilities. This vision entails a hierarchical control architecture in which a myriad of microgrids, each locally controlled at the prosumer level, coordinates within the distribution level with their correspondent distribution system operator (i.e. area controllers). The various area controllers are managed by a Wide Area Monitoring, Protection and Control operator. The smart grid has been devised to address the grid main challenges; however, some technical barriers are yet to be overcome. These barriers include the need to develop new control techniques and algorithms that enable flexible transitions between operational modes of a single controller, and effective coordination between hierarchical control layers. In addition, there is a need to understand the reliability impacts of increased dependence on communication networks. In an attempt to tackle the aforementioned barriers, in my work, novel controllers to manage the prosumer and distribution networks were developed and analyzed. Specifically, the following has been accomplished at the prosumer level, we: 1) designed and implemented a DC MG testbed with minimal off-the-shelf components to enable testing new control techniques with significant flexibility and reconfiguration capability; 2) developed a communication-based hybrid state/event driven control scheme that aims at reducing the communication load and complexity, processor computations, and consequently system cost while maintaining resilient autonomous operation during all possible scenarios including major emergencies; and 3) analyzed the effect of communication latency on the performance of centralized ICT-based DC microgrids, and developed mathematical models to describe the behavior of microgrids during latency. In addition, we proposed a practical solution to mitigate severe impacts of latency. At the distribution level, we: 1) developed a model for an IEEE distribution test network with multiple MGs integrated[AM1] [PL2] ; 2) developed a control scheme to manage community MGs to mitigate RES intermittency and enhance the grid resiliency, deferring the need for infrastructure upgrade; and 3) investigated the optimal placement and operation of community MGs in distribution networks using complex network analysis, to increase distribution networks resilience. At the transmission level (T.L), New York State T.L was modeled. A case study was conducted on Long Island City to study the impact of high penetration of renewable energy resources on the grid resilience in the transmission level. These research accomplishments should pave the way and help facilitate a smooth transition towards the future smart grid.