2,294 research outputs found
A survey on modeling of microgrids - from fundamental physics to phasors and voltage sources
Microgrids have been identified as key components of modern electrical
systems to facilitate the integration of renewable distributed generation
units. Their analysis and controller design requires the development of
advanced (typically model-based) techniques naturally posing an interesting
challenge to the control community. Although there are widely accepted reduced
order models to describe the dynamic behavior of microgrids, they are typically
presented without details about the reduction procedure---hampering the
understanding of the physical phenomena behind them. Preceded by an
introduction to basic notions and definitions in power systems, the present
survey reviews key characteristics and main components of a microgrid. We
introduce the reader to the basic functionality of DC/AC inverters, as well as
to standard operating modes and control schemes of inverter-interfaced power
sources in microgrid applications. Based on this exposition and starting from
fundamental physics, we present detailed dynamical models of the main microgrid
components. Furthermore, we clearly state the underlying assumptions which lead
to the standard reduced model with inverters represented by controllable
voltage sources, as well as static network and load representations, hence,
providing a complete modular model derivation of a three-phase inverter-based
microgrid
Ancillary Services in Hybrid AC/DC Low Voltage Distribution Networks
In the last decade, distribution systems are experiencing a drastic transformation
with the advent of new technologies. In fact, distribution networks are no longer passive
systems, considering the current integration rates of new agents such as distributed generation,
electrical vehicles and energy storage, which are greatly influencing the way these systems are
operated. In addition, the intrinsic DC nature of these components, interfaced to the AC system
through power electronics converters, is unlocking the possibility for new distribution topologies
based on AC/DC networks. This paper analyzes the evolution of AC distribution systems,
the advantages of AC/DC hybrid arrangements and the active role that the new distributed agents
may play in the upcoming decarbonized paradigm by providing different ancillary services.Ministerio de Economía y Competitividad ENE2017-84813-RUnión Europea (Programa Horizonte 2020) 76409
Smart microgrids and virtual power plants in a hierarchical control structure
In order to achieve a coordinated integration of distributed energy resources in the electrical network, an aggregation of these resources is required. Microgrids and virtual power plants (VPPs) address this issue. Opposed to VPPs, microgrids have the functionality of islanding, for which specific control strategies have been developed. These control strategies are classified under the primary control strategies. Microgrid secondary control deals with other aspects such as resource allocation, economic optimization and voltage profile improvements. When focussing on the control-aspects of DER, VPP coordination is similar with the microgrid secondary control strategy, and thus, operates at a slower time frame as compared to the primary control and can take full advantage of the available communication provided by the overlaying smart grid. Therefore, the feasibility of the microgrid secondary control for application in VPPs is discussed in this paper. A hierarchical control structure is presented in which, firstly, smart microgrids deal with local issues in a primary and secondary control. Secondly, these microgrids are aggregated in a VPP that enables the tertiary control, forming the link with the electricity markets and dealing with issues on a larger scale
Secondary Frequency and Voltage Control of Islanded Microgrids via Distributed Averaging
In this work we present new distributed controllers for secondary frequency
and voltage control in islanded microgrids. Inspired by techniques from
cooperative control, the proposed controllers use localized information and
nearest-neighbor communication to collectively perform secondary control
actions. The frequency controller rapidly regulates the microgrid frequency to
its nominal value while maintaining active power sharing among the distributed
generators. Tuning of the voltage controller provides a simple and intuitive
trade-off between the conflicting goals of voltage regulation and reactive
power sharing. Our designs require no knowledge of the microgrid topology,
impedances or loads. The distributed architecture allows for flexibility and
redundancy, and eliminates the need for a central microgrid controller. We
provide a voltage stability analysis and present extensive experimental results
validating our designs, verifying robust performance under communication
failure and during plug-and-play operation.Comment: Accepted for publication in IEEE Transactions on Industrial
Electronic
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
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