Survivability of Autonomous Microgrid During Overload Events (original) (raw)
Related papers
IEEE Access
Autonomous microgrids (MGs) are being installed in large remote areas to supply power where access to the utility grid is unavailable or infeasible. The power generation of such standalone MGs is largely dominated by renewable based energy sources where overloading or power deficiencies can be common due to the high intermittency and uncertainty in both load and power generation. Load-shedding is the most common mechanism to alleviate these problems to prevent system instability. To minimize load-shedding, most MGs are equipped with local battery energy storage (BES) systems to provide additional support. Furthermore, in the event of severe overloading or when BES capacity is insufficient to alleviate the overload, neighboring MGs can be provisionally coupled to provide mutual support to each other which is a more effective, economic and reliable approach. Such a coupling is preferred to be via power electronic converters to enhance the autonomy of the MGs. This paper proposes a two-stage, coordinated power sharing strategy among BESs and coupled MGs for overload management in autonomous MGs, through dynamic frequency control. Both local BES and the neighboring MGs can work in conjunction or individually to supply the required overload power demand. For this, BES' state of charge should be above a minimum level and extra power generation capacity needs to be available in the neighboring MGs. A predefined framework with appropriate constraints and conditions, under which the power exchange will take place, are defined and formulated. The proposed mechanism is a decentralized approach, operating based on local frequency and state of charge measurements, and without any data communication amongst the MGs. The dynamic performance of such a network, is evaluated through extensive simulation studies in PSIM R and verifies that the proposed strategy can successfully alleviate the overloading situation in the MGs through proper frequency regulation. INDEX TERMS Battery energy storage, dynamic frequency control, interconnection converter, coupled microgrids, overload management.
2009
This paper introduces the results of a research project whose objective is to extend obtained capabilities of a resilient microgrid to a conventional distribution network. This system has been previously sized and optimized to fully operate in an autonomous way. The presented work is an advanced interface control system for grid connection of this cluster in order to provide the over power in compliance with the distribution network. Especially, a frequency regulation function is added into the control system. As a result, the Distribution System Operator considers this locally controlled cluster as a single producer.
Real Time-Based under Frequency Control and Energy Management of Microgrids
Electronics
In this paper, an efficient under frequency control and the energy management of a distributed energy resources (DERs)-based microgrid is presented. The microgrid is composed of a photovoltaic (PV), double-fed induction generator (DFIG)-based wind and diesel generator with critical and non-critical loads. The system model and the control strategy are developed in a real time digital simulator (RTDS). The coordination and power management of the DERs in both grid-connected and islanded operation modes are implemented. During power imbalances and frequency fluctuations caused by fault or islanding, an advanced automatic load shedding control is implemented to regulate and maintain the microgrid frequency at its rated value. One distinct feature implemented for the load shedding operation is that highly unbalanced critical loads are connected to the microgrid. The diesel generator provides the required inertia in the islanded mode to maintain the microgrid rated frequency by operating ...
Control of Microgrids: Aspects and Prospects
A microgrid is a controllable component of the smart grid defined as a part of distribution network capable of supplying its own local load even in the case of disconnection from the upstream network. Microgrids incorporate large amount of renewable and non-renewable distributed generation (DG) that are connected to the system either directly or by power electronics (PE) interface. The diversity of technologies used in DGs and loads, high penetration of DGs, economic operation of DGs, dynamics of low-inertia conventional DGs and PE interfaced inertialess DGs and smart operation by means of enhanced communication infrastructure have raised challenges in widespread utilization of microgrids as basis of smart grids. Power quality, protection, economic and secure operation, active management, communication, dynamics and control of microgrids are among the most important issues under research both in academy and industry. Technical concerns over dynamics of microgrids especially in autonomous (island) mode necessitate revision of current paradigms in control of energy systems. This paper addresses current challenges towards controlling microgrids and surveys dynamic modeling, stability and control of microgrids. Future trends in realizing smart grids through aggregation of microgrids and research needs in this path are discussed at the end of this paper.
A Comprehensive Review on Modeling, Control, Protection and Future Prospects of Microgrid
Imminent constraints such as sky rocketing energy costs and need for expansion of generation & distribution systems attributable to increase in demand of power has led to revolution in generation system and evolution of Microgrid concept. Various operating principles and configuration of Microgrid are discussed in this paper focusing its operation in grid tied as well standalone operation mode. Possible controlling schemes and protection strategies are also suggested in this paper keeping in mind expected future prospects and challenges that can come in way while interfacing Microgrid with the main utility grid.
Overload Prevention in an Autonomous Microgrid using Battery Storage Units
A new control strategy for smooth transition of a battery storage unit (BSU) is proposed in this paper to prevent overloading in an autonomous hybrid microgrid. The BSU is controlled to come online to prevent overloading to the distributed generators (DGs) in the autonomous microgrid and to go offline when the load demand is less than the total rating of the DGs in the microgrid. The microgrid can contain either inertial DG or non–inertial DGs, which are controlled in a frequency droop. The sensing of switching on and switching off of the BSU depends on the frequency signal, which is developed in the paper. The proposed strategy is validated through PSCAD/EMTDC simulation studies.
Autonomous control of microgrids
2006 IEEE Power Engineering Society General Meeting, 2006
Application of individual distributed generators can cause as many problems as it may solve. A better way to realize the emerging potential of distributed generation is to take a system approach which views generation and associated loads as a subsystem or a "microgrid". The sources can operate in parallel to the grid or can operate in island, providing UPS services. The system will disconnect from the utility during large events (i.e. faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. Utilization of waste heat from the sources will increase total efficiency, making the project more financially attractive. Laboratory verification of the Consortium for Electric Reliability Technology Solutions (CERTS) microgrid control concepts are included. Index Terms-CHP, distributed generation, intentional islanding, inverters, microgrid, power vs. frequency droop, voltage droop, 1 This work was supported in part by the California Energy Commission (150-99-003).
A Review of Control Strategies for Microgrids
Global demand for electrical energy has never been higher than it is currently. This high demand for electricity has driven need for innovative and sustainable power production schemes. The current power system is therefore challenged with the need for quality, reliable and sustainable power production. In most countries, the system is aging, making it require more resources to meet contemporary challenges, coupled with the requirements to maintain a clean environment and mitigate environmental disasters. These lead to the microgrid concept. Deployment and use of the microgrid comes with new challenges-control and protection. In this paper, some of the most obvious control challenges of microgrid operations have been articulated. Nine (9) of the recent control strategies in literature have also been presented in this paper, including a brief explanation on the fundamental principles of the proposed strategies. Finally, this paper also presents a comparison of the strengths and weaknesses associated with the control strategies in literature.
Suggested New Voltage and Frequency Control Framework for Autonomous Operation of Microgrids
2013
Decentralized control strategies are popular candidates in microgrids control because of their reliability and performance. Conventionally, droop control (as a main decentralized strategy) is been utilized in order to prevent permanent droop of voltage and frequency after change in loads and also to share generated power between distributed generation units. In this paper, a new droop control strategy was introduced to control the voltage and frequency of autonomous microgrids. Following a review of the basic droop equations, it was concluded that the new form of droop equations enhanced the voltage and frequency control performance better than conventional droop equations. The voltage control behavior in the proposed method was within the acceptable range, and the frequency also returned to the nominal value after a change in loads. The simplicity and accurateness of the proposed method is a unique characteristic compared with the other recent control methods. Simulation studies sh...