Micro-grid autonomous operation during and subsequent to islanding process
TL;DR: In this paper, the authors investigated preplanned switching events and fault events that lead to islanding of a distribution subsystem and formation of a micro-grid, and they concluded that an appropriate control strategy for the power electronically interfaced DG unit can ensure stability of the microgrid and maintain voltage quality at designated buses, even during islanding transients.
Abstract: This paper investigates (i) preplanned switching events and (ii) fault events that lead to islanding of a distribution subsystem and formation of a micro-grid. The micro-grid includes two distributed generation (DG) units. One unit is a conventional rotating synchronous machine and the other is interfaced through a power electronic converter. The interface converter of the latter unit is equipped with independent real and reactive power control to minimize islanding transients and maintain both angle stability and voltage quality within the micro-grid. The studies are performed based on a digital computer simulation approach using the PSCAD/EMTDC software package. The studies show that an appropriate control strategy for the power electronically interfaced DG unit can ensure stability of the micro-grid and maintain voltage quality at designated buses, even during islanding transients. This paper concludes that presence of an electronically-interfaced DG unit makes the concept of micro-grid a technically viable option for further investigations.
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TL;DR: The major issues and challenges in microgrid control are discussed, and a review of state-of-the-art control strategies and trends is presented; a general overview of the main control principles (e.g., droop control, model predictive control, multi-agent systems).
Abstract: The increasing interest in integrating intermittent renewable energy sources into microgrids presents major challenges from the viewpoints of reliable operation and control. In this paper, the major issues and challenges in microgrid control are discussed, and a review of state-of-the-art control strategies and trends is presented; a general overview of the main control principles (e.g., droop control, model predictive control, multi-agent systems) is also included. The paper classifies microgrid control strategies into three levels: primary, secondary, and tertiary, where primary and secondary levels are associated with the operation of the microgrid itself, and tertiary level pertains to the coordinated operation of the microgrid and the host grid. Each control level is discussed in detail in view of the relevant existing technical literature.
2,358 citations
Cites background from "Micro-grid autonomous operation dur..."
...microgrid, whereas inverter output controllers should control and regulate the output voltages and currents [19], [20], [32], [54], [55]....
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...1) Droop-Based Methods: Controlling DER units based on droop characteristics is ubiquitous in the literature [20], [55], [56], [71]–[75]....
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...Given their speed requirements and reliance on local measurements, islanding detection, output control and power sharing (and balance) control are included in this category [19], [20], [22]....
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TL;DR: In this article, the feasibility of control strategies to be adopted for the operation of a microgrid when it becomes isolated is evaluated and the need of storage devices and load shedding strategies is evaluated.
Abstract: This paper describes and evaluates the feasibility of control strategies to be adopted for the operation of a microgrid when it becomes isolated. Normally, the microgrid operates in interconnected mode with the medium voltage network; however, scheduled or forced isolation can take place. In such conditions, the microgrid must have the ability to operate stably and autonomously. An evaluation of the need of storage devices and load shedding strategies is included in this paper.
2,276 citations
Cites background from "Micro-grid autonomous operation dur..."
...Local MS controllers can receive information from the MGCC about the generation profile and control accordingly the corresponding MS....
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...In this context, a MicroGrid (MG) can be defined as an LV network (e.g., a small urban area, a shopping center, or an industrial park) plus its loads and several small modular generation systems connected to it, providing both power and heat to local loads [combined heat and power (CHP)]....
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...…value in the interior of the electrodes, the temperature in the fuel-cell is presumed to be always stable, only ohmic losses are considered, assuming that the working conditions are far away from the upper and lower extreme values of current, and the Nernst equation is assumed to be…...
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TL;DR: In this article, real and reactive power management strategies of EI-DG units in the context of a multiple DG microgrid system were investigated. And the results were used to discuss applications under various microgrid operating conditions.
Abstract: This paper addresses real and reactive power management strategies of electronically interfaced distributed generation (DG) units in the context of a multiple-DG microgrid system. The emphasis is primarily on electronically interfaced DG (EI-DG) units. DG controls and power management strategies are based on locally measured signals without communications. Based on the reactive power controls adopted, three power management strategies are identified and investigated. These strategies are based on 1) voltage-droop characteristic, 2) voltage regulation, and 3) load reactive power compensation. The real power of each DG unit is controlled based on a frequency-droop characteristic and a complimentary frequency restoration strategy. A systematic approach to develop a small-signal dynamic model of a multiple-DG microgrid, including real and reactive power management strategies, is also presented. The microgrid eigen structure, based on the developed model, is used to 1) investigate the microgrid dynamic behavior, 2) select control parameters of DG units, and 3) incorporate power management strategies in the DG controllers. The model is also used to investigate sensitivity of the design to changes of parameters and operating point and to optimize performance of the microgrid system. The results are used to discuss applications of the proposed power management strategies under various microgrid operating conditions
1,531 citations
Cites background from "Micro-grid autonomous operation dur..."
...The utility grid is expected to support the difference in real/reactive power requirements and maintain the frequency [6]....
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TL;DR: This paper reviews the status of hierarchical control strategies applied to microgrids and discusses the future trends.
Abstract: Advanced control strategies are vital components for realization of microgrids. This paper reviews the status of hierarchical control strategies applied to microgrids and discusses the future trends. This hierarchical control structure consists of primary, secondary, and tertiary levels, and is a versatile tool in managing stationary and dynamic performance of microgrids while incorporating economical aspects. Various control approaches are compared and their respective advantages are highlighted. In addition, the coordination among different control hierarchies is discussed.
1,234 citations
TL;DR: In this article, the authors present a comprehensive literature review of AC and DC microgrid (MG) systems in connection with distributed generation (DG) units using renewable energy sources (RESs), energy storage systems (ESS) and loads.
Abstract: This paper presents the latest comprehensive literature review of AC and DC microgrid (MG) systems in connection with distributed generation (DG) units using renewable energy sources (RESs), energy storage systems (ESS) and loads. A survey on the alternative DG units' configurations in the low voltage AC (LVAC) and DC (LVDC) distribution networks with several applications of microgrid systems in the viewpoint of the current and the future consumer equipments energy market is extensively discussed. Based on the economical, technical and environmental benefits of the renewable energy related DG units, a thorough comparison between the two types of microgrid systems is provided. The paper also investigates the feasibility, control and energy management strategies of the two microgrid systems relying on the most current research works. Finally, the generalized relay tripping currents are derived and the protection strategies in microgrid systems are addressed in detail. From this literature survey, it can be revealed that the AC and DC microgrid systems with multiconverter devices are intrinsically potential for the future energy systems to achieve reliability, efficiency and quality power supply.
1,004 citations
References
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Book•
01 Oct 1995
TL;DR: In this paper, the authors present a power quality evaluation procedure for the purpose of measuring the power quality of a power supply. But, they do not define the specific classes of power quality problems.
Abstract: CHAPTER 1: INTRODUCTION What is Power Quality? Power Quality -- Voltage Quality Why Are We Concerned About Power Quality? The Power Quality Evaluation Procedure Who Should Use This Book Overview of the Contents CHAPTER 2: TERMS AND DEFINITIONS Need for a Consistent Vocabulary General Classes of Power Quality Problems Transients Long-Duration Voltage Variations Short-Duration Voltage Variations Voltage Imbalance Waveform Distortion Voltage Fluctuation Power Frequency Variations Power Quality Terms Ambiguous Terms CBEMA and ITI Curves References CHAPTER 3: VOLTAGE SAGS AND INTERRUPTIONS Sources of Sags and Interruptions Estimating Voltage Sag Performance Fundamental Principles of Protection Solutions at the End-User Level Evaluating the Economics of Different Ride-Through Alternatives Motor-Starting Sags Utility System Fault-Clearing Issues References CHAPTER 4: TRANSIENT OVERVOLTAGES Sources of Transient Overvoltages Principles of Overvoltage Protection Devices for Overvoltage Protection Utility Capacitor-Switching Transients Utility System Lightning Protection Managing Ferroresonance Switching Transient Problems with Loads Computer Tools for Transients Analysis References CHAPTER 5: FUNDAMENTALS OF HARMONICS Harmonic Distortion Voltage versus Current Distortion Harmonics versus Transients Harmonic Indexes Harmonic Sources from Commercial Loads Harmonic Sources from Industrial Loads Locating Harmonic Sources System Response Characteristics Effects of Harmonic Distortion Interharmonics References Bibliography CHAPTER 6: APPLIED HARMONICS Harmonic Distortion Evaluations Principles for Controlling Harmonics Where to Control Harmonics Harmonic Studies Devices for Controlling Harmonic Distortion Harmonic Filter Design: A Case Study Case Studies Standards of Harmonics References Bibliography CHAPTER 7: LONG-DURATION VOLTAGE VARIATIONS Principles of Regulating the Voltage Devices for Voltage Regulation Utility Voltage Regulator Application Capacitors for Voltage Regulation End-User Capacitor Application Regulating Utility Voltage with Distributed Resources Flicker References Bibliography CHAPTER 8: POWER QUALITY BENCHMARKING Introduction Benchmarking Process RMS Voltage Variation Indices Harmonics Indices Power Quality Contracts Power Quality Insurance Power Quality State Estimation Including Power Quality in Distribution Planning References Bibliography CHAPTER 9: DISTRIBUTED GENERATION AND POWER QUALITY Resurgence of DG DG Technologies Interface to the Utility System Power Quality Issues Operating Conflicts DG on Distribution Networks Siting DGDistributed Generation Interconnection Standards Summary References Bibliography CHAPTER 10: WIRING AND GROUNDING Resources Definitions Reasons for Grounding Typical Wiring and Grounding Problems Solutions to Wiring and Grounding Problems Bibliography CHAPTER 11: POWER QUALITY MONITORING Monitoring Considerations Historical Perspective of Power Quality Measuring Instruments Power Quality Measurement Equipment Assessment of Power Quality Measurement Data Application of Intelligent Systems Power Quality Monitoring Standards References Index INDEX
1,991 citations
17 Sep 1991
TL;DR: The advanced static VAr compensator (ASVC) as mentioned in this paper is based on the principle that a self-commutating static inverter can be connected between three-phase AC power lines and an energy storage device, such as an inductor or capacitor, and controlled to draw mainly reactive current from the lines.
Abstract: The advanced static VAr compensator (ASVC) is based on the principle that a self-commutating static inverter can be connected between three-phase AC power lines and an energy-storage device, such as an inductor or capacitor, and controlled to draw mainly reactive current from the lines. This capability is analogous to that of the rotating synchronous condenser and it can be used in a similar way for the dynamic compensation of power transmission systems, providing voltage support, increased transient stability, and improved damping. The authors present a simplified mathematical model of the ASVC that has made it possible to derive the transfer functions needed for control system synthesis. The resulting control system designs are briefly outlined and further analysis is presented to show the behaviour of the ASVC when the line voltage is unbalanced or distorted. The analysis is based on a vectorial transformation of variables, first described by R.H. Park (1928) for AC machine analysis, and later, using complex numbers, by W.V. Lyon (1954) in the theory of instantaneous symmetrical components.
1,039 citations
01 Jul 1993
TL;DR: In this paper, two fundamentally different types of invertor can be used for this purpose, one providing control of output voltage magnitude and phase angle, and the other having only phase angle control.
Abstract: The advanced static Var compensator (now widely known as the static condenser or STATCON) uses a high power self-commutating inverter to draw reactive current from a transmission line. Two fundamentally different types of invertor can be used for this purpose, one providing control of output voltage magnitude and phase angle, and the other having only phase angle control. For each of these types, the governing equations are derived, and frequency domain analysis is used to obtain the relevant transfer functions for control system synthesis. Further analysis is provided to determine the response of the STATCON to negative sequence and harmonic voltage components on the transmission line. The results are illustrated with measured waveforms obtained from a scaled analogue model of an 80 MVAr STATCON.<
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974 citations
"Micro-grid autonomous operation dur..." refers background or methods in this paper
...The control system of the converter is represented in the d-q-0 frame and utilizes the concept of instantaneous power to control real/reactive power exchange with the system by specifying d and q components of converter currents [11], [12]....
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..., through the control of the q-component of converter current, adjusts its reactive power injection [11] to maintain the voltage at bus 3; even though this results in injecting reactive Fig....
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TL;DR: In this paper, the requirements of an islanding, or "loss of grid", protection for a dispersed storage and generation unit are examined, and the principal methods used for this type of relaying are outlined.
Abstract: The requirements of an islanding, or 'loss of grid', protection for a dispersed storage and generation unit are examined, and the principal methods used for this type of relaying are outlined. A new protection algorithm is introduced which is based on the rate of change of power as measured at the generator's terminals. The responses of the different measurands are examined for a selection of power system operating conditions in order to demonstrate the operation of this type of protection. The new protection algorithm is shown to trip for loss of grid and for load fluctuations while the dispersed storage and generation unit is operating independently of the utility supply following a loss of grid, and for an out-of-synchronism reconnection of the utility supply to the dispersed storage and generation unit. It is also shown to remain stable for major load fluctuations while the utility supply remains connected to the dispersed generator system. >
277 citations
"Micro-grid autonomous operation dur..." refers methods in this paper
...Several active and passive techniques have been introduced to detect an islanding condition, using local power system measurements [8]–[10]....
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07 Aug 2002
TL;DR: In this article, the main related technical issues are discussed together with the DGs modelling requirements for their analysis, and the main technical issues of the micro-grid are discussed and discussed in detail.
Abstract: Increased penetration of small modular generation technologies interconnected to distribution systems forms a new type of power system, the micro-grid. Micro grids can provoke several technical problems in the operation of the grid, or face technical challenges in their operation and control, when operated as autonomous systems. In this paper the main related technical issues are discussed together with the DGs modelling requirements for their analysis.
177 citations