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Journal ArticleDOI

A Voltage and Frequency Droop Control Method for Parallel Inverters

09 Jul 2007-IEEE Transactions on Power Electronics (IEEE)-Vol. 22, Iss: 4, pp 1107-1115
TL;DR: In this paper, a new control method for the parallel operation of inverters operating in an island grid or connected to an infinite bus is described, where each inverter supplies a current that is the result of the voltage difference between a reference ac voltage source and the grid voltage across a virtual complex impedance.
Abstract: In this paper, a new control method for the parallel operation of inverters operating in an island grid or connected to an infinite bus is described. Frequency and voltage control, including mitigation of voltage harmonics, are achieved without the need for any common control circuitry or communication between inverters. Each inverter supplies a current that is the result of the voltage difference between a reference ac voltage source and the grid voltage across a virtual complex impedance. The reference ac voltage source is synchronized with the grid, with a phase shift, depending on the difference between rated and actual grid frequency. A detailed analysis shows that this approach has a superior behavior compared to existing methods, regarding the mitigation of voltage harmonics, short-circuit behavior and the effectiveness of the frequency and voltage control, as it takes the R to X line impedance ratio into account. Experiments show the behavior of the method for an inverter feeding a highly nonlinear load and during the connection of two parallel inverters in operation.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a detailed analysis of the main operation modes and control structures for power converters belonging to micro-grids is carried out, focusing mainly on grid-forming, grid-feeding, and grid-supporting configurations.
Abstract: The enabling of ac microgrids in distribution networks allows delivering distributed power and providing grid support services during regular operation of the grid, as well as powering isolated islands in case of faults and contingencies, thus increasing the performance and reliability of the electrical system. The high penetration of distributed generators, linked to the grid through highly controllable power processors based on power electronics, together with the incorporation of electrical energy storage systems, communication technologies, and controllable loads, opens new horizons to the effective expansion of microgrid applications integrated into electrical power systems. This paper carries out an overview about microgrid structures and control techniques at different hierarchical levels. At the power converter level, a detailed analysis of the main operation modes and control structures for power converters belonging to microgrids is carried out, focusing mainly on grid-forming, grid-feeding, and grid-supporting configurations. This analysis is extended as well toward the hierarchical control scheme of microgrids, which, based on the primary, secondary, and tertiary control layer division, is devoted to minimize the operation cost, coordinating support services, meanwhile maximizing the reliability and the controllability of microgrids. Finally, the main grid services that microgrids can offer to the main network, as well as the future trends in the development of their operation and control for the next future, are presented and discussed.

2,621 citations

Journal ArticleDOI
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 "A Voltage and Frequency Droop Contr..."

  • ...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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Journal ArticleDOI
TL;DR: The idea of operating an inverter to mimic a synchronous generator (SG) is motivated and developed, and the inverters that are operated in this way are called synchronverters.
Abstract: In this paper, the idea of operating an inverter to mimic a synchronous generator (SG) is motivated and developed. We call the inverters that are operated in this way synchronverters. Using synchronverters, the well-established theory/algorithms used to control SGs can still be used in power systems where a significant proportion of the generating capacity is inverter-based. We describe the dynamics, implementation, and operation of synchronverters. The real and reactive power delivered by synchronverters connected in parallel and operated as generators can be automatically shared using the well-known frequency- and voltage-drooping mechanisms. Synchronverters can be easily operated also in island mode, and hence, they provide an ideal solution for microgrids or smart grids. Both simulation and experimental results are given to verify the idea.

2,115 citations

Journal ArticleDOI
TL;DR: Decentralized, distributed, and hierarchical control of grid-connected and islanded microgrids that mimic the behavior of the mains grid is reviewed.
Abstract: This paper presents a review of advanced control techniques for microgrids. This paper covers decentralized, distributed, and hierarchical control of grid-connected and islanded microgrids. At first, decentralized control techniques for microgrids are reviewed. Then, the recent developments in the stability analysis of decentralized controlled microgrids are discussed. Finally, hierarchical control for microgrids that mimic the behavior of the mains grid is reviewed.

1,702 citations


Cites background or methods from "A Voltage and Frequency Droop Contr..."

  • ...The authors of [20] adopt the first approach....

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  • ...connected uninterruptible power systems (UPSs) in order to avoid mutual control wires while obtaining good power sharing [16]–[20]....

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Journal ArticleDOI
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

References
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Book
01 Jan 1980
TL;DR: This well-respected, market-leading text discusses the use of digital computers in the real-time control of dynamic systems and thoroughly integrates MATLAB statements and problems to offer readers a complete design picture.
Abstract: From the Publisher: This well-respected, market-leading text discusses the use of digital computers in the real-time control of dynamic systems The emphasis is on the design of digital controls that achieve good dynamic response and small errors while using signals that are sampled in time and quantized in amplitude Both classical and modern control methods are described and applied to illustrative examples The strengths and limitations of each method are explored to help the reader develop solid designs with the least effort Two new chapters have been added to the third edition offering a review of feedback control systems and an overview of digital control systems Updated to be fully compatible with MATLAB versions 4 and 5, the text thoroughly integrates MATLAB statements and problems to offer readers a complete design picture The new edition contains up-to-date material on state-space design and twice as many end-of-chapter problems to give students more opportunities to practice the material

3,756 citations


"A Voltage and Frequency Droop Contr..." refers background in this paper

  • ...10 and incorporates disturbance estimation as well as reference following [18]....

    [...]

Journal ArticleDOI
28 Sep 1991
TL;DR: In this article, a control scheme for parallel-connected inverters in a standalone AC supply system is presented, which uses feedback of only those variables that can be measured locally at the inverter and does not need communication of control signals between the inverters.
Abstract: A scheme for controlling parallel-connected inverters in a standalone AC supply system is presented. This scheme is suitable for control of inverters in distributed source environments such as in isolated AC systems, large and distributed uninterruptible power supply (UPS) systems, photovoltaic systems connected to AC grids, and low-voltage DC power transmission meshes. A key feature of the control scheme is that it uses feedback of only those variables that can be measured locally at the inverter and does not need communication of control signals between the inverters. This is essential for the operation of large AC systems, where distances between inverters make communication impractical. It is also important in high-reliability UPS systems where system operation can be maintained in the face of a communication breakdown. Real and reactive power sharing between inverters can be achieved by controlling two independent quantities: the power angle and the fundamental inverter voltage magnitude. Simulation results are presented. >

1,550 citations

Journal ArticleDOI
TL;DR: In this article, a phase-locked loop (PLL) system under distorted utility conditions is presented and a control model of the PLL system is developed and recommendations are made on tuning of this model specially for operation under common utility distortions such as line notching, voltage unbalance/loss, and frequency variations.
Abstract: Operation of a phase locked loop (PLL) system under distorted utility conditions is presented. A control model of the PLL system is developed and recommendations are made on tuning of this model specially for operation under common utility distortions such as line notching, voltage unbalance/loss, and frequency variations. The PLL is completely implemented in software without any filters. All analytical results are experimentally verified.

1,061 citations


"A Voltage and Frequency Droop Contr..." refers background in this paper

  • ...The rotation angle for Park’s transformation is obtained from a phase locked loop (PLL), regulating to zero by use of a proportional-integral (PI) regulator [17]....

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Book
01 Jan 1972
TL;DR: In this paper, the basic concepts of a Power System Control of Power and Frequency Control of Voltage and Reactive Power Load Flows Fault Analysis Stability Limits Direct Current Transmission Overvoltages and Insulation Requirements Overhead Lines and Underground Cables Protection Appendices Index.
Abstract: Basic Concepts Components of a Power System Control of Power and Frequency Control of Voltage and Reactive Power Load Flows Fault Analysis Stability Limits Direct Current Transmission Overvoltages and Insulation Requirements Overhead Lines and Underground Cables Protection Appendices Index.

757 citations

Journal ArticleDOI
08 Oct 2000
TL;DR: In this article, a small-signal analysis for parallel-connected inverters in stand-alone AC supply systems is presented, which is based on frequency and voltage droops, which depends on the local variable measurements and does not need control interconnections.
Abstract: This paper presents a small-signal analysis for parallel-connected inverters in stand-alone AC supply systems. The control technique of the inverters is based on frequency and voltage droops, which depends on the local variable measurements and does not need control interconnections. Simulation and experimental results show that the system is well represented by the small-signal model. Some root locus plots for the system are provided, which make the stability studies and design easier.

558 citations