A Self-Organizing Strategy for Power Flow Control of Photovoltaic Generators in a Distribution Network
TL;DR: In this article, the authors developed a distributed control algorithm that will regulate the power output of multiple photovoltaic generators (PVs) in a distribution network, where the cooperative control methodology from network control theory is used to make a group of PV generators converge and operate at the same ratio of available power, which is determined by the status of the distribution network and the PV generators.
Abstract: The focus of this paper is to develop a distributed control algorithm that will regulate the power output of multiple photovoltaic generators (PVs) in a distribution network. To this end, the cooperative control methodology from network control theory is used to make a group of PV generators converge and operate at certain (or the same) ratio of available power, which is determined by the status of the distribution network and the PV generators. The proposed control only requires asynchronous information intermittently from neighboring PV generators, making a communication network among the PV units both simple and necessary. The minimum requirement on communication topologies is also prescribed for the proposed control. It is shown that the proposed analysis and design methodology has the advantages that the corresponding communication networks are local, their topology can be time varying, and their bandwidth may be limited. These features enable PV generators to have both self-organizing and adaptive coordination properties even under adverse conditions. The proposed method is simulated using the IEEE standard 34-bus distribution network.
Citations
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TL;DR: This work shows that a network of loads and DC/AC inverters equipped with power-frequency droop controllers can be cast as a Kuramoto model of phase-coupled oscillators, and proposes a distributed integral controller based on averaging algorithms, which dynamically regulates the system frequency in the presence of a time-varying load.
819 citations
Cites background from "A Self-Organizing Strategy for Powe..."
...See [26,27] for a broad overview, and [35,29,4,32] for various works....
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TL;DR: In this article, the authors proposed a distributed secondary voltage control of micro-grids based on the distributed cooperative control of multi-agent systems, where each distributed generator only requires its own information and the information of some neighbors.
Abstract: This paper proposes a secondary voltage control of microgrids based on the distributed cooperative control of multi-agent systems. The proposed secondary control is fully distributed; each distributed generator only requires its own information and the information of some neighbors. The distributed structure obviates the requirements for a central controller and complex communication network which, in turn, improves the system reliability. Input-output feedback linearization is used to convert the secondary voltage control to a linear second-order tracker synchronization problem. The control parameters can be tuned to obtain a desired response speed. The effectiveness of the proposed control methodology is verified by the simulation of a microgrid test system.
728 citations
Cites background from "A Self-Organizing Strategy for Powe..."
...Distributed cooperative control is recently introduced in power systems [19], to regulate the output power of multiple photovoltaic generators....
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...Long communication links are not desired [19]....
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TL;DR: This study proposes a secondary voltage and frequency control scheme based on the distributed cooperative control of multi-agent systems that is fully distributed such that each distributed generator only requires its own information and the information of its neighbours on the communication digraph.
Abstract: This study proposes a secondary voltage and frequency control scheme based on the distributed cooperative control of multi-agent systems. The proposed secondary control is implemented through a communication network with one-way communication links. The required communication network is modelled by a directed graph (digraph). The proposed secondary control is fully distributed such that each distributed generator only requires its own information and the information of its neighbours on the communication digraph. Thus, the requirements for a central controller and complex communication network are obviated, and the system reliability is improved. The simulation results verify the effectiveness of the proposed secondary control for a microgrid test system.
432 citations
TL;DR: In this article, the authors proposed a microgrid concept, which is a small-scale power system consisting of local generation, local loads, and energy storage systems, which provides guaranteed power quality for local loads such as hospitals, economic centers, apartments and universities.
Abstract: Existing electric power distribution networks are operating near full capacity and facing rapid changes to address environmental concerns and improve their reliability and sustainability. These concerns are satisfied through the effective integration and coordination of distributed generators (DGs), which facilitate the exploitation of renewable energy resources, including wind power, photovoltaics, and fuel cells [1]. Although DGs can be of rotating machinery type, more recently, DGs have been designed to support renewable energy resources by electronic interfacing through voltage source inverters (VSI). Each DG corresponds to one energy source, and its control inputs are given to the interface VSI [1]-[5]. The successful coordination of DGs can be realized through microgrids, which are small-scale power systems consisting of local generation, local loads, and energy storage systems. Microgrids are autonomous subsystems with dedicated control systems that provide guaranteed power quality for local loads such as hospitals, economic centers, apartments, and universities. The microgrid concept, with its local control and power quality support, allows for the scalable integration of local power resources and loads into the existing power grid and enables a high penetration of distributed generation [5]-[10].
281 citations
TL;DR: A droop-based distributed cooperative control scheme for microgrids under a switching communication network with non-uniform time-varying delays that guarantees the stability and reliability of the microgrid.
Abstract: This paper develops a droop-based distributed cooperative control scheme for microgrids under a switching communication network with non-uniform time-varying delays. We first design a pinning-based frequency/voltage controller containing a distributed voltage observer and then design a consensus-based active/reactive power controller, which are employed into the secondary control stage to generate the nominal set points used in the primary control stage for different distributed generators (DGs). By this approach, the frequencies and the weighted average value of all DGs’ voltages can be pinned to the desired values while maintaining the precise active and reactive power sharing. With the proposed scheme, each DG only needs to communicate with its neighbors intermittently, even if their communication networks are local and time-varying, and their variant delays may be non-uniform. Sufficient conditions on the requirements for the network connectivity and the delay upper bound that guarantee the stability and reliability of the microgrid are presented. The effectiveness of the proposed control scheme is verified by the simulation of a microgrid test system.
267 citations
Cites background from "A Self-Organizing Strategy for Powe..."
...In this case, the network variability [26] and communication delays [27], [28] are usually unavoidable and can not be negligible for the system stability analysis....
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...For instance, if the utilization ratio αi is desired to converge to α∗ i , then the designer can introduce the gain of ki = α ∗ α∗ i such that the transformed utilization ratio of kiαi converges to the common ratio α∗ [26]....
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References
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Book•
01 Jan 1994
TL;DR: In this article, the authors present a model for the power system stability problem in modern power systems based on Synchronous Machine Theory and Modelling, and a model representation of the synchronous machine representation in stability studies.
Abstract: Part I: Characteristics of Modern Power Systems. Introduction to the Power System Stability Problem. Part II: Synchronous Machine Theory and Modelling. Synchronous Machine Parameters. Synchronous Machine Representation in Stability Studies. AC Transmission. Power System Loads. Excitation in Stability Studies. Prime Mover and Energy Supply Systems. High-Voltage Direct-Current Transmission. Control of Active Power and Reactive Power. Part III: Small Signal Stability. Transient Stability. Voltage Stability. Subsynchronous Machine Representation in Stability Studies. AC Transmission. Power System Loads. Excitation in Stability Studies. Prime Mover and Energy Supply Systems, High-Voltage Direct-Current Transmission. Control of Active Power and Reactive Power. Part III: Small Signal Stability. Transient Stability. Voltage Stability. Subsynchronous Oscillations. Mid-Term and Long-Term Stability. Methods of Improving System Stability.
13,467 citations
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
"A Self-Organizing Strategy for Powe..." refers background in this paper
...Among the possibilities, the high-level control can be designed to be either a balanced generator in the islanding operation, or a virtual power plant for load management [20], or a smart agent for maintaining frequency or a desired voltage profile [ 1 ], [6], and so on. Relevant to this paper is the study in [21] where the power at the feeder is kept constant such that all the rest of the load demands are picked up by DGs....
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...N recent years, there has been an increasing number of distributed generators (DGs) integrated into the modern distribution network [ 1 ]–[3]....
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...On the other hand, a decentralized control mode, such as the maximum photovoltaic power tracking (MPPT), constant voltage and frequency (VF) with droop mode, or the feeder power flow control mode [ 1 ], [2], [15], [16], is useful in the distribution network if there are only a few DGs present....
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TL;DR: In this article, the authors present an overview of the key issues concerning the integration of distributed generation into electric power systems that are of most interest today and analyze the repercussions in transmission system operation and expansion that result from the connection of large amounts of DG of different energy conversion systems focusing on issues related with impacts in steady state operation.
1,317 citations
TL;DR: In this article, the authors introduce a survey of this revolutionary approach of DGs, which will change the way electric power systems operate along with their types and operating technologies, and survey the operational and economical benefits of implementing DGs in the distribution network.
966 citations
Book•
19 Feb 2009TL;DR: In this paper, a new framework based on matrix theory is proposed to analyze and design cooperative controls for a group of individual dynamical systems whose outputs are sensed by or communicated to others in an intermittent, dynamically changing, and local manner.
Abstract: In this paper, a new framework based on matrix theory is proposed to analyze and design cooperative controls for a group of individual dynamical systems whose outputs are sensed by or communicated to others in an intermittent, dynamically changing, and local manner. In the framework, sensing/communication is described mathematically by a time-varying matrix whose dimension is equal to the number of dynamical systems in the group and whose elements assume piecewise-constant and binary values. Dynamical systems are generally heterogeneous and can be transformed into a canonical form of different, arbitrary, but finite relative degrees. Utilizing a set of new results on augmentation of irreducible matrices and on lower triangulation of reducible matrices, the framework allows a designer to study how a general local-and-output-feedback cooperative control can determine group behaviors of the dynamical systems and to see how changes of sensing/communication would impact the group behaviors over time. A necessary and sufficient condition on convergence of a multiplicative sequence of reducible row-stochastic (diagonally positive) matrices is explicitly derived, and through simple choices of a gain matrix in the cooperative control law, the overall closed-loop system is shown to exhibit cooperative behaviors (such as single group behavior, multiple group behaviors, adaptive cooperative behavior for the group, and cooperative formation including individual behaviors). Examples, including formation control of nonholonomic systems in the chained form, are used to illustrate the proposed framework.
937 citations
"A Self-Organizing Strategy for Powe..." refers methods in this paper
...The above general method can be used to verify or establish the sequential completeness condition, and the details can be found in [18, 23]....
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...[18] Z....
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...The above sequential completeness condition is a very precise method to schedule local communication, and it is also the necessary and sufficient condition for any properly-designed cooperative system to converge [18, 23]....
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...This resulting control problem becomes the so-called network control problem which has systematically been studied in recent years and also successfully applied to such fields as cooperative robotic control [18, 19]....
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