scispace - formally typeset

Journal ArticleDOI

Hierarchical control of droop-controlled DC and AC microgrids — a general approach towards standardization

01 Nov 2009-Vol. 58, Iss: 1, pp 158-172

TL;DR: The hierarchical control derived from ISA-95 and electrical dispatching standards to endow smartness and flexibility to MGs is presented and results are provided to show the feasibility of the proposed approach.
Abstract: DC and AC Microgrids are key elements to integrate renewable and distributed energy resources as well as distributed energy storage systems. In the last years, efforts toward the standardization of these Microgrids have been made. In this sense, this paper present the hierarchical control derived from ISA-95 and electrical dispatching standards to endow smartness and flexibility to microgrids. The hierarchical control proposed consist of three levels: i) the primary control is based on the droop method, including an output impedance virtual loop; ii) the secondary control allows restoring the deviations produced by the primary control; and iii) the tertiary control manage the power flow between the microgrid and the external electrical distribution system. Results from a hierarchical-controlled microgrid are provided to show the feasibility of the proposed approach.
Topics: Microgrid (60%), Voltage droop (54%), AC power (52%), Distributed generation (52%)
Citations
More filters

Journal ArticleDOI
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.

1,923 citations


Cites background from "Hierarchical control of droop-contr..."

  • ...controlling the voltage and frequency of the ac waveforms provided to the microgrid in stand-alone mode [59], [60] and gridsupporting inverters will contribute to guarantee a proper voltage profile along the microgrid extension....

    [...]

  • ...Microgrid power converters can competently participate in regulating the grid voltage profile, mainly in LV grids, by means of controlling the active and reactive power delivery through droop control algorithms [47], [60], [70]....

    [...]


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.

1,884 citations


Cites background from "Hierarchical control of droop-contr..."

  • ...A hierarchical control scheme is proposed in [50] to improve the flexibility and expansibility of droop-based microgrids....

    [...]

  • ...gent performance requirements [50]–[53]....

    [...]

  • ...However, the conventional droop control method has several disadvantages [50], [78], [80], [81]: • Poor transient performance or instability issues due to the use of average values of active and reactive power over a cycle....

    [...]


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.

1,459 citations


Cites background from "Hierarchical control of droop-contr..."

  • ...This three-level hierarchical control is organized as follows [33]....

    [...]


Journal ArticleDOI
Ali Bidram1, Ali Davoudi1Institutions (1)
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.

1,010 citations


Cites background from "Hierarchical control of droop-contr..."

  • ...Thus, (3) is not valid for microgrid applications [12], [45]....

    [...]

  • ...Block diagram of the secondary and tertiary controls [12]....

    [...]

  • ...Then, the error signals are processed by individual controllers as in (52); the resulting signals ( and ) are sent to the primary controller of the DER to compensate for the frequency and voltage deviations [12]...

    [...]

  • ...facilitates an economically optimal operation [12], [13]....

    [...]

  • ...where , and are the controllers parameters [12]....

    [...]


Journal ArticleDOI
Abstract: This paper presents a review of control strategies, stability analysis, and stabilization techniques for dc microgrids (MGs). Overall control is systematically classified into local and coordinated control levels according to respective functionalities in each level. As opposed to local control, which relies only on local measurements, some line of communication between units needs to be made available in order to achieve the coordinated control. Depending on the communication method, three basic coordinated control strategies can be distinguished, i.e., decentralized, centralized, and distributed control. Decentralized control can be regarded as an extension of the local control since it is also based exclusively on local measurements. In contrast, centralized and distributed control strategies rely on digital communication technologies. A number of approaches using these three coordinated control strategies to achieve various control objectives are reviewed in this paper. Moreover, properties of dc MG dynamics and stability are discussed. This paper illustrates that tightly regulated point-of-load converters tend to reduce the stability margins of the system since they introduce negative impedances, which can potentially oscillate with lightly damped power supply input filters. It is also demonstrated that how the stability of the whole system is defined by the relationship of the source and load impedances, referred to as the minor loop gain. Several prominent specifications for the minor loop gain are reviewed. Finally, a number of active stabilization techniques are presented.

822 citations


Cites background or methods from "Hierarchical control of droop-contr..."

  • ...either output power or output current can be selected as the feedback signal in droop control [3], [29]....

    [...]

  • ...1) Decentralized control: DCLs do not exist and power lines are used as the only channel of communication....

    [...]

  • ...MGs can operate autonomously or be grid-connected, and depending on the type of voltage in the point of common coupling (PCC), ac, and dc MGs can be distinguished [3]....

    [...]

  • ...Some of the functionalities that can be accomplished by using DCLs include secondary/tertiary control, real-time optimization, unit commitment, and internal operating mode changing (see Fig....

    [...]

  • ...the conventional approach uses a centralized controller which collects information from all units via low-bandwidth DCLs [3], a very active field of research is focused on resolution of these problems via distributed control1 [22], [23]....

    [...]


References
More filters

Book
01 Jan 1994-
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.

13,462 citations


Journal ArticleDOI
Hassan Farhangi1Institutions (1)
Abstract: Exciting yet challenging times lie ahead. The electrical power industry is undergoing rapid change. The rising cost of energy, the mass electrification of everyday life, and climate change are the major drivers that will determine the speed at which such transformations will occur. Regardless of how quickly various utilities embrace smart grid concepts, technologies, and systems, they all agree onthe inevitability of this massive transformation. It is a move that will not only affect their business processes but also their organization and technologies.

2,695 citations


"Hierarchical control of droop-contr..." refers background in this paper

  • ...DC and ac MGs have been proposed for different applications, and hybrid solutions have been developed [1]–[12]....

    [...]


Journal ArticleDOI
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.

2,118 citations


Journal ArticleDOI
28 Sep 1991-
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. >

1,369 citations


Journal ArticleDOI
TL;DR: This paper deals with the design of the output impedance of uninterruptible power system (UPS) inverters with parallel-connection capability, and proposes novel control loops to achieve both stable output impedance and proper power balance.
Abstract: This paper deals with the design of the output impedance of uninterruptible power system (UPS) inverters with parallel-connection capability. In order to avoid the need for any communication among modules, the power-sharing control loops are based on the P/Q droop method. Since in these systems the power-sharing accuracy is highly sensitive to the inverters output impedance, novel control loops to achieve both stable output impedance and proper power balance are proposed. In this sense, a novel wireless controller is designed by using three nested loops: 1) the inner loop is performed by using feedback linearization control techniques, providing a good quality output voltage waveform; 2) the intermediate loop enforces the output impedance of the inverter, achieving good harmonic power sharing while maintaining low output voltage total harmonic distortion; and 3) the outer loop calculates the output active and reactive powers and adjusts the output impedance value and the output voltage frequency during the load transients, obtaining excellent power sharing without deviations in either the frequency or the amplitude of the output voltage. Simulation and experimental results are reported from a parallel-connected UPS system sharing linear and nonlinear loads.

965 citations


"Hierarchical control of droop-contr..." refers background in this paper

  • ...Usually, ZD is designed to be bigger than Zo; in this way, the total equivalent output impedance is mainly dominated by ZD [17]....

    [...]

  • ...The primary-control level can also include the virtual outputimpedance loop in which the output voltage can be expressed as [17]...

    [...]


Performance
Metrics
No. of citations received by the Paper in previous years
YearCitations
202217
2021356
2020444
2019509
2018428
2017444