Distributed Cooperative Secondary Control for Voltage Unbalance Compensation in an Islanded Microgrid

Abstract

This paper presents a distributed cooperative control scheme for voltage unbalance compensation in an islanded microgrid (MG). By letting each distributed generator (DG) share the compensation effort cooperatively, unbalanced voltage in sensitive load bus (SLB) can be compensated. The concept of contribution level for compensation is first proposed for each local DG to indicate its compensation ability. A two-layer secondary compensation architecture consisting of communication layer and compensation layer is designed for each local DG. A totally distributed strategy involving information sharing and exchange is proposed, which is based on finite-time average consensus and newly developed graph discovery algorithm. This strategy does not require the whole system structure as a prior and can detect the structure automatically. The proposed scheme not only achieves similar voltage unbalance compensation performance to the centralized one, but also brings some advantages, such as communication fault tolerance and plug-and-play property. Case studies including communication failure, contribution level variation and DG plug-and-play are discussed and tested to validate the proposed method.

Distributed Secondary Voltage and Frequency Control for Islanded Microgrids With Uncertain Communication Links

“…T , this together with (11) and (13) give the desired objective (6). Now we conclude that if the elements of gain matrices, Γ V , Ξ V , Γ ω , and Ξ ω , are selected to satisfy condition (12), then the designed distributed discrete-time voltage and frequency controllers (3) with control inputs (8) can restore all DERs' voltage magnitudes and frequencies in a MG to their desired values as long as each of the communication digraphsĜ(A V ) andĜ(A ω ) contains a spanning directed tree.…”

“…In view of this, some DSC approaches have been proposed to achieve voltage/frequency restoration [8], [14], reactive sharing [9], [17], imbalance voltage compensation [13], etc. Specially, based on the distributed cooperative control of multi-agent systems [10], [11], a DSC method for voltage regulation was proposed [8], which relies on the feedback linearization technique with high gains.…”

“…However, high gain has a negative impact on the overall stability of MGs. Then, a DSC for voltage imbalance compensation was investigated in [13], which guarantees the achievement of voltage regulation in a finite time. To regulate the power output of a MG dynamics consisting of a large number of DERs, a pinning-based DSC scheme was then presented with uncertain communication topologies [12], which is of benefit to meet the common requirements of line switches and plug-and-play operation in MGs.…”

“…Moreover, those impacts on the stability of low-voltage MGs are more severe than that of high-voltage ones [17]- [18]. Besides, it has been recognized that the perturbations existed in the information exchanges among DERs are usually unavoidable [13], [19], [20], which inspires us to take the impacts of communication disturbances and noises on the system stability into account when we design DSC schemes for MGs.…”

MAS-Based Distributed Coordinated Control and Optimization in Microgrid and Microgrid Clusters: A Comprehensive Overview

“…The secondary control, which can be centralized [132][133][134][135][136] or decentralized [137][138][139][140][141], is used to eliminate the deviation of output voltage and frequency in the primary control. In case of an AC MG, the frequency and amplitude restoration controllers G ω and G E can be denoted as follows:…”