Distributed Microgrid Control Research Articles

Enhanced Power and Energy Coordination for Batteries Under the Real-Time Closed-Loop, Distributed Microgrid Control

Hierarchical controls, consisting of primary, secondary, and tertiary layers to realize different functionalities at different time scales, have been applied for microgrids to achieve the stable and economic operations. However, in islanded microgrids with pure renewables (i.e., wind, solar, and battery storage systems (BSS) only), the three layers shall interact rather tightly and frequently in order to effectively leverage limited capabilities of available resources against disturbances. To this end, this paper discusses a more responsive control framework, including the distributed schemes for individual primary, secondary, and tertiary control layers as well as the real-time closed-loop scheme for a prompt coordination of the three layers. Thus, the proposed control framework could promote real-time interaction of resources in islanded microgrids with limited communication and computation burdens. Based on this, an enhanced control module design for BSSs of different configurations is further discussed to optimally coordinate their power and energy states with improved operational stability and economics. The steady-state analysis confirms the compatibility of the designed power and energy goals in tracking optimal power and energy equilibria simultaneously, and a customized Lyapunov candidate function is used to prove the asymptotic stability of the overall control framework. The hardware-in-the-loop simulation validates efficacy of the designed control framework in promptly mitigating disturbances and effectively achieving convergence to the optimal economic equilibria.

Three-stage Defensive Framework for Distributed Microgrid Control Against Cyberattacks

With the wide integration of various distributed communication and control techniques, the cyber-physical microgrids face critical challenges raised by the emerging cyberat-tacks. This paper proposes a three-stage defensive framework for distributed microgrids against denial of service (DoS) and false data injection (FDI) attacks, including resilient control, communication network reconfiguration, and switching of local control. The resilient control in the first stage is capable of tackling simultaneous DoS and FDI attacks when the connectivity of communication network could be maintained under cyberat-tacks. The communication network reconfiguration method in the second stage and the subsequent switching of local control in the third stage based on the software-defined network (SDN) layer aim to cope with the network partitions caused by cyber-attacks. The proposed defensive framework could effectively mitigate the impacts of a wide range of simultaneous DoS and FDI attacks in microgrids without requiring the specific assumptions of attacks and prompt detections, which would not incorporate additional cyberattack risks. Extensive case studies using a 13-bus microgrid system are conducted to validate the effectiveness of the proposed three-stage defensive framework against the simultaneous DoS and FDI attacks.

Employing Interacting Qubits for Distributed Microgrid Control

To empower flexible and scalable operations, distributed control of multi-inverter microgrids, based on classical communication networks among distributed energy resources, has attracted considerable attention as it can guarantee synchronization and provide suitable remedies to the problem of improper power sharing. Notwithstanding this, resilience of the current schemes on classical communication makes microgrids vulnerable to cyber attacks. Inspired by recent revolutionary breakthroughs in quantum communication, in this paper, we devise a novel synchronization mechanism. We extend the synchronization framework utilized in distributed control algorithms to networks of quantum systems by generating pinning terms and coupling mechanism for the new synchronization rule via exploiting proper quantum jump operators and observables, and show that the quantum system will converge to a time-variant target state. Our devised quantum distributed controller (QDC) gives rise to a novel quantum communication scheme for distributed control of microgrids and enables microgrids to exploit the state-of-the-art quantum communication frameworks as communication infrastructure. Test results on two representative AC and DC networked microgrids validate the efficacy and universality of the quantum distributed control.

Push-Sum-Enabled Resilient Microgrid Control

This letter devises a distributed microgrid control allowing for time-varying networks utilizing a continuous-time push-sum algorithm. The novelty of the push-sum-based approach lies in: 1) the ability to deal with unbalanced cyber network which represents unreliable communication among distributed energy resources (DERs); 2) the capability of switching among communication networks so as to provide non-interrupted operation; and 3) resiliency against cyber attacks. Case studies verify the efficacy of the new distributed microgrid control strategy and its capability of providing communication robustness while ensuring resilient frequency regulation and active power sharing.

Agent-Based Coordinated Control of Power Electronic Converters in a Microgrid

This paper presents the implementation of an agent-based architecture suitable for the coordination of power electronic converters in stand-alone microgrids. To this end, a publish-subscribe agent architecture was utilized as a distributed microgrid control platform. Over a distributed hash table (DHT) searching overlay, the publish-subscribe architecture was identified based on a numerical analysis as a scalable agent-based technology for the distributed real-time coordination of power converters in microgrids. The developed framework was set up to deploy power-sharing distributed optimization algorithms while keeping a deterministic time period of a few tens of milliseconds for a system with tens of converters and when multiple events might happen concurrently. Several agents participate in supervisory control to regulate optimum power-sharing for the converters. To test the design, a notional shipboard system, including several converters, was used as a case study. Results of implementing the agent-based publish-subscribe control system using the Java Agent Development Framework (JADE) are presented.

Fixed-time observer-based distributed secondary voltage and frequency control of islanded AC microgrids

This paper deals with the problem of voltage and frequency control of distributed generators (DGs) in AC islanded microgrids. The main motivation of this work is to obviate the shortcomings of conventional centralized and distributed control of micro-grids by providing a better alternative control strategy with better control performance than state-of-the art approaches. A distributed secondary control protocol based on a novel fixed-time observer-based feedback control method is designed for fixed-time frequency and voltage reference tracking and disturbance rejection. Compared to the existing secondary microgrid controllers, the proposed control strategy ensures frequency and voltage reference tracking and disturbance rejection before the desired fixed-time despite the microgrid initial conditions, parameters uncertainties and the unknown disturbances. Also, the controllers design and tuning is simple, straightfor-ward and model-free.i.e, the knowledge of the microgrid parameters, topology, loads or transmission lines impedance are not needed in the design procedure. The use of distributed control approach enhances the reliability of the system by making the control system geographically distributed along with the power sources, by using the neighboring DGs informations instead of the DG’s local informations only and by cooperatively rejecting external disturbances and maintaining the frequency and the voltage at their reference values at any point of the microgrid. The efficiency of the proposed approach is verified by comparing its performance in reference tracking and its robustness to load power variations to some of the works in literature that addressed distributed secondary voltage and frequency control.

Resilient Information Architecture Platform for the Smart Grid: A Novel Open-Source Platform for Microgrid Control

Microgrids are seen as an effective way to achieve reliable, resilient, and efficient operation of the power distribution system. Core functions of the microgrid control system are defined by the IEEE Standard 2030.7; however, the algorithms that realize these functions are not standardized, and are a topic of research. Furthermore, the corresponding controller hardware, operating system, and communication system to implement these functions vary significantly from one implementation to the next. In this article, we introduce an open-source platform, resilient information architecture platform for the smart grid (RIAPS), ideally suited for implementing and deploying distributed microgrid control algorithms. RIAPS provides a design-time tool suite for development and deployment of distributed microgrid control algorithms. With support from a number of run-time platform services, developed algorithms can be easily implemented and deployed into real microgrids. To demonstrate the unique features of RIAPS, we propose and implement a distributed microgrid secondary control algorithm capable of synchronized and proportional compensation of voltage unbalance using distributed generators. Test results show the effectiveness of the proposed control and the salient features of the RIAPS platform.

A Polyhedral Approximation Framework for Convex and Robust Distributed Optimization

In this paper we consider a general problem set-up for a wide class of convex and robust distributed optimization problems in peer-to-peer networks. In this set-up convex constraint sets are distributed to the network processors who have to compute the optimizer of a linear cost function subject to the constraints. We propose a novel fully distributed algorithm, named cutting-plane consensus, to solve the problem, based on an outer polyhedral approximation of the constraint sets. Processors running the algorithm compute and exchange linear approximations of their locally feasible sets. Independently of the number of processors in the network, each processor stores only a small number of linear constraints, making the algorithm scalable to large networks. The cutting-plane consensus algorithm is presented and analyzed for the general framework. Specifically, we prove that all processors running the algorithm agree on an optimizer of the global problem, and that the algorithm is tolerant to node and link failures as long as network connectivity is preserved. Then, the cutting plane consensus algorithm is specified to three different classes of distributed optimization problems, namely (i) inequality constrained problems, (ii) robust optimization problems, and (iii) almost separable optimization problems with separable objective functions and coupling constraints. For each one of these problem classes we solve a concrete problem that can be expressed in that framework and present computational results. That is, we show how to solve: position estimation in wireless sensor networks, a distributed robust linear program and, a distributed microgrid control problem.