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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. [ABSTRACT FROM AUTHOR]

Power buffers can help improve the inertia in DC microgrids and supply the additional power demand during short load transients. This article investigates distributed event‐triggered control of power buffers over an unreliable network, subject to packet losses and transmission delays. For each power buffer, a distributed event‐triggered control law regulates the input impedance while altering its stored energy. Moreover, a dynamic event‐triggered communication mechanism determines the time sequence of control updates and data transmissions among power buffers. An appealing feature of this mechanism is a designable positive minimum inter‐event time despite packet losses and transmission delays. The closed‐loop system is shown to be exponentially stable. Controller/hardware‐in‐the‐loop studies validate the theoretical findings. [ABSTRACT FROM AUTHOR]

Chondroitin sulphate is a sulphated glycosaminoglycan biopolymer composed over 100 individual sugars. Chondroitin sulphate nanoparticles (NPs) loaded with catechin were prepared by an ionic gelation method using AlCl3 and optimised for polymer and cross‐linking agent concentration, curing time and stirring speed. Zeta potential, particle size, loading efficiency, and release efficiency over 24 h (RE24 %) were evaluated. The surface morphology of NPs was investigated by scanning electron microscopy and their thermal behaviour by differential scanning calorimetric. Antioxidant effect of NPs was determined by chelating activity of iron ions. The cell viability of mesenchymal stem cells was determined by 3‐[4, 5‐dimethylthiazol‐2‐yl]‐2, 5‐diphenyl tetrazolium bromide assay and the calcification of osteoblasts was studied by Alizarin red staining. The optimised NPs showed particle size of 176 nm, zeta potential of −20.8 mV, loading efficiency of 93.3% and RE24 % of 80.6%. The chatechin loaded chondroitin sulphate NPs showed 70‐fold more antioxidant activity, 3‐fold proliferation effect and higher calcium precipitation in osteoblasts than free catechin. [ABSTRACT FROM AUTHOR]

This study investigates the bipartite output containment control of general linear heterogeneous multi‐agent systems on signed communication networks with antagonistic interactions, modelled as negative weights on the digraph. The authors first formulate a new control problem referred to as the bipartite output containment. This control paradigm aims to make each follower's output converge to a dynamic convex hull spanned by the outputs and the sign‐inverted outputs of multiple leaders. Second, the authors prove that the bipartite output containment problem can be solved by making some suitably defined signed output containment errors go to zero asymptotically. Then, the authors construct three different control protocols, using full‐state feedback, static output‐feedback, and dynamic output‐feedback designs. These control protocols are based on a distributed feed‐forward approach, which requires a feedback gain to make the closed‐loop system matrix stable, and a feed‐forward gain to drive trajectories of the closed‐loop system toward a subspace that renders the regulated signed output containment errors zero. Numerical simulations are performed to validate the proposed control protocols. [ABSTRACT FROM AUTHOR]

In this study, a unified distributed static output-feedback (OPFB) control protocol is presented for multi-agent systems. The proposed approach is unified in the sense that it is applicable to both homogeneous and heterogeneous multi-agent systems. Despite its importance, distributed OPFB control design is not considered for heterogeneous systems in the literature. Moreover, as will be shown, existing static OPFB controllers for homogeneous systems are vulnerable to attacks on sensors and actuators. More precisely, it is shown that a compromised agent can make an intact agent turn away from the leader if there is a directed path of any length from the compromised agent to the intact agent. To overcome these shortcomings, a distributed OPFB controller is presented which is (i) applicable to both homogeneous and heterogeneous systems, and (ii) is resilient against attacks on sensors and actuators. The proposed framework prevents attacks on sensors and actuators from propagating across the network and, thus, guarantees synchronisation of intact agents to the leader. To further improve the resiliency and guarantee synchronisation of even compromised agents, a disturbance compensator is designed. A significant advantage of this approach is that no assumption on topological connectivity and the number of agents under attack is required. [ABSTRACT FROM AUTHOR]

In this study, a unified distributed static output‐feedback (OPFB) control protocol is presented for multi‐agent systems. The proposed approach is unified in the sense that it is applicable to both homogeneous and heterogeneous multi‐agent systems. Despite its importance, distributed OPFB control design is not considered for heterogeneous systems in the literature. Moreover, as will be shown, existing static OPFB controllers for homogeneous systems are vulnerable to attacks on sensors and actuators. More precisely, it is shown that a compromised agent can make an intact agent turn away from the leader if there is a directed path of any length from the compromised agent to the intact agent. To overcome these shortcomings, a distributed OPFB controller is presented which is (i) applicable to both homogeneous and heterogeneous systems, and (ii) is resilient against attacks on sensors and actuators. The proposed framework prevents attacks on sensors and actuators from propagating across the network and, thus, guarantees synchronisation of intact agents to the leader. To further improve the resiliency and guarantee synchronisation of even compromised agents, a disturbance compensator is designed. A significant advantage of this approach is that no assumption on topological connectivity and the number of agents under attack is required. [ABSTRACT FROM AUTHOR]