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1. A New Communication-less Harmonic-based Protection Architecture for Meshed Microgrids

   https://doi.org/10.1109/ECCE.2018.8557587  

   Beheshtaein, Siavash ; Cuzner, Robert ; Benigni, Andrea ; Savaghebi, Mehdi ; Guerrero, Josep M. ( September 2018 , 2018 IEEE Energy Conversion Congress and Exposition (ECCE))

   This paper presents a novel noncommunication protection architecture based on utilizing the selected Distributed Generators (DGs) which provide high-frequency harmonics for harmonic-based overcurrent relays to detect and isolate three-phase faults in meshed microgrids. The most prominent features of this structure include limited number of DGs required to inject harmonics, no need for using centralized communication system, and the fault can be detected and located in all conditions such as load disconnection/connection and DG disconnection/connection. The optimum Time Dial Settings (TDSs) of these relays are obtained by solving a coordination problem with Particle Swarm Optimization (PSO) algorithm. Real-time results are produced using OPAL-RT to show the effectiveness of the proposed method for two different locations of faults in a meshed microgrid. 

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2. Asynchronous Periodic Distributed Event-Triggered Voltage and Frequency Control of Microgrids

   https://doi.org/10.1109/tpwrs.2021.3059158  

   Mohammadi, Keywan ; Azizi, Elnaz ; Choi, Jeewon ; Hamidi Beheshti, Mohammad Taghi ; Bidram, Ali ; Bolouki, Sadegh ( February 2021 , IEEE Transactions on Power Systems)

   null (Ed.)

   In this paper, we introduce a distributed secondary voltage and frequency control scheme for an islanded ac microgrid under event-triggered communication. An integral type event-triggered mechanism is proposed by which each distributed generator (DG) periodically checks its triggering condition and determines whether to update its control inputs and broadcast its states to neighboring DGs. In contrast to existing event-triggered strategies on secondary control of microgrids, the proposed event-triggered mechanism is able to handle the consensus problem in case of asynchronous communication. Under the proposed sampled-data based event-triggered mechanism, DGs do not need to be synchronized to a common clock and each individual DG checks its triggering condition periodically, relying on its own clock. Furthermore, the proposed method efficiently reduces communication rate. We provide sufficient conditions under which microgrid's frequency and a critical bus voltage asymptotically converge to the nominal frequency and voltage, respectively. Finally, effectiveness of our proposed method is verified by testing different scenarios on an islanded ac microgrid benchmark in the MATLAB/Simulink environment as well as a hardware-in-the-loop (HIL) platform, where the physical system is modeled in the Opal-RT and the cyber system is realized in Raspberry Pis. 

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3. A Modified Secondary-Control Based Fault Current Limiter for Four-Wire Three Phase DGs

   https://doi.org/10.1109/TIE.2018.2851970  

   Beheshtaein, Siavash ; Savaghebi, Mehdi ; Cuzner, Rob ; Golestan, Saeed ; Guerrero, Josep M. ( July 2018 , IEEE Transactions on Industrial Electronics)

   Fault Current Limiters (FCLs) are one of the main solutions to upcoming challenges in microgrid protection. Regarding the high penetration of distributed generations (DGs) in future power system, designing cheap and effective FCL is a necessity. The present study addresses this issue by proposing an embedded FCL operating based on modifying the secondary control of four-wire DG. As this method is presented for a four-wire system, besides very low implementing cost, it has independency and flexibility to only limit the current of DG faulted phase. This study also provides real-time simulation results by OPAL-RT to compare the proposed method with a virtual-impedance-based FCL to validate its effectiveness. Finally, experimental results are presented to validate the effectiveness of the proposed FCL. 

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4. Droop-Free Distributed Control of DC Microgrids with Voltage Profile Guarantees and Relaxed Current Sharing

   https://doi.org/10.1109/ISGTEurope52324.2021.9640069  

   Mohiuddin, Sheik M. ; Qi, Junjian ( October 2021 , 2021 IEEE PES Innovative Smart Grid Technologies Europe (ISGT Europe))

   This paper presents a droop-free distributed secondary control for DC microgrids with admissible voltage profile guarantees. The control objectives are achieved through an average voltage regulator, voltage variance regulator, and a relaxed current sharing regulator. Regulations of the global average voltage to the microgrid rated voltage is ensured by the average voltage regulator and regulations of the global voltage variance to a predetermined reference is enabled by the voltage variance regulator. In order to achieve the objectives of voltage regulation, the current sharing from one of the DGs which may be owned by the microgrid community is relaxed. The global dynamic model of the DC microgrid with the proposed control is derived. Besides, steady-state analysis is performed to show that all objectives can be achieved. Finally, simulations on a 4-DG DC microgrid test system are performed to validate the efficacy of the proposed control. 

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5. An unsupervised cyberattack detection scheme for AC microgrids using Gaussian process regression and one‐class support vector machine anomaly detection

   https://doi.org/10.1049/rpg2.12753  

   Choi, Jeewon ; Roshanzadeh, Behshad ; Martínez‐Ramón, Manel ; Bidram, Ali ( May 2023 , IET Renewable Power Generation)

   This paper addresses the cybersecurity of hierarchical control of AC microgrids with distributed secondary control. The false data injection (FDI) cyberattack is assumed to alter the operating frequency of inverter‐based distributed generators (DGs) in an islanded microgrid. For the microgrids consisting of the grid‐forming inverters with the secondary control operating in a distributed manner, the attack on one DG deteriorates not only the corresponding DG but also the other DGs that receive the corrupted information via the distributed communication network. To this end, an FDI attack detection algorithm based on a combination of Gaussian process regression and one‐class support vector machine (OC‐SVM) anomaly detection is introduced. This algorithm is unsupervised in the sense that it does not require labelled abnormal data for training which is difficult to collect. The Gaussian process model predicts the response of the DG, and its prediction error and estimated variances provide input to an OC‐SVM anomaly detector. This algorithm returns enhanced detection performance than the standalone OC‐SVM. The proposed cyberattack detector is trained and tested with the data collected from a 4 DG microgrid test model and is validated in both simulation and hardware‐in‐the‐loop testbeds.

    

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