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1. 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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2. 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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3. Droop-Free Distributed Frequency Control of Hybrid PV-BES Microgrid with SOC Balancing and Active Power Sharing

   https://doi.org/10.1109/PESGM48719.2022.9916737  

   Mohiuddin, Sheik M. ; Yogarathnam, Amirthagunaraj ; Yue, Meng ; Qi, Junjian ( July 2022 , 2022 IEEE Power & Energy Society General Meeting (PESGM))

   In this paper, we propose a droop-free distributed frequency control for the hybrid photovoltaic and battery energy storage (PV-BES) based microgrid. A distributed state of charge (SOC) balancing regulator achieves balanced SOC among the distributed generators (DGs) with BES utilizing a distributed average SOC estimator and the power sharing regulator ensures proportional power sharing among the PV-BES based DGs. These regulators generate two frequency correction terms which are then added to the microgrid rated frequency to generate references for the lower level controllers. The performance of the proposed distributed control is validated through real-time simulations in OPAL-RT, which demonstrates the effectiveness of the proposed control in achieving frequency regulation, SOC balancing, and active power sharing in the hybrid PV-BES units under both islanded and grid-connected operation modes. 

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4. Cybersecure Distributed Voltage Control of AC Microgrids

   https://doi.org/10.1109/icps.2019.8733378  

   Bidram, Ali ; Damodaran, Lakshmisree ; Fierro, Rafael ( May 2019 , 2019 IEEE/IAS 55th Industrial and Commercial Power Systems Technical Conference (I&CPS))

   In this paper, the cybersecurity of distributed secondary voltage control of AC microgrids is addressed. A resilient approach is proposed to mitigate the negative impacts of cyberthreats on the voltage and reactive power control of Distributed Energy Resources (DERs). The proposed secondary voltage control is inspired by the resilient flocking of a mobile robot team. This approach utilizes a virtual time-varying communication graph in which the quality of the communication links is virtualized and determined based on the synchronization behavior of DERs. The utilized control protocols on DERs ensure that the connectivity of the virtual communication graph is above a specific resilience threshold. Once the resilience threshold is satisfied the Weighted Mean Subsequence Reduced (WMSR) algorithm is applied to satisfy voltage restoration in the presence of malicious adversaries. A typical microgrid test system including 6 DERs is simulated to verify the validity of proposed resilient control approach. 

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5. A Corrective Scheme to Prevent Adverse Dynamic Interaction of Grid-forming Inverters

   Muhammad F. Umar ; Mohsen Hosseinzadehtaher ; Mohammad B. Shadmand ; Hanif Livani ; Mohammed Ben-Idris ( January 2023 , Innovative Smart Grid Technologies)

   This paper proposes a control scheme that prevents the adverse dynamic interactions between the heterogeneously controlled grid-forming inverters (GFMI) in power electronics dominated grid (PEDG) towards a resilient self-driving grid. The primary controller of GFMIs in a grid cluster can vary based on their manufacturers such as virtual synchronous generation, droop control, power synchronization control, etc. Therefore, this can introduce heterogeneity among the network of GFMIs in PEDG. Resultantly, during the interconnection of GFMIs that are based on heterogenous primary controller poses various synchronization and dynamic interaction challenges in PEDG. For instance, severe fluctuations in frequency and voltage, high ROCOF, unintended reactive power circulation that poses a threat on the overall transient stability of the PEDG. Therefore, to mitigate these adverse dynamic interactions among the heterogeneously controlled GFMIs, a force enclaved homogenization (FEH) control is proposed in a supervisory level controller. This will autonomously adjust inertia coefficients of the each GFMI to have homogenous transient response and will enforce coherency among the heterogenous DGs. This will prevent the PEDG from the adverse dynamic interactions during an interconnection and load disturbance. Various case studies are presented that validates the effectiveness of the proposed FEH control. 

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