Islanded AC Microgrid Research Articles

Resilient distributed secondary control for islanded AC microgrids under FDI attacks

For islanded AC microgrids under bounded and time-varying false data injection (FDI) attacks on actuators and communication links, a resilient distributed secondary control strategy is proposed to stabilize frequency and voltage at the reference values, and to achieve the optimal active power sharing. To mitigate the impact of FDI attacks on the stability of the islanded microgrid, extended-state observers are introduced to estimate the impact. Compared with the currently presented resilient distributed control strategies, which ensure the bounded stability of microgrids, the control objective that the synchronization of every distributed generator’s voltage and frequency to the reference values and the achievement of the optimal active power sharing is maintained by the proposed resilient control strategy. An example of an islanded AC microgrid is given to verify the proposed method.

Trust-Based Detection and Mitigation of Cyber Attacks in Distributed Cooperative Control of Islanded AC Microgrids

In this study, we address the challenge of detecting and mitigating cyber attacks in the distributed cooperative control of islanded AC microgrids, with a particular focus on detecting False Data Injection Attacks (FDIAs), a significant threat to the Smart Grid (SG). The SG integrates traditional power systems with communication networks, creating a complex system with numerous vulnerable links, making it a prime target for cyber attacks. These attacks can lead to the disclosure of private data, control network failures, and even blackouts. Unlike machine learning-based approaches that require extensive datasets and mathematical models dependent on accurate system modeling, our method is free from such dependencies. To enhance the microgrid’s resilience against these threats, we propose a resilient control algorithm by introducing a novel trustworthiness parameter into the traditional cooperative control algorithm. Our method evaluates the trustworthiness of distributed energy resources (DERs) based on their voltage measurements and exchanged information, using Kullback-Leibler (KL) divergence to dynamically adjust control actions. We validated our approach through simulations on both the IEEE-34 bus feeder system with eight DERs and a larger microgrid with twenty-two DERs. The results demonstrated a detection accuracy of around 100%, with millisecond range mitigation time, ensuring rapid system recovery. Additionally, our method improved system stability by up to almost 100% under attack scenarios, showcasing its effectiveness in promptly detecting attacks and maintaining system resilience. These findings highlight the potential of our approach to enhance the security and stability of microgrid systems in the face of cyber threats.

A New Composite Control Strategy for Large-Signal Stabilization of Constant Power Loads in Islanded AC Microgrids

A New Composite Control Strategy for Large-Signal Stabilization of Constant Power Loads in Islanded AC Microgrids

Privacy-preserving distributed frequency control for AC microgrids with constrained communication

Distributed control of AC microgrids is one of the most popular methods in the islanded operation mode. Whereas, most of the existing studies either do not consider the potential threat of privacy security or rely on the assumption of ideal communication networks. To this end, this paper presents a novel privacy-preserving distributed secondary frequency control strategy for the privacy protection problem of an islanded AC microgrid with constrained communication. The key contributions of this paper are threefold. (1) Different from the existing privacy-preserving approaches used in AC microgrids, a time-varying function is introduced to mask interactive information such that the frequency cannot be reconstructed by malicious attackers. (2) An event-triggered communication scheme is employed to cope with the constrained communication environment. (3) A privacy-preserving distributed event-triggered control strategy with communication delay is developed such that the frequency restoration and active power sharing of the microgrid are guaranteed. Moreover, the maximum communication delay that the proposed control can withstand is analyzed. Simulation results show the properties of the privacy preservation, the decrease of communication load, and the bounded communication delay allowed in the proposed control strategy.

A modified droop-based decentralized control strategy for accurate power sharing in a PV-based islanded AC microgrid

This paper introduces a novel droop-based decentralized control scheme to address the power-sharing challenges within a PV-fed islanded AC microgrid. This novel approach integrates both conventional (P-f/Q-V) and virtual impedance concepts to optimize and manage the precise distribution of active and reactive power among parallel operating inverters posing a significant research challenge. The conventional droop control methods encounter limitations such as voltage and frequency deviations and inaccuracies in power-sharing due to line impedance disparities. To overcome these limitations, the proposed solution integrates an enhanced virtual impedance control loop alongside the conventional control loop (P-f/Q-V). The efficacy of this approach is showcased through simulations conducted using the OPAL-RT OP4510 simulator within the MATLAB/Simulink platform. The Real-time simulation outcomes confirm the efficiency of the suggested control strategy, guaranteeing precise distribution of both active and reactive power while upholding stable voltage and frequency profiles within the system.

A Novel Observer-Centric Approach for Detecting Faults in Islanded AC Microgrids With Uncertainties

A Novel Observer-Centric Approach for Detecting Faults in Islanded AC Microgrids With Uncertainties

A Resilient Control for Distributed Energy Storage Units in an Islanded AC Microgrid

A high number of charge/discharge cycles results in premature aging of Distributed Energy Storage Units (DESUs). Since classical droop control does not consider this issue and leads to MG voltage and frequency fluctuations in steady state, controls such as State of Charge (SoC) synchronization control are used to minimize DESUs number of charge/discharge cycles. However, few methods in the literature investigate frequency and voltage (f & V) restoration while ensuring a functional SoC equalization control in both charge and discharge modes. In this paper, an Adaptive Frequency Droop based on Virtual Power (AFDVP) method is proposed to achieve DESUs SoC equalization to prolong their lifespan while ensuring MG voltage and frequency regulation. In addition, AFDVP strategy ensures optimal use of second life batteries, since they are naturally less solicited due to the decrease in their capacity. DESUs SoC equalization is achieved thanks to virtual active powers using a PI controller. A complete stability analysis is provided to choose optimal parameters for the proposed distributed control. Experimental tests are performed to check the performance of the AFDVP technique in several study cases. A comparison is also performed with a SoC equalization strategy from the literature.

SECOND ORDER SLIDING MODE CONTROL FOR ISLANDED AC MICROGRIDS WITH RENEWABLE POWER RESOURCES

Microgrids have attracted a lot of attention and are the future power systems. This paper proposes a new control scheme for islanded AC microgrid (MG) using master-slave technique. Stability and high performance are vital for islanded MG. Two second order sliding mode controls (SMCs) are designed in stationary reference frame for master and slave units to control the voltage and powers respectively. Both designed controls guarantee the convergence of considered outputs to their reference values. The proposed controls are robust, simple, chattering free and only need local measurements. The control method proposed in this paper can be easily extended to microgrids with any number of slave units and parallel connected inverters. The effectiveness of the proposed control scheme is verified through simulation results in SIMULINK/MATLAB environment and compared to feedback linearization control and a modified conventional SMC.

Controller Hardware-in-the-Loop Testbed of a Distributed Consensus Multi-Agent System Control under Deception and Disruption Cyber-Attacks

The impact of communication disturbances on microgrids (MGs) needs robust and scalable Information Communication Technology (ICT) infrastructure for efficient MG control. This work builds on advances in the Internet of Things (IoT) to provide a practical platform for testing the impact of various cyber-attacks on a distributed control scheme for a Multi-Agent System (MAS). This paper presents a Controller Hardware-in-the-Loop (CHIL) testbed to investigate the impact of various cyber-attacks and communication disruptions on MGs. A distributed consensus secondary control scheme for a MAS within an MG cyber-physical system (CPS) is proposed. The proposed cyber-physical testbed integrates a real-time islanded AC microgrid on RT-Lab, secondary controllers implemented on single-board computers, and an attacker agent on another single-board computer. Communication occurs via a UDP/IP network between OPAL-RT and controller agents, as well as between the agents. Through meticulous experimentation, the efficacy of the proposed control strategy using the developed platform is validated. Various attacks were modeled and launched including deception attacks on sensors, actuators, and their combinations, as well as disruption attacks. The ramifications of both deception and disruption cyber-attacks on system performance are analyzed.

Distributed robust control of frequency and active power-sharing ratio regulation in islanded AC microgrids

Distributed robust control of frequency and active power-sharing ratio regulation in islanded AC microgrids

Remote Multinodal Voltage Unbalance Compensation in Islanded AC Microgrids

Remote Multinodal Voltage Unbalance Compensation in Islanded AC Microgrids

Impact and Integration of Electric vehicles on renewable energy based Microgrid: Frequency profile improvement by a-SCA optimized FO-Fuzzy PSS approach

The modelling of an electric vehicle along with its integration and impact over a renewable energy based microgrid topology is well addressed in this manuscript. The frequent charging and discharging of the electric vehicle makes an oscillation over grid frequency. The performance especially frequency of an islanded AC microgrid is also affected seriously under the actions of different uncertainties like load dynamics, wind fluctuation in wind plant, solar intensity variation of PV plant etc. In order to maintain standard frequency, this research work aims to regulate the net power generation of the system in response to total demand. To monitor net generation, this work has intended a fractional order fuzzy power system stabilizer (FO-Fuzzy PSS) control scheme in several dynamic situations. The proposed FO-Fuzzy PSS control scheme acts as most potential candidate to pertain stability in system frequency in above discussed disturbances. The controller gains are tuned optimally with suggesting an advanced- Sine Cosine Algorithm (a-SCA) under different conditions. The performance of the optimal FO- Fuzzy PSS controller is compared over standard fuzzy controller and PID controller in regard to frequency regulation of microgrid system. It is observed that proposed FO-Fuzzy PSS control scheme has the credential to reduce settling time of ΔF1 (area1 microgrid frequency) by 98.60% and 250.82% over fuzzy controller & PID controller correspondingly. Further, the dynamic optimal performance of the proposed a-SCA is compared over original SCA and PSO techniques to justify its superiority.

Analysis and control of large-signal stability with storage in small scale islanded AC microgrids

The analysis of small-signal stability in AC microgrids has yielded numerous findings. However, investigating large-signal stability remains a major difficulty and has received limited attention in research. The article presents the establishment of a non-linear reduced-order model for small-scale AC microgrids with storage. The model considers the changes in converter structure that occur during large disturbances. Next, we will analyse the system’s stability under large-signal conditions and identify the underlying unstable mechanism. The impact of limitation links on system stability is significant, as they result in structural changes. The proposal of “virtual synchronous damping control” (VSD) aims to improve the stability of AC microgrids by addressing the issues caused by an unstable mechanism. The validation of the proposed analysis and control methods are demonstrated by examining relevant case studies in MATLAB/Simulink.

Distributed Secondary Frequency Control for AC Microgrids Using Load Power Forecasting Based on Artificial Neural Network

In islanded ac microgrids with heterogeneous distributed generations (DGs), secondary frequency control (SFC) can restore the frequency that deviates from the nominal level due to the primary P-f droop control. Traditionally, to realize SFC, the instantaneous frequency needs to be directly measured or estimated to produce frequency compensations, which increases system cost and complexity. In this paper, a new spatial load power forecasting for distributed secondary frequency control (SLPF-DSFC) based on artificial neural networks is proposed. Without frequency measurement, it can effectively eliminate frequency deviations and autonomously cope with various load changes by optimizing active power outputs from DGs. The distributed average and pinning protocols based on graph theory are also included. Comprehensive case studies demonstrate that the proposed SLPF-DSFC method shows superior performance over conventional SFC approaches in terms of frequency stabilization and voltage harmonics reduction during load variations, SFC startup/shutdown, as well as communication delays.

Fractional Order Controller For Power Control in AC Islanded PV Microgrid using Electric Vehicles

Background: Microgrids conquer a significant role in the evolution of distributed and modern grids from the traditional electricity system. However, microgrids with renewable energy sources connected to them often incur grid instability issues, due to the intermittent nature of these sources. Objective: This work aims to study Microgrids with Electric vehicles as a backup energy source and maintain the system’s frequency that can overcome this issue. Methods: This paper uses an autonomous control algorithm in an islanded ac microgrid to regulate the active power depending on the irradiation and load scenarios, thereby maintaining the system frequency and stability. The controller also keeps track of the battery's charge level, keeping it from overcharging or over-discharging conditions. The PI (Proportional Integral) and Fractional Order Proportional Integral (FOPI) controllers were compared, with the best controller utilized for system simulations. Results: Simulations are presented with MATLAB/Simulink for an Islanded Photo Voltaic AC microgrid system with the electric vehicle's battery connected to it as a source of backup energy. The system's effect is exhibited under varied irradiations and load levels, and the findings demonstrate the control algorithm's adaptability. Conclusion: This work attempts to discover the capability of the control technique to maintaining the stability of an AC islanded microgrid system under diverse irradiation and load situations, thereby maintaining the system's frequency and the State of Charge (SoC) of the battery of an electric vehicle under specified levels.

Improved Droop Controller for Distributed Generation Inverters in Islanded AC Microgrids

Stability in island microgrids is crucial for efficient power distribution among distributed generation (DG) inverters. Conventional droop control, while effective in power sharing, poses challenges with voltage stability due to frequency and voltage deviations resulting from changing load power. Such deviations can lead to system instability, impacting power flows within each inverter. Therefore, this paper introduces a proposed droop control approach that effectively tackles the issues of frequency and voltage deviation, aiming to restore them to their rated values and significantly enhance transient response in power flows among inverters. The novel method incorporates integrating controllers for frequency and voltage, coupled with the utilization of virtual impedances. These virtual impedances, comprising virtual positive/negative-sequence impedance (VPI/VNI) loops at the fundamental frequency and a virtual harmonic impedance (VHI) loop at harmonic frequencies, play a crucial role in overcoming mismatched line impedance conditions, ultimately improving overall system performance. Simulation results demonstrate the effectiveness and outstanding performance of inverters operating in parallel within an island AC microgrid. The proposed approach ensures stable voltage and frequency levels in all operational states, regardless of varying load conditions.

Distributed Secondary Resilient Controller Design for Islanded AC Microgrids Under Stealthy Frequency Sensor Attack

Distributed Secondary Resilient Controller Design for Islanded AC Microgrids Under Stealthy Frequency Sensor Attack

A Unified Cyber Attack Detection and Mitigation Framework for an Islanded AC Microgrid

A Unified Cyber Attack Detection and Mitigation Framework for an Islanded AC Microgrid

Multiagent-Based Nonlinear Generalized Minimum Variance Control for Islanded AC Microgrids

Voltage regulation, frequency restoration, and reactive/active power sharing are the crucial tasks of the microgrid's secondary control, especially in the islanding operating mode. Because sensors and communication links in a microgrid are subject to noise, it is of paramount value to design a noise-resilient secondary voltage and frequency control. This paper proposes a minimum variance control approach for the secondary control of AC microgrids that can effectively perform noise attenuation, voltage/frequency restoration, and reactive/active power sharing. To this end, the nonlinear generalized minimum variance (NGMV) control approach is introduced to the islanded microgrid's secondary control system. The effectiveness of the proposed control approach is verified by simulating two microgrid test systems in MATLAB.

Auxiliary Network-Enabled Attack Detection and Resilient Control of Islanded AC Microgrid

Auxiliary Network-Enabled Attack Detection and Resilient Control of Islanded AC Microgrid