Biblio

With the proliferation of data in Internet-related applications, incidences of cyber security have increased manyfold. Energy management, which is one of the smart city layers, has also been experiencing cyberattacks. Furthermore, the Distributed Energy Resources (DER), which depend on different controllers to provide energy to the main physical smart grid of a smart city, is prone to cyberattacks. The increased cyber-attacks on DER systems are mainly because of its dependency on digital communication and controls as there is an increase in the number of devices owned and controlled by consumers and third parties. This paper analyzes the major cyber security and privacy challenges that might inflict, damage or compromise the DER and related controllers in smart cities. These challenges highlight that the security and privacy on the Internet of Things (IoT), big data, artificial intelligence, and smart grid, which are the building blocks of a smart city, must be addressed in the DER sector. It is observed that the security and privacy challenges in smart cities can be solved through the distributed framework, by identifying and classifying stakeholders, using appropriate model, and by incorporating fault-tolerance techniques.

Advanced Persistent Threat (APT) is a professional stealthy threat actor who uses continuous and sophisticated attack techniques which have not been well mitigated by existing defense strategies. This paper proposes an APT-style cyber-attack tested for distributed energy resources (DER) in cyber-physical environments. The proposed security testbed consists of: 1) a real-time DER simulator; 2) a real-time cyber system using real network systems and a server; and 3) penetration testing tools generating APT-style attacks as cyber events. Moreover, this paper provides a cyber kill chain model for a DER system based on a latest MITRE’s cyber kill chain model to model possible attack stages. Several real cyber-attacks are created and their impacts in a DER system are provided to validate the feasibility of the proposed security testbed for DER systems.

This paper presents a user-friendly design method for accurately sizing the distributed energy resources of a stand-alone microgrid to meet the critical load demands of a military, commercial, industrial, or residential facility when the utility power is not available. The microgrid combines renewable resources such as photovoltaics (PV) with an energy storage system to increase energy security for facilities with critical loads. The design tool's novelty includes compliance with IEEE standards 1562 and 1013 and addresses resilience, which is not taken into account in existing design methods. Several case studies, simulated with a physics-based model, validate the proposed design method. Additionally, the design and the simulations were validated by 24-hour laboratory experiments conducted on a microgrid assembled using commercial off the shelf components.

Increasing penetration of distributed energy resources (DERs) in distribution networks expands the cyberattack surface. Moreover, the widely used standard protocols for communicating DER inverters such as Modbus is more vulnerable to data-integrity attacks and denial of service (DoS) attacks because of its native clear-text packet format. This paper proposes a distributed intrusion detection system (D-IDS) architecture and algorithms for detecting anomalies on the DER Modbus communication. We devised a model-based approach to define physics-based threshold bands for analog data points and transaction-based threshold bands for both the analog and discrete data points. The proposed IDS algorithm uses the model- based approach to develop Modbus-specific IDS rule sets, which can enhance the detection accuracy of the anomalies either by data-integrity attacks or maloperation on cyber-physical DER Modbus devices. Further, the IDS algorithm autogenerates the Modbus-specific IDS rulesets in compliance with various open- source IDS rule syntax formats, such as Snort and Suricata, for seamless integration and mitigation of semantic/syntax errors in the development and production environment. We considered the IEEE 13-bus distribution grid, including DERs, as a case study. We conducted various DoS type attacks and data-integrity attacks on the hardware-in-the-loop (HIL) CPS DER testbed at ISU to evaluate the proposed D-IDS. Consequently, we computed the performance metrics such as IDS detection accuracy, IDS detection rate, and end-to-end latency. The results demonstrated that 100% detection accuracy, 100% detection rate for 60k DoS packets, 99.96% detection rate for 80k DoS packets, and 0.25 ms end-to-end latency between DERs to Control Center.

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.

A major challenge for utilities is energy theft, wherein malicious actors steal energy for financial gain. One such form of theft in the smart grid is the fraudulent amplification of energy generation measurements from DERs, such as photo-voltaics. It is important to detect this form of malicious activity, but in a way that ensures the privacy of customers. Not considering privacy aspects could result in a backlash from customers and a heavily curtailed deployment of services, for example. In this short paper, we present a novel privacy-preserving approach to the detection of manipulated DER generation measurements.

The contemporary power distribution system is facing an increase in extreme weather events, cybersecurity threats and even physical threats such as terrorism. Therefore there is a growing interest towards resiliency estimation and improvement. In this paper the resiliency enhancement strategy by means of Distributed Energy Resources and Automated Switches is presented. Resiliency scores are calculated using Analytical Hierarchy Process. The developed algorithm was validated on the modified IEEE 123 node system. It provides the most resiliency feasible network that satisfies the primary goal of serving the critical loads.

Energy Distribution Grids are considered critical infrastructure, hence the Distribution System Operators (DSOs) have developed sophisticated engineering practices to improve their resilience. Over the last years, due to the "Smart Grid" evolution, this infrastructure has become a distributed system where prosumers (the consumers who produce and share surplus energy through the grid) can plug in distributed energy resources (DERs) and manage a bi-directional flow of data and power enabled by an advanced IT and control infrastructure. This introduces new challenges, as the prosumers possess neither the skills nor the knowledge to assess the risk or secure the environment from cyber-threats. We propose a simple and usable approach based on the Reference Model of Information Assurance & Security (RMIAS), to support the prosumers in the selection of cybesecurity measures. The purpose is to reduce the risk of being directly targeted and to establish collective responsibility among prosumers as grid gatekeepers. The framework moves from a simple risk analysis based on security goals to providing guidelines for the users for adoption of adequate security countermeasures. One of the greatest advantages of the approach is that it does not constrain the user to a specific threat model.

This paper focuses on the secure integration of distributed energy resources (DERs), especially pluggable electric vehicles (EVs), with the power grid. We consider the vehicle-to-grid (V2G) system where EVs are connected to the power grid through an `aggregator' In this paper, we propose a novel Cyber-Physical Anomaly Detection Engine that monitors system behavior and detects anomalies almost instantaneously (worst case inspection time for a packet is 0.165 seconds1). This detection engine ensures that the critical power grid component (viz., aggregator) remains secure by monitoring (a) cyber messages for various state changes and data constraints along with (b) power data on the V2G cyber network using power measurements from sensors on the physical/power distribution network. Since the V2G system is time-sensitive, the anomaly detection engine also monitors the timing requirements of the protocol messages to enhance the safety of the aggregator. To the best of our knowledge, this is the first piece of work that combines (a) the EV charging/discharging protocols, the (b) cyber network and (c) power measurements from physical network to detect intrusions in the EV to power grid system.1Minimum latency on V2G network is 2 seconds.

Today's smart-grids have seen a clear rise in new ways of energy generation, transmission, and storage. This has not only introduced a huge degree of variability, but also a continual shift away from traditionally centralized generation and storage to distributed energy resources (DERs). In addition, the distributed sensors, energy generators and storage devices, and networking have led to a huge increase in attack vectors that make the grid vulnerable to a variety of attacks. The interconnection between computational and physical components through a largely open, IP-based communication network enables an attacker to cause physical damage through remote cyber-attacks or attack on software-controlled grid operations via physical- or cyber-attacks. Transactive Energy (TE) is an emerging approach for managing increasing DERs in the smart-grids through economic and control techniques. Transactive Smart-Grids use the TE approach to improve grid reliability and efficiency. However, skepticism remains in their full-scale viability for ensuring grid reliability. In addition, different TE approaches, in specific situations, can lead to very different outcomes in grid operations. In this paper, we present a comprehensive web-based platform for evaluating resilience of smart-grids against a variety of cyber- and physical-attacks and evaluating impact of various TE approaches on grid performance. We also provide several case-studies demonstrating evaluation of TE approaches as well as grid resilience against cyber and physical attacks.

Transactive energy systems (TES) are emerging as a transformative solution for the problems that distribution system operators face due to an increase in the use of distributed energy resources and rapid growth in scalability of managing active distribution system (ADS). On the one hand, these changes pose a decentralized power system control problem, requiring strategic control to maintain reliability and resiliency for the community and for the utility. On the other hand, they require robust financial markets while allowing participation from diverse prosumers. To support the computing and flexibility requirements of TES while preserving privacy and security, distributed software platforms are required. In this paper, we enable the study and analysis of security concerns by developing Transactive Energy Security Simulation Testbed (TESST), a TES testbed for simulating various cyber attacks. In this work, the testbed is used for TES simulation with centralized clearing market, highlighting weaknesses in a centralized system. Additionally, we present a blockchain enabled decentralized market solution supported by distributed computing for TES, which on one hand can alleviate some of the problems that we identify, but on the other hand, may introduce newer issues. Future study of these differing paradigms is necessary and will continue as we develop our security simulation testbed.

It has been recently proposed that the reactive power injection of distributed energy resources (DERs) can be used to regulate the voltage across the power distribution network, and simple distributed control laws have been recently developed in the literature for performing such distributed Volt/VAR control. However, enabling the reactive-power injection capability of DERs also opens the door for potential adversarial attacks. Specifically, the adversary can compromise a subset of the DERs and use their reactive power to disrupt the voltage profile across the distribution network. In this paper, we study the potential damage (in terms of the voltage disruption) of such adversarial attacks and how to mitigate the damage by controlling the allowable range of reactive power injection at each bus. Somewhat surprisingly and contrary to the intuition that the reactive power injection at legitimate buses should help mitigating the voltage disruption inflicted by the adversary, we demonstrate that an intelligent attacker can actually exploit the response of the legitimate buses to amplify the damage by two times. Such a higher level of damage can be attained even when the adversary has no information about the network topology. We then formulate an optimization problem to limit the potential damage of such adversarial attacks. Our formulation sets the range of the reactive power injection on each bus so that the damage by the adversary is minimized, subject to the constraint that the voltage mismatch (without attack) can still be maintained within a given threshold under an uncertainty set of external inputs. Numerical results demonstrate the validity of our analysis and the effectiveness of our approach to mitigate the damage caused by such attacks.

The eleven papers in this special section focus on power electronics-enabled autonomous systems. Power systems are going through a paradigm change from centralized generation to distributed generation and further onto smart grid. Millions of relatively small distributed energy resources (DER), including wind turbines, solar panels, electric vehicles and energy storage systems, and flexible loads are being integrated into power systems through power electronic converters. This imposes great challenges to the stability, scalability, reliability, security, and resiliency of future power systems. This section joins the forces of the communities of control/systems theory, power electronics, and power systems to address various emerging issues of power-electronics-enabled autonomous power systems, paving the way for large-scale deployment of DERs and flexible loads.

We study the problem of aggregator’s mechanism design for controlling the amount of active, or reactive, power provided, or consumed, by a group of distributed energy resources (DERs). The aggregator interacts with the wholesale electricity market and through some market-clearing mechanism is incentivized to provide (or consume) a certain amount of active (or reactive) power over some period of time, for which it will be compensated. The objective is for the aggregator to design a pricing strategy for incentivizing DERs to modify their active (or reactive) power consumptions (or productions) so that they collectively provide the amount that the aggregator has agreed to provide. The aggregator and DERs’ strategic decision-making process can be cast as a Stackelberg game, in which aggregator acts as the leader and the DERs are the followers. In previous work [Gharesifard et al., 2013b,a], we have introduced a framework in which each DER uses the pricing information provided by the aggregator and some estimate of the average energy that neighboring DERs can provide to compute a Nash equilibrium solution in a distributed manner. Here, we focus on the interplay between the aggregator’s decision-making process and the DERs’ decision-making process. In particular, we propose a simple feedback-based privacy-preserving pricing control strategy that allows the aggregator to coordinate the DERs so that they collectively provide the amount of active (or reactive) power agreed upon, provided that there is enough capacity available among the DERs. We provide a formal analysis of the stability of the resulting closed-loop system. We also discuss the shortcomings of the proposed pricing strategy, and propose some avenues of future work. We illustrate the proposed strategy via numerical simulations.