Karen L. Butler-Purry

Towards a Framework for Cyber Attack Impact Analysis of the Electric Smart Grid

This paper presents a framework for cyber attack impact analysis of a smart grid. We focus on the model synthesis stage in which both cyber and physical grid entity relationships are modeled as directed graphs. Each node of the graph has associated state information that is governed by dynamical system equations that model the physics of the interaction (for electrical grid components) or functionality (for cyber grid elements). We illustrate how cause-effect relationships can be conveniently expressed for both analysis and extension to large-scale smart grid systems.

Characterization of transients in transformers using discrete wavelet transforms

This paper presents the characterization of transients resulting from faults in transformers using discrete wavelet transform (DWT). This characterization will aid in the development of an automatic detection method for internal incipient faults in the transformers. The detection method can provide information to predict failures ahead of time so that the necessary corrective actions are taken to prevent outages and reduce down times. The analyzed data are obtained from simulations and experiments for different normal and abnormal operating cases such as external faults, internal short circuit faults, magnetizing inrush, and internal incipient faults. The simulation method and experiment setup are discussed. The experiments and simulations are conducted on a single-phase transformer as an example case. The results of applying the DWT are discussed.

Towards modelling the impact of cyber attacks on a smart grid

This paper provides an introduction to cyber attack impact analysis in the smart grid and highlights existing research in the field. We present an impact analysis framework where we focus on the model synthesis stage where both cyber and physical grid entity relationships are modelled as directed graphs. Each node of the graph has associated state information that is governed by dynamical system equations that model the physics of the interaction (for electrical grid components) or functionality (for cyber grid elements). We illustrate how cause-effect relationships can be conveniently expressed for both analysis and extension to large-scale smart grid systems.

Self-healing reconfiguration for restoration of naval shipboard power systems

Naval shipboard power systems form a critical component of the U.S. defense infrastructure. When there is a fault in a shipboard power system either due to battle damage or material casualty, it is important to quickly isolate the fault and restore supply to as many loads as possible. This paper presents an automated self-healing strategy for reconfiguration for service restoration in naval shipboard power systems. The proposed method is illustrated on a system developed based on a typical surface combatant ship.

Potential Power Quality Benefits of Electric Vehicles

Electric vehicles (EVs) are likely to have a continued presence in the light-vehicle market in the next few decades. As a result, EV charging will put an extra burden on the distribution grid and adjustments need to be made in some cases. On the other hand, EVs have the potential to support the grid as well. This paper presents a single-phase bidirectional charger topology which pairs up a photovoltaic (PV) source with an EV charger resulting in production cost reduction. The presented topology is then used for vehicle-to-grid (V2G) services. The main focus of this paper is on power quality services which only slightly discharge the battery. Among these services, it studies the possibility of local reactive injection of EVs connected to the grid through a single-phase charger to compensate for voltage drops caused by motor startup or inductive loads. It also studies the possibility of active power injection of EVs for short time periods during PV transients in cloudy weather to keep the system stable. It also studies the potential of EVs to help during low voltage ride-through of the PV sources. The studies are performed using Simulink simulations and a real-time implementation in Real Time Digital Simulator (RTDS). The results demonstrate the effectiveness of power quality V2G services with small wear on the EV battery.

Impact of Distributed Generation on the IEEE 34 Node Radial Test Feeder with Overcurrent Protection

The use of distributed generation (DG) in power systems has many possible benefits, but also presents many challenges. Notable among these challenges is the effect DG can have on overcurrent protection. This paper contains results pertinent to the addition of DG to the IEEE 34 node test feeder. After an overcurrent protection scheme was implemented for the benchmark system, DG of various sizes was added at specific locations. The impact of these generators was evaluated in terms of steady state normal and short circuit currents as well as protection coordination. In the studies performed so far, generally DG did not adversely affect protection selectivity and coordination for penetration levels of 20% of the original feeder load, but there were some problematic situations. The overcurrent protection must be modified so that the circuit remains correctly protected for specific DG cases.

A Framework for Modeling Cyber-Physical Switching Attacks in Smart Grid

Security issues in cyber-physical systems are of paramount importance due to the often safety-critical nature of its associated applications. A first step in understanding how to protect such systems requires an understanding of emergent weaknesses, in part, due to the cyber-physical coupling. In this paper, we present a framework that models a class of cyber-physical switching vulnerabilities in smart grid systems. Variable structure system theory is employed to effectively characterize the cyber-physical interaction of the smart grid and demonstrate how existence of the switching vulnerability is dependent on the local structure of the power grid. We identify and demonstrate how through successful cyber intrusion and local knowledge of the grid an opponent can compute and apply a coordinated switching sequence to a circuit breaker to disrupt operation within a short interval of time. We illustrate the utility of the attack approach empirically on the Western Electricity Coordinating Council three-machine, nine-bus system under both model error and partial state information.

Multi-Agent System-Based Real-Time Load Management for All-Electric Ship Power Systems in DC Zone Level

All-electric ship power systems have finite generation and include a large portion of dynamic loads and nonlinear loads relative to the total power capacity. Therefore, the load demand and power generation of the system should be matched in real-time. In this paper, a novel multi-agent system-based real-time load management technique is proposed to optimally determine the switch status of loads in DC zones while satisfying the operating constraints of the system in real-time. The multi-agent system cooperative control protocol is developed based on a proposed reduced-order agent model and artificial potential function of the multi-agent system, which aims to maximize the energized loads in the all-electric ship power system. The cooperative controller aims to cooperatively achieve the group objectives that are difficult to reach by centralized controller. Further, simulation results verify the viability and performance of the proposed technique in PSCAD/EMTDC software.

Shipboard power restored for active duty

Network reconfiguration for restoration in a military shipboard power system is a very important task that is performed in order to restore loads as a result of battle damage or system faults. This article features an expert-system-based reconfiguration methodology for load restoration in shipboard power systems. The power system considered in the present study is based on the layout profile of a US surface combatant ship. The methodology developed will determine whether the loads that lost supply are restorable. When considering loads, it gives precedence to high priority loads. It also determines if there is any violation of current constraints of any cables and voltage constraints at load nodes. If the load is restorable, as suggested by an expert system, and there is no violation of any constraints, then the load is said to be restorable and the operation sequence required in restoring that load would be given as the output. A CAD drawing of the power system and a database of the system information has been developed using a geographic information system (GIS). A software tool incorporating failure assessment and expert system restoration methodology was developed using Visual C++, Multilogic Exsys Developer, Alternate Transients Program (ATP), and Microsoft Access. Microstation has been used for GIS. Various fault cases were designed, and the developed tool was used to run them and perform expert system restoration.

Dynamic Model Predictive-Based Energy Management of DG Integrated Distribution Systems

This paper presents a new dynamic control strategy to control active and reactive power in distributed-generation integrated distribution systems. The distribution system comprises several microgrids that have a local energy-management system. The proposed method improves voltage and frequency profile in the distribution system by applying control action ahead of time. Moreover, the proposed method can operate with minimal topology information of the microgrid as it directly balances generation and consumption of power in the microgrid. Another advantage of the proposed method is that it can use fast and expensive sources, such as gas turbine generators, to balance power during transients and let slower and cheaper generators gradually take over after the transients are damped out. The proposed method can be implemented online. Therefore, it can efficiently use the time-variant reactive capabilities of the DGs to compensate reactive power needs of the system.