Power System State Estimation and Renewable Energy Optimization in Smart Grids

The future smart grid will benefit from real-time monitoring, automated outage management, increased renewable energy penetration, and enhanced consumer involvement. Among the many research areas related to smart grids, this dissertation will focus on two important topics: power system state estimation using phasor measurement units (PMUs), and optimization for renewable energy integration. In the first topic, we consider power system state estimation using PMUs, when phase angle mismatch exists in the measurements. In particular, we build a measurement model that takes into account the measurement phase angle mismatch. We then propose algorithms to increase state estimation accuracy by taking into account the phase angle mismatch. Based on the proposed measurement model, we derive the posterior Cramér-Rao bound on the estimation error, and propose a method for PMU placement in the grid. Using numerical examples, we show that by considering the phase angle mismatch in the measurements, the estimation accuracy can be significantly improved compared with the traditional weighted least-squares estimator or Kalman filtering. We also show that using the proposed PMU placement strategy can increase the estimation accuracy by placing a limited number of PMUs in proper locations. In the second topic, we consider optimization for renewable energy integration in smart grids. We first consider a scenario where individual energy users own on-site renewable generators, and can both purchase and sell electricity to the main grid. Under this setup, we develop a method for parallel load scheduling of different energy users, with the goal of reducing the overall cost to energy users as well as to energy providers. The goal is achieved by finding the optimal load schedule of each individual energy user in a parallel distributed manner, to flatten the overall load of all the energy users. We then consider the case of a micro-grid, or an isolated grid, with a large penetration of renewable energy. In this case, we jointly optimize the energy storage and renewable generator capacity, in order to ensure an uninterrupted power supply with minimum costs. To handle the large dimensionality of the problem due to large historical datasets used, we reformulate the original optimization problem as a consensus problem, and use the alternating direction method of multipliers to solve for the optimal solution in a distributed manner

Distribution System Disturbance Analysis and Outage Management Using Hybrid Data-Driven and Physics-Based Approaches

Securing cyber-power distribution systems (DS) against malicious events is critical with the integration of distributed energy resources (DERs), supporting automation and increasing vulnerabilities. Situational awareness utilizing power data (e.g., data from distribution phasor measurement units (D-PMUs)) and cyber data (e.g., network packets data) is the main focus of this dissertation by means of which, an opportunity for real-time monitoring and decision-making is provided. To further improve the DS’s reliable and resilient operation, in this Ph.D. work, the aim has been put towards the development of an automated tool consisting of multiple modules to precisely investigate any type of data anomalies, followed by root cause finding. For this purpose, a data aggregation scheme is developed to synchronize the resolution and time stamp of multiple metering sources throughout the DS, using an enhancement of the conventional Kalman Filter, named Ensemble Extended Kalman Filter (EEKF). EEKF is implemented as an automated module by exploiting the real-time measurements as well as deriving the system physics. Furthermore, this dissertation develops online cyber-physical event detection and classification as well as proposal of the novel Outage Root Cause Analysis (ORCA) system. Different sections of the work have been tested on IEEE and OPAL-RT test systems as well as real-filed measurements from installed actual hardwares

Cyber-Physical Security of Power Distribution Systems

Smart grids have been witnessing continuous and rapid radical developments in the recent years. With the aim towards a more sustainable energy system, the share of distributed generation resources is ever-increasing and transforming the traditional operations of the power grids. Along with these allocated resources, an ensemble of smart measurement devices, multiple communication layers, sophisticated distributed control techniques and interconnection of system equipment represent the pillars that support the modernization of these power networks. This progress has undoubtedly enabled a more efficient and accurate operation of the power networks. At the same time, it has created vulnerability points and challenges that endanger the safety and security of the smart grids operation. The cyber-physical security of smart grids has consequently become a priority and a major challenge to ensure a reliable and safe operation of the power grid. The resiliency of the grid depends on our ability to design smart grid that can withstand threats and be able to mitigate against different attack scenarios. Cyber-physical security is currently an active area of research, and threats that target critical operation components have been classified and investigated in the literature. However, many of the research efforts have focused on the threats on the transmission level, with the intention of extending the protection, detection and mitigation strategies to the distribution level. Nevertheless, many of the performed analysis is not suitable for Power Distribution Systems (PDS) due to the inherently different characteristics of these systems. This thesis first investigates and addresses the stealthy False Data Injection (FDI) attacks on the PDS, which target the Distribution Systems Optimal Power (DSOPF) Flow and are not detectable by traditional Bad Data Detection (BDD) methods. The attacks formulation is based on the Branch Current State Estimation (BCSE), which allows separation of the phases, thus full analysis on the unbalanced three-phase system is performed. In specific, it is shown how an adversary, having access to system measurements and topology, is able to maximize the system losses. By launching FDI attacks that target the Distribution Systems State Estimation (DSSE), the adversary constructs the attack vectors that drive the objective function in the opposite direction of optimality. Optimal attack strategy effects is investigated. The results demonstrate the increase in system losses after corrupting the measurements. Second, a machine learning technique is proposed as a protection measure against the cyber-physical threats to detect the FDI attacks. Although FDI vectors cannot be detected by conventional BDD techniques, exploiting the historical data enables a more thorough analysis and a better detection advantage of anomalies in the measurements. Recurrent Neural Networks (RNN) is applied on the stream of data measurements to identify any anomaly, which represents a compromised measurement, by analyzing multiple points across the measurement vector and multiple time steps. The temporal correlation of data points is the basis of identifying attack vectors. The results of the RNN model indicate an overall strong ability to detect the stealthy attacks

Grid-Connected Renewable Energy Sources

The use of renewable energy sources (RESs) is a need of global society. This editorial, and its associated Special Issue “Grid-Connected Renewable Energy Sources”, offers a compilation of some of the recent advances in the analysis of current power systems that are composed after the high penetration of distributed generation (DG) with different RESs. The focus is on both new control configurations and on novel methodologies for the optimal placement and sizing of DG. The eleven accepted papers certainly provide a good contribution to control deployments and methodologies for the allocation and sizing of DG

Wireless Sensor Data Transport, Aggregation and Security

abstract: Wireless sensor networks (WSN) and the communication and the security therein have been gaining further prominence in the tech-industry recently, with the emergence of the so called Internet of Things (IoT). The steps from acquiring data and making a reactive decision base on the acquired sensor measurements are complex and requires careful execution of several steps. In many of these steps there are still technological gaps to fill that are due to the fact that several primitives that are desirable in a sensor network environment are bolt on the networks as application layer functionalities, rather than built in them. For several important functionalities that are at the core of IoT architectures we have developed a solution that is analyzed and discussed in the following chapters. The chain of steps from the acquisition of sensor samples until these samples reach a control center or the cloud where the data analytics are performed, starts with the acquisition of the sensor measurements at the correct time and, importantly, synchronously among all sensors deployed. This synchronization has to be network wide, including both the wired core network as well as the wireless edge devices. This thesis studies a decentralized and lightweight solution to synchronize and schedule IoT devices over wireless and wired networks adaptively, with very simple local signaling. Furthermore, measurement results have to be transported and aggregated over the same interface, requiring clever coordination among all nodes, as network resources are shared, keeping scalability and fail-safe operation in mind. Furthermore ensuring the integrity of measurements is a complicated task. On the one hand Cryptography can shield the network from outside attackers and therefore is the first step to take, but due to the volume of sensors must rely on an automated key distribution mechanism. On the other hand cryptography does not protect against exposed keys or inside attackers. One however can exploit statistical properties to detect and identify nodes that send false information and exclude these attacker nodes from the network to avoid data manipulation. Furthermore, if data is supplied by a third party, one can apply automated trust metric for each individual data source to define which data to accept and consider for mentioned statistical tests in the first place. Monitoring the cyber and physical activities of an IoT infrastructure in concert is another topic that is investigated in this thesis.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Microgrids: Planning, Protection and Control

This Special Issue will include papers related to the planning, protection, and control of smart grids and microgrids, and their applications in the industry, transportation, water, waste, and urban and residential infrastructures. Authors are encouraged to present their latest research; reviews on topics including methods, approaches, systems, and technology; and interfaces to other domains such as big data, cybersecurity, human–machine, sustainability, and smart cities. The planning side of microgrids might include technology selection, scheduling, interconnected microgrids, and their integration with regional energy infrastructures. The protection side of microgrids might include topics related to protection strategies, risk management, protection technologies, abnormal scenario assessments, equipment and system protection layers, fault diagnosis, validation and verification, and intelligent safety systems. The control side of smart grids and microgrids might include control strategies, intelligent control algorithms and systems, control architectures, technologies, embedded systems, monitoring, and deployment and implementation

Sparsity and Coordination Constraints on Stealth Data Injection Attacks

In this thesis, data injection attacks (DIAs) to smart grid within Bayesian framework is studied from two perspectives: centralized and decentralized systems. The fundamental limits of the data injection attacks are characterized by the information measures. Specifically, two metrics, mutual information and the Kullback-Leibler (KL) divergence, quantifies the disruption caused by the attacks and the corresponding stealthiness, respectively. From the perspective of centralized system, a unique attacker constructs the attacks that jointly minimize the mutual information acquired from the measurements about the state variables and the KL divergence between the distribution of measurements with and without attacks. One of the main contributions in the centralized attack construction is the sparsity constraints. Two scenarios where the attacks between different locations are independent and correlated are studied, respectively. In independent attacks, the challenge of the combinatorial character of identifying the support of the sparse attack vector is circumvented by obtaining the closed-form solution to single measurement attack problem followed by a greedy construction that leverages the insight distilled. In correlated attacks, the challenge is tackled by incorporating an additional measurement that yields sequential sensor selection problem. The sequential procedure allows the attacker to identify the additional sensor first and character the corresponding covariances between the additional measurement and the compromised measurements. Following the studies on sparse attacks, a novel metric that describes the vulnerability of the measurements on smart grids to data integrity attacks is proposed. The new metric, coined vulnerability index (VuIx), leverages information theoretic measures to assess the attack effect on the fundamental limits of the disruption and detection tradeoff. The result of computing the VuIx of the measurements in the system yields an ordering of the measurements vulnerability based on the level of the exposure to data integrity attacks. The assessment on the measurements vulnerability of IEEE test systems observes that power injection measurements are overwhelmingly more vulnerable to data integrity attacks than power flow measurements. From the perspective of decentralized system, the attack constructions are determined by a group of attackers in a cooperative manner. The interaction between the attackers is formulated as a game with a normal form. The uniqueness of the Nash Equilibrium (NE) is characterized in different games where the attackers have different objectives. Closed-form expression for the best response of the attackers in different games are obtained and followed by best response dynamics that leads to the NEs. The sparsity constraint is considered in decentralized system where the attackers have limited access to sensors. The attack construction with sparsity constraints in decentralized system is also formulated as a game with a normal form. The uniqueness of the NE and the closed-form expression for the best response are obtained

Advances and Technologies in High Voltage Power Systems Operation, Control, Protection and Security

The electrical demands in several countries around the world are increasing due to the huge energy requirements of prosperous economies and the human activities of modern life. In order to economically transfer electrical powers from the generation side to the demand side, these powers need to be transferred at high-voltage levels through suitable transmission systems and power substations. To this end, high-voltage transmission systems and power substations are in demand. Actually, they are at the heart of interconnected power systems, in which any faults might lead to unsuitable consequences, abnormal operation situations, security issues, and even power cuts and blackouts. In order to cope with the ever-increasing operation and control complexity and security in interconnected high-voltage power systems, new architectures, concepts, algorithms, and procedures are essential. This book aims to encourage researchers to address the technical issues and research gaps in high-voltage transmission systems and power substations in modern energy systems