Robust condition monitoring for modern power conversion

The entire US electrical grid contains assets valued at approximately $800 billion, and many of these assets are nearing the end of their design lifetimes. In addition, there is a growing dependence upon power electronics in mission-critical assets (i.e. for drives in power plants and naval ships, wind farms, and within the oil and natural-gas industries). These assets must be monitored. Diagnostic algorithms have been developed to use certain key performance indicators (KPI) to detect incipient failures in electric machines and drives. This work was designed to be operated in real-time on operational machines and drives. For example the technique can detect impending failures in both mechanical and electrical components of a motor as well as semiconductor switches in power electronic drives. When monitoring power electronic drives, one is typically interested in the failure of power semiconductors and capacitors. To detect incipient faults in IGBTs, for instance, one must be able to track KPIs such as the on-state voltage and gate charge. This is particularly challenging in drives where one must measure voltages on the order of one or two volts in the presence of significant EMI. Sensing techniques have been developed to allow these signals to be reliably acquired and transmitted to the controller. This dissertation proposes a conservative approach for condition monitoring that uses communications and cloud-based analytics for condition monitoring of power conversion assets. Some of the potential benefits include lifetime extension of assets, improved efficiency and controllability, and reductions in operating costs especially with remotely located equipment

Integrated Geomechanical Characterization of Anisotropic Gas Shales: Field Appraisal, Laboratory Testing, Viscoelastic Modelling,and Hydraulic Fracture Simulation

This research provides a multiscale geomechanical characterization workflow for ultra-tight and anisotropic Goldwyer gas shales by integrating field appraisal, laboratory deformation and ultrasonic testing, viscoelastic modelling, and hydraulic fracture simulation. The outcome of this work addresses few of the practical challenges in unconventional reservoirs including but not limited to (i) microstructure & compositional control on rock mechanical properties, (ii) robust estimation of elastic anisotropy, (iii) viscous stress relaxation to predict the least principal stress Shmin at depth from creep, (iv) influence of specific surface area on creep, and (v) impact of stress layering on hydraulic fracturing design

Feasible, Robust and Reliable Automation and Control for Autonomous Systems

The Special Issue book focuses on highlighting current research and developments in the automation and control field for autonomous systems as well as showcasing state-of-the-art control strategy approaches for autonomous platforms. The book is co-edited by distinguished international control system experts currently based in Sweden, the United States of America, and the United Kingdom, with contributions from reputable researchers from China, Austria, France, the United States of America, Poland, and Hungary, among many others. The editors believe the ten articles published within this Special Issue will be highly appealing to control-systems-related researchers in applications typified in the fields of ground, aerial, maritime vehicles, and robotics as well as industrial audiences

Sensors Fault Diagnosis Trends and Applications

Fault diagnosis has always been a concern for industry. In general, diagnosis in complex systems requires the acquisition of information from sensors and the processing and extracting of required features for the classification or identification of faults. Therefore, fault diagnosis of sensors is clearly important as faulty information from a sensor may lead to misleading conclusions about the whole system. As engineering systems grow in size and complexity, it becomes more and more important to diagnose faulty behavior before it can lead to total failure. In the light of above issues, this book is dedicated to trends and applications in modern-sensor fault diagnosis

Coordination of Generator Protection and Control in the Over and Under Excited Regions

This thesis deals with the coordination of protection and control functions associated with the synchronous generators. The excitation control functions are a key component in maintaining the stability of machines and the network. The overall objective of coordination is simple; to allow excitation control functions, the automatic recovery from excursions beyond normal limits, and only take protective action as a last resort. This thesis focuses on four areas of generator control and protection : a) Loss of excitation protection, b) Dynamic underexcitation coordination, c) Dynamic Overexcitation coordination, and d) a generic protective relay development platform for hardware and software development. Loss of excitation (LOE) is a condition in the underexcited region that presents a risk of severe damage to a generator. The state of the art in the detection of a loss of excitation condition is based on the principle that, for a zero Thevenin voltage, the generator becomes a reactance as seen from the power system. The difficulty in detecting a loss of excitation is that several other disturbances may temporarily present a similar behavior, for instance a fault followed by a power swing. In this part of the work, a new algorithm for the detection of a loss of excitation condition is proposed by using the Support Vector Machine (SVM) classification method and a careful design of the necessary feature vectors. The proposed method is robust to changes in conditions including initial load, fault types, line impedance, as well as generator parameter inaccuracies. Coordination in the underexcited region presents difficulties due to the commonly used static characteristics instead of dynamic simulation. The underexcited limit presents an overload characteristic that is not normally known or used. Once the limit is exceeded, the limiting control action is a control loop that presents a dynamic behavior not typically represented in studies in the current industry practice. It is also important to properly model and include dynamic performance of protection functions. An important consideration not typically taken into account is the actual stability limit, which depends on the characteristics and the mode of excitation control used. This thesis includes all the above considerations necessary to achieve the required coordination using the more accurate dynamic simulations. Specific scenarios that present risk to the machine or the system are included to assess the coordination achieved. A real generator from the Alberta power system is used as a case study to demonstrate the proposed coordination methodology. Coordination in the overexcited region again presents practical difficulties due to static characteristics instead of dynamic simulation of conditions that exercise the overexcitation limits. The problems observed relate to coordination methodology and modeling methods for both protection and control limits. Once the limit boundary characteristic is exceeded, the limiting action is a control loop that presents dynamic behavior that needs to be represented. Similar considerations need to be made with the protection function protecting against rotor overload. Current modeling methods mostly use low bandwidth simulations, i.e., transient stability studies. A modeling methodology as well as specific model improvements to the IEEE ST1A excitation control model are proposed to achieve the required coordination. The ST1A type is one model that can represent a wide variety of system models from different manufacturers. The proposed modeling methodology applies to high bandwidth simulations such as electromagnetic simulations. Specific important scenarios, such as severe temporary reactive overload or severe power swing conditions, where the protection and control are required to coordinate but that present risk to the machine or the system are proposed as part of the coordination considerations. The detection of LOE conditions by the proposed SVM method and by traditional methods was implemented in hardware by using a digital signal processor (DSP) platform and tested using real time power system simulations. A new platform for real time protective relay development was designed and used for the purpose of implementation. In the proposed platform, a processor independent code is used so that development can be performed using native host computer development tools. By using the proposed platform-independent code, off line testing can be performed either interactively or in batch mode for evaluating multiple cases

Maximum risk reduction with a fixed budget in the railway industry

Decision-makers in safety-critical industries such as the railways are frequently faced with the complexity of selecting technological, procedural and operational solutions to minimise staff, passengers and third parties’ safety risks. In reality, the options for maximising risk reduction are limited by time and budget constraints as well as performance objectives. Maximising risk reduction is particularly necessary in the times of economic recession where critical services such as those on the UK rail network are not immune to budget cuts. This dilemma is further complicated by statutory frameworks stipulating ‘suitable and sufficient’ risk assessments and constraints such as ‘as low as reasonably practicable’. These significantly influence risk reduction option selection and influence their effective implementation. This thesis provides extensive research in this area and highlights the limitations of widely applied practices. These practices have limited significance on fundamental engineering principles and become impracticable when a constraint such as a fixed budget is applied – this is the current reality of UK rail network operations and risk management. This thesis identifies three main areas of weaknesses to achieving the desired objectives with current risk reduction methods as: Inaccurate, and unclear problem definition; Option evaluation and selection removed from implementation subsequently resulting in misrepresentation of risks and costs; Use of concepts and methods that are not based on fundamental engineering principles, not verifiable and with resultant sub-optimal solutions. Although not solely intended for a single industrial sector, this thesis focuses on guiding the railway risk decision-maker by providing clear categorisation of measures used on railways for risk reduction. This thesis establishes a novel understanding of risk reduction measures’ application limitations and respective strengths. This is achieved by applying ‘key generic engineering principles’ to measures employed for risk reduction. A comprehensive study of their preventive and protective capability in different configurations is presented. Subsequently, the fundamental understanding of risk reduction measures and their railway applications, the ‘cost-of-failure’ (CoF), ‘risk reduction readiness’ (RRR), ‘design-operationalprocedural-technical’ (DOPT) concepts are developed for rational and cost-effective risk reduction. These concepts are shown to be particularly relevant to cases where blind applications of economic and mathematical theories are misleading and detrimental to engineering risk management. The case for successfully implementing this framework for maximum risk reduction within a fixed budget is further strengthened by applying, for the first time in railway risk reduction applications, the dynamic programming technique based on practical railway examples