Induction Motors

AC motors play a major role in modern industrial applications. Squirrel-cage induction motors (SCIMs) are probably the most frequently used when compared to other AC motors because of their low cost, ruggedness, and low maintenance. The material presented in this book is organized into four sections, covering the applications and structural properties of induction motors (IMs), fault detection and diagnostics, control strategies, and the more recently developed topology based on the multiphase (more than three phases) induction motors. This material should be of specific interest to engineers and researchers who are engaged in the modeling, design, and implementation of control algorithms applied to induction motors and, more generally, to readers broadly interested in nonlinear control, health condition monitoring, and fault diagnosis

Analysis of artificial intelligence in industrial drives and development of fault deterrent novel machine learning prediction algorithm

Industrial sectors rely on electrical inverter drives to power their various load segments. Because the majority of their load is nonlinear, their drive system behaviour is unpredictable. Manufacturers continue to invest much in research and development to ensure that the device can resist any disturbances caused by the power system or load-side changes. The literature in this field of study depicts numerous effects caused by harmonics, a sudden inrush of currents, power interruption in all phases, leakage current effects and torque control of the system, among others. These and numerous other effects have been discovered as a result of research, and the inverter drive has been enhanced to a more advanced device than its earlier version. Despite these measures, inverter drives continue to operate poorly and frequently fail throughout the warranty term. This failure analysis is used as the basis for this research work, which presents a method for forecasting faulty sections using power system parameters. The said parameters were obtained by field-test dataset analysis in industrial premises. The prediction parameter is established by the examination of field research test data. The same data are used to train the machine learning system for future pre-emptive action. When exposed to live data feeds, the algorithm may forecast the future and suggest the same. Thus, when comparing the current status of the device to the planned study effort, the latter provides an advantage in terms of safeguarding the device and avoiding a brief period of total shutdown. As a result, the machine learning model was trained using the tested dataset and employed for prediction purposes; as a result, it provides a more accurate prediction, which benefits end consumers rather than improving the power system\u27s grid-side difficulties

Fault tolerant drives for safety critical applications

PhD ThesisThe correct operation of adjustable speed drives, which form part of a larger system, is often essential to the operation of the system as a whole. In certain applications the failure of such a drive could result in a threat to human safety and these applications are termed 'safety critical'. The chance of a component failure resulting in non-operation of the drive can be dramatically reduced by adopting a fault tolerant design. A fault tolerant drive must continue to operate throughout the occurrence of any single point failure without undue disturbance to the power output. Thereafter the drive must be capable of producing rated output indefinitely in the presence of the fault. The work presented in this thesis shows that fault tolerance can be achieved without severe penalties in terms of cost or power to mass ratio. The design of a novel permanent magnet drive is presented and a 'proof of concept' demonstrator has been built, based on a 20 kW, 13000 RPM aircraft fuel pump specffication. A novel current controller with near optimal transient performance is developed to enable precise shaping of the phase currents at high shaft speeds. The best operating regime for the machine is investigated to optimise the power to mass ratio of the drive. A list of the most likely electrical faults is considered. Some faults result in large fault currents and require rapid detection to prevent fault propagation. Several novel fault sensors are discussed. Fault detection and identification schemes are developed, including new schemes for rapid detection of turn to turn faults and power device short circuit faults. Post fault control schemes are described which enable the drive to continue to operate indefinitely in the presence of each fault. Finally, results show the initially healthy drive operating up to, through and beyond the introduction of each of the most serious faults.EPSR

On the potential of parallel powertrains to reduce the cost of energy from offshore wind turbines

Offshore wind turbine operating conditions are challenging with access for maintenance being limited by weather to a greater degree than for onshore turbines, resulting in prolonged downtime and reduced availability. This makes operational costs (helicopter, crew transfer or heavy lift vessels) more expensive, leads to loss of energy production and tends to increase the cost of energy of offshore wind farms. It is therefore important to investigate potential strategies that could improve availability, energy production and at the same time reduce operation and maintenance (O&M) cost and cost of energy in the long run. One possible option for availability improvement and cost of energy reduction is through the powertrain design. Most of the existing wind turbine types could be distinguished through their powertrain configurations. Conventional wind turbine powertrain exhibits single-input-single-output topology (one gearbox coupled to a generator with a power converter) while some exist with no gearbox (gearless drive). Although some of the geared and gearless powertrains have some good availability, yet they are still susceptible to prolonged downtime and consequently significant energy loss. This has alarmed the need to introduce the concept of parallelism into the design of offshore wind turbine powertrain. This research, therefore, focusses on a configuration with single-input-multiple-output (parallel powertrain) subsystems as a strategy for improvements in availability, energy production and cost of energy reduction. The novelty of this work comes from the availability improvement of small parallel subsystem with reduced failure rate, extra energy production at failure states, reduction in (O&M) cost due to high repair rate and the resulting cost of energy reduction of parallel powertrain. The highest-level research question amongst all of the research questions answered in this work is: "Can parallel powertrains reduce the cost of energy of offshore wind turbines?" In attempting to address this key question and other secondary research questions, in Chapter 3 the author carries out survey and analysis of failure and repair rate data from published sources to determine how they vary with powertrain configuration, power ratings, and sizes. In Chapter 4, a baseline powertrain availability and that of different parallel powertrains are evaluated using Markov state space model (MSSM). In Chapter 5, the annual energy production (AEP) of parallel powertrain is analysed using Raleigh probability distribution and the rated power in order to quantify any extra benefit at below rated wind speed. The ideal AEP is analysed at rated power, rated wind speed and at no-failure state. Also, the losses and efficiency of parallel powertrain at failure states are evaluated. Chapter 6 estimates the O&M costs of parallel powertrains using offshore accessibility tool. Chapter 7 calculates the cost of energy of parallel powertrain using AEP and O&M cost results from previous chapters in combination to initial capital cost (ICC). Finally, a general conclusion is made in Chapter 8. The novel results from each chapter provide some new insight into the potential of the parallel powertrain. The thesis concludes that an increase in the number of parallel systems, N, does not automatically lead to a higher availability for a wind turbine powertrain; however, when failure and repair rates scale with module power ratings then there is an improvement. It is possible to have extra AEP at below rated wind speed and at the various failure states of parallel powertrain. Potential reduction in the cost of energy is also observed with the parallel powertrain at below rated wind speed and failure states.The results shown in this thesis will be useful for offshore wind farm developers, operators and wind turbine manufacturers. It can be useful to developers when deciding and selecting the type of powertrain. Operators can gain insight into the driving factors of O&M costs. Manufacturers can consider which type of wind turbine powertrain to develop and manufacture to satisfy one of their key customer requirements, a lower cost of energy.Offshore wind turbine operating conditions are challenging with access for maintenance being limited by weather to a greater degree than for onshore turbines, resulting in prolonged downtime and reduced availability. This makes operational costs (helicopter, crew transfer or heavy lift vessels) more expensive, leads to loss of energy production and tends to increase the cost of energy of offshore wind farms. It is therefore important to investigate potential strategies that could improve availability, energy production and at the same time reduce operation and maintenance (O&M) cost and cost of energy in the long run. One possible option for availability improvement and cost of energy reduction is through the powertrain design. Most of the existing wind turbine types could be distinguished through their powertrain configurations. Conventional wind turbine powertrain exhibits single-input-single-output topology (one gearbox coupled to a generator with a power converter) while some exist with no gearbox (gearless drive). Although some of the geared and gearless powertrains have some good availability, yet they are still susceptible to prolonged downtime and consequently significant energy loss. This has alarmed the need to introduce the concept of parallelism into the design of offshore wind turbine powertrain. This research, therefore, focusses on a configuration with single-input-multiple-output (parallel powertrain) subsystems as a strategy for improvements in availability, energy production and cost of energy reduction. The novelty of this work comes from the availability improvement of small parallel subsystem with reduced failure rate, extra energy production at failure states, reduction in (O&M) cost due to high repair rate and the resulting cost of energy reduction of parallel powertrain. The highest-level research question amongst all of the research questions answered in this work is: "Can parallel powertrains reduce the cost of energy of offshore wind turbines?" In attempting to address this key question and other secondary research questions, in Chapter 3 the author carries out survey and analysis of failure and repair rate data from published sources to determine how they vary with powertrain configuration, power ratings, and sizes. In Chapter 4, a baseline powertrain availability and that of different parallel powertrains are evaluated using Markov state space model (MSSM). In Chapter 5, the annual energy production (AEP) of parallel powertrain is analysed using Raleigh probability distribution and the rated power in order to quantify any extra benefit at below rated wind speed. The ideal AEP is analysed at rated power, rated wind speed and at no-failure state. Also, the losses and efficiency of parallel powertrain at failure states are evaluated. Chapter 6 estimates the O&M costs of parallel powertrains using offshore accessibility tool. Chapter 7 calculates the cost of energy of parallel powertrain using AEP and O&M cost results from previous chapters in combination to initial capital cost (ICC). Finally, a general conclusion is made in Chapter 8. The novel results from each chapter provide some new insight into the potential of the parallel powertrain. The thesis concludes that an increase in the number of parallel systems, N, does not automatically lead to a higher availability for a wind turbine powertrain; however, when failure and repair rates scale with module power ratings then there is an improvement. It is possible to have extra AEP at below rated wind speed and at the various failure states of parallel powertrain. Potential reduction in the cost of energy is also observed with the parallel powertrain at below rated wind speed and failure states.The results shown in this thesis will be useful for offshore wind farm developers, operators and wind turbine manufacturers. It can be useful to developers when deciding and selecting the type of powertrain. Operators can gain insight into the driving factors of O&M costs. Manufacturers can consider which type of wind turbine powertrain to develop and manufacture to satisfy one of their key customer requirements, a lower cost of energy

Robust fault tolerant control of induction motor system

Research into fault tolerant control (FTC, a set of techniques that are developed to increase plant availability and reduce the risk of safety hazards) for induction motors is motivated by practical concerns including the need for enhanced reliability, improved maintenance operations and reduced cost. Its aim is to prevent that simple faults develop into serious failure. Although, the subject of induction motor control is well known, the main topics in the literature are concerned with scalar and vector control and structural stability. However, induction machines experience various fault scenarios and to meet the above requirements FTC strategies based on existing or more advanced control methods become desirable. Some earlier studies on FTC have addressed particular problems of 3-phase sensor current/voltage FTC, torque FTC, etc. However, the development of these methods lacks a more general understanding of the overall problem of FTC for an induction motor based on a true fault classification of possible fault types.In order to develop a more general approach to FTC for induction motors, i.e. not just designing specific control approaches for individual induction motor fault scenarios, this thesis has carried out a systematic research on induction motor systems considering the various faults that can typically be present, having either “additive” fault or “multiplicative” effects on the system dynamics, according to whether the faults are sensor or actuator (additive fault) types or component or motor faults (multiplicative fault) types.To achieve the required objectives, an active approach to FTC is used, making use of fault estimation (FE, an approach that determine the magnitude of a fault signal online) and fault compensation. This approach of FTC/FE considers an integration of the electrical and mechanical dynamics, initially using adaptive and/or sliding mode observers, Linear Parameter Varying (LPV, in which nonlinear systems are locally decomposed into several linear systems scheduled by varying parameters) and then using back-stepping control combined with observer/estimation methods for handling certain forms of nonlinearity.In conclusion, the thesis proposed an integrated research of induction motor FTC/FE with the consideration of different types of faults and different types of uncertainties, and validated the approaches through simulations and experiments

Advancements in Flux Switching Machine Optimization : Applications and Future Prospects

This work was supported by the Commonwealth Scholarship Commission, U. K., under Grant Number: NGCN-180-2021Peer reviewe

Fault Diagnosis and Fault Tolerant Control of Wind Turbines: An Overview

Wind turbines are playing an increasingly important role in renewable power generation. Their complex and large-scale structure, however, and operation in remote locations with harsh environmental conditions and highly variable stochastic loads make fault occurrence inevitable. Early detection and location of faults are vital for maintaining a high degree of availability and reducing maintenance costs. Hence, the deployment of algorithms capable of continuously monitoring and diagnosing potential faults and mitigating their effects before they evolve into failures is crucial. Fault diagnosis and fault tolerant control designs have been the subject of intensive research in the past decades. Significant progress has been made and several methods and control algorithms have been proposed in the literature. This paper provides an overview of the most recent fault diagnosis and fault tolerant control techniques for wind turbines. Following a brief discussion of the typical faults, the most commonly used model-based, data-driven and signal-based approaches are discussed. Passive and active fault tolerant control approaches are also highlighted and relevant publications are discussed. Future development tendencies in fault diagnosis and fault tolerant control of wind turbines are also briefly stated. The paper is written in a tutorial manner to provide a comprehensive overview of this research topic

Health Condition Monitoring and Fault-Tolerant Operation of Adjustable Speed Drives

Adjustable speed drives (ASDs) have been extensively used in industrial applications over the past few decades because of their benefits of energy saving and control flexibilities. However, the wider penetration of ASD systems into industrial applications is hindered by the lack of health monitoring and fault-tolerant operation techniques, especially in safety-critical applications. In this dissertation, a comprehensive portfolio of health condition monitoring and fault-tolerant operation strategies is developed and implemented for multilevel neutral-point-clamped (NPC) power converters in ASDs. Simulations and experiments show that these techniques can improve power cycling lifetime of power transistors, on-line diagnosis of switch faults, and fault-tolerant capabilities.The first contribution of this dissertation is the development of a lifetime improvement Pulse Width Modulation (PWM) method which can significantly extend the power cycling lifetime of Insulated Gate Bipolar Transistors (IGBTs) in NPC inverters operating at low frequencies. This PWM method is achieved by injecting a zero-sequence signal with a frequency higher than that of the IGBT junction-to-case thermal time constants. This, in turn, lowers IGBT junction temperatures at low output frequencies. Thermal models, simulation and experimental verifications are carried out to confirm the effectiveness of this PWM method. As a second contribution of this dissertation, a novel on-line diagnostic method is developed for electronic switch faults in power converters. Targeted at three-level NPC converters, this diagnostic method can diagnose any IGBT faults by utilizing the information on the dc-bus neutral-point current and switching states. This diagnostic method only requires one additional current sensor for sensing the neutral-point current. Simulation and experimental results verified the efficacy of this diagnostic method.The third contribution consists of the development and implementation of a fault-tolerant topology for T-Type NPC power converters. In this fault-tolerant topology, one additional phase leg is added to the original T-Type NPC converter. In addition to providing a fault-tolerant solution to certain switch faults in the converter, this fault-tolerant topology can share the overload current with the original phase legs, thus increasing the overload capabilities of the power converters. A lab-scale 30-kVA ASD based on this proposed topology is implemented and the experimental results verified its benefits

An Overview on Fault Diagnosis, Prognosis and Resilient Control for Wind Turbine Systems

Wind energy is contributing to more and more portions in the world energy market. However, one deterrent to even greater investment in wind energy is the considerable failure rate of turbines. In particular, large wind turbines are expensive, with less tolerance for system performance degradations, unscheduled system shut downs, and even system damages caused by various malfunctions or faults occurring in system components such as rotor blades, hydraulic systems, generator, electronic control units, electric systems, sensors, and so forth. As a result, there is a high demand to improve the operation reliability, availability, and productivity of wind turbine systems. It is thus paramount to detect and identify any kinds of abnormalities as early as possible, predict potential faults and the remaining useful life of the components, and implement resilient control and management for minimizing performance degradation and economic cost, and avoiding dangerous situations. During the last 20 years, interesting and intensive research results were reported on fault diagnosis, prognosis, and resilient control techniques for wind turbine systems. This paper aims to provide a state-of-the-art overview on the existing fault diagnosis, prognosis, and resilient control methods and techniques for wind turbine systems, with particular attention on the results reported during the last decade. Finally, an overlook on the future development of the fault diagnosis, prognosis, and resilient control techniques for wind turbine systems is presented