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In this thesis, a sensorless control method of permanent magnet synchronous machines (PMSMs), whose machine neutral points are accessible, for all speeds and at standstill is proposed, researched and developed. The sensorless method is called Direct Flux Control (DFC). The different voltages between a machine neutral point and an artificial neutral point are required for the DFC method. These voltages are used to extract flux linkage signals as voltage signals, which are necessary to approximate electrical rotor positions by manipulating the flux linkage signals. The DFC method is a continuous exciting method and based on an asymmetry characteristic and machine saliencies. The DFC method is validated by implementing on both software and hardware implementation. A cooperative simulation with Simplorer for the driving circuit and programming the DFC and Maxwell for doing finite element analysis with the machine design is selected as the software simulation environment. The machine model and the DFC method are validated and implemented. Moreover, the influences of different machine structures are also investigated in order to improve the quality of the measured voltages. The hardware implementation has been employed on two test benches, i.e. for small machines and for big machines. Both test benches use a TriCore PXROS microcontroller platform to implement the DFC method. There are several PMSMs, both salient poles and non-salient poles, which are used to validate the DFC method. The flux linkage signals are also analyzed. The approximation of the flux linkage signal is derived and proposed. A technique to remove the uncertainty of the calculated electrical rotor position based on the inductance characteristics has been found and implemented. The electrical rotor position estimation method has been developed based on the found flux linkage signal approximation function and analyzed by comparing with other calculation techniques. Moreover, the calculated electrical rotor position is taken into account to either assure or show the relation with the exact rotor position by testing on the hardware environment. The closed loop speed sensorless control of PMSMs with DFC is presented and executed by using the assured calculated electrical rotor position to perform the DFC capability. This thesis has been done in the Electric Machines, Drives and Power Electronics Laboratory, South Westphalia University of Applied Sciences, Soest, Germany.

Since 1996 direct femtosecond inscription in transparent dielectrics has become the subject of intensive research. This enabling technology significantly expands the technological boundaries for direct fabrication of 3D structures in a wide variety of materials. It allows modification of non-photosensitive materials, which opens the door to numerous practical applications. In this work we explored the direct femtosecond inscription of waveguides and demonstrated at least one order of magnitude enhancement in the most critical parameter - the induced contrast of the refractive index in a standard borosilicate optical glass. A record high induced refractive contrast of 2.5×10-2 is demonstrated. The waveguides fabricated possess one of the lowest losses, approaching level of Fresnel reflection losses at the glassair interface. High refractive index contrast allows the fabrication of curvilinear waveguides with low bend losses. We also demonstrated the optimisation of the inscription regimes in BK7 glass over a broad range of experimental parameters and observed a counter-intuitive increase of the induced refractive index contrast with increasing translation speed of a sample. Examples of inscription in a number of transparent dielectrics hosts using high repetition rate fs laser system (both glasses and crystals) are also presented. Sub-wavelength scale periodic inscription inside any material often demands supercritical propagation regimes, when pulse peak power is more than the critical power for selffocusing, sometimes several times higher than the critical power. For a sub-critical regime, when the pulse peak power is less than the critical power for self-focusing, we derive analytic expressions for Gaussian beam focusing in the presence of Kerr non-linearity as well as for a number of other beam shapes commonly used in experiments, including astigmatic and ring-shaped ones. In the part devoted to the fabrication of periodic structures, we report on recent development of our point-by-point method, demonstrating the shortest periodic perturbation created in the bulk of a pure fused silica sample, by using third harmonics (? =267 nm) of fundamental laser frequency (? =800 nm) and 1 kHz femtosecond laser system. To overcome the fundamental limitations of the point-by-point method we suggested and experimentally demonstrated the micro-holographic inscription method, which is based on using the combination of a diffractive optical element and standard micro-objectives. Sub-500 nm periodic structures with a much higher aspect ratio were demonstrated. From the applications point of view, we demonstrate examples of photonics devices by direct femtosecond fabrication method, including various vectorial bend-sensors fabricated in standard optical fibres, as well as a highly birefringent long-period gratings by direct modulation method. To address the intrinsic limitations of femtosecond inscription at very shallow depths we suggested the hybrid mask-less lithography method. The method is based on precision ablation of a thin metal layer deposited on the surface of the sample to create a mask. After that an ion-exchange process in the melt of Ag-containing salts allows quick and low-cost fabrication of shallow waveguides and other components of integrated optics. This approach covers the gap in direct fs inscription of shallow waveguide. Perspectives and future developments of direct femtosecond micro-fabrication are also discussed.

Recent commitments to reduce greenhouse gas emissions in the electricity industry associated with the electrification of segments of heat and transport sectors pose significant challenges of unprecedented proportions . The unique features of Energy Storage Systems (ESS) coupled with the flexibility of providing services to multiple sectors of the electricity industry, make it a key technology to tackle current and upcoming challenges in the electricity industry. Although ESS have the potential to support future system integration with large amounts of renewable generation, the potential value that ESS brings to stakeholder s and its associated economics are not well understood to date. In addition, further research is needed on its business model in various markets and system conditions, in particular in the value associated with each service or set of services. In this context, the conducted research has addressed ESS operational aspects when considering a multiple services portfolio provided to various stakeholders and sensitive to market and system conditions. New ESS operational frameworks together with a computationally efficient modelling framework are proposed for a better understanding of ESS business models. The novelty introduced with this work is associated with a multiple service business model for ESS which considers services to distribution network operators, system operators, low capacity value generation and participation in the energy market. In addition, the economic aspects of ESS considering various operating policies for maximum revenue is also investigated and enhances the understanding of ESS to develop appropriate market mechanisms and allow efficient deployment of ESS in the electricity industry.

A collective action situation involves a group of people working together for a common good or to resolve a common problem, even if their individual goals may be in conflict with the common goal, and each other's goals. Moreover, it may be difficult for individuals to recognise that they are involved in a collective action situation, or that their (relatively small) individual actions have an impact on the collective. A community energy system for local energy generation and distribution is an example where community members need to collaborate on energy allocation, but may be 'collectively unaware' of incipient problems, such as blackouts, that originate from depletion of the fixed amounts of energy that are available. Even if aware of the incipient problem, they may be equally unaware of how their individual actions contribute to the collective goal of resolving it. In this thesis, we propose that socio-technical systems can be used for computer - supported collective action, and in particular, that collective awareness can be enhanced by appropriate features of the system interface, therefore increasing the opportunities and prospects for successful collective action. Specifically, collective awareness is defined as an attribute of communities that helps them solve collective action problems. In relation to Elinor Ostrom's institutional design principles for self-governing institutions, this definition is translated into requirements for interface design and display which promote collective awareness, including different interface elements, visualisation, social networking, feedback and incentives. To test the hypothesis, we design and implement a serious game for a community energy system, integrating the Imprudence viewer to support an immersive 3D environment, the Presage2 agent-based simulation platform to model different components, and OpenSimulator application server to support real-time interactions. In this game, the participants have to avoid a collective blackout by individually reducing their energy consumption by synchronising and coordinating their actions. We then design and implement an interface to the game with a set of features that meet these interface requirements, and configure the system. Finally, we report the results of the experiments, which show that when visualisation, social networking, feedback and incentives are added to the serious game interface, users become 'collectively aware' of potential energy problems and they successfully coordinate their behaviour to avoid them. These results highlight the significant potential of serious games and gamification in the development of infrastructure support for community energy systems, and also indicate a more beneficial approach to the use of smart meters in such systems: i.e. not just as a monitor for pricing and consumption, but as a key enabler for direct action, feedback and incentivisation. Furthermore, it provides the basis for defining a set of interface design principles for 'smarter' socio-technical systems which promote successful computer-supported collective action.

This thesis considers the operation of corrective System Protection Schemes (SPS) in electricity networks. Such systems have the potential to greatly enhance the utilisation of the network, but malfunctions may expose the system to blackouts. Choosing the optimal operational strategy is therefore subject to a cost-benefit trade-off between the benefits of increased system utilisation and the risk of outages. This thesis proposes to formulate the problem in three different phases, namely steady-state, SPS action and response and impact assessment. This is used to formalise the objective of the network operator from a system perspective: minimising the operational costs considering unreliable SPS operation. This thesis also presents a generic modelling framework for SPS failure modes and related impact assessments. From an optimisation perspective, the problem presents two major difficulties. First, the computation of the load-shedding impact may require the analysis of a complex dynamical system. The second barrier is that the set of possible SPS outcomes is potentially large, and depends on the decision variables (generator dispatch and SPS configuration). The problem is firstly addressed in a simple system which serves to illustrate the salient properties of the problem at hand. It is demonstrated that the optimal SPS configurations are always part of a finite set of 'candidate solutions' that are associated with the provision of security against specific outcomes scenarios of the SPS (including its failure modes). The same network is used to investigate SPS operational benefits and risks in a year-round basis. Next, this thesis proposes a heuristic method to address the two complexities described above. The method is tested on the RTS 24-Bus IEEE System. Impact assessments are performed in a basic cascading simulator which provides a range of possible impacts from SPS malfunction scenarios. The method is shown to provide an optimised balance between benefits and risks.

This thesis focuses on the design of non-harmonic motion-powered wireless sensing systems using piezoelectric energy harvesting. Most of the published work on the topic of inertial energy harvesting focussed on the analysis and design of the energy harvester modules only. A limited amount of work has involved the implementation of energy harvesters into a wireless sensing system, which is an important application of energy harvesters. This project presents an approach to simplify the design of a wireless sensing system so that a single piezoelectric energy harvester can be used as the power supply. A piezoelectric device structure with impulse output was proposed and an equivalent circuit model was built to simulate the performance. Both a large-scale and a small-scale piezoelectric pulse generator were produced for experimental demonstration, based on the proposed structure. A passive pre-biasing mechanism was introduced to improve the performance of the pulse generator, and the improvement was demonstrated by comparing the outputs of the prototypes in the pre-biased case to the outputs in the unbiased case. The comparison results showed that the output energy was increased by 38% for the large-scale prototype and 76% for the small-scale prototype. Load transmission circuits, suitable for the piezoelectric pulse generator, were discussed and simulated, and an impulse-powered transmitter circuit based on the Colpitts oscillator was built, which could encode the signal from a sensor by frequency modulation. By combining the piezoelectric pulse generator module and the impulse-powered transmitter module together, a fully functional piezoelectric system was achieved, for the first time, allowing instantaneous wireless monitoring of signals from a passive sensor using frequency modulation.

This work presents some contributions to the fields of approximation, analysis and control of large-scale systems. Consequently the Thesis consists of three parts. The first part covers approximation topics and includes several contributions to the area of model reduction. Firstly, model reduction by moment matching for linear and nonlinear time-delay systems, including neutral differential time-delay systems with discrete-delays and distributed delays, is considered. Secondly, a theoretical framework and a collection of techniques to obtain reduced order models by moment matching from input/output data for linear (time-delay) systems and nonlinear (time-delay) systems is presented. The theory developed is then validated with the introduction and use of a low complexity algorithm for the fast estimation of the moments of the NETS-NYPS benchmark interconnected power system. Then, the model reduction problem is solved when the class of input signals generated by a linear exogenous system which does not have an implicit (differential) form is considered. The work regarding the topic of approximation is concluded with a chapter covering the problem of model reduction for linear singular systems. The second part of the Thesis, which concerns the area of analysis, consists of two very different contributions. The first proposes a new "discontinuous phasor transform" which allows to analyze in closed-form the steady-state behavior of discontinuous power electronic devices. The second presents in a unified framework a class of theorems inspired by the Krasovskii-LaSalle invariance principle for the study of "liminf" convergence properties of solutions of dynamical systems. Finally, in the last part of the Thesis the problem of finite-horizon optimal control with input constraints is studied and a methodology to compute approximate solutions of the resulting partial differential equation is proposed.

The market for plug-in electric vehicles is expected to grow significantly over the next few years as a number of automobile manufacturers have released electric vehicle models onto the market. The charging demand of wide-scale use of EVs may have a significant impact on domestic electricity loads and could risk overloading the power distribution system unless appropriate charging strategies are applied to prevent this. In order to quantify the future electric vehicle charging demand, it is necessary to gain a good understanding of current privately owned car use. In this thesis, domestic car use patterns have been studied in detail by analysing the United Kingdom Time of Use Survey 2000 data. The key findings show that weekday car use patterns are rather different than weekend ones. The majority of domestic cars are used for commuting to work during week days. Car activities, such as depart from home and arrive home are highly correlated and dependent on time of the day. Cumulative driving times are significantly dependent on the car arrival time. In most research, the relationship among these types of events are often ignored, which leads to errors in the calculation of charging demand. Three high resolution Monte Carlo simulation models are structured based on these domestic car use statistics in order to represent the weekday car use patterns; they represent three different approaches to trying to capture the complex dependencies associated with car use. The return time dependent Monte Carlo model utilise car returning home probabilities and the cumulative driving period dependent on arrival home time statistics. The single time increment Monte Carlo model uses two-state probability distributions of car departure and arrival to reproduce the weekday car location status. Although the correlation between car departure and arrival home events are not explicitly captured in this model, the multiple time increments Monte Carlo model captures this relationship by sampling from car away and parking period time dependent probability distributions. xviii Validation of the simulation results shows that all three models generate acceptably accurate car use patterns with home as the primary parking location. In the later part of the thesis, assessments the impact of electric vehicle home charging on the distribution network have been performed for two case studies; one focuses on the peak load impact on substation transformers, and the other one examines individual household voltages (at 230V low voltage level). For the specific network considered, it is shown that distribution substation transformers (i.e. primary and secondary) will face increasing peak load due to electric vehicle charging in the case that householders start charging as soon as they arrive home. It is recognised for the first time that domestic car use behaviour has effects on the household electricity consumption model and to reflect this the household electricity model has been modified to account for the changes in occupancy associated with car movements. In the low voltage case study, the household voltage issue has been investigated for this specific network by performing power flow calculations, and shows that a household, located at the end of a long service cable, suffers under voltage before the substation feeder reaches its thermal limit. In the last part of the thesis, several vehicle charging strategies have been developed to mitigate the problem of overloading the substation transformer. It is shown that a simple time delay to charging strategy creates an additional peak load on the substation loading profile; however, with a random time delay, overloading of the substation can be avoided. The potential role of EVs as responsive demand has been explored with the aim of utilising vehicle charging to support local power system operation with surplus wind generation. An algorithm is proposed that can effectively shift vehicle charging by implementing a linear cost function to track the surplus wind generation.

There are ambitious plans for renewable energy sources to provide a significant contribution to the future energy mix. The huge potential capacity and relative maturity compared to other offshore technologies has resulted in a strong commercial focus on offshore wind, particularly in Europe. However, costs of offshore wind remain significantly higher than conventional generation approaches as well as onshore wind. Reducing the cost associated with operations and maintenance of offshore wind remains a key challenge in decreasing lifetime cost of energy and achieving cost parity with alternative generation technologies. The combination of nascent turbine and infrastructure design, moving into more challenging sea state and wind environments and the highly commercial nature of the industry has prevented the maintenance costs of offshore wind being adequately reduced through early operating experience alone. In order to accelerate the reduction of costs and critically to understand the uncertainty associated with future sites and novel operating strategies, it is necessary to simulate maintenance operations. This thesis has developed an offshore wind operations and maintenance expenditure model and specified a decision support methodology for this purpose. The models enable the quantification of the influence of cost drivers for current and future offshore wind farms and provide an improved understanding of the uncertainty associated with operating decisions. Using the developed models, a detailed sensitivity analysis of the influence on lifetime costs from operational climate, failure behaviour, wind farm configuration and external cost drivers has been carried out to provide new insights on the industry. Operational climate and failure behaviour are identified as the critical cost drivers and sources of uncertainty currently. In addition, a detailed analysis of operational strategies for major repairs that involve the use of high cost, specialist vessels has been carried out for the first time, identifying the strengths and weaknesses of different strategies. Finally, a case study demonstrating how decision support models can be used to determine the optimal strategy choices for operators and reduce uncertainty has been performed. The analysis in this thesis provides new insights on the industry and the developed methodologies have the potential to deliver significant financial savings in the future.