The development of sustainable generation, a reliable electricity supply and affordable tariffs are the primary requirements to address the uncertainties in different future energy scenarios. Due to the predicted increase in Distributed Generation (DG) and load profile changes in future scenarios, there are significant operational and planning challenges facing netwrok operators. These changes in the power system distribution network require a new Active Network Management (ANM) control system to manage distribution constraint issues such as thermal rating, voltage, and fault levels. The future smart grid focuses on harnessing the control potential from demand side via bidirectional power flow, transparent information communication, and contractual customer participation. Demand Side Management (DSM) is considered as one of the effective solutions to defer network capacity reinforcement, increase energy efficiency, facilitate renewable access, and implement low carbon energy strategy. From the Distribution Network Operator's (DNO) perspective, the control opportunity from Demand Response (DR) and Decentralized Energy Resource (DER) contributes on capacity investment reduction, energy efficiency, and enable low carbon technologies. This thesis develops a new decentralized control system for dealing effectively with the constraint issues in the Medium Voltage (MV) distribution network. In the decentralized control system, two novel control approaches are proposed to autonomously relieve the network thermal constraint via DNO's direct control of the real power in network components during the operation period. The first approach, Demand Response for Power Flow Management (DR-PFM), implements the DSM peak clipping control of Active Demand (AD), whilst the second approach, Hybrid Control for Power Flow Management (HC-PFM), implements the hybrid control of both AD and DER. The novelty of these two new control algorithms consists in the application of a Constraint Satisfaction Problem (CSP) based programming model on decision making of the real power curtailment to relieve the network thermal overload. In the Constraint Programming (CP) model, three constraints are identified: a preference constraint, and a network constraint. The control approaches effectively solve the above constraint problem in the CSP model within 5 seconds' time response. The control performance is influenced by the pre-determined variable, domain and constraint settings. These novel control approaches take advantages on flexible control, fast response and demand participation enabling in the future smart grid.

An important research topic in engineering and science is the miniaturization of systems and components, where small size and weight, low power consumption and low manufacturing cost can offer new functionalities. In recent years the fields of optics and fluidics have merged to create the area of research known as "optofluidics". The unique properties of fluids (compression, flow, and variable refractive index) can be combined with optical devices to create systems with advantages in optical measuring, communication and imaging areas. Variable optical attenuators (VOAs) are components in optical communication networks for managing optical power levels. This thesis is focused on the design, fabrication and characterization of two novel optofluidics based single-mode fibre VOAs ("continuous fibre" type VOA and "fibre gap" type VOA). The first VOA is constructed from a side-polished optical fibre which is characterized by a sloping shape profile of the external cladding thickness. The fibre is positioned on top of a platform which exploits electrowetting-on-dielectric (EWOD) techniques to move a liquid droplet. By moving a liquid droplet across EWOD platform (and along the polished region of the fibre), optical attenuation can be obtained. The droplet, whose refractive index is equal to or higher than the refractive index of the fibre core, is accessing and leaking radiation from the optical evanescent field of the polished fibre which then modifies the optical attenuation. The level of attenuation depends on the position of the droplet; the attenuation increases as the cladding thickness reduces and the droplet moves closer to the fibre core. The second VOA is a fibre gap device, where a ferrofluid shutter/actuator is located in the gap between lensed single mode optical fibres. The ferrofluid shutter movement is controlled by a magnetic field and changes the light propagation between fibres. The level of attenuation is defined by the shutter position.

In this thesis a novel controller for providing greater flexibility of operation of wind turbines known as the Power Adjusting Controller (PAC) is presented. The controller takes the form of an augmentation to a wind turbine's full envelope controller, allowing it to be applied to any horizontal axis, pitch regulated, variable speed wind turbine. Conventional wind turbine control seeks to maximise the power output of a wind turbine whilst minimising the loads on the turbine, controlling on the error in generator speed via demands to the blade pitch actuator and generator torque actuator. The PAC uses additions to the full envelope controller inputs and outputs to alter the power output of the turbine by an additional input value ∆P. It is ensured that the operation of the full envelope controller is not compromised by the PAC. Testing of the PAC using lumped parameter models of wind turbines and full aero-elastic models makes clear a requirement for a wind speed estimator within the PAC that incorporates the effects of dynamic inflow. A novel wind speed estimator that accounts for dynamic inflow by redefining blade element momentum theory solely in terms of the dynamics at the rotor is therefore developed and incorporated into the PAC. Limits are designed to ensure that the operating point of a wind turbine with the PAC is kept within a safe operational envelope, and a system of flags and sub-flags is developed to allow easy integration of the PAC into a hierarchical wind farm control structure. The effect of using the PAC on the wind turbine loads is investigated, with the ultimate loads introduced by operation of the PAC found to be within the range of normal operating loads and the impact of prolonged reduction of the power output found to reduce the lifetime damage equivalent loads in most cases.

This thesis investigates the design, analysis, and operation of modular multilevel converters (MMC) for HVDC applications. Based on the operation principles of the MMC, the operation of MMC under asymmetrical arm impedance conditions is analysed using three equivalent sub-circuits at different freqeuncy. Detail analysis of the impact of asymmetrical conditions on the differential-mode current, the common-mode current and sub-module (SM) capacitor voltages, is performed. Based on the analysis, the corresponding control targets and an improved control strategy are designed to improve the operation performance. Considering the advantages of half-bridge based SM (HBSM) and full-bridge based SM (FBSM), a hybrid MMC (H-MMC) configuration consisting of FBSMs and HBSMs is proposed. By adopting the negative voltage state for some of the FBSMs, the output voltage range is extended to increase converter power transmission capability. By considering the relationships between the AC and DC voltages, AC, DC and arm currents, the ratio of the numbers of the FBSM to HBSM is analysed in order to maintain capacitor voltage balance and retain DC fault blocking capability. An equivalent circuit for the H-MMC is proposed, which considers each arm to be consisted of two individual voltage sources. This model is used to analyse SM capacitor voltage balancing and ripple. A two-stage selection and sorting algorithm is developed to ensure capacitor voltage balancing among the SMs. The proposed H-MMC is compared to other topologies in terms of power device utilization and power losses, and it shows that the H-MMC has higher device utilization and lower power loss than the conventional FBSM based MMC; Furthermore, The DC fault ride-through capability of the H-MMC are discussed. It is found that the H-MMC can not only isolate the DC fault, but also coniture operating at a wide DC voltage range from zero to rated value. Such two features of the H-MMC show the advantages in the hybrid configurations over the conventional FBSM and HBSM systems. Finally, two applications based on the proposed H-MMC are presented; one is a high power DC/DC converter with fault blocking capability for interconnecting large HVDC systems, and the other is a hybrid HVDC transmission system comprising a wind farm side VSC based on the H-MMC and a grid side LCC for transmitting wind power to AC grid.

The smart rotor is an upgrade to the wind turbine rotor that facilitates active modification of the blade aerodynamics, thus allowing enhanced control of the rotor loads. In this thesis a number of research areas relating to the smart rotor are explored and advanced. The synthesised wind field spatial and temporal requirements are assessed, suggesting the current guidelines, of less than 5m spatial and 10Hz temporal resolutions, are more than adequate. Also regarding the wind field, it is shown that the smart rotor provides the greatest percentage benefits when there is high wind shear, but low turbulence intensity. An analytical approach to selecting the chord-width of trailing edge flaps, based on thin aerofoil theory, is presented. Demonstrating a trade-off between flap size, flap actuator requirements and load reductions. The unsteady aerodynamics of trailing edge flaps and their modelling in Bladed is also considered, showing only a limited requirement to develop the aerodynamic code. A comparison of individual pitch and smart rotor controllers shows that both methods can achieve similar load reductions. The main benefit of using a smart rotor system is the lower pitch motion. The smart rotor is also shown to reduce pitch motion by supplementing collective pitch control. The trade between pitch actuator requirements, load reductions and the cost of smart rotor control, is therefore considered the defining factor in valuing the smart rotor, rather than purely load reductions. Finally, a fault scenario of a single jammed flap is detected and corrected for. With results suggesting that even unreliable systems can achieve a significant lifetime fatigue load reduction. These studies are conducted using a methodical process detailed in this thesis, such that future researchers may build upon this work. Access to the models and code developed are provided in the appendix.

A modification to the Asymmetrically Clipped Optical OFDM (ACO-OFDM) technique, a well reported non-coherent optical implementation is proposed. A Modified ACO-OFDM (MACO-OFDM) system is developed to improve system performance at the expense of spectral efficiency. A MACO-OFDM system model is defined underpinned by a detailed mathematical framework verified through Monte Carlo simulations. System performance is compared to that of conventional ACO-OFDM. A 1.5 dB saving is achieved in the Bit Error Rate (BER) performance of 4-QAM ACO-OFDM after applying the proposed modification; the theoretical and simulation results are in good agreement. As the constellation size increases, the improvement in BER performance decreases. The research then treats the impact of atmospheric turbulence on the performance of both conventional ACO-OFDM and the proposed MACO-OFDM system. A Single Input Multiple Output (SIMO) approach using multiple receivers is employed to mitigate the impact of atmospheric turbulence. The performance of MACO-OFDM outperforms that of ACO-OFDM by nearly 3 dB, 4 dB, and 5 dB as the number of receiving apertures (nRx) increases as 1, 2, and 4 respectively in weak atmospheric turbulence; in moderate turbulence the performance is improved by 2 dB, and 4.5 dB for nRx=2, and nRx=4; and in strong turbulence, the BER performance is enhanced by nearly 2 dB and 4 dB for nRx=2 and nRx=4. The channel capacity of MACO-OFDM has been shown to be half that of conventional ACO-OFDM. The capacity of SIMO MACO-OFDM architecture in atmospheric turbulent channel is evaluated.

The research develops an approach to preserving energy in Wireless Sensor Networks (WSNs). Energy is a constrained resource, and thus increasing the lifetime of nodes to extend the flexibility of network deployments and ease maintenance is a core challenge; the network can operate unattended, autonomously and deliver applications for longer periods of time without human intervention. Energy is an especially limited resource for WSNs since invariably, nodes are battery powered and any scheme that extends the viability of the limited energy resource is much sought after. Inherent to the principles of WSNs is that each node is designed through a restricted set of resources and is equipped with the ability to gather, store, process and communicate data. In comparison to processing, transmitting/receiving data is very costly in terms of power consumption. Thus a viable strategy to conserve energy is to limit the amount energy owing to receiving and transmitting data through embedding intelligence within the protocol stack. The dynamic adjustment of the transmission power according to an application requested success rate, implemented through an extension of data embedded in the message packets is proposed and evaluated. Although a reduction in the transmission success rate results through lost packets, the level of energy savings is not compromised by an excessive increase in packet loss owing to a non-linear trade-off between the level of transmission power and transmission success. The dissertation introduces the motivation and background to the solution, defines the mathematical framework with which the approach to energy saving is founded and presents the emulation environment in which the performance of the solution has been evaluated. The expected energy savings owing to the utilisation of the scheme is presented and compared with techniques reported in the literature. Results show that notable energy saving is achievable with the proposed scheme.

Clean, affordable energy is essential for continued growth of the economy in a country. Almost every country's laws and policies put in place in the last decade encourage energy suppliers to incorporate large amounts of renewable generation (wind and solar). This has changed the traditional mix of (3)4z(Bfuels(3)4y (Bused for energy generation. Integrating these resources into a reliable and affordable power system will require an unprecedented level of cooperative action within the electric industry, related utilities and the state. Power grid has existing flexibility in the system to cost-effectively integrate wind resources but, as operated today, more can be done. Integration involves managing the variability (the range of expected electricity generation output) and uncertainty (when and how much that generation will change during the day) of energy resources. Wind is one kind of free energy and this (3)4z(Bmust-take(3)4y (Bwind power generation is integrated into th e system operation. In this thesis, the impacts on the combined conventional generators, the transmission lines and the operation costs will be examined under different system operation conditions (constrained and unconstrained) with increasing wind power penetration. The firm scheduled bilateral contract from the conventional generation can cause transmission congestion and free wind power cannot be integrated into the power system operation sufficiently. This thesis proposes a combined pool/bilateral trade model to cooperate with wind power output fluctuations to increase the utilisation of wind farm which are currently constrained by the transmission networks. The one-step optimal power flow model dispatches the pool in combination with the curtailed part of fixed bilateral contracts from conventional generators. The aim is integrating maximum wind energy in the power system while minimizing costs. A dynamic wind turbine model is used to identify the impacts of integrating wind power into system operation; the Weibull Distribution Function is used to analyze the problem of wind distribution; and the Monte Carlo Simulation (MCS) method is used to simulate the output of wind power generation. The proposed combined pool/bilateral trade model is applied to the modified IEEE-9 bus system for verification and validation. Following this, the analysis on IEEE-30 bus system is the comparison studies with the proposed one-step combined pool/bilateral trade model under different bidding prices. Two case studies with different market strategies through the proposed method are introduced, with different volume values of the firm bilateral contracts and the different payments for the curtailment bids. The simulation results show the relative level of pool versus bilateral trading and these influences on the performance in terms of individual power generation levels and costs. The well-proven software tools MATLAB and MATPOWER support the study.

Large components with complex geometries, made of composite materials, have become very common in modern structures. To cope with future demand projections, it is necessary to overcome the current non-destructive testing (NDT) bottlenecks encountered during the inspection phase of manufacture. This thesis investigates several aspects of the introduction of automation within the inspection process of complex parts. The use of six-axis robots for product inspection and non-destructive testing systems is the central investigation of this thesis. The challenges embraced by the research include the development of a novel controlling approach for robotic manipulators and of novel path-planning strategies. The integration of robot manipulators and NDT data acquisition instruments is optimized. An effective and reliable way to encode the NDT data through the interpolated robot feedback positions is implemented. The viability of the new external control method is evaluated experimentally. The observed maximum position and orientation errors are respectively within 2mm and within 1 degree, over an operating envelope of 3m³. A new software toolbox (RoboNDT), aimed at NDT technicians, has been developed during this work. RoboNDT is intended to transform the robot path-planning problem into an easy step of the inspection process. The software incorporates the novel path-planning algorithms developed during this research and is shaped to overcome practical limitations of current OLP software. The software has been experimentally validated using scans on real high value aerospace components. RoboNDT delivers tool-path errors that are lower than the errors given by commercial off-line path-planning software. For example the variability of the standoff is within 10 mm for the tool-paths created with the commercial software and within 4.5 mm for the RoboNDT tool-paths, over a scanned area of 1.6m². The output of this research was used to support a 3-year industrial project, called IntACom and led by TWI on behalf of major aerospace sponsors. The result is a demonstrator system, currently in use at TWI Technology Centre, which is capable of inspecting complex geometries with high throughput. The IntACom system can scan real components 2.8 times faster than traditional 3-DoF scanners deploying phased-array inspection and 6.7 times faster than commercial gantry systems deploying traditional single-element inspection.

The reliable operation of protection systems depends on the correct settings of protective devices, which can be extremely numerous and complex within modern protection schemes. It has been realised that, despite multiple instances of checking, and verification and quality control processes, setting errors may remain undetected until an in-service mal-operation event is experienced. Furthermore, while the network evolves, the originally correct settings may be rendered erroneous under certain specific (unanticipated) situations. These issues present a strong need for a solution that allows comprehensive validation of settings and checking of the actual performance of the protection system with the settings applied in a variety of operational contexts. To address these requirements, this thesis presents the outcomes of research concerned with developing and demonstrating an intelligent system-based solution incorporating hybrid Rule-Based (RB) and Model-Based (MB) approaches - the system has been termed the Power system Protection Smart Tool (PPST). It is shown that the combined RB and MB approaches are effective in complementing each other for the settings and performance validation tasks with enhanced reliability and automation. The advantages of the proposed methodology are demonstrated through case studies with actual network and settings data. To maximise the applicability of the developed scheme, the considerable challenges of automating the use of existing settings data stored in a wide range of proprietary formats is also reported. A solution that has been developed which represents settings using IEC 61850 standardised file format and data model is described, along with a proposed methodology that will enable power utilities to migrate from existing approaches to the proposed future approach based on standardised protection settings. Adoption of these recommendations would facilitate a shift from protection systems being largely single-vendor solutions to becoming truly open platforms, capable of supporting the settings validation system as reported in this thesis and any other future applications that require access to and/or manipulation of protection settings. Conclusions and future work concerned with moving the developed system to becoming a "business as usual" application are also included.