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Deep learning in computer vision is becoming increasingly popular and useful for tracking object movement in many application areas, due to data collection burgeoning from the rise of the Internet of Things (IoT) and Big Data. So far, computer vision has been used in industry predominantly for quality inspection purposes such as surface defect detection; however, an emergent research area is the application for process monitoring involving tracking moving machinery in real time. In steelmaking, the deployment of computer vision for process monitoring is hindered by harsh environments, poor lighting conditions and fume presence. Therefore, application of computer vision remains unplumbed. This paper proposes a novel method for tracking hot metal ladles during pouring in poor lighting. The proposed method uses contrast-limited adaptive histogram equalisation (CLAHE) for contrast enhancement, Mask R-CNN for segmentation prediction and Kalman filters for improving predictions. Pixel-level tracking enables pouring height and rotation angle estimation which are controllable parameters. Flame severity is also estimated to indicate process quality. The method has been validated with real data collected from ladle pours. Currently, no publications presenting a method for tracking ladle pours exist. The model achieved a mean average precision (mAP) of 0.61 by the Microsoft Common Objects in Context (MSCOCO) standard. It measures key process parameters and process quality in processes with high variability, which significantly contributes to process enhancement through root-cause analysis, process optimisation and predictive maintenance. With real-time tracking, predictions could automate ladle controls for closed-loop control to minimise emissions and eliminate variability from human error.

Regular and reliable access to energy is critical to the foundations of a stable and growing economy. The Nigerian transmission network generates more electricity than is consumed but, due to unpredicted outages, customers are often left without electrical power for several hours during the year. This paper aims to assess the present reliability indices of the Nigerian transmission network, and to determine the impact of HVDCs on system reliability. In the first part of this paper, the reliability of the Nigerian transmission system is quantified by building a model in DIgSILENT PowerFactory and carrying out a reliability study based on data provided by the Nigerian transmission-system operator. Both network indices and load-point indices are evaluated, and the weakest points in the network are identified. In the second part of the paper, an HVDC model is built and integrated into the existing network at the locations identified by the reliability study. A comparative study using two different HVDC connections is then carried out, to determine the critical impact of HVDC on system reliability. The reliability results indicate that the weakest points of the transmission system are the radial feeders, and the highest impact could be achieved by spanning an HVDC line between two busbars located at the two extremes of a radial feeder: Azura and Yola.

The small area of the United Kingdom relative to weather systems makes renewable energy sources variable on short time scales. Short term variability is therefore a growing concern with increasing amounts of renewable energy integration. In this work, we address how tidal energy can contribute to reducing medium-term variability in the future UK energy mix. Two tidal integration scenarios are defined for 2050: for each scenario, a 5-min interval generation profile is calculated using an oceanographic model of UK tides, and the medium-term variability is assessed. Here we show that tidal power shows a lower level of variability compared to other resources. During spring tides, a national network of tidal power stations can produce continuous, although variable, electricity. It is then shown that tidal energy and storage can provide year-round continuous and constant power output, i.e. baseload generation. Therefore, we conclude that tidal energy can provide positive contributions and complement other renewable energy sources.

The outdoor performance of large area Organic Photovoltaics (OPVs) is investigated in this work. Initially, the diurnal performance of the three modules is determined and found to be similar. Subsequently module degradation is monitored, and it is found that the larger area module displays a significantly greater stability as compared to the smallest area module, in fact the larger module displays a T50% (time to fall to 50% of its original value) of 191 days whilst the smallest module displays a T50% of 57 days. This is attributed to an increased level of water infiltration due to a larger perimeter-to-area ratio. These findings are then used to verify a computer simulation model which allows the model parameters, series and shunt resistances, to be calculated. It is determined that the series resistance is not an obvious obstruction at these module sizes. The findings of this work provide great promise for the application of OPV technology on a larger scale.

The subject of this work is the development of a load flow model for the Nigerian 330 kV transmission system. The model has been developed in DIgSILENT PowerFactory based on data provided by the Nigerian Electricity system operator (NESO). Two scenarios (summer and winter) were considered: for each scenario, load data, generator data, and transmission line parameters were used as inputs to the model. The voltage profiles resulting from the load flow were compared with the original data, and some discrepancies were found. Assumptions and modifications were made to achieve load flow results that were closer to the system data. The results show that in summer and winter, power generated was 4804.10 MW and 4394.41 MW, respectively. The bus voltages were within the voltage magnitude of 0.85 pu and 1.05 pu, according to the local grid code. The model documented in this paper will be used as a baseline for reliability and stability studies. This research aims to identify potential reinforcements to the 330 kV Nigerian transmission system to meet future electricity demand.

Due to the interaction converter control, pre-existing distortion and grid impedance, the harmonic levels caused by renewable energy sources (RESs) are continuously changing, and their assessment requires the use of dedicated computer models. Several time-domain models have been proposed to carry out this analysis, however, they fall short of at least one requirement: either they do not provide accurate results, or they require an excessively long simulation time. This paper presents a novel time-domain model to address the gap described above: the proposed model employs average functions and a novel switching emulator. Therefore, it is referred to as ‘average model with switching emulator’ (AMSE). The proposed model is compared with existing models, and the results indicate that the AMSE meet both requirements stated above, as it accurately represents harmonic distortion while reducing significantly the simulation time. The second part of the paper discusses mitigating solutions to harmonic amplification in systems with a high penetration of VSCs, and shows the effectiveness of using an Active Filter to reduce harmonic levels in system experiencing resonance conditions.

Power quality disturbances commonly observed in power systems have been studied for decades, resulting in numerous algorithms for detecting the events that affect the voltage and/or current waveforms. However, a considerable amount of disturbances is not visually observable in the raw waveforms, especially switching operations. These events must be detected through an alternative feature, such as abrupt variations in the root-mean-square (rms) voltage profile. This study examines the methods commonly used for detecting power quality disturbances in the waveform or rms voltage profile domains and identifies their limitations. Afterwards, a novel step change detector is proposed based on a modified median filter and rms voltage gradient values to overcome the deficiencies of the existing methods. The effectiveness of the proposed method is assessed by applying it to both simulated and field data. This assessment shows that the method detects all switching events with no false positives for the datasets under analysis.

The growing adoption of decentralised renewable energy generation (such as solar photovoltaic panels and wind turbines) and low-carbon technologies will increase the strain experienced by the distribution networks in the near future. In such a scenario, energy storage is becoming a key alternative to traditional expensive reinforcements to network infrastructure, due to its flexibility, decreasing costs and fast deployment capabilities. In this work, an end-to-end data-driven solution to optimally design the control of a battery unit with the aim of reducing the peak electricity demand is presented. The proposed solution uses state-of-the-art machine learning methods for forecasting electricity demand and PV generation, combined with an optimisation strategy to maximise the use of photovoltaic energy to charge the energy storage unit. To this end, historical demand, weather, and solar energy generation data collected at the Stentaway Primary substation near Plymouth, UK, and at other six locations were employed.

Electric vehicle (EV) charging stations fed by photovoltaic (PV) panels allow integration of various low-carbon technologies, and are gaining increasing attention as a mean to locally manage power generation and demand. This paper presents novel control schemes to improve coordination of an islanded PV-fed DC bus EV charging system during various disturbances, including rapid changes of irradiance, EV connection and disconnection, or energy storage unit (ESU) charging and discharging. A new hybrid control scheme combining the advantages of both master–slave control and droop control is proposed for a charging station supplying 20 EVs for a total power of 890 kW. In addition, a three-level (3L) boost converter with capacitor voltage balance control is designed for PV generation, with the aim to provide high voltage gain while employing a small inductor. The control techniques are implemented in a simulation environment. Various case studies are presented and analysed, confirming the effectiveness and stability of the control strategies proposed for the islanded charging system. For all tested conditions, the operating voltage is maintained within 5% of the rated value.

A voltage unbalance compensation method using three single–phase battery energy storage systems (BESSs) is proposed in this paper. A novel control strategy based on orthogonal signal generation is presented to regulate active and reactive power injection from the BESS inverters. A modified version of the ’IEEE 13 node’ benchmark three–phase distribution system is built in MATLAB / Simulink and three case studies are illustrated to verify the effectiveness of the proposed compensation method.

The voluminous amount of raw waveform data recorded by triggerless power quality monitors contain conspicuous and inconspicuous disturbance events. Data reduction and detection techniques are needed to efficiently extract useful information hidden in the raw data and identify power quality disturbances. The overall objective of this study is to use step changes in the rms voltage profile as an alternative triggering feature for automatically detecting switching events. The full characterization of the event is based on processing a small portion of the voltage waveform selected around the detected rms voltage step change. A filtering method is proposed to smooth out rapid fluctuations in the rms voltage profile during steady-state operation, while preserving the sharp edges caused by rms voltage step changes. Once the rms voltage profile has been filtered, adaptive limits based on the median absolute deviation are computed for detecting rms voltage step changes. The effectiveness of the proposed technique is evaluated using triggerless voltage waveforms to detect capacitor switching events. The use of the filtered rms voltage profile allows accurate detection of capacitor energizing and de-energizing events, while more than 50% of the detections in the unfiltered profile correspond to false-positives.

Z -source inverters (ZSIs) are single-stage power converters with both voltage buck and boost capabilities provided by the unique impedance network and the ability to operate during shoot-through states. This study proposes a novel non-linear adaptive backstepping method for dc-side controllers in a multi-loop control scheme of the ZSI in grid-tied photovoltaic (PV) systems. Despite the variability of the capacitor and inductor values in the ZSI impedance network, the proposed controller guarantees robust and stable operation under varying levels of PV irradiance and temperature. The shoot-through duty ratio of the ZSI is obtained directly from the output of an MPPT algorithm and the measured PV and inductor currents. This strategy overcomes the disadvantages of the conventional approach such as the non-minimum phase at the dc side of the ZSI. It also eliminates the need to linearise the voltage/current characteristics of the PV arrays and ZSI model. The ac-side controllers consist of an outer proportional-integral voltage controller and an inner deadbeat current controller to achieve unity power factor and stable capacitor voltage in spite of grid voltage fluctuations. The efficacy of the proposed adaptive backstepping controller and the multi-loop control scheme is validated by offline and hardware-in-the-loop real-time simulations.

With increasing penetration of distributed generators (DGs), existing distribution grids are becoming weaker. As a result, voltage regulation in distribution grids impose a significant challenge and can be improved by introducing additional control apparatuses. In this paper, a transformerless static synchronous series compensator (T-SSSC) is adopted to maximise the power transfer between DGs and a weak grid by improving grid voltage stability. A new control strategy is introduced to reduce the number of switching events during the operation of a T-SSSC, thus limiting the switching losses. Furthermore, a new droop based control scheme is proposed to minimise the voltage unbalance between phases. A medium voltage distribution grid with embedded T-SSSCs modelled in Simulink has been used to verify the effectiveness of the proposed control schemes. For completeness, the performance a T-SSSC is investigated following a sudden change in grid short circuit level.

This paper presents a stand-alone dc-bus Electric Vehicle (EV) charging station system using a photovoltaic (PV) source. The proposed topology includes a PV panel, an energy storage unit (ESU), and two EVs. Each unit is controlled independently; a voltage regulation scheme is implemented within the ESU converter to ensure the dcbus voltage is maintained at the nominal level under varying operating conditions. Two different operating scenarios are studied, and the results confirm that the algorithm developed allows regulating the dcbus voltage either with varying solar irradiance or when EV s are connected and disconnected from the dc grid. The proposed design offers lower energy conversion losses compared to the ac configuration and reduces energy demand on the existing ac distribution grid. It also finds applications in remote areas where parking facilities are provided for recreational purpose.

Temporal variability in renewable energy presents a major challenge for electrical grid systems. Tides are considered predictable due to their regular periodicity; however, the persistence and quality of tidal-stream generated electricity is unknown. This paper is the first study that attempts to address this knowledge gap through direct measurements of rotor-shaft power and shore-side voltage from a 1 MW, rated at grid-connection, tidal turbine (Orkney Islands, UK). Tidal asymmetry in turbulence parameters, flow speed and power variability were observed. Variability in the power at 0.5 Hz, associated with the 10-min running mean, was low (standard deviation 10–12% of rated power), with lower variability associated with higher flow speed and reduced turbulence intensity. Variability of shore-side measured voltage was well within acceptable levels (∼0.3% at 0.5 Hz). Variability in turbine power had 2 = 85% and ∼14% error). Therefore, the predictability and quality of tidal-stream energy was high and may be undervalued in a future, high-penetration renewable energy, electricity grid.

The number of battery energy storage systems (BESSs) installed in the United Kingdom and worldwide is growing rapidly due to a variety of factors, including technological improvements, reduced costs and the ability to provide various ancillary services. The aim of this paper is to carry out a comprehensive literature review on this technology, its applications in power systems and to identify potential future developments. At first, the main BESSs projects in the UK are presented and classified. The parameters provided for each project include rated power, battery technology and ancillary services provided, if any. In the next section, the most commonly deployed ancillary services are classified and described. At the same time, the nomenclature found in the literature is explained and harmonised. The second part of the paper focuses on future developments and research gaps: ancillary services that currently are not common but that are likely to be deployed more widely in the future will be described, and more general research topics related to the development of BESSs for power system applications will be outlined.

This paper proposes a novel power flow formulation and solution algorithm for a generalized large-scale interconnected transmission system encompassing multi-frequency HVac and HVdc grids having arbitrary numbers of buses, topologies, and operating frequencies. Back-to-back and ac/dc voltage-source converters are employed to interconnect and control the voltage and power interchange between two power grids operating at different frequencies. The power Flow formulation is based on a steady-state model of back-to-back and ac/dc converters operated in centralized and distributed droop control strategies. Each power grid is represented by a set of nonlinear power balance equations. These equations are solved simultaneously using a unified power flow algorithm, taking into account generator and converter limits. It is shown that the solution convergence is achieved rapidly despite the system size, topology, and converter control strategies. The efficacy and accuracy of the proposed steady-state solution algorithm are demonstrated by comparing the numerical solution to the one obtained by time-domain electromagnetic models of multi-frequency HVac and HVdc transmission systems with fully controllable back-to-back and ac/dc converters. The results obtained by using the proposed algorithm and the time-domain simulation are practically identical.

The subject of this work is the investigation of the power quality impact resulting from connecting a STATCOM to a distribution system. The STATCOM is used to provide voltage regulation, however, this device has an impact on the power quality at the PCC. This impact will be quantified for different STATCOM configurations (including two-level and multilevel inverter), output filter design and modulation techniques. The main conclusion of the analysis is that the STATCOM does not significantly impact the low frequency harmonics, however, for some configurations the THD limits are exceeded. It will be shown that changing the modulation technique does not change significantly voltage distortion at the point of common coupling (PCC), while increasing the number of levels and modifying the output filter design have a more evident effect. Future work on this topic will include the study of more complex system with existing harmonic distortion prior to connecting the STATCOM, to evaluate interaction of this device with other sources of harmonics.

The DMAIC (Define, Measure, Analyze, Implement and Control) approach is a well-established approach used to improve industrial processes and products. The DMAIC approach is mostly used as part of quality assurance processes, but this paper will show that it can be applied to investigation of root cause analysis of equipment failure. Specifically, the piece of equipment under investigation is a circuit breaker used in a distribution system. A second contribution of this paper is to provide suggestions on approaches to overcome modeling challenges related to lack of data, both in terms of measurements and in terms of system parameters.

Voltage sags and swells are power quality events commonly observed in power systems; however, none of the existing methods allows determining their point-on-wave inception and recovery instants (and consequently, their duration) accurately in all cases. The primary goal of this paper is to determine these instants with little or no delay, by calculating the absolute rms voltage difference between two adjacent sliding windows. The proposed method is based on the assumption that this difference is maximum when the sample under analysis corresponds to either the inception or the recovery instant. This method is valid for both sag and swell events, with or without transients. Evaluation of the proposed method performance for different types of events shows that it is robust and highly accurate in determining the inception and recovery instants. The estimation error for the majority of the events analyzed is either zero or one sample (each sample corresponds to a phase angle difference of 2.81 $^\circ$ ), while the worst performance is three samples.

Due to the high number of photovoltaic (PV) inverters installed, in some regions of the UK the power generated under peak conditions exceeds the transmission system capacity limits. With the aim to mitigate this condition and operate the grid within its design limits, utilities curtail PV output power, thus causing financial loss for the PV system owners and limiting the use of the installed components. The control system proposed in this paper allows using the PV inverter as an Active Filter (AF), when the output power is curtailed, thus improving the system power quality and exploiting the installed MVA. A novel contribution is the description of a harmonic derating coefficient which limits harmonic current injection based on the fundamental current generated by the inverter. The proposed application fits within the scope of the smart grid, where multi-functional inverters can be controlled by utilities to improve grid operating conditions.

This chapter is intended to discuss the most general approach to harmonic studies, which can be applied to shunt FACT devices and to all devices regulated by means of power electronic switches, such as wind power plants. This approach is supported by international standards. Some specific installations may require special considerations that are not addressed in detail in this chapter; however, specific references are provided for further reading whenever these special conditions are identified.

Camp Reach is a two-week summer engineering enrichment program for seventh grade girls, with continuing mentoring, communications, and activities for participants as they advance from seventh grade through high school. Camp Reach was founded in 1997 and the selection of participants has been designed to allow for longitudinal studies to evaluate the long-term effects of the program. This paper will present the main features of Camp Reach, the methodology used to perform the longitudinal studies, relevant results and a summary of lessons learned.

This paper details the transient operation of a wind energy conversion system (WECS) used simultaneously as an active filter and power generator. This study is intended to address the system response to two types of transient phenomena: voltage dips (fast transients) and wind speed variations (slow transients). The system response to voltage dips is governed by the electrical system dynamics and control method and results in the evaluation of the WECS low-voltage ride through capability. The study of the system response to wind speed variations requires a complete mechanical model to be included. Simulation results are presented for a typical WECS, and a discussion is carried out dealing with the generalization of the present work to other configurations.

A three-phase distributed constants model for high-voltage windings of a transformer is presented. The mutual couplings between phase coils are considered introducing some approximations. Applying the Clarke transformation to the proposed model, the voltage and current surge waves are provided by a simple numerical method. In this way, the model can be used to design the insulation between the turns of a single coil and between the windings and the iron core. A comparison of the numeric results obtained by applying the proposed method with the results obtained by other authors confirms the validity of the model. Moreover, further results are obtained: the proposed approach allows also finding the voltage and current waveforms for asymmetric faults.

Active filters (AFs) compensate harmonic currents demanded by non linear or time variants loads, with the aim to draw sinusoidal currents from the source. Different control strategies for AF have been proposed: among them, p-q theory is the most popular. However, the p-q strategy presents some drawbacks. As already reported in the literature, unexpected harmonic frequencies are generated in the source current as a consequence of such a control strategy. The aim of this paper is to provide, by means of the space vector approach to the p-q theory, analytical expressions that allow to determine the order and the amplitude of the harmonic components in the source current as function of load current or voltage harmonic distortion. By means of these expressions the limits and drawbacks of p-q strategies are quantified and a tool able to quantitatively predict the results of such a control is provided. Simulation results presented in the literature are interpreted according to the proposed expressions; moreover, further simulations are carried out in order to analyze some relevant cases not considered in previous works.

The number of distributed resources for renewable energy installed worldwide has been increasing rapidly in the last decade, and the great majority of these installations consist of solar panels and wind turbines. Other renewable sources of energy are not exploited to the same level: for instance, tidal energy is still a minute portion of the global energy capacity, in spite of the large amount of potential energy stored in tidal waves, and of the successful experience of the few existing plants. The world’s second largest tidal range occurs in the UK but at the moment tidal installations in this country are limited to a few prototypes. More recently, there has been a renewed interest in harnessing tidal energy in the UK, and a few tidal lagoon projects have been evaluated by the UK government. This paper provides an overview of the historical and current developments of tidal plants, a description of operation of tidal lagoons, challenges and opportunities for their integration within the UK energy systems and solutions to improve the dispatchability of tidal energy. The concepts described in the paper are applied to a tidal project proposed for South Wales.

The subject of this paper is telephone interference caused by harmonics in distribution systems. The first part of the paper presents a theoretical analysis of the phenomenon with a detailed discussion of the role of ground currents and harmonic sequence order. Applicable standards, acceptable interference levels and mitigating solutions are also summarized. The second part of the paper describes modeling and simulations of a typical distribution system. Simulation results show the importance of controlling harmonics on the feeder to limit telephone interference concerns.

This paper presents a preliminary study meant to determine the economic feasibility of partially using distributed generators (DGs) as active filters (AFs) meant to sink current harmonics injected by nonlinear loads (NLs) connected at the same feeder as the DG. Such approach may avoid the installation of dedicated AFs, nevertheless it may cause exceeding thermal stressing of insulation and solid state switches.

This paper describes a novel control method for a WECS (Wind Energy Conversion System) meant to partially operate as an AF (Active Filter). The control is defined in an equivalent reference frame obtained by applying the Park Transformation to the three-phase quantities. The zero-sequence component is includd in the control system; this feature enables the compensation of zero-sequence harmonics. The effectiveness of the proposed methodology is quantified in terms of current spectra and reduction of the voltage and current THD at the Point of Common Coupling (PCC). The proposed application results in higher power loss in the power converters that connects the generator rotor to the PCC with respect to sinusoidal operation. Nevertheless, it is proved that the WECS derating enables the reduction of the power converters' power loss. Voltage distortion at the windings terminals and power converters' terminals is a second consequence of the proposed application, and the peak stator and rotor voltage is an important design parameter in the choice of the solid state devices.

Fuzzy inference systems are presently employed in the presence of uncertain models, or when deterministic models are too complex to be implemented. Input data to fuzzy inference systems are generally represented by crisp variables also when they represent experimental measurement results, thus disregarding measurement uncertainty. Since recent works have shown that measurement results can be effectively represented, together with their associated uncertainty, by fuzzy variables, this paper proposes a modified fuzzy inference system characterized by considering fuzzy variables as input data.

This study explains how a Steinmetz compensator works. Past explanations are based on phasor diagrams and do not address the basic physical phenomena of electromagnetic energy flow. This paper uses the Poynting vector to detect and understand the process of compensation and restoration of symmetry in an unbalanced system.

This work deals with the steady-state operation of wind energy conversion systems (WECSs) used simultaneously as active filters (AFs) and power generators. This application is motivated by the increasing number of non-linear loads (NLLs) on the power grid and by the possibility to offer an economical alternative to the installation of dedicated filters that sink the harmonic currents injected by such loads. The main contributions of this paper are as follows: (i) three different control systems that allow the simultaneous use of the WECS as AF and power generator are presented; (ii) compensation of triplen harmonics is addressed; (iii) additional power losses due to AF operation, leading to the derating of the WECS, are quantified; (iv) results based on numerical simulations are provided.

Voltage sags and swells occur often in power systems; however, determining the duration of these events is not straightforward. Seven methods for estimating the inception and recovery points (and consequently, the duration) of voltage sags and swells are surveyed: threshold rms voltage, waveform envelope, discrete wavelet transform, missing voltage, dq transformation, numerical matrix, and peak detector. Each method has its own strengths and weaknesses; however, no one method works on all conditions. An algorithmic approach to determining inception and recovery points is suggested. Such approach employs one method in combination with other methods based on the event characteristics.

Voltage rise is one of the major concerns that limits the photovoltaic (PV) hosting capacity or the maximum amount of PV generation that a distribution circuit can accommodate. This paper examines the effectiveness of low-voltage distribution static compensators (LV-DSTATCOMs) in increasing the PV hosting capacity of distribution circuits by mitigating voltage rise. Stochastic analysis framework is used to determine the PV hosting capacity while an iterative placement technique is used to identify effective device locations. To provide insights on the optimal device size, number, and control settings, sensitivity analysis is carried out. The results show that, with appropriate size and control settings, installation of few LV-DSTATCOMs in a distribution circuit can significantly increase its PV hosting capacity. For the circuit under consideration, a set of 23 devices has increased the PV hosting capacity from 15% to 100% of the median day time peak load.

The problem of identifying the sources injecting periodic disturbances in the electric systems is a critical point in the assessment of the electric Power Quality. The available methods, based on a deterministic approach, do not always provide correct results under the different possible operating conditions. This paper proposes an innovative method, based on a Fuzzy inference and shows significant simulation results.