Since the onset of automation, industry has relied on adjustable speed drives to accurately control the speed of motors. Recent advances have increased the number of adjustable speed drives hitting the market. The proper operation of the speed drives requires electrical supply with relatively high power quality which is not the case in most industrial facilities. Power quality problems such as harmonic, sag, swell, flicker, and unbalance can trip the speed drive with a wrong message, which is referred as a premature tripping. Although the power quality problems can be mitigated by using custom power devices, they are bulky and costly. Moreover, they themselves might adversely affect the operation of the adjustable speed drive. A comprehensive study done in this thesis presents the overlooked effect of the custom power devices on the speed drive stability. It is found that the speed drive system might trip due to its interaction with custom power devices. Obviously, it is vital to increase ASD immunity to premature tripping because of poor power quality or custom power. This thesis offers fast, efficient and robust algorithms to achieve this immunity by retrofitting the ASD control unit and integrating the power conditioning function with the adjustable speed drive. Therefore, the power quality problem is mitigated and the drive system performance is significantly enhamced. Such integration requires the modification of the control unit by considering various elements such as envelope tracking, phase-locked loop, symmetrical component extraction, and the controller. Simple but robust and fast algorithms are proposed for such elements based on a newly developed energy operator algorithm. The developed energy operator and the developed algorithms overcome the drawbacks of the existing algorithms.

Since the onset of automation, industry has relied on adjustable speed drives to accurately control the speed of motors. Recent advances have increased the number of adjustable speed drives hitting the market. The proper operation of the speed drives requires electrical supply with relatively high power quality which is not the case in most industrial facilities. Power quality problems such as harmonic, sag, swell, flicker, and unbalance can trip the speed drive with a wrong message, which is referred as a premature tripping. Although the power quality problems can be mitigated by using custom power devices, they are bulky and costly. Moreover, they themselves might adversely affect the operation of the adjustable speed drive. A comprehensive study done in this thesis presents the overlooked effect of the custom power devices on the speed drive stability. It is found that the speed drive system might trip due to its interaction with custom power devices. Obviously, it is vital to increase ASD immunity to premature tripping because of poor power quality or custom power. This thesis offers fast, efficient and robust algorithms to achieve this immunity by retrofitting the ASD control unit and integrating the power conditioning function with the adjustable speed drive. Therefore, the power quality problem is mitigated and the drive system performance is significantly enhamced. Such integration requires the modification of the control unit by considering various elements such as envelope tracking, phase-locked loop, symmetrical component extraction, and the controller. Simple but robust and fast algorithms are proposed for such elements based on a newly developed energy operator algorithm. The developed energy operator and the developed algorithms overcome the drawbacks of the existing algorithms.

This research suggests a novel voltage control scheme that can compensate for voltage sag and swell conditions in three-phase power systems. Faults occurring in power distribution systems or facilities in plants cause the voltage sag or swell. For sensitive loads, even voltage sags of short duration can cause serious problems in the entire system. In order to mitigate power interruptions, this research proposes a scheme called Voltage Sag Supporter utilizing a PWM (Pulse Width Modulation)-Switched Autotransformer. The proposed scheme is able to quickly recognize the voltage sag or swell condition, and it can correct the voltage by either boosting the input voltage during voltage sag events or reducing the input voltage during voltage swell events. Among existing methods, the scheme based on the inverter system such as dynamic voltage restorers (DVR) require an inverter, a rectifier, and a step-up down transformer, which makes the system expensive. AC converters can be used for the purpose of the research. However, they consist of two solid-state switches per one phase and include energy storage devices such as reactors and capacitors. The switching device for the high voltage application is relatively expensive so that this research suggests a scheme utilizing only one switch for the output voltage control, which makes the system more stable and cost effective. The proposed scheme can be applied at any voltage and provides cost and size advantages over existing methods due to the reduced number of switching components and no need of energy storage devices. Simulations and experiments have been carried out to verify the validity of the proposed scheme, and prototype experiments are being done to confirm the control scheme.

Abstract This thesis summarizes some of the voltage sag indices that are currently used by the industry. Power quality monitoring results obtained at two science based industrial parks are used to estimate the voltage quality of the electricity service and make comparison with data of a foreign utility company that are available in the literature. Fault position method is used in this study to estimate the distribution of voltage sag vulnerability areas due to the network topology ok in 2005. Comparison of the exposed area is presented. An assessment is conducted for the application of fault position method to estimate the fault location by using fault simulations results and power quality monitoring data.

Σκοπός της παρούσας εργασίας είναι η μελέτη της έννοιας «ποιότητα ηλεκτρικής ισχύος» σε ότι έχει να κάνει με τον ορισμό της έννοιας, παραδείγματα προβλημάτων ποιότητας ισχύος στο δίκτυο και σε ηλεκτρικά συστήματα καθώς και ανάλυση των αιτιών και των επιπτώσεων των προβλημάτων αυτών. Επίσης γίνεται μελέτη των απαιτήσεων γείωσης, ώστε να εξασφαλίζεται η αξιοπιστία του συστήματος και κατ΄επέκταση η ποιότητα ισχύος σε ηλεκτρικά συστήματα. Στο πρώτο κεφάλαιο γίνεται αναφορά στην έννοια της αξιοπιστίας των συστημάτων ηλεκτρικής ενέργειας, των κριτηρίων που την εξασφαλίζουν, καθώς και τη σημασία που αυτή έχει για το σχεδιασμό των σύγχρονων συστημάτων. Στο δεύτερο κεφάλαιο ορίζεται η έννοια της ποιότητας ηλεκτρικής ισχύος, ενώ αναφέρονται και χαρακτηριστικά παραδείγματα μέσα από τα οποία εμφανίζεται. Επιπλέον παρουσιάζονται τα αίτια πρόκλησης του κάθε προβλήματος και των επιπτώσεων που φέρουν αυτά στα φορτία του συστήματος. Στο τρίτο κεφάλαιο γίνεται ανάλυση των αιτιών προβλημάτων αξιοπιστίας των συστημάτων, τα οποία επηρεάζουν την ποιότητα ισχύος και οδηγούν σε διακοπές τροφοδοσίας. Τα προβλήματα αυτά οφείλονται σε σφάλματα του εξοπλισμού των συστημάτων διανομής αλλά και σε εξωτερικούς παράγοντες όπως είναι η ίδια η φύση, οι καιρικές συνθήκες και η ανθρώπινη αμέλεια. Στο τέταρτο κεφάλαιο εξετάζεται η έννοια της ποιότητας ισχύος στο σύστημα διανομής του εξηλεκτρισμένου πλοίου καθώς και σε αιολικά πάρκα κατά την ενσωμάτωση ανεμογεννητριών στο δίκτυο. Παρουσιάζονται προβλήματα ποιότητας ισχύος, καθώς και οι αιτίες πρόκλησής τους με τις αντίστοιχες επιπτώσεις. Στο πέμπτο κεφάλαιο παρουσιάζονται γενικές έννοιες για τις γειώσεις, τρόποι γείωσης σε ηλεκτρικές εγκαταστάσεις χαμηλής και μέσης τάσης, κατηγορίες ηλεκτροδίων γείωσης και τέλος μελέτη της αντίστασης γείωσης και των παραγόντων εξάρτησής της. Στο έκτο κεφάλαιο παρουσιάζονται κάποιες γενικές απαιτήσεις γειώσεων του εξοπλισμού ηλεκτρικών εγκαταστάσεων σχετικά με την επιλογή των αγωγών και τις καλύτερες δυνατές συνδεσμολογίες. Επίσης αναφέρονται προβλήματα λόγω μη αξιόπιστης γείωσης και τέλος γίνεται μελέτη του συστήματος γείωσης ενός αιολικού πάρκου για διάφορους τρόπους σχεδιασμού αυτού του συστήματος. Στο έβδομο κεφάλαιο παρουσιάζονται απαιτήσεις γείωσης και διασυνδέσεων στον εξοπλισμό του συστήματος διανομής ενός εξηλεκτρισμένου πλοίου. Στο όγδοο κεφάλαιο παραθέτονται τα συμπεράσματα της παραπάνω μελέτης σε σχέση με την απαιτούμενη ποιότητα ισχύος και την αποτελεσματική γείωση των συστημάτων. / The purpose of the paper is to study the concept of “power quality” as regards its definition, examples of power quality problems in grid and electrical systems as well as the analysis at the causes and impacts of these problems. Besides, we are going to study grounding requirements to ensure the system’s reliability and, thus, the power quality in electrical systems. The first chapter refers to the concept of reliability of power systems, the criteria to ensure it and its importance in designing modern power systems. The second chapter defines the concept of power quality and mentions examples through which it appears. Besides, there is a presentation of the causes of each problem and its impacts on the loads of electrical systems. The third chapter analyzes the system’s reliability problems which affect the power quality and lead to power outage. These problems are due to the faults in the equipment of distribution systems and other factors such as the nature itself, the weather and human negligence. The fourth chapter examines the concept of power quality in the distribution system of an all-electric ship and in wind farms in integrating wind turbines into the grid. There is also a presentation of power quality problems, their causes and effects. The fifth chapter presents general concepts of grounding, ground methods in low and middle voltage electrical installations, categories of ground electrodes and, finally, the study of grounding resistance and the factors on which it depends. The sixth chapter presents some general requirements for the grounding of the equipment of electrical installations regarding the selection of conductors and the best possible connections. It also mentions problems due to unreliable grounding and, finally, it studies the grounding system of a wind farm for different ways of the design of this system. The seventh chapter presents grounding and connection requirements in the equipment of the distribution system of an all-electric ship. The eighth chapter presents the conclusions of the study above in correlation with the required power quality and the effective grounding of the systems.

I takt med att dagens samhälle ställer högre krav på störningsfri elleverans samt en vilja till att ständigt förbättra elkvaliteten. Detta ger elkvalitet och elkvalitetsmätningar en större betydelse för både elleverantörerna och deras kunder.Som ett led i att säkerställa en god elkvalitet behövs speciella instrument som mäter och analyserar de parametrar som orsakar en försämrad elkvalitet. Dagens problematik är att många moderna utrustningar påverkar elkvaliteten negativt samtidigt som andra moderna installerade utrustningar är mera störningskänsliga. Genom att installera ett heltäckande elkvalitetssystem för mätning av elkvalitet kan problem upptäckas innan dessa ger upphov till driftstörningar eller skador på ansluten utrustning. Idag mäts framförallt elkvalitet på elleverantörernas 10, 40 och 130 kV nät. Ambitionen är att få bättre övervakning på lågspänningsnäten 0,4 kV.I detta arbete visas ett förslag på hur ett integrerat elkvalitetssystem bestående av både elnätsanalysatorer och energimätare utrustade med en elkvalitetsmodul kan utformas. Med ett integrerat system fås en överblick enklare fram ifall någon av lågspänningskunderna bidragit till en försämrad elkvalitet. / Today's society places a greater demands on interference-free electric distribution and a desire for a constant efficiency on power quality. Power quality and power quality measurements are continually becoming a more important issue to both the electricity suppliers and their customers.As a part of ensuring good power there's a requirement for special instruments that measure and analyses the parameters that is the cause of deterioration of power quality. Today's problem is that many modern devices has a negative effect on power quality while other modern devices are more sensitive to disturbance. By installing a comprehensive power quality system for measurement of power quality, some problems can be detected before they give rise to malfunction or damaging any of the connected equipment. As today, measurements on power quality are mainly focus on the suppliers' 10, 40 and 130 kV grid, with the ambition of creating a better surveillance on the low voltage grid, 0.4 kV.In this report a proposal of how an integrated power quality system consisting both of power quality analyzers and energy meters equipped with a power quality module could be designed. With an integrated system there will be easier to detect of someone of the low voltage costumers contributes to a deterioration of power quality.

This thesis assesses the voltage unbalance in distribution networks due to load asymmetry or line asymmetry, based on measurement data from a limited number of monitors. The main outcomes of this research are a probabilistic methodology for estimating both momentary and long term unbalance and an optimal monitor placement providing the highest accuracy for the monitored level of unbalance. With increasing numbers of large single-phase loads and distributed generation integrated into the power system, the future distribution network is expected to be more flexible, robust and “smart”. This results in the requirement for high quality of electricity supply to be delivered to customers and is a challenge for the operation of the system. As the unbalance results in excessive heating, accelerated thermal ageing, reduction of efficiency and financial losses, the unbalance should be regulated to be below the statutory limit. Given the fact that unbalance is a long term phenomenon that may not cause any triggering of protection or faulty response of equipment, it can be only determined from available data such as loading levels of a network and the incomplete monitored voltage of a network. Due to limited monitoring in the network and therefore insufficient data, unbalance may be unobservable. This thesis therefore aims to develop a methodology to increase the observability of unbalance in the network in spite of limited monitoring. This research uses Voltage Unbalance Factor (VUF) to quantify the level of unbalance. The first major part investigates the unbalance caused by asymmetrical loadings. By properly identifying the source of unbalance, the basic patterns of propagation of unbalance under possible scenarios are revealed and a methodology of probabilistic estimation of unbalance can be developed accordingly. Seen from the MV level of distribution networks, the loads are usually in the constant power form. Therefore, the variation in the load can be modelled by changing either active power or reactive power or both of them, depending on the data availability. The combinations of daily loading curve at buses and the normally distributed power factors in three phases of loads are used to create an unbalanced condition at the sources. Realistic assumptions of power factors and reasonable categories of types of loads result in realistic modelling of the unbalanced load. The probabilistic VUFs at different buses in the network are calculated and the weak areas in the network are identified using heat maps. The simulation results match the real VUF levels measured in the distribution network. The second part of the thesis explores the influence of asymmetrical lines in addition to the asymmetrical loading on propagation of unbalance. The last part provides a guideline for optimal monitor placement for unbalance. Two methods, manual ranking of buses and automatic optimization using Genetic Algorithm, are proposed. The two methods indicate the same optimal locations for monitor placement in the network. The developed methodologies enable the assessment of unbalance in the network when monitoring is limited and can be applied to real networks to assess the level of unbalance at non-monitored buses.

The problem with the implementation of the PV generators is that majority of the UNDP offices are in developing and underdeveloped countries. Majority of these countries experience various problems with the power quality from the national electrical grid. There is also a second problem with the installed PV system, the problem is that the installed PV sources show a significant decrease in the expected annual yield ranging from 10 % – 60 % in some cases. The main aim of this thesis is to analyze the power quality in three countries (Nepal, Sao Tome and Namibia) and find the correlation between power quality and PV generation. This aim is done in five steps. The first step is the collection of measured data from the grid for a specific period of one year from July 2020 to August 2021. The collected data includes the current, voltage, power factor, frequency, reactive and active power. To achieve this, the Acuvim II power quality analyzer was sent to these three countries. In the second step, a literature review is done to research about power quality problems, identifying the power quality problems and analyzing the problems created by these identified power quality problems. In the three countries, undervoltage, overvoltage, swells, and sags where the main power quality problems which were recorded. The third step is a system case study process in which an in-depth analysis is done on the three PV systems and a simulation is done to understand the solar parameters which includes the specific yield, and performance ratio. The fourth step involves comparing the collected data from the PQ analyzer with the simulation results and determine the effects the power quality problems and system design have on the low annual yield. Also, the yearly amount of overvoltage and undervoltage in the three countries within the analysis period was analyzed. The voltage and fluctuation analysis also includes other power quality parameters which were measured. The collected parameters were analyzed and the correlation between the electrical grid requirements in the three countries were made with the recorded data. The final step involves recommending improvements and optimization techniques for the three systems to improve life cycle cost and long-term vision. Thus, analyzed results and simulated results are compared to evaluate the performance. The PV system in Namibia had the best grid conditions with all the grid parameters operating within the defined grid limits, there was a 30 % reduction in annual energy production in the Nepal system due to poor power quality conditions which included overvoltage, undervoltage, and frequency deviations. There was also a 50 % energy loss in the annual production of the PV systeminstalled in Sao Tome. Sao Tome also had the highest number of recorded outages with an average of 6 – 7 hours of outages recorded daily. Power quality problems recorded in Sao Tome included voltage fluctuation problems and frequency deviations.

Due to the increasing trend towards energy saving of white goods appliances and the commercial viability of power electronic components, there has been an expansion in the use of solid state electronics and variable frequency drive motors in these applications. However, a major drawback of using such energy efficient loads is the introduction of current harmonics onto the local distribution grid. Furthermore, the proliferation of such devices elevates the harmonic content of the supply voltage and the ensuing potential impact on residential distribution networks. This thesis investigates the harmonic content generated by some representative household appliances and suggests a solution to minimize current harmonics by means of active filtering. An active filter circuit is proposed and simulations will be undertaken to compare filter performance when used as an active front end versus a feeder input compensator. Further, a hardware design of the filter was implemented to experimentally verify the filter operation. / Thesis / Master of Applied Science (MASc)

With the rapid development of power systems, more and more smart devices are installed in power industries, and each of them is gathering tons of information every day.Due to the data explosion and the difficulty of processing these data, data visualization, a big data technology, has become a trend. With the help of information technology, the visualization of real-time data has been achieved in power industries and there are multiple successful examples such as one-line diagram, load flow dashboard and equipment dashboard.In fault analysis group, digital fault recorders are essential to record and report an event.They are triggered when a fault occurs and corresponding report is generated instantly.However, people seldom utilize the historical data from DFRs to analyze the power quality issues.Therefore, this thesis presents the development of a power quality dashboard by using the collected data from DFRs.Three related power quality analyses have been accomplished in this paper: voltage and current variation, harmonics and unbalance components.Recursive algorithm is applied to compute the phasors and errors; Discrete Fourier Transform is utilized to extract harmonics from the samples; and the symmetric components are calculated by "A"-matrix transformation.The start page for the dashboard is a google map with all the DFR markers, and after double-clicking the marker, the report page will be opened.With the reports, engineers can not only monitor the event but also analyze out the possible causes and characteristics for a fault.For those renewable energy substation, the harmonic contents can be supervised so that the damages and losses can be significantly reduced by identifying the high harmonics.Ultimately, the goal of the dashboard is to achieve warning status and harmonic gradient mapping in the future. / Master of Science