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The doctoral thesis proposes a synchronization event detection method suitable for establishing a common time base across devices using power-line communication. The technique facilitates the creation of a synchronization procedure for smart grid terminal devices, thus bringing to the low-voltage segment new functionalities already known from the higher voltage levels of the distribution network. High-precision, zero-cross line voltage detection was employed as the synchronization event. The use of the PLL (phase-locked loop) was considered and analyzed as a potentially applicable option; however, such a solution proved to be insufficiently robust against interference. Further, an FFT-based approach was designed and reviewed. The technique performs zero-cross detection, but only for the fundamental harmonic component that remains the same across the entire network. The influence of incoherent sampling on the FFT, too, was tested during the development of the method; in this context, coherent sampling was found to constitute an essential prerequisite for accurate detection as it allows us to eliminate the spectral leakage error. The impact of an AD converter on the detection accuracy was also evaluated. The proposed approach ensures the accuracy required for all common measurements and operations to improve the production, distribution, and consumption of electricity through smart grids.

This diploma thesis deals with the design and testing of a system for powerline communication, enabling control of LED lights. The work first describes the basic principles of powerline communication, specifies the communication bands and summarizes the basic functional requirements for communication within the system for LED lighting control. It also describes the method of selecting a modem for powerline communication, the design of a test module with this modem and also the method of testing real communication between two test modules, including test results. The most comprehensive part of the work describes the design of hardware and software of the universal PLC module and how to use it. In addition, it referes to the development tools used as an example of implementation in LED lighting. At the end of the work are summarized the results of testing the proposed system.

Examensarbetet kommer att göra en jämförande analys av driftsäkerhet med trådade signaler till en Remote Terminal Unit (RTU) och en Programmable Logic Controller (PLC) med busstyrning. Rapporten genomfördes som ett uppdrag av Skellefteå Kraft AB för att se om det möjligt att byta till PLC- med busstyrning. Rapporten redogör för grundläggande beskrivning för skillnaden mellan de här två system och kommer att undersöka vilken som är driftsäkrare och lönsammare med hänsyn till krav enligt Svenska Kraftföretagens riktlinjer för dammsäkerhet (Ridas).Med hjälp av kurslitteratur, ABB handboken, internet websidor samt intervjuar med Skellefteå Kraft AB:s personal har arbetets resultat visat att busstyrning med PLC kommer att fungera driftsäkert samt kommer att bli lönsamt jämfört med trådade signaler till RTU. Resultat visat även att det finns ingenting som hindrar att installera busstyrning enligt Ridas men vissa funktioner bör installeras. Rapporten är avgränsat genom att inte ta upp eventuella krav från miljöbalken. / This thesis will make a comparative analysis of the operation safety of the wire connection to Remote Terminal Unit (RTU) and Programmable Logic Controller (PLC) with bus-controller. The report describes the basic description of the difference between these two systems and will explore which is safer and more economic with consideration to qualification according to Swedish energy companies' guidelines for dam safety (Ridas).Through course literature, ABB Bok, internet web sits and interviews with Skellefteå Kraft AB staff the result of this report have been created.The report results prove that PLC with bus-controller will operate operationally safe and profitable compared to wire connection to RTU. Results also showed that there is nothing which prevents to install bus-controller according to RIDAS but certain features should be installed.

Radio frequency (RF) spectrum congestion motivates the search for alternative communication techniques to complement radio systems. Visible light communications (VLC) is an emerging technology that exploits the recent and ever-growing increase in the usage of energy-efficient light emitting diodes (LEDs) to imperceptibly modulate the optical power output of LEDs to enable communication and augment RF networks. Orthogonal frequency-divison multiplexing (OFDM) has been proposed as a modulation scheme for VLC due to its high spectral efficiency, ease of channel estimation and equalization, resistance to inter-symbol interference (ISI) and frequency-selective fading, efficient implementation using the Fast Fourier Transform (FFT), and compatibility with RF and power-line communication (PLC) standards that use OFDM. One of the major drawbacks of conventional OFDM techniques is the high peak-to-average power ratio (PAPR) of OFDM signals. The peaks of the OFDM signals are clipped due to the limited dynamic range of the LED, which translates the high PAPR of the OFDM signal into non-linear distortion (NLD). This signal distortion causes bit-error rate (BER) performance degradation, especially at high optical signal-to-noise ratios (SNRs) typical of indoor VLC scenarios. In this thesis, a new family of modulation techniques, termed spatial optical OFDM (SO-OFDM), is proposed with the aim of reducing the PAPR of conventional DC-biased optical OFDM (DCO-OFDM) by making use of the large number of LEDs typically available in indoor lighting settings. Each LED group signal is a narrowband signal consisting of a small number of subcarriers, and thus has a smaller PAPR than the original OFDM signal. Firstly, SO-OFDM is introduced and its two key concepts of frequency-to-space mapping and spatial summing are explained. Frequency-to-space mapping is achieved by allocating a subset of OFDM subcarriers to each LED. Each LED group signal is a narrowband signal consisting of a small number of subcarriers, and thus has a smaller PAPR than the original OFDM signal. Several design variations of the subcarrier assignment to LEDs are introduced and are shown through simulations, to reduce PAPR, and NLD noise due to clipping, and improve the BER performance at high SNRs as compared to DCO-OFDM. In addition, luminous efficacy is identified as an important lighting design parameter that is impacted by modulation. Relative luminous efficacy is defined as the ratio of the luminous efficacy of a modulated LED to that of an LED driven by a DC signal, and is introduced as a metric to assess the impact of modulation on LED lighting. Relative luminous efficacy links communication parameters such as signal variance to lighting design requirements. Secondly, a low-complexity amplify-and-forward (AF) scheme is proposed for an integrated power-line communication/visible-light communication (PLC/VLC) where SO-OFDM is used for the VLC link. Frequency translation of the incoming PLC signal is used to increase the usable bandwidth of the LED. The use of both frequency translation and SO-OFDM leads to capacity gains over DCO-OFDM in the high SNR regime. Finally, a low-complexity variant of SO-OFDM, termed square-wave SO-OFDM (SW-SO-OFDM), is proposed. Square-wave SO-OFDM uses square-wave carriers instead of sinusoidal waves to modulate a single OFDM subcarrier signal per LED. By using square-wave carriers, SW-SO-OFDM eliminates the need for digital-to-analog converters (DACs), digital predistortion (DPD), and the FFT operation. Squarewave SO-OFDM is also shown, through simulations, to achieve BER performance gains over SO-OFDM and DCO-OFDM. In addition, an experimental demonstration of SW-SO-OFDM with 64 QAM modulation on subcarriers is described. / Thesis / Doctor of Philosophy (PhD) / Visible-light communications (VLC) is an emerging technology that exploits the increasingly widespread use of light-emitting diodes (LEDs) for indoor lighting, and modulates the optical power output of the LED for data transmission. Among the various modulation techniques that have been proposed for VLC, orthogonal frequency-division multiplexing (OFDM) offers high data rates, resistance to channel impairments, and simple channel estimation and equalization. However, OFDM signals suffer from a high peak-to-average power ratio (PAPR) which degrades the efficiency of the power amplifier in the transmitter and hinders the communication performance. In this thesis, a new multiple-LED modulation technique, termed spatial optical OFDM (SO-OFDM), is proposed to reduce the PAPR. Using a frequency-to-space mapping, SO-OFDM divides the wideband high-PAPR OFDM signal into multiple narrowband low-PAPR signals and assigns each signal to a group of LEDs. Spatial summing of the transmitted signals occurs at the receiver allowing for the use of a conventional OFDM receiver. Several variations of SO-OFDM are introduced and are shown, using simulations, to reduce the PAPR, combat non-linear distortion (NLD), and improve the bit-error rate (BER) performance at high signal-to-noise ratios (SNRs), typical of VLC systems. Spatial optical OFDM is also applied to a practical scenario where its PAPR reduction capability is used to improve the overall capacity of a proposed system that integrates power-line communication (PLC) and VLC. A low-complexity variant of SO-OFDM, that uses square-wave carriers and simplifies the transmitter design by eliminating the need for digital predistortion (DPD) and digital-to-analog converters (DACs) is also proposed, and tested experimentally.

Η BPL τεχνολογία είναι μια υποσχόμενη τεχνολογία η οποία προσφέρει τηλεπικοινωνιακές υπηρεσίες μέσω των γραμμών ηλεκτρικής ενέργειας και η οποία τα τελευταία χρόνια γνωρίζει ραγδαία ανάπτυξη. Σκοπός της παρούσας διπλωματικής εργασίας είναι η παρουσίαση της BPL τεχνολογίας και η υλοποίηση της με τρεις διαφορετικούς τρόπους σε συγκεκριμένο ηλεκτρικό δίκτυο. Στο πρώτο κεφάλαιο γίνεται μια γενική αναφορά στην BPL τεχνολογία. Παρουσιάζονται τα επίπεδα του δικτύου ηλεκτρικής ενέργειας τα οποία συμμετέχουν σε ένα BPL δίκτυο, τα διάφορα δίκτυα πρόσβασης, οι αρχιτεκτονικές και ο εξοπλισμός τους, καθώς και διάφορα προβλήματα που αντιμετωπίζει η συγκεκριμένη τεχνολογία. Στο δεύτερο κεφάλαιο περιγράφονται τα επίπεδα του BPL δικτύου. Αναλύονται οι διάφορες τεχνικές διαμόρφωσης όπως η OFDM (ορθογώνια μέθοδος διαμόρφωσης με διαίρεση συχνότητας) και η διαμόρφωση απλωμένου φάσματος. Επίσης γίνεται αναφορά στη διαχείρηση σφαλμάτων, στο BPL MAC στρώμα καθώς και στα πρωτόκολλα 802.11. Στο τρίτο κεφάλαιο αναφέρονται οι διάφορες τηλεπικοινωνιακές υπηρεσίες που προσφέρονται από την BPL τεχνολογία καθώς και οι εφαρμογές του έξυπνου δικτύου (Smart Grid) και του έξυπνου σπιτιού (Smart Home) που υλοποιούνται με τη συγκεκριμένη τεχνολογία. Στο τέταρτο κεφάλαιο γίνεται μια σύντομη αναφορά στην τεχνολογία των οπτικών ινών και στο τρόπο με τον οποίο η τεχνολογία αυτή θα χρησιμοποιηθεί ως δίκτυο κορμού το οποίο θα φτάνει μέχρι και τους μετασχηματιστές μέσης/χαμηλής τάσης. Επίσης παρουσιάζεται και η PON-BPL τεχνολογία. Στο πέμπτο και τελευταίο κεφάλαιο πραγματοποιείται η σχεδίαση του BPL δικτύου πρόσβασης με τρεις διαφορετικές αρχιτεκτονικές σε περιοχή της Λακωνίας της οποίας το ηλεκτρικό δίκτυο ψηφιοποιήθηκε με τη χρήση ενός προγράμματος GIS (Γεωγραφικά Συστήματα Πληροφοριών) και συγκεκριμένα του Mapinfo. Στη συνέχεια γίνεται σύγκριση των αρχιτεκτονικών ως προς το κόστος και την ταχύτητα. / BPL technology is a promising technology that offers telecommunications services through power lines, which in the recent years is facing a rapid development. The object of this specific project is the presentation of BPL technology and its realization in three different ways on a specific power grid. In the first chapter there is a general reference to BPL technology. Also it includes a presentation of the levels of the power grid which participate in a specific BPL network. Furthermore there is a presentation of the various access network, their architectures, equipment and various problems faced by this technology. The second chapter contains the description of the levels of BPL network. Also various modulation techniques like OFDM (Orthogonal Frequency Division Multiplexing) and spread-spectrum configuration are analyzed. Finally there is a reference to the management of errors, BPL MAC layer and to the protocols 802.11 as well. In the third chapter there is a reference about the various telecommunication services which are provided via BPL technology as well a reference for the implementations of the Smart Grid and Smart House which are realized with the specific technology. At chapter four a brief reference is conducted about the optical fiber technology and about the manner in which this technology will be used as a backbone which reaches up the medium/low voltage transformers. Also PON-BPL technology is presented. Finally in the fifth and last chapter takes place the design of BPL access network with three different architectures in an area of Laconia whose power grid digitized by using a GIS program (Geographic Information Systems), namely the Mapinfo. Eventually there is a comparison between architectures as concern the cost and the speed of realization needed.