Voltage control on an uninhabited autonomous vehicle electrical distribution system

More-electric vehicle technology is becoming prevalent in a number of transportation systems because of its ability to improve efficiency and reduce costs. This paper examines the specific case of an Uninhabited Autonomous Vehicle (UAV), and the system topology and control elements required to achieve adequate dc distribution voltage bus regulation. Voltage control methods are investigated and a droop control scheme is implemented on the system. Simulation results are also presented.

A compact free space quantum key distribution system capable of daylight operation

A free space quantum key distribution system has been demonstrated. Consideration has been given to factors such as field of view and spectral width, to cut down the deleterious effect from background light levels. Suitable optical sources such as lasers and RCLEDs have been investigated as well as optimal wavelength choices, always with a view to building a compact and robust system. The implementation of background reduction measures resulted in a system capable of operating in daylight conditions. An autonomous system was left running and generating shared key material continuously for over 7 days. © 2009 Published by Elsevier B.V..

Local Storage Meets Local Demand: A Technical Solution to Future Power Distribution System

Future power systems are expected to integrate large-scale stochastic and intermittent generation and load due to reduced use of fossil fuel resources, including renewable energy sources (RES) and electric vehicles (EV). Inclusion of such resources poses challenges for the dynamic stability of synchronous transmission and distribution networks, not least in terms of generation where system inertia may not be wholly governed by large-scale generation but displaced by small-scale and localised generation. Energy storage systems (ESS) can limit the impact of dispersed and distributed generation by offering supporting reserve while accommodating large-scale EV connection; the latter (load) also participating in storage provision. In this paper, a local energy storage system (LESS) is proposed. The structure, requirement and optimal sizing of the LESS are discussed. Three operating modes are detailed, including: 1) storage pack management; 2) normal operation; and 3) contingency operation. The proposed LESS scheme is evaluated using simulation studies based on data obtained from the Northern Ireland regional and residential network.

A NEW DC UPS FOR DC POWER DISTRIBUTION SYSTEM IN DATA CENTER

In recent years, the 380V DC and 48V DC distribution systems have been extensively studied for the latest data centers. It is widely believed that the 380V DC system is a very promising candidate because of its lower cable cost compared to the 48V DC system. However, previous studies have not adequately addressed the low reliability issue with the 380V DC systems due to large amount of series connected batteries. In this thesis, a quantitative comparison for the two systems has been presented in terms of efficiency, reliability and cost. A new multi-port DC UPS with both high voltage output and low voltage output is proposed. When utility ac is available, it delivers power to the load through its high voltage output and charges the battery through its low voltage output. When utility ac is off, it boosts the low battery voltage and delivers power to the load form the battery. Thus, the advantages of both systems are combined and the disadvantages of them are avoided. High efficiency is also achieved as only one converter is working in either situation. Details about the design and analysis of the new UPS are presented. For the main AC-DC part of the new UPS, a novel bridgeless three-level single-stage AC-DC converter is proposed. It eliminates the auxiliary circuit for balancing the capacitor voltages and the two bridge rectifier diodes in previous topology. Zero voltage switching, high power factor, and low component stresses are achieved with this topology. Compared to previous topologies, the proposed converter has a lower cost, higher reliability, and higher efficiency. The steady state operation of the converter is analyzed and a decoupled model is proposed for the converter. For the battery side converter as a part of the new UPS, a ZVS bidirectional DC-DC converter based on self-sustained oscillation control is proposed. Frequency control is used to ensure the ZVS operation of all four switches and phase shift control is employed to regulate the converter output power. Detailed analysis of the steady state operation and design of the converter are presented. Theoretical, simulation, and experimental results are presented to verify the effectiveness of the proposed concepts.

Real-time PMU monitoring of an IEEE 5-Bus Network implemented on OPAL system

This thesis studies the state-of-the-art of phasor measurement units (PMUs) as well as their metrological requirements stated in the IEEE C37.118.1 and C37.118.2 Standards for guaranteeing correct measurement performances. Communication systems among PMUs and their possible applicability in the field of power quality (PQ) assessment are also investigated. This preliminary study is followed by an analysis of the working principle of real-time (RT) simulators and the importance of hardware-in-the-loop (HIL) implementation, examining the possible case studies specific for PMUs, including compliance tests which are one of the most important parts. The core of the thesis is focused on the implementation of a PMU model in the IEEE 5-bus network in Simulink and in the validation of the results using OPAL RT-4510 as a real-time simulator. An initial check allows one to get an idea about the goodness of the results in Simulink, comparing the PMU data with respect to the load-flow steady-state information. In this part, accuracy indices are also calculated for both voltage and current synchrophasors. The following part consists in the implementation of the same code in OPAL-RT 4510 simulator, after which an initial analysis is carried out in a qualitative way in order to get a sense of the goodness of the outcomes. Finally, the confirmation of the results is based on an examination of the attained voltage and current synchrophasors and accuracy indices coming from Simulink models and from OPAL system, using a Matlab script. This work also proposes suggestions for an upcoming operation of PMUs in a more complex system as the Digital Twin (DT) in order to improve the performances of the already-existing protection devices of the distribution system operator (DSO) for a future enhancement of power systems reliability.

A regulatory framework for short-term stochastic maintenance outage scheduling in smart grids

The current regulatory framework for maintenance outage scheduling in distribution systems needs revision to face the challenges of future smart grids. In the smart grid context, generation units and the system operator perform new roles with different objectives, and an efficient coordination between them becomes necessary. In this paper, the distribution system operator (DSO) of a microgrid receives the proposals for shortterm (ST) planned outages from the generation and transmission side, and has to decide the final outage plans, which is mandatory for the members to follow. The framework is based on a coordination procedure between the DSO and other market players. This paper undertakes the challenge of optimization problem in a smart grid where the operator faces with uncertainty. The results show the effectiveness and applicability of the proposed regulatory framework in the modified IEEE 34- bus test system.

Loistehon säätö ja kompensointi

Kantaverkkoyhtiö Fingrid Oy on tarkastellut kantaverkosta otettua tai tuotettua loistehoa alueittain Fingridin määrittelemällä maantieteellisellä tavalla. Alue koostuu liittymispisteistä, jotka ovat yksittäisten verkkoyhtiöiden liittymispisteitä. Yhden alueen sisällä voi siis olla monia eri verkkoyhtiöiden liittymispisteitä. Vuodesta 2016 alkaen loistehon tarkastelu vaihtuu aluetarkastelusta liittymispistetarkasteluun. Liittymispistetarkasteluun siirtymisen myötä tulee verkkoyhtiöiden investoida erinäisiin kompensointiratkaisuihin, jotta yksittäisten liittymispisteiden loistehot pysyvät Fingridin asettaman loistehon tarkasteluikkunan sisällä. Työssä perehdytään erinäisiin kompensointiratkaisuihin ja niiden kytkentöihin sekä kytkentöjen vaikutuksiin olemassa olevaan sähköverkkoon. Lisäksi työssä käsitellään tuulivoimaloiden hyödyntämistä loistehon säädössä. Esimerkkitapauksessa tarkastellaan erästä Caruna Oy:n verkkoa ja pohditaan teknistä ja mahdollisimman taloudellista kompensointiratkaisua kyseiseen verkkoon. Työn lopputulos on, että maakaapeloinnin määrän kasvaessa loistehon kompensoinnin tarve kasvaa. Näin ollen Fingrid Oy:ltä tarvitaan selkeitä linjauksia moneen ongelmakohtaan, kuten tuotanto-kulutuspisteen loistehon tarkasteluun. Lisäksi Energiavirastolta tarvitaan kannusteita loistehon kompensointiin, sillä verkkoyhtiöiden liiketoiminta perustuu regulaatiomalliin ja kompensointilaitteiston yksikköhinnasto on hyvin suppea.

Verkostoskenaarioiden arviointi sähkön jakeluverkkotoiminnan valvontamenetelmien kannalta

Tämän työn tavoitteena oli selvittää sähkön jakeluverkkotoiminnan valvontamenetelmien muutoksien vaikutuksia Loiste Sähköverkko Oy:n talouteen neljännellä ja viidennellä valvontajaksolla. Tarkastelua varten tehtiin talousmalli, joka mallintaa verkkoyhtiön taloutta vuoteen 2040 asti. Talousmallissa mallinnettiin kaikkien kannustimien vaikutus paitsi innovaatio- ja toimitusvarmuuskannustimien vaikutus. Talousmallinnuksen perusperiaate oli, että mitä ei pystytä kattamaan siirtotuloilla, rahoitetaan vieraalla pääomalla, kun kassavirran minimitaso ja investointitaso ovat valittu. Talousmallilla tarkasteltiin neljää erilaista verkostoskenaariota. Tarkasteltavat verkostoskenaariot olivat kehittämissuunnitelman mukainen skenaario, nopeutettu kehittämissuunnitelman mukainen skenaario, kaapelointipainotteinen skenaario ja kunnossapitopainotteinen skenaario. Verkon arvon kehittyminen verkostoskenaarioissa mallinnettiin Loiste Sähköverkko Oy:n investointimallilla ja kuvattiin talousmallinnusta varten jälleenhankinta-arvon, nykykäyttöarvon, investointien ja tasapoistojen kehittymisellä vuoteen 2029 asti. Työn tulosten perusteella kehittämissuunnitelman mukaisessa skenaariossa vieraan pääoman määrä pysyy kohtuullisena ja mahdollistaa kohtuullisen kassavirran tarkastelujakson lopussa. Nopeutetussa kehittämissuunnitelman mukaisessa skenaariossa ja kaapelointipainotteisissa skenaariossa vieraan pääoman määrä kasvaa merkittävästi, mikä voi lisätä liiketaloudellisia riskejä, mutta toisaalta mahdollistavat korkeamman kassavirran tarkastelujakson lopussa. Kunnossapitopainotteisessa skenaariossa vieraan pääoman määrä on matala, mutta kassavirta myös pysyy matalana tarkastelujakson loppuun asti.

Distributed generators as providers of reactive power support - A market approach

Traditionally, ancillary services are supplied by large conventional generators. However, with the huge penetration of distributed generators (DGs) as a result of the growing interest in satisfying energy requirements, and considering the benefits that they can bring along to the electrical system and to the environment, it appears reasonable to assume that ancillary services could also be provided by DGs in an economical and efficient way. In this paper, a settlement procedure for a reactive power market for DGs in distribution systems is proposed. Attention is directed to wind turbines connected to the network through synchronous generators with permanent magnets and doubly-fed induction generators. The generation uncertainty of this kind of DG is reduced by running a multi-objective optimization algorithm in multiple probabilistic scenarios through the Monte Carlo method and by representing the active power generated by the DGs through Markov models. The objectives to be minimized are the payments of the distribution system operator to the DGs for reactive power, the curtailment of transactions committed in an active power market previously settled, the losses in the lines of the network, and a voltage profile index. The proposed methodology was tested using a modified IEEE 37-bus distribution test system. © 1969-2012 IEEE.

A probabilistic approach to the estimation of regional photovoltaic power generation using meteorological data

In Germany the upscaling algorithm is currently the standard approach for evaluating the PV power produced in a region. This method involves spatially interpolating the normalized power of a set of reference PV plants to estimate the power production by another set of unknown plants. As little information on the performances of this method could be found in the literature, the first goal of this thesis is to conduct an analysis of the uncertainty associated to this method. It was found that this method can lead to large errors when the set of reference plants has different characteristics or weather conditions than the set of unknown plants and when the set of reference plants is small. Based on these preliminary findings, an alternative method is proposed for calculating the aggregate power production of a set of PV plants. A probabilistic approach has been chosen by which a power production is calculated at each PV plant from corresponding weather data. The probabilistic approach consists of evaluating the power for each frequently occurring value of the parameters and estimating the most probable value by averaging these power values weighted by their frequency of occurrence. Most frequent parameter sets (e.g. module azimuth and tilt angle) and their frequency of occurrence have been assessed on the basis of a statistical analysis of parameters of approx. 35 000 PV plants. It has been found that the plant parameters are statistically dependent on the size and location of the PV plants. Accordingly, separate statistical values have been assessed for 14 classes of nominal capacity and 95 regions in Germany (two-digit zip-code areas). The performances of the upscaling and probabilistic approaches have been compared on the basis of 15 min power measurements from 715 PV plants provided by the German distribution system operator LEW Verteilnetz. It was found that the error of the probabilistic method is smaller than that of the upscaling method when the number of reference plants is sufficiently large (>100 reference plants in the case study considered in this chapter). When the number of reference plants is limited (<50 reference plants for the considered case study), it was found that the proposed approach provides a noticeable gain in accuracy with respect to the upscaling method.

Datahubin merkitys jakeluverkonhaltijalle case: Vantaan Energia Sähköverkot Oy

Tavoitteena oleva hiilineutraali energiantuotanto muokkaa sähköntuotannosta sykkivämpää ja vaatii kulutuksen sopeutumista siihen. Tämä synnyttää tarpeen kansallisia markkinoita laajemmille sähkön vähittäismarkkinoille ja vaatii kuluttajilta aktiivisempaa roolia markkinoilla. Pohjoismaiset kantaverkkoyhtiöt ovat alkaneet valmistella pohjoismaisia sähkömarkkinoita sähkön vähittäiskaupan avaamiselle. Sähkön vähittäiskaupan avautuminen eri maiden välillä vaatii kansallisten markkinamenetelmien yhtenäistämistä varsinkin taseselvityksen ja tiedonvaihdon osalta. Tässä työssä tutkitaan Suomessa vuonna 2019 käyttöönotettavan keskitetyn tiedonvaihtojärjestelmän, Datahubin, vaikutuksia jakeluverkonhaltijalle. Vaikutuksia tarkastellaan Vantaan Energia Sähköverkot Oy:n näkökulmasta. Työssä kartoitetaan jakeluverkonhaltijan nykyisiä liiketoiminnan pääprosesseja ja niihin liittyvää tiedonvaihtoa eri markkinaosapuolten kanssa prosessien toteutuksessa. Lisäksi työssä esitellään jakeluverkonhaltijan nykyisten liiketoiminnan pääprosessien toteuttaminen Datahubissa. Jakeluverkonhaltijan liiketoiminnan nykyisiä pääprosesseja ja tiedonvaihtoa verrataan Datahubin kautta suoritettaviin prosesseihin. Työssä todettiin Datahubin korjaavan jakeluverkonhaltijan liiketoiminannan nykyisissä pääprosesseissa havaittuja ongelmia ja mahdollistavan prosessien tehostamisen. Datahub ei sinällään muuta nykyisiä jakeluverkonhaltijan liiketoimintaprosesseja merkittävästi, mutta mahdollistaa prosessien kehittämisen markkinoiden muutoksen mukana. Datahubin kokonaisvaltainen hyödyntäminen on toimijoiden itsensä käsissä, niiltä osin, kun sähkömarkkinalaki ei velvoita tiettyyn toimintamalliin. Jakeluverkonhaltijan liiketoimintaprosessien osalta suurin muutos kohdistuu jakeluverkonhaltijan taseselvitykseen, joka siirtyy kokonaisuudessaan Datahubin tehtäväksi. Datahub tulee kaventamaan jakeluverkonhaltijan roolia markkinapaikalla ja siksi jakeluverkonhaltijoiden tulisi kartoittaa liiketoiminnan laajentamisen tarvetta ja mahdollisuuksia tulevaisuudessa.