VPLIV ELEKTRIČNIH VOZIL NA ZANESLJIVOST ELEKTROENERGETSKEGA SISTEMA

BOŽIČ, DUŠAN (author), Pantoš, Miloš (mentor)

Zagotavljanje zanesljive oskrbe odjemalcev z električno energijo predstavlja primarno nalogo elektroenergetskih sistemov, na kar kaže tudi spreminjanje načina regulacije sistemskih operaterjev v dereguliranih trgih z električno energijo. Regulatorji pri regulaciji sistemskih operaterjev namreč vse pogosteje uvajajo regulacijo kakovosti dobave električne energije, ki v ospredje postavlja prav zanesljivost sistema. Prihodki sistemskih operaterjev so pri regulaciji kakovosti dobave električne energije zaradi uporabe nagrajevalno penalizacijskih shem namreč neposredno odvisni od zanesljivosti sistema. Posledično si sistemski operaterji želijo cenovno učinkovitega zagotavljanja zanesljivosti sistema, kar pa bo v prihodnosti ob večanju porabe kot posledica vse večjega števila električnih vozil v sistemu vse prej kot lahka naloga. V literaturi in razpravah strokovnjakov se največkrat izpostavlja, da bo potrebno ob povečanem številu električnih vozil elektroenergetski sistem podpreti z novimi viri ali posegi v porabo, da bi se zagotovila pričakovana stopnja zanesljivosti. Neizpodbitno velja, da vozila predstavljajo dodatno obremenitev sistema, saj iz njega črpajo energijo potrebno za transport, vendar pa se v literaturi redko zasledi matematično in analitsko podkrepljenost tovrstnih razprav. To dejstvo predstavlja motivacijo za raziskave v okviru te doktorske naloge. Za celovito predstavitev obravnavane tematike zato v prvem delu doktorske disertacije podajamo pregled področja zanesljivosti elektroenergetskega sistema in tehnologije električnih vozil. Pri tem odgovorimo na štiri ključna vprašanja v zvezi z zanesljivostjo elektroenergetskega sistema, in sicer kaj zanesljivost sistema sploh je, kako jo zagotavljamo, kako jo merimo in kakšna je cena (ne)zanesljivosti sistema. V nadaljevanju pri predstavitvi tehnologije električnih vozil uvodoma predstavimo različne tipe električnih vozil, ki jih poznamo. Električna vozila v osnovi delimo na baterijska električna vozila in hibridna vozila, pri čemer hibridna vozila delimo še naprej na serijske in vzporedne hibride. Prav posebno vrsto električnih vozil pa predstavljajo vozila s pogonom na gorivne celice. V okviru predstavitve električnih vozil nato podamo možnosti njihove uporabe v okviru elektroenergetskega sistema kot jih vidijo avtorji v literaturi. Avtorji v literaturi predvidevajo, da bo mogoče električna vozila uporabljati pri upravljanju s porabo v sistemu, pri maksimizaciji dobička na trgu z električno energijo, pri maksimizaciji izrabe obnovljivih virov energije in pri zagotavljanju sistemskih storitev, pri čemer se v literaturi omenjata predvsem regulacija frekvence in napetosti v sistemu. Naštetim poglavjem na koncu dodamo še poglavje o uporabi električnih vozil za zagotavljanje zanesljivosti elektroenergetskega sistema, ki bralca uvede v tematiko drugega dela doktorske naloge. V drugem delu naloge predstavimo novo metodo za vrednotenje ukrepov za zagotavljanje zanesljivosti elektroenergetskega sistema in nov način optimizacije polnjenja in praznjenja električnih vozil, ki omogoča maksimizacijo zanesljivost elektroenergetskega sistema ob prisotnosti električnih vozil v sistemu. Metodi predstavljata izvirna znanstvena prispevka doktorske disertacije. Metoda za vrednotenje ukrepov za zagotavljanje zanesljivosti elektroenergetskega sistema je primarno namenjena sistemskim operaterjem za načrtovanje investicij v dereguliranih trgih z električno energijo. Pri regulaciji kakovosti dobave električne energije so namreč prihodki sistemskih operaterjev neposredno odvisni od zanesljivosti sistema. Pri spremembi regulatornega okvira se zato pokaže potreba po novem pristopu k investicijskemu načrtovanju elektroenergetskega sistema. Uporaba predlagane metode zmanjšuje tveganja, ki jih prinaša nov način regulacije, saj temelji na simulaciji učinkov predvidenih investicijskih kandidatov na zanesljivost sistema. Pri tem metoda investicijske kandidate med seboj primerja na podlagi kazalnikov učinkovitosti investicij, ki predstavljajo novost in so eden od izvirnih prispevkov znanosti v disertaciji. Čeprav v okviru metode kazalnike uporabljamo za primerjavo različnih investicijskih kandidatov, pa so kazalniki splošni in jih je moč uporabiti tudi za vrednotenje morebitnih drugih ukrepov za zagotavljanje zanesljivosti elektroenergetskega sistema. To dokazuje njihova uspešna uporaba v zaključku doktorske naloge, kjer s pomočjo kazalnikov primerjamo dva načina zagotavljanja zanesljivosti sistema. Prvi način predvideva optimizacijo polnjenja in praznjenja električnih vozil, drugi način pa predvideva izgradnjo nove elektrarne v sistemu. V zadnjem delu disertacije predstavljamo inovativen način zagotavljanja zanesljivosti elektroenergetskega sistema, in sicer z optimizacijo polnjenja in praznjenja električnih vozil v sistemu. Predlagana optimizacijska metoda predstavlja osrednji izvirni znanstveni prispevek doktorske disertacije. Metoda temelji na optimizaciji časa in trajanja polnjenja in praznjenja električnih vozil, z njeno uporabo pa je mogoče v elektroenergetski sistem vključiti veliko število električnih vozil, ne da bi se pri tem zanesljivost sistema poslabšala. Prav nasprotno, izkaže se namreč, da je mogoče s pomočjo metode zanesljivost sistema, do določene mere celo izboljšati. Ugotovljeno dejstvo daje električnim vozilom možnost sodelovanja pri nudenju sistemske storitve zagotavljanja rezerve moči, pri čemer bi lahko z optimizacijo polnjenja in praznjenja električnih vozil celo nadomeščali klasične proizvodne vire v sistemu. Pri tem bi uporabniki vozil za nudenje storitve pričakovali določeno finančno nadomestilo. Doktorsko disertacijo sklenemo z analizo ekonomske primerjave omenjenih načinov zagotavljanja rezerve moči v elektroenergetskem sistemu.

• Language: Slovenian
• Keywords: električna vozila, zanesljivost elektroenergetskega sistema, optimizacijske metode, sistemske storitve, kazalniki učinkovitosti investicij
• Work type: Doctoral dissertation
• Organization: FE - Faculty of Electrical Engineering
• Year: 2017
• PID: 20.500.12556/RUL-94825
• COBISS.SI-ID: 11804756
• Publication date in RUL: 07.09.2017

Secondary language

• Language: English
• Title: IMPACT OF ELECTRIC-DRIVE VEHICLES ON POWER SYSTEM RELIABILITY

Abstract

Providing reliable distribution of electric energy represents a main goal of every electric power system, which is also reflected in changing of regulation of distribution system operators by regulatory authorities in deregulated and re-regulated electricity markets. In deregulated and re-regulated electricity markets, regulatory authorities are increasingly adopting performance based regulation for distribution system operators. A performance based regulation regime provides distribution utilities with incentives for economic efficiency gains, and at the same time discourages them from sacrificing service reliability while pursuing these incentives. With increasing consumption in power systems as a result of increasing number of electric vehicles this can present a difficult task. Prevailing opinion of authors in the literature is that with increasing number of electric vehicles new generation units will have to be built or consumption reductions will have to be introduced in the power system in order to maintain a sufficient level of power system reliability. It is indisputable truth that charging of electric vehicles represents an additional stress for the power system, but claims in the literature lack of mathematical explanation and that was the main motivation for the research conducted as part of this doctoral thesis. For a comprehensive presentation of topics covered first part of the doctoral thesis provides an overview of the reliability of the power system and electric vehicle technology. The first part also answers to four key questions regarding power system reliability, namely, what is power system reliability, how is reliability of power system maintained, how it can be measured and what is the price of (un)reliability of a power system. Further on we present all different types of electric vehicles available on the market today. Electric vehicles can be divided into two categories, battery electric vehicles and hybrid vehicles where hybrid vehicles can be further divided into the serial and parallel hybrids. Besides battery and hybrid electric vehicles there is also a special category of electric vehicles that are powered by fuel cells. Further on we discuss different uses of electric vehicles in the context of electric power systems as seen by authors in the literature. The authors predict that electric vehicles will be used for demand side management, maximization of profits in electricity markets, maximization of use of renewable energy and provision of ancillary services. At the end of the first part of the thesis we also included a chapter about the use of electric vehicles for provision of power system reliability that introduces the reader to the content of the second part of the thesis. In the second part of the thesis we present a new method for assessment of efficiency of measures for power system reliability provision and a new optimization model of charging and discharging of electric vehicle batteries in order to maximize power system reliability with the use of energy from electric vehicles. Aforementioned methods represent an original scientific contribution of the doctoral dissertation. The method for assessment of efficiency of measures for power system reliability provision is primarily intended for system operators to plan investments in deregulated electricity markets. Since yearly budget of distribution utilities under performance based regulation mainly depends on their ability to perform cost effective investments that maintain sufficient level of power system reliability, new approach to investment planning is needed with the transition to the new regulatory regime. The use of proposed method reduces financial risk associated with the new regulatory regime, since it is based on simulation of the effect of different investment candidates on power system reliability. Comparison of different investment candidates is based on new investment efficiency indices which are also an original scientific contribution of the doctoral dissertation. Although presented method uses indices for comparison of different investment candidates, the indices are general and can also be used for assessment of any other measures for power system reliability provision. This is proved in the second part of the doctoral thesis, where we use the indices to compare two different ways of power system reliability provision. The first solution envisions an optimization of charging and discharging of electric vehicles and the second solution envisions a construction of a new generation unit in the power system. The last part of the doctoral dissertation is dedicated to presentation of new innovative way of provision of power system reliability with optimization of charging and discharging of electric vehicles connected to electric power system. Presented method represents a main original scientific contribution of this doctoral thesis. The method is based on optimization of time and duration of charging and discharging of electric vehicles. With the use of proposed method a large number of electric vehicles can be simultaneously connected to the power grid without deterioration of the power system reliability. As it turns out it is even possible to increase the power system reliability to some extent with the use of proposed method. Aforementioned fact gives electric vehicles a possibility to participate in power system reserve provision, where they could even replace conventional generation units in the system. For providing ancillary services the owners of electric vehicles would also be entitled to some monetary compensation. Doctoral thesis is concluded by comparison of these two ways of reserve provision in electric power system.

• Keywords: electric vehicles, power system reliability, optimization methods, ancillary services, investment efficiency indices