Coordinated charging of electric vehicles through demand response in distribution grids
Author
Selvam, Gokula Krishnan
Term
4. term
Education
Publication year
2021
Submitted on
2021-01-08
Pages
67
Abstract
This thesis investigates coordinated charging of electric vehicles as a source of flexibility in low-voltage distribution grids in the Danish context. The central question is whether demand response can organize EV charging so that flexibility is delivered without causing voltage violations or congestion. A residential LV feeder is modeled with realistic household demand and a time-dependent EV model based on charging start times, state-of-charge distributions, and battery characteristics. Load-flow analyses assess the baseline impact of uncoordinated charging at different penetration levels (100% and 50%) on bus voltages and transformer and line loading over a winter day. Two coordinated charging strategies are implemented and compared against the base case: a price-based demand response using day-ahead market prices and an incentive-based demand response. Their operation shifts charging over time and is evaluated using state-of-charge trajectories, nodal voltage profiles, and transformer loading. The results are presented in figures and discussed, indicating that coordinated charging can time-shift demand and has the potential to improve voltage profiles and reduce loading relative to uncoordinated charging. The study outlines a practical demand-response framework for integrating EVs into distribution grids while respecting operational limits.
Denne afhandling undersøger koordineret opladning af elbiler som en fleksibilitetsressource i lavspændingsdistributionsnet med udgangspunkt i den danske kontekst. Det centrale spørgsmål er, om efterspørgselsrespons kan styre elbilers opladning, så der leveres fleksibilitet uden at skabe spændingsafvigelser eller kapacitetsmæssige flaskehalse. Et bolig-lavspændingsnet modelleres med realistiske husholdningsprofiler og en tidsafhængig elbilmodel baseret på starttidspunkter for opladning, state-of-charge-fordelinger og batteriparametre. Laststrømsanalyser bruges til at vurdere basispåvirkningen af ukoordineret opladning ved forskellige penetrationsgrader (100 % og 50 %) på busspændinger samt transformer- og linjebelastning over en vinterdøgnscyklus. To koordinerede opladningsstrategier implementeres og sammenlignes med basisfaldet: en prisbaseret efterspørgselsrespons, der udnytter day-ahead-elpriser, og en incitamentsbaseret efterspørgselsrespons. Strategiernes evne til at tidsforskyde opladningen vurderes via udviklingen i batteriers ladetilstand, spændingsprofiler i nettet og transformatorbelastning. Resultaterne præsenteres i figurer og diskuteres med fokus på, at koordineret opladning kan flytte forbruget til mere gunstige perioder og potentielt forbedre spændingsprofiler samt reducere belastning sammenlignet med ukoordineret opladning. Studiet skitserer dermed en praktisk ramme for anvendelse af efterspørgselsrespons til at integrere elbiler i distributionsnet under hensyntagen til driftsbegrænsninger.
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