Voltage Unbalance Compensation in the Distribution Grid through Distributed Generation
Author
Muller Llano, Enrique
Term
4. term
Education
Publication year
2015
Submitted on
2015-06-03
Pages
75
Abstract
Integrationen af decentral elproduktion i distributionsnettet er steget markant. Når der opstår overskud fra vedvarende energikilder, kan elektricitet løbe opstrøms fra lokale generatorer mod højere spændingsniveauer (omvendt effektflow), hvilket ændrer nettets adfærd. Det kan give overspændinger og spændingsusymmetri, hvor de tre faser ikke har samme spænding. Klassiske kompenseringsmetoder er udviklet til transmissionsnettet og forudsætter et højt reaktans‑til‑modstands‑forhold (X/R) og et stærkt net (højt kortslutningsforhold, SCR). Distributionsnet har typisk lavt X/R‑forhold, så der kræves en anden tilgang. I denne afhandling analyseres flere metoder, hvor den nettilsluttede konverter i en decentral energikilde (DER) bruges til at kompensere spændingsusymmetri i distributionsnet. Metodernes funktion er verificeret ved simuleringer i PowerFactory 15.
The share of distributed generation in distribution grids has grown rapidly. When surplus energy from renewable sources is fed in, electricity can flow upstream from local generators toward higher‑voltage levels (reverse power flow), changing how the grid behaves. This can cause overvoltages and voltage unbalance, where the three phases do not have the same voltage. Traditional compensation methods are designed for the transmission system and assume a high reactance‑to‑resistance (X/R) ratio and a strong grid (high short‑circuit ratio, SCR). Distribution grids typically have a low X/R ratio, so a different approach is needed. This thesis analyzes several ways to use the grid‑connected converter of a distributed energy resource (DER) to compensate voltage unbalance in distribution networks. The operation of these methods is verified through simulations in PowerFactory 15.
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