1

T

Investigation of cloud indicators

for low voltage distribution grid

transformers Solar Resource and Forecast Data for High PV Penetration

jointly with IEA – International Energy Agency PVPS Task 14 & IEA SHC Task 46

01.10.2013, Paris

Holger Ruf

Marion Schroedter-Homscheidt

Hans Georg Beyer

Florian Meier

Gerd Heilscher

Contents

Motivation & Targets

Test Site & Background

Measured Raw Data

Approach & Results

Conclusion & Outlook

2

3

Research Target

Investigation of correlation between clouds and voltage at a low voltage transformer

Is it possible to calculate the bus bar voltage with satellite data?

Why Clouds and not only irradiance? Additional necessary information atmospheric extinction due to clouds and aerosols

difficult to distinguish between cloudy and clear cases when looking at the voltage and/or irradiance conditions

nearly impossible to distinguish between overcast and scattered cloud cases from irradiance data

Test site 1

Structure

Status End 2012

133 Houses

21 PV Systems

230 kWp

Consumption

~ 1000 MWh

Generation

~230 MWh 4

Regional

breaker

450m

Bus bar voltage

Influencing Variable

Voltage depends on Load

Generation

Medium voltage

Load following standard load profile

Generation following irradiance

DSO: „Medium voltage is fix 10.2 kV“ (???) 5

+10% (EN 50160)

-10% (EN 50160)

UN U

U

t

Raw measured data

Voltage at Clear Sky

6

No similarity even under clear sky condition

Dynamic in the Voltage

Influence of the Medium Voltage

7

Dependency on

medium voltage

Dependency of

load and generation

Will get steeper

with larger PV share

or weaker grid

Approach (1/2)

Removing Medium Voltage

Influence

Necessary inputs: Transformer parameters available

Power flows measured at the transformer

8

dvtransformer

Approach (2/2)

Removing Load Influence

Necessary inputs: Apparent power measured at transformer

Power consumption adopted standard load profile

9

dvtransformer, only PV

Results (1/2)

Example for Overcast Day

10

Clo

ud

Typ

e O

pti

ca

lly

thic

k

Results (2/2)

Mean values

Clear sky

Overcast

Voltage rise: reduction of the voltage drop over the transformer

11

Conclusion and Outlook

Quantifying cloud influence to low voltage grid

Voltage is not suitable due to medium voltage

influence

Voltage drop over transformer is usable

Validation with simulation

Days between clear sky and overcast more

complex; satellite data to be used for scattered

situation detection

Voltage inside the grid more data necessary

Bias verification difficult

Suggestions and hints???

12

13

Hochschule Ulm

Institut für Energie- und Antriebstechnik

Eberhard Finckh Str. 11

89075 Ulm

Prof. Gerd Heilscher, Holger Ruf

0731-50 28360

0179-5978 024

heilscher@hs-ulm.de

ruf@hs-ulm.de

Marion Schroedter-Homscheidt

Deutsches Zentrum für Luft- und Raumfahrt

marion.schroedter-homscheidt@dlr.de

Hans Georg Beyer

University of Agder

hans-georg.beyer@uia.no

Florian Meier

SWU Netze GmbH

florian.meier@swu.de The research has received funding from the European union´s Seventh Framework Programme under Grant

Agreement no 262892 (ENDORSE project) and from the German Federal Ministry for the Environment,

Nature Conservation and Nuclear Safety (BMU) under Agreement no. 0325385 (SYSPV-NS project).

Thank you for your attention