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LOCAL STORAGE IN LV DISTRIBUTION NETWORKS

VAKGROEP < ELEKTRISCHE ENERGIE, SYSTEMEN EN AUTOMATISERING >

ONDERZOEKSGROEP < EELAB LEMCKO >

CONTACT :

Prof. Dr. ir. Jan Desmet

EELAB/Lemcko – Universiteit Gent

JanJ.Desmet@ugent.be

3

MAIN RESEARCH:IMPACT AND INTERACTION OF RES AND NLL ON LV & MV NETWORKS

OUTLINE

Introduction

Challenges

Production versus Consumption

Dimensioning of local storage

Implementation

Conclusions

4

DG DG

Congestion of the LV distribution network

–Local unbalance due to unsynchronised consumption and production

–Voltage congestion over the feeder

Local solutions

Centralised versus Decentralised

INTRODUCTION

6

INTRODUCTION

Simulation of a week via modelling –

Averaged data

Load profile of household

Yield profile of Lemcko sun test field

Matching profiles:

Lente Zomer HerfstWinter Winter

Medium wind (<400kVA) Sun

0

100

200

300

400

500

600

700

800

900

1.000

8:30:55 9:42:55 10:54:55 12:06:55 13:18:55 14:30:55 15:42:55 16:54:55 18:06:55

Verm

ogen

[W]

Amorf Open

Polykristalijn Tracker

Dunne Film Gesloten

Polykristalijn Open

Amorf Gesloten

Monokristalijn Open

Amorf Tracker

Polykristalijn Gesloten

Dunne Film Open

Monokristalijn Gesloten

RES Production

CHALLENGES

PV-installations create overload conditions for the distribution network

Existing LS – networks are designed for energy consumption

Simultaneity of power consumption: 0,25 à 0,3 for LV end users

Simultaneity of PV production in feeder: ± 1

Injection of PV-installations in LV networks mainly single phase

No balanced injection over the feeders

Voltage at end users must fulfill the EN50160 requirements

GRIDCHALLENGES

Cumulative neutral point displacement

Unbalance due to single phase loads

in three phase system: ABCABC

CHALLENGES

Unbalance due to single phase loads

in three phase system: ABCCBA

Compensating neutral point displacement

CHALLENGES

– OLTC (On load tap changer)• Automatic regulation of voltage level as a function of both injected or consumed power

• Current distribution transformers only have the typical 3/5/7 Off Circuit Tap Changers (OCTC)

– DSM• Hugh control potential in both residential and industrial installations

• In residential installations: future challenge – consumer plays an important role, much more than financial incentives

– Storage• Integration nowadays is possible

• Prosumers use a ready to use grid interactive system, without active control from their side

0 2 4 6230

231

232

233

234

235

236

237

Tijd [Uren]

Spannin

g [

V]

Injectieprofiel woning 18 - 4 kW

Injectieprofiel woning 2 - 2,5 kW

Injectieprofiel woning 1 - 3,8 kW

ManagementCHALLENGES

Active control of end users and the grid

Consumption as a function of availability of energy

Buffering or storage of energy

Storage - Averaged on yearly base

StorageCHALLENGES

13

Dimensioning:

• Self consumption Ratio

• Generated PV-energy instantaneous consumed

• ZC = EEV / EPV

Without Storage = 27,7%

Load and Yield of a household

PRODUCTION VERSUS CONSUMPTION

14

PRODUCTION VERSUS CONSUMPTION Dimensioning:

• Self providing Ratio

• Demand power instantaneous provided by PV installation

Without Storage = 27,7%

Load and Yield of a household

• ZV = EEP / E1

Optimisation

Over dimensioningUnder-

dimensioning

Self

consumption Generated energy by PV

installation, instantaneous

consumed – Decreases by

increasing installed PV peak

power

Self providing Demand power

instantaneous provided by

the PV installation –

Increases with increasing

installed PV peak power

Self consumption - Zc

Self providing - Zv

Ratio Year-yield/Year-consumption [pu]

Ratio S

elf-c

onsum

ption/S

elf-p

rovid

ing

[pu]

DIMENSIONING OF LOCAL STORAGE

Evaluation criteria?

• Self consumption ratio Production Green – Consumption Dashed

• Self providing ratio Consumption Light Blue – Self provided Dashed

Looking for balancing

DIMENSIONING OF LOCAL STORAGE

• Related to the yearly consumption in MWh

• Peak power of the PV installation

MWhPV Yearly Yield /MWhYear-consumption (no installed kWpeak!)

• Level of storage

Effective (!) storage capacity in kWh/MWhYear-consumption

To convert to useful storage level of the batteries (DOD)

Model: Based on year profiles of 25 households-models(Data Leest/Hombeek)

DIMENSIONING OF LOCAL STORAGE

Optimisation – Using storage

0 kWh/MWh

0.5 kWh/MWh

1 kWh/MWh

1,5 kWh/MWh

2 kWh/MWh3 kWh/MWh4 kWh/MWh5 kWh/MWh

Ratio S

elf-c

onsum

ption/S

elf-p

rovid

ing

[pu]

Ratio Year-yield/Year-consumption [pu]

Self consumption - Zc

Self providing - Zv

Over dimensioningUnder-

dimensioning

DIMENSIONING OF LOCAL STORAGE

Based on PV and storage capacity on 25 real households-models:

Assumptions:

In Figures (example):

‒ Averaged household consumption: 4,5MWh

Battery capacity: 1 kWh/MWh x 4,5MWh = 4,5kWh (Usable capacity!!)

PV-Yield: 1,11 x 4,5MWh = 5MWh

Zc, Zv = 55%

Storage capacity: 1 kWh/MWh ± 0,35

PV-Yield: 1,11 p.u. ± 0,08

Zc, Zv: 55% ± 0,03

DIMENSIONING OF LOCAL STORAGE

Storage capacity dimensioned as a function of the installed

peak power of the PV-installation

Averaged curve for the 25 households:

In figures (example):‒ Averaged household consumption: 4,5MWh

‒ Averaged PV Yield: 2,7MWh (2,7 / 4,5 = 0,6 p.u.)

Battery capacity: 0,65 kWh/MWh x 4,5MWh ≈ 2,9kWh (Useful capacity!!)

0,65

Ratio Year-yield/Year-consumption [pu]

Sto

rage C

apacity [

kW

h/M

Wh]

DIMENSIONING OF LOCAL STORAGE

Zc, Zv are function of the peak power of the PV installation:

In figures (Example):

‒ Averaged household consumption: 4,5MWh

‒ Averaged PV Yield: 2,7MWh (2,7 / 4,5 = 0,6 p.u.)

Battery capacity: 0,65 kWh/MWh x 4,5MWh ≈ 2,9kWh

(Useful capacity!!)

Zc ≈ 70%

Zv ≈ 40%

0,70,4

Ratio Year-yield/Year-consumption [pu]

Ratio S

elf-c

onsum

ption/S

elf-p

rovid

ing [pu]

Self

consumption

Self providing

DIMENSIONING OF LOCAL STORAGE

Battery use

Averaged on daily base

Averaged on 10 minutes base

Averaged on yearly base

IMPLEMENTATION

Ride trough: Simulation vs. Measurements

Hours a Day [Hr]

SO

C [%

]

Load

Yield

Power Out

Power – Sim.

Power -

Meas.

Battery-Sim.

Battery-

Meas.

Pow

er

[kW

]P

ow

er

[kW

]

IMPLEMENTATION

Comparison simulations/reality

Evaluation Big difference between the simulations and the real

measurements

Difference mainly caused by load cycle of battery system:‒ Limited load current

‒ Charging-curves

‒ Battery efficiency

‒ Battery technology

‒ BMS

14 of March 2014 Zc Zv

Without PV-battery system 17,1% 19,3%

Simulation with 1kWh/Mwh 78,6% 73,7%

Measurements with 1kWh/Mwh 60,5% 27,9%

Validation

IMPLEMENTATION

Testing in “Live” Lab

Free programmable power sources

240kVApeak 3Phase AC

15*1kW PV installations

Event #107 at 30/10/2014 16:38:31,100

Waveforms

Ev ent Details/Waveforms

16:38:31,1

30/10/2014

Thursday

16:38:31,2 16:38:31,3 16:38:31,4 16:38:31,5

-20000

-10000

0

10000

20000

Vol

ts

A V B V C V

-1.0

-0.5

0.0

0.5

1.0

Am

ps

A I B I C I

C re ate d wi th Dr an V iew 6 .1 5.3

PV battery systems create solutions for both DNO and prosumer

Off grid autonomy increases, decongestion of the distribution grid,…

Effect of storage on Zc, Zv is depending on load profilePending on consumer

Pending on yearly yield & consumption

Dimensioning of PV-battery systems is not an exact science,

consequently optimal storage capacity only can be targeted Using a relative small battery (in capacity) is needed for optimal solution

Island operation only based on batteries is barely possible!

Both choice and use of battery systems is crucial

Relatively small storage system of 1kWh/MWh can provide a

ride through solution up to 3 hours

CONCLUSIONS

Prof. dr. ir. Jan Desmet

Full Professor - Manager Researchgroup EELAB-Lemcko

Ghent University – Faculty of Engineering and Architecture

Department Energy and Systems

Research group EELAB - Lemcko

Campus Kortrijk

Graaf Karel de Goedelaan 34

B-8500 Kortrijk

Tel.: +32 56 24 12 39

Fax: +32 56 24 12 34

janj.desmet@ugent.be

www.lemcko.be

Thank you for your attention