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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
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
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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
www.lemcko.be
Thank you for your attention