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Shaban Awili
December 2015
by
Integrating Smart Transformers (SST) Into
Distribution Substations
Page 2Cigré SCB1
Agenda
SST Research Motivation
Smart Transformer Technology Overview
System Integration Requirement
Impact on Distribution Substation
Cost Implications
System-oriented analysis summary
Identify
(SST) Advantages
Understand
(SST) Challenges
Develop
Comparison Framework
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Transmission HV Distribution MV Distribution LV
The Inevitable Change
“Our aim is that by 2027
we will have an activeElectricity Network That Maximises Renewables Usage” Said John Byrne
ESB
CONSUMER
USAGE
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The Smart iFuture
Smart Transformer
Add Functions Add Benefits
Potential Issues
Consumer ControlAdd Control
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“It is a box that can take energy in any form – it doesn’t care whether it is AC or DC – and it will provide energy on the secondary side with very few losses and to the
specifications set by the client.” By Dr: Aedan Kernan
Smart Transformer Overview
AC-DC Rectifier
Converts HV-AC (LF)
into HV-DC voltage
Dual Active Bridge (DAB)
Uses HF Transformer &
Switches to Convert HV-DC
into LV-DC voltage
DC-AC Inverter Converts
LV-DC into
LV-AC (LF) voltage
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SST Components/Applications
Source: http://www.marketsandmarkets.com/PressReleases/solid-transformer.asp
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SST Based Distribution System
B
E
C
DCL
CL A
F
LOAD DRER DESD
REL REL
REL REL
HV/MV (SST)
Based Substation
MV/LV (SST)
Based Substation
SST
SS
TS
ST
SST
10 kV
10 kV
400V
38 kV
Section3
Section2
Section1
FID FID
FID
RE
LR
EL
FID
FREEDM system
RE
LR
EL
REL
Distributed Renewable Energy
Resources (DRERs)
Distributed Energy Storage
Devices (DESDs)
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A
F
SST Fault Scenarios
B
E
C
DCL
CL
LOAD DRER DESD
REL REL
REL REL
SST
SS
TS
ST
SST
10 kV
10 kV
400V
38 kV
Section3
Section2
Section1
FID FID
Voltage below 0.8 Pu
IGBTs contained
in the SST
rectifier are blocked
Current is limited to
2 pu at
Terminals
SST is removed
by the Under
Voltage Protection
Current in Ter C
and D Does not
Exceed Maximum
current
FID FID
The over current
does not occur on
the primary
side of the SST
DRER/DESD keep
feeding the load
as backup
RE
LR
EL
RE
LR
EL
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Overloading Capabilities (LFT)
IEC 60076-7 Loading Guide
IEC 60076-5, Specifies The required short-circuit current withstand duration to be 2s.
Normal Cyclic Loading
� A higher ambient temperature or a higher than rated load current is applied during part of the cycle.
� 100 % for normal operation load
� Current (p.u.) up to 1,5
� Top-oil temperature 105 (oC)
� Hot-spot temperature 140 (oC)
Long–Time Emergency Cyclic Loading
� Loading resulting from the prolonged outage of some system elements that will not be reconnected before a steady state.
� 150 % for temporary overload
� Current (p.u.) 1,5
� Top-oil temperature 115 (oC)
� Hot-spot temperature 140 (oC)
Short-Time Emergency Loading
� Unusually heavy loading due to the occurrence of one or more unlikely events which seriously disturb normal system loading.
� 180% for temporary half hour overload
� Current (p.u.) 1,8
� Top-oil temperature 115 (oC)
� Hot-spot temperature 160 (oC)
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Overloading Capabilities (SST)
The power electronics components reduces the overload capability during load peaks.
The control action could provide a solution tothe overloading problem during the transients faults
The SST higher realization costs do not allow to oversize
In contrast with the grid components requirement of bearing currents higher than the rated values for
longer periods.
The SST needs new procedures for dealing with the over loading
conditions
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Overloading Control Concept (SST)
Photovoltaic (PV) plant equipped with a Battery Energy Storage System (BESS).
The BESS contributes to limit the power fluctuation in the feeder.
Manage a possible overload without derating the SST.
This will reduce the current and enhances the SST security against the
overload situation.
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Overloading Capabilities (SST)
Concept of the Coordinated Frequency and Voltage Overload Control.
Voltage and frequency of the master controller are set to nominal values (OS I).
The Master controller changes the frequency thought the DG droop controller (OS II).
After 35s Insufficient power contribution is After 35s Insufficient power contribution is reached and DG is not sufficient to control
frequency.
Master controller starts changing the voltage level at LV terminal of SST
The transformer overload is avoided for total of 60 sec (OS III).
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Impact on Substation Design (Physical Design)
(LFT) Fire Protection Transformer Design consideration
Table 16 : IEC 61936-1 2002 Recommendations for separation distancesbetween outdoor transformer and buildings
Transformer
Type
Liquid
Volume (l)
To
Other Transformers or non
Combustible Building
Surfaces [m]
To
Combustible
Building
Surfaces [m]
Oil Insulated
Transformers
> 2,000 <
20,0005 10
ABB 10 MVA 6,156 5 10
Horizontal Separation (a)[m]
Vertical Separation (b)[m]
5 15.2
5m
5m
5m 5m
Page 14Cigré SCB1
Impact on Substation Design (Physical Design)
(LFT) Transformer Substation Layout
10 MVA LFT
18%Potential
Reduction
SubstationArea m2
(LFT) Original Area
m2
(LFT) clearance Area
m2
(SST) Required Area
m2
PotentialArea
Reduction m2
1500 12 302 6 290
Reduction Oil
System Size
In Volume
Up to50% SST
ReductionIn Volume
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Cost Implications (LFT)
Total ownership cost consist of several components:
� Purchase price
� The Installation Costs
� Value of the Energy Losses
� Maintenance Costs
� Decommissioning Costs
Life Cycle Cost Breakdown
Factors A, B (€/kW), that depend on transformer type, size, loading conditions, as well as cost of capital, energy market
forecasts, expected transformer life.
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Cost Implications (SST)
Costs are estimated by means of component cost models for high-volume production
� Approximately factor of five more
expensive purchasing price.
� Produces roughly two to three
times higher losses.
� It offers reduction in the footprint,
weight and volume.
� It eliminates all associated costs
with using oil.
� Offers savings in the civil, transport
and installation costs.
� TOC will be higher due to the
higher purchasing price and higher
losses.
Weight Breakdown Material Cost Breakdown
“Solid State Transformer Market worth $204.3 Million by 2020” MarketsandMarkets : Market Research Consulting Firm
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SST System Benefits
Unlike the conventional (LFT) the (SST) offers additional system benefits that should be
considered when comparing to (LFT)
Universal
Fault Isolation
Instantaneous Voltage Regulations
Integrates Energy Storage
Actively Change Power Characteristics
Improve Power Quality
Provide DC Power
Provides ability to utilise input or output in AC or DC power.
Protects the load from power supply disturbances
Eliminates the tap changer requirement
Provides backup and reduces outages length
Control voltage and frequency levels will reduce the system losses
Provide reactive power compensation and system harmonic filtering
In substations it could be used to feed control equipment or to feed DC micro grid
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Summary
Identify
(SST) Advantages
Understand
(SST) Challenges
Develop
Comparison Framework
� Flexibility,
� Intelligence / Controllability
� Significant Potential in Smart Grid applications
� Reduction in Footprint
� Eliminating Fire Hazardous and the use of oil.
� Protection Integration Requirement
� Overloading Capability
� Additional losses implications
� New Asset Reliability
� LFT Represents a truly Experienced Competitor to (SST)
� Functionality
� Reliability
� Size, Wight and Volume
� Efficiency / Cost
� SST can only be judged in the context of a given application
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So What Shall we Do ?
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Any Questions
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Irishtimes.com, 'Engineers Ireland: Smart power to revolutionise future use of electricity', 2014. [Online]. Available:
http://www.irishtimes.com/sponsored/engineers-ireland-smart-power-to-revolutionise-future-use-of-electricity-1.1951236. [Accessed: 27- Nov-
2015].
[1]
Smartgrid_Roadmap, 2015. [Online]. Available: http://www.seai.ie/Publications/Statistics_Publications/SEAI_2050_Energy_Roadmaps/Smartgrid_Roadmap.pdf. [Accessed: 27- Nov-2015].
Leonardo-energy.org, 'Cost-competitive solid-state distribution transformers online within two years | Leonardo ENERGY', 2015. [Online]. Available: http://www.leonardo-energy.org/blog/cost-competitive-solid-state-distribution-transformers-online-within-two-years. [Accessed: 27- Nov- 2015].
P. Tatcho, H. Li, Y. Jiang and L. Qi, 'A Novel Hierarchical Section Protection Based on the Solid State Transformer for the Future Renewable Electric Energy Delivery and Management (FREEDM) System', IEEE Trans. Smart Grid, vol. 4, no. 2, pp. 1096-1104, 2013.
De Carne, G.; Buticchi, G.; Liserre, M.; Marinakis, P.; Vournas, C., "Coordinated frequency and Voltage Overload Control of Smart Transformers," in PowerTech, 2015 IEEE Eindhoven , vol., no., pp.1-5, June 29 2015-July 2 2015
Huber, J.E.; Kolar, J.W., "Volume/weight/cost comparison of a 1MVA 10 kV/400 V solid-state against a conventional low-frequency distribution transformer," in Energy Conversion Congress and Exposition (ECCE), 2014 IEEE , vol., no., pp.4545-4552, 14-18 Sept. 2014
2015. [Online]. Available: http://static.mimaterials.com/midel/documents/sales/Guide_for_Transformer_Fire_Safety_Practices.pdf. [Accessed: 27- Nov- 2015].
2015. [Online]. Available: http://www02.abb.com/global/coabb/coabb051.nsf/0/8aa3946a6ad8e7c6c12577880053e1d8/$file/ABB+SPT+Transformers+-+Customer+Value+Proposition.pdf. [Accessed: 27- Nov- 2015].
2015. [Online]. Available: http://Solid State Transformer Market worth $204.3 Million by 2020. [Accessed: 27- Nov- 2015].
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
References