VSC-HVDC Protection Requirements - Cardiff...
Transcript of VSC-HVDC Protection Requirements - Cardiff...
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VSC-HVDC
Protection
Requirements
6th HVDC Colloquium – DTU, Roskilde - Denmark
Ataollah Mokhberdoran
PhD Candidate at University of Porto
Researcher at Automation & Switchgear
Unit of EFACEC Company, Portugal
Offshore Wind Industry
Installed Capacity and Average Wind Farm Size
Source:EWEA
Onshore wind sites are almost rareOnshore wind sites are in northern partsSolar sites are in the southern parts
Offshore Wind Industry
Generation moves to borders
Population is far from generation
Demand for transmitting bulk amount of the energy over long distances
Point to point transmission lines
Multi-terminal and meshed grid
EWEA Target
2030
Offshore:
150GWOnshore:
250GW
Multi-Terminal HVDC Grid
Multi-Terminal HVDC Grid
VSC
VSC
VSCVSC
VSC
AC
Grid
AC
AC DC
Bus
LineInternal
Protective Issues:
AC Side:
Loss of Synchronism
Frequency Deviation
Symmetric Faults
Asymmetric Faults
DC Side:HVDC Line Faults:
Pole to Ground
Pole to Pole
DC Bus Faults:
Pole to Ground
Pole to Pole
Component Level:
Capacitors, Switches,
Diodes, …
Multi-Terminal HVDC Grid
VSC
VSC
VSCVSC
VSC
AC Side Faults Can be Handled because of full control
on VSC at AC side fault.
Handling DC side faults is challenging!
DC Line Parameters
Converter Main Circuit Topology
Diodes Overload Capability
IGBTs Surge Capability
DC Grid Stability Issues
DC Link Capacitors Voltage Limitation
Bypass Circuit Capability
Fault Current Contribution
What do we want to save!?
VSC
VSC
VSCVSC
VSC
Large I2t Capability
Diodes: Limited Surge Current
IGBT or IGCT: Limited Surge Current
Capacitors: Limited Voltage
Capacitors: Limited di/dt
(1) Core
(3) Sheath(4) Insulater(5) Armor
(6) Insulator(2) Insulator
VSC
2Cdc
2Cdc
+
_
Power IGBTs
Realized by Soft Punch Through Chip Technology
3 Standard Isolation Voltages (4, 6 and 10.2kVRMS)
Low Forward Voltage Drop Then Low Losses
AlSiC Base-plate (Good thermal cycling capability)
AlN isolation (Low thermal resistance)
Soft Switching behavior, Large Safe Operation Area
RBSOA
Power IGBTs
Reduced Pressure Uniformity Requirement
Optimized for Series Connections: Mechanically & Electrically
Multi-level Converters with 6 or More Devices Mechanically in series
Stable Short-circuit Failure Mode (SCFM)
Reduced Flatness of Heat Sink Tolerance
Chips contacted by common pole-piece Chips contacted by individual springs
Power IGBTs
FZ500R65KE3
V_CES = 6500V
I_Cnom = 500A
A High Power IGBT
Power IGBTs
FZ500R65KE3
V_CES = 6500V
I_Cnom = 500A
A High Power IGBT
Power Diodes
FZ500R65KE3
V_CES = 6500V
I_Cnom = 500A
A High Power IGBT
Topologies
fR
cableR cableL
dcC
dcC
chokeL
Large Capacitor Contribution
AC Grid Contribution
Anti-parallel Diodes Stressed
Pole to Pole Fault
Capacitor Contribution
AC Grid Contribution
Anti-parallel Diodes Stressed
Pole to Ground Fault
Topologies
Large Capacitor Contribution
AC Grid Contribution
Anti-parallel Diodes Stressed
Pole to Pole Fault
Topologies
Partial Capacitor Contribution
IGBTs Blocked
Anti-parallel Diodes Stressed
Pole to Pole Fault
Topologies
Topologies
Topologies
Possible Capacitor Contribution
SM Capacitor Charged up
DC Fault Blocked
Pole to Pole Fault
IGBTs Stressed Before Blocking
IGBTs Blocked
Topologies
Topologies
Almost the same circuit
topology as MMC but redrawn
Topologies
Topologies
Less Switch than F-Bridge
Less Smoothness
Higher Voltage Sub-modules
DC Fault Tolerant
More Switch than H-Bridge
Topologies
Source: Tim Green’s Presentation at University of Strathclyde, Dec 2014
Topologies
Source of Figures: Stephen Finney’s Presentation at University of Strathclyde, Dec 2014
Diode currents in an MMC converter under DC fault conditions
Topologies
Reduced Pressure Uniformity Requirement
Each One Has Its Pros and Cons
Fault Tolerant Topologies:
- Can Reduce the Need for DC Circuit Breaker
- Have Higher Power Losses
- What about the Selectivity?
Half- Bridge based Topologies:
- Good Efficiency
- Defenceless Against the DC side Faults
- Requires Fast DC Fault Current Breaking
Fault causes rapidly changing currents in all lines
Selectivity: Only the affected element must be switched
IGBTs cannot withstand high overloads
Diodes are More Vulnerable
Fast enough (DC: no inductance XL to limit the current)
Only in case of DC fault and not during load change or AC fault
Remarks on DC Grid Protections
Fault location (branch) detection within a few milliseconds
Too fast for communication between measurement devices
Independent detection systems
Opening at both sides of the faulted line
No opening of other branches?
Backup in case this fails
New superfast DC breakers are needed (≈ 5 ms)
Source: Dirk Van Hertem, Lecture at Strathclyd University, Glasgow, Scotland, Dec 2014
HVDC Circuit Breaker
HVDC Circuit Breaker
CB
Surge Arrestor
cCcL
cR
sIoI
aI
cI
L
Surge Arrestor Surge Arrestor
CB
IGBT IGBT
Small Size IGBT
Breaker
Surge Arrestor
Main Breaker
Surge Arrestor
IGBT IGBT
Ultra Fast
Disconnector
IsolatorL
Surge Arrestor
vR
dcL
LiT
Mechanical Circuit Breaker
Solid-state Circuit Breaker
Hybrid Circuit Breaker
Fast DC Circuit Breakers
Solid-state Circuit Breaker
• Ultra Fast
Interruption Time
• 800kV, 5kA expected
Maximum Ratings
• High, up to 30% of Related VSC
Conduction Losses
• Surge Arrestors
Energy Absorption
• Very High
Surge Voltage
• Fast
Interruption Time
• 320kV, 16kA Expected
Maximum Ratings
• Low, up to 1% of Related VSC
Conduction Losses
• Surge Arrestors
Energy Absorption
• Very High
Surge Voltage
Hybrid Circuit BreakerSmall Size IGBT
Breaker
Surge Arrestor
Main Breaker
Surge Arrestor
IGBT IGBT
Ultra Fast
Disconnector
IsolatorL
Main Breaker Unit
Fast DC Circuit Breakers
Hybrid Circuit Breaker
Solid-state Circuit Breaker Metal Contacts and Semiconductors
Conducting the current in
normal operation
Main interrupter in
fault condition
IGBT Breaker
Surge Arrestor
Main Breaker
IGBT IGBT
Ultra Fast
Disconnector
IsolatorL
Fast DC Circuit Breakers
f
sc n delay
diI I t
dt
. . scCB DC line sc line
diV V R i L
dt
DCV
1
lineR 1
lineL2
lineR 2
lineLBreaker
BRVLV
Short
Circuit
Fault
sci
Load
Fast DC Circuit Breakers
SSCB
Short
Circuit
Fault
R line
L line
i sc
V DC Load
R v
Short
Circuit
Fault
R lineL
line
i sc
V DC Load
R v
SSCB
Two Main Solid-state DC Circuit Breaker Topologies
Main Breaker Unit
NP
G2
S2
D2
NP
G2
S2
D2
20131-Diode+Rv based2-SiC-BGSIT based
Main Breaker
IGBT IGBTL
L’
L’’
L’
L’’
20141-Coupled Inductors based
2-Seperated Rv based
N
P
G2 S2
D2
NP
G2 S2
D2
Surge Arrestor
Capacitor
2015SiC based
2010Thyristor based
General Requirements
• High rate of rise of fault current
• Save converters
• Protec. algorithms
• Footprint
• Surge arrestor
• Limitations as energy absorbers
• Reducing the Reliability of the Device
• Surge arrestor
• High overvoltage
• Insulation problem
• Increase the cost of devices
Quick
Interruption
Action
Stored
Energy
Dissipation
Surge
Voltage
Issue
Proposed Method
C
Short-Circuit
Fault
L iLicon
DC +
-
Auxiliary
Branch
Breaker
C
Short-Circuit
Fault
L iLicon
DC +
-
Auxiliary
Branch
Breaker
C
Short-Circuit
Fault
L iLicon
DC +
-
Auxiliary
Branch
Breaker
Pending Patent, No. 108775, 2015, Ataollah Mokhberdoran, Adriano Carvalho, Nuno Silva, Hélder Leite, António Carrapatoso
Proposed Method
Employs a pre-charged capacitorTo feed the fault current during and after main breaker unit interruption
Prevent the sudden reduction of voltage of beginning of the line
Change the final equivalent circuit to a RLC circuit
No surge VoltageNatural response of the RLC circuit
Ultra-fast actionThe converter current is interrupted very quickly (in the range of few hundred micro seconds)
C
Short-Circuit
Fault
L iLicon
DC +
-
Auxiliary
Branch
Breaker
Pending Patent, No. 108775, 2015, Ataollah Mokhberdoran, Adriano Carvalho, Nuno Silva, Hélder Leite, António Carrapatoso
SSCB in A System
Transmission
Line
VSC1
SSCB1
CCB
SSCB2
TF
LL
Rch
chL R L
Tch
CCB
TF Rch
Tch
chLR L
LL
VSC2
Pending Patent, No. 108775, 2015, Ataollah Mokhberdoran, Adriano Carvalho, Nuno Silva, Hélder Leite, António Carrapatoso
Aggregated Model
2 1
1 22
fault cable
cable
R R R C
L L L
1
2
max.
CVR
k I
1 2
1 2
2
4 cableL L LC
R
22
2
1 2 1 2 1
10
.
fault cable
cable cable
R R Rd i t di ti t
dt L L L dt L L L C
+_
C 1
t=0
R 2
R S
VDC
t=0
2L RCable CableL
R fault
sw1
sw21L
LiCBi
Ci
B
(t)
(t) (t)A
Aggregated Model
SSCB 2- Positive Pole
SSCB 4- Negative Pole
HVDC Cable
Short
Circuit Fault
HVDC Cable
SSCB1- Positive Pole
SSCB 3- Negative Pole
HVDC Cable
HVDC Cable
R6
L1
C3
L2 L3L4 T4
R8 L7
T2C2
C4
C1
L5 L6 L8
R2 R4
2 1
1 2
2 2 2
2 2
fault cable
cable
R R R C
L L L
1
2
max.
CVR
k I
1 2
1 2
2
4 cableL L LC
R
2 1
1 22
fault cable
cable
R R R C
L L L
Aggregated Model
SSCB in A System
SSCB1 XLPE Cable – 90km SSCB2
SSCB3 XLPE Cable – 90km SSCB4
A BC
VSC- 1 VSC-2
MMC
X R1 1 XR 22
T1T2
Ip1 I line,p
1
Ip2I line,p
2 VCB,2+
_+_
VCB, 1
Bus1 Bus2
MMC
In1
I line,n
1
_VCB, 3 + Ip2
I line,n2
VCB,4_+
(1) Core
(2) Insulator(3) Sheath
(4) Insulater
(5) Armor
(6) Insulator
Table I: Assumed system parametersMMC Power 1000MVA Cable Length 90km Transformer Y/D
Nominal
Voltage±320kV Smoothing Reactor 15mH AC source 230kV
Configuration Sym. monopole Fault Impedance 0.1Ω MMC Type Half-bridge
Table II: Designed SSCB parametersIth 3kA R1 3kΩ L1 50µH
C1 350µF R2 30Ω L2 10mH
TABLE III
DC CABLE DATA
LayerRadius
(mm)
Resistivity
(Ωm)
Rel.
permeability
Rel.
permittivity
(1) Core 25.2 1.72*10-8 1 1
(2) Insulator 40.2 - 1 2.3
(3) Sheath 43.0 2.20*10-7 1 1
(4) Insulator 48.0 - 1 2.3
(5) Armor 53.0 1.80*10-7 10 1
(6) Insulator 57.0 - 1 2.1
Point to Point MMC-HVDC
SSCB1 XLPE Cable – 90km SSCB2
SSCB3 XLPE Cable – 90km SSCB4
A BC
VSC- 1 VSC-2
MMC
X R1 1 XR 22
T1T2
Ip1 I line,p
1
Ip2I line,p
2 VCB,2+
_+_
VCB, 1
Bus1 Bus2
MMC
In1
I line,n
1
_VCB, 3 + Ip2
I line,n2
VCB,4_+
Point to Point MMC-HVDC
SSCB1 XLPE Cable – 90km SSCB2
SSCB3 XLPE Cable – 90km SSCB4
A BC
VSC- 1 VSC-2
MMC
X R1 1 XR 22
T1T2
Ip1 I line,p
1
Ip2I line,p
2 VCB,2+
_+_
VCB, 1
Bus1 Bus2
MMC
In1
I line,n
1
_VCB, 3 + Ip2
I line,n2
VCB,4_+
Point to point MMC-HVDC
SSCB1 XLPE Cable – 90km SSCB2
SSCB3 XLPE Cable – 90km SSCB4
A BC
VSC- 1 VSC-2
MMC
X R1 1 XR 22
T1T2
Ip1 I line,p
1
Ip2I line,p
2 VCB,2+
_+_
VCB, 1
Bus1 Bus2
MMC
In1
I line,n
1
_VCB, 3 + Ip2
I line,n2
VCB,4_+
Multi-Terminal Model
Link 12
CB12
Link 34
Lin
k 1
3
Lin
k 2
4
CB21
CB14
CB41
CB
13
CB
24
CB
42
CB43CB34
CB
31
IGBT
Driver
Control
System
Current
Measurement
Circuit
Thyristor
Triger Cr.
Voltage
Measurement
CircuitThyristor
Triger Cr.
Main Breaker Unit
Multi-Terminal Model
Comparison
SSCBs are installed
Fault Close to Bus1
Developed Topology of SSCB
Main Breaker Unit
Developed Topology of SSCB
Main Breaker Unit
Main Breaker Unit Main Breaker Unit
loss sw sat CBP N V I
Fault Tolerant Converters can Reduce the Need for DCCB but not Eliminate
Summary
Pre-Block Current Stress Must be Considered in Sizing of IGBTs
Pre-Bypass Stress on Anti-Parallel Diodes, Specially Surge Current
Impact of VSC Control during the DC Fault should be Studied
New DC Fault Current Breaking Concept Proposed
Employs Common Components
Shows Improved Characteristics
Thank you for your attention
Questions?
Photo by: Ataollah Mokhberdoran