Transcript FACTS devices - Calvin College

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Lecture 3
Advanced FACTS Devices and Applications:
Performance, Power Quality and Cost
Considerations
Paulo F. Ribeiro, BSEE, MBA, PHD, PE
CALVIN COLLEGE
Engineering Department
Grand Rapids, MI 49546
http://engr.calvin.edu/PRibeiro_WEBPAGE/
[email protected]
P. Ribeiro
June, 2002
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FACTS
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P. Ribeiro
The Concept
History / Background - Origin of FACTS, Opportunities, Trends
System Architectures and Limitations
Power Flow Control on AC Systems
Application Studies and Implementation
Basic Switching Devices
Conditioners: SVC, STATCOM, TCSC, UPFC, SMES
Specification, Cost Considerations and Technology Trends
Impact of FACTS in interconnected networks
Market Assessment, Deregulation and Predictions
June, 2002
2
The Concept
P. Ribeiro
X
V

P    P   P   P
X
V
tg
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The Concept and Challenges
A transmission system can carry power up to its thermal loading limits. But in practice the
system has the following constraints:
-Transmission stability limits
-Voltage limits
-Loop flows
Transmission stability limits: limits of transmittable power with which a transmission system can
ride through major faults in the system with its power transmission capability intact.
Voltage limits: limits of power transmission where the system voltage can be kept within
permitted deviations from nominal.
Loop flows can be a problem as they are governed by the laws of nature which may not be
coincident with the contracted path. This means that power which is to be sent from point ”A” to
point ”B” in a grid will not necessarily take the shortest, direct route, but will go uncontrolled
and fan out to take unwanted paths available in the grid.
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June, 2002
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The Concept
FACTS devices
FACTS are designed to remove such constraints and to meet planners´, investors´ and operators´ goals
without their having to undertake major system additions. This offers ways of attaining an increase of
power transmission capacity at optimum conditions, i.e. at maximum availability, minimum
transmission losses, and minimum environmental impact. Plus, of course, at minimum investment cost
and time expenditure.
The term ”FACTS” covers several power electronics based systems used for AC power transmission.
Given the nature of power electronics equipment, FACTS solutions will be particularly justifiable in
applications requiring one or more of the following qualities:
-Rapid dynamic response
-Ability for frequent variations in output
-Smoothly adjustable output.
Important applications in power transmission involving FACTS and Power Quality devices:
SVC (Static Var Compensators), Fixed * as well as Thyristor-Controlled Series Capacitors (TCSC) and
Statcom. Still others are PST (Phase-shifting Transformers), IPC (Interphase Power Controllers), UPFC
(Universal Power Flow Controllers), and DVR (Dynamic Voltage Restorers).
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June, 2002
5
History, Concepts, Background, and Issues
Origin of FACTS
-Oil Embargo of 1974 and 1979
-Environmental Movement
-Magnetic Field Concerns
-Permit to build new transmission lines
-HVDC and SVCs
-EPRI FACTS Initiative (1988)
-Increase AC Power Transfer (GE and DOE Papers)
-The Need for Power semiconductors
Why we need transmission interconnection
-Pool power plants and load centers to minimize generation cost
-Important in a deregulated environment
Opportunities for FACTS
Increase power transfer capacity
SVC (Nebraska GE 1974, Minnesota Westinghouse 1975, Brazil Siemens 1985)
TCSC, UPFC AEP 1999
Trends
-Generation is not being built
-Power sales/purchases are being
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June, 2002
6
System Architectures and Limitations
System Architecture
Radial, interconnected areas, complex network
Power Flow in an AC System
Power Flow in Parallel and Meshed Paths
Transmission Limitations
Steady-State (angular stability, thermal limits, voltage limits)
Stability Issues (transient, dynamic, voltage and SSR)
System Issues (Post contingency conditions, loop flows, short-circuit levels)
Power Flow and Dynamic Stability Considerations
Controllable Parameters
Basic FACTS Devices - Impact of Energy Storage
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June, 2002
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Power Flow Control on AC Systems
Radial
Parallel
Meshed
Power Flow in Parallel Paths
Power Flow in a Meshed Systems
What limits the loading capability?
Power Flow and Dynamic Considerations
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June, 2002
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Power Flow Control on AC Systems
50% Series Compensation
Relative Importance of Controllable Parameters
Control of X can provide current control
When angle is large X can provide power control
Injecting voltage in series and perpendicular to the current flow, can increase or
decrease
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June, 2002
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FACTS Applications and Implementations
Transmission Transfer Capacity Enhancement
Steady State
Issues
Voltage Limits
Thermal Limits
Angular Stability Limits
Loop Flows
Dynamic
Issues
Traditional Solutions
Breaking
Resistors Load
Shedding
Advanced Solutions
FACTS
Energy Storage
Fixed
Compensation
Line
Reconfiguration
Transmission
Link
Better
Protection
FACTS
Increased
Inertia
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Devices
June, 2002
Transient Stability
Damping Power Swings
Post-Contingency Voltage
Control
Voltage Stability
Subsynchronous Res.
Enhanced
Power Transfer
and Stability
SVC
STATCOM
TCSC, SSSC
UPFC
10
FACTS Devices
Shunt Connected
Static VAR Compensator (SVC)
Static Synchronous Compensator (STATCOM)
Static Synchronous Generator - SSG
Battery Energy Storage System (BESS)
Superconducting Magnetic Energy Storage (SMES)
Energy Storage
Combined Series and Series-Shunt Connected
Static Synchronous Series Controllers (SSSC)
Thyristor Controlled Phase-Shifting Transformer or
Phase Angle Regulator (PAR)
Interline Power Flow Controller (IPFC)
Thyristor Controlled Series Capacitor (TCSC)
Unified Power Flow Controller (UPFC)
Relative Importance of Different Types of Controllers
Shunt, Shunt-Series
P. Ribeiro
June, 2002
Energy Storage
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Power Electronics - Semiconductor Devices
Diodes
Transistors
IGBT
Thyristors
SCR, GTO, MTO, ETO, GCT, IGCT, MCT
Devices
Diode (pn Junction)
Silicon Controlled Rectifier (SCR)
Gate Turn-Off Thyristor (GTO) GE
MOS Turn-Off Thyristor (MTO) SPCO
Emitter Turn-Off Thyristor (ETO) Virginia Tech
Integrated Gate-Commutated Thyristor (IGCT) Mitsubishi, ABB
MOS-Controlled Thyristor (MCT) Victor Temple
Insulated Gate Bipolar Transistor (IGBT)
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June, 2002
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Power Electronics - Semiconductor Devices
Principal Characteristics
Voltage and Current
Losses and Speed of Switching
Speed of Switching
Switching Losses
Gate-driver power and energy requirements
Parameter Trade-off
Power requirements for the gate
di/dt and dv/dt capability
turn-on and turn-off time
Uniformity
Quality of silicon wafers
IGBT has pushed out the conventional GTO as IGBTs ratings go up.
IGBTs - Low-switching losses, fast switching, current-limiting capability
GTOs - large gate-drive requirements, slow-switching, high-switching losses
IGBTs (higher forward voltage drop)
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June, 2002
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Power Electronics - Semiconductor Devices
Decision-Making Matrix
System
VSI
CSI
Commutation
Approach
Natural
Forced
Switching
Technology
Synchronous
PWM
Transition
Approach
Hard
Soft
Circuit
Topology
Two-Level
Multi-Level
Device
Type
P. Ribeiro
SCR
June, 2002
GTO
IGBT
MCT
MTO
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AC Transmission Fundamentals (Series Compensation)
E1 / 1
E2 / 2
P&Q
I
X
Changes in X will increase or decrease real power flow for a fixed angle or change angle for a fixed power flow.
Alternatively, the reactive power flow will change with the change of X. Adjustments on the bus voltage have
little impact on the real power flow.
Vc
Vx
I
P1 = E1 . E2 . sin () / (X - Xc)
Vs
Real Power Angle Curve
2
Vseff = Vs + Vc
Vr
Xeff = X - Xc
Vx
2
Vc
P1( x  delta  V1)
Vxo
1
Vs
Vseff
0
0
0
0
0.5
1
1.5
2
delta
2.5
3
Vr
I
3.5
3.14
Phase Angle
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June, 2002
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AC Transmission Fundamentals (Voltage-Series and Shunt Comp.)
E1 / 1
P&Q
E2 / 2
I
X
P
Injected Voltage
E1
E1 - E2
I
E2
Integrated voltage series injection and bus voltage regulation (unified) will
directly increase or decrease real and reactive power flow.
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AC Transmission Fundamentals (Stability Margin)
Improvement of Transient Stability With FACTS Compensation
Equal Area Criteria
Q/V
with VAR compensation (ideal midpoint)
Amargin
A2
no compensation
A1
A1 = Acceleration Energy
1
2
3
A2 = Deceleration Energy
Therefore, FACTS compensation can increase
1 - prior to fault
crit
power transfer without reducing the stability margin
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June, 2002
Phase Angle 2 - fault cleared
3 - equal area
3 >crit - loss of synchronism
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Voltage Source Vs. Current Source Converters
CSC
Device Type
Device Characteristic
Symmetry
Adv
Dis
Thyristor
Self-Commutation
Symmetrical
Thyristor
Self-Commutation
Asymmetrical
Adv
Dis
+
Short-Circuit Current
Lower
+
Higher
Rate of Rise of Fault
Current
Losses
Limited by DC Reactor
+
Fast Rise (Due to capacitor discharge)
Higher
-
Lower
+
AC Capacitors
DC Capacitors
Required
Not Required
+
+
Not Required
Required
Valves dv/dt
Lower
(AC Capacitors)
More Complex
Depends on Current Flowing
through Energy Storage
+
Higher
Interface with AC System
Reactive Power Generation
Performance
Harmonics
P. Ribeiro
VSC
Less Complex
Independent of Energy Storage
+
+
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Voltage Source Converters
S hun tC om p en sa toi n
S e r ies C om p en sa toi n
V
S ys etm bu s
V
S ys etm bu s
V
C oup lni g
T ran s of m
r er
C oup lni g
T ran s of m
r er
I
X
I
T ran s of m
r e r el a kage
ni du c at n ce
X
Vo
Vo
DC A
-C
Sw itch ni g
C on ve r te r
DC A
-C
Sw itch ni g
C on ve r te r
Cs
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T ran s of m
r e r el a kage
ni du c at n ce
Cs
+
+
V dc
V dc
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Voltage Source Converters
Basic 6-Pulse, 2-level, Voltage-Source Converter
di c
ea
eb
ec
ai
Ta1
D a1 Tb1
D b1 T c1
bi
D c1
V dc
+
Cs
V dc
ci
2
H y po h
t e tci a l
neu tra lpo ni t
V dc
Ta2
D a2 Tb2
D b2 T c2
D c2
2
ea
Vdc
eb
Vdc
ec
Vdc
eab
[a ]
ebc
eca
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ia
ib
ic
D
Ta 1
a1
Ta2
D
a2
D
b1
Tb1
D
Tb2
D
c1 b2
June, 2002
Tc2
20
[b ]
Voltage Source Converters
2, 3, 5-level, VSC Waveforms
vd c
2
vd c
2
+
e ou t
vd c
2
v dc
+
vd c
2
v dc
+
2 v dc
v dc
N eu tra l
m
( di -) po ni t
vd c
e ou t
+
1
v dc
+
2
+ v dc
N e u tra l
m
( di -) p o ni t
e ou t

vd c
P. Ribeiro
+
- v dc
v dc
June, 2002
+
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Voltage Source Converters
Output voltage control of a two-level VSC
v =V 0
it
v= V s n
io
v o= V o ( ) 
t
*
t
 =  * 
 
v o (  )
v o (  )
 
v oF (  )= V (+  ) s n
i  t t
(v+ v )d c
v d c nom ni a l
(v - v )d c
t
C
idc
 v d c= 1 i d c d t
C
i d c = f  
v oF (  )= V (+  ) s n
it
P. Ribeiro
vdc
June, 2002
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FACTS Technology - Possible Benefits
• Control of power flow as ordered. Increase the loading capability of lines to their
thermal capabilities, including short term and seasonal.
• Increase the system security through raising the transient stability limit, limiting
short-circuit currents and overloads, managing cascading blackouts and
damping electromechanical oscillations of power systems and machines.
• Provide secure tie lines connections to neighboring utilities and regions thereby
decreasing overall generation reserve requirements on both sides.
• Provide greater flexibility in siting new generation.
• Reduce reactive power flows, thus allowing the lines to carry more active power.
• Reduce loop flows.
• Increase utilization of lowest cost generation.
P. Ribeiro
June, 2002
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FACTS and HVDC: Complimentary Solutions
HVDC
Independent frequency and control
Lower line costs
Power control, voltage control,
stability control
FACTS
Power control, voltage control,
stability control
Installed Costs (millions of dollars)
Throughput MW
HVDC 2 Terminals
FACTS
2000 MW
500 MW
1000 MW
2000 MW
$ 40-50 M
$ 75-100M
$120-170M
$200-300M
$ 5-10 M
$ 10-20M
$ 20-30M
$ 30-50M
(*)Hingorani/Gyugyi
P. Ribeiro
June, 2002
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FACTS and HVDC: Complimentary Solutions
HVDC Projects: Applications
Submarine cable
Long distance overhead transmission
Underground Transmission
Connecting AC systems of different or incompatible frequencies
Large market potential for FACTS is within the ac system on a value-added basis, where:
• The existing steady-state phase angle between bus nodes is reasonable
• The cost of a FACTS device solution is lower than HVDC or other alternatives
• The required FACTS controller capacity is less than 100% of the transmission throughput rating
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June, 2002
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FACTS Attributes for Different Controllers
FACTS Controller
Static Synchronous Compensator
(STATCOM without storage)
Static Synchronous Compensator
(STATCOM with storage, BESS, SMES,
large dc capacitor)
Static VAR Compensator (SVC, TCR,
TCS, TRS
Thyristor-Controlled Braking Resistor
(TCBR)
Static Synchronous Series Compensator
(SSSC without storage)
Static Synchronous Series Compensator
(SSSC with storage)
Thrystor-Controlled Series Capacitor
(TCSC, TSSC)
Thyristor-Controlled Series Reactor
(TCSR, TSSR)
Thyristor-Controlled Phase-Shifting
Transformer (TCPST or TCPR)
Unified Power Flow Controller (UPFC)
Thyristor-Controlled Voltage Limiter
(TCVL)
Thyristor-Controlled Voltage Regulator
(TCVR)
Interline Power Flow Controller (IPFC)
P. Ribeiro
Control Attributes
Voltage control, VAR compensation, damping oscillations, voltage
stability
Voltage control, VAR compensation, damping oscillations, transient
and dynamic stability, voltage stability, AGC
Voltage control, VAR compensation, damping oscillations, transient
and dynamic stability, voltage stability
Damping oscillations, transient and dynamic stability
Current control, damping oscillations, transient and dynamic stability,
voltage stability, fault current limiting
Current control, damping oscillations, transient and dynamic stability,
voltage stability
Current control, damping oscillations, transient and dynamic stability,
voltage stability, fault current limiting
Current control, damping oscillations, transient and dynamic stability,
voltage stability, fault current limiting
Active power control, damping oscillations, transient and dynamic
stability, voltage stability
Active and reactive power control, voltage control, VAR
compensation, damping oscillations, transient and dynamic stability,
voltage stability, fault current limiting
Transient and dynamic voltage limit
Reactive power control, voltage control, damping oscillations,
transient and dynamic stability, voltage stability
Reactive power control, voltage control, damping oscillations,
transient and dynamic stability, voltage stability
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FACTS Implementation - STATCOM
P&Q
E1 / 1 I
E2 / 2
X
Regulating Bus Voltage
Can Affect Power Flow Indirectly / Dynamically
P1 = E1 (E2 . sin ())/X
P. Ribeiro
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FACTS Implementation - TCSC
E1 / 1
P&Q
E2 / 2
X
Line Impedance Compensation
Can Control Power Flow Continuously
P1 = E1 (E2 . sin ()) / Xeff
Xeff = X- Xc
The alternative solutions need to be distributed; often series compensation has to be installed in several places along a line but many of the
other alternatives would put both voltage support and power flow control in the same location. This may not be useful. For instance, if
voltage support were needed at the midpoint of a line, an IPFC would not be very useful at that spot. TCSC for damping oscillations ...
P. Ribeiro
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FACTS Implementation - SSSC
E1 / 1
P&Q
E2 / 2
I
X
P1 = E1 (E2 . sin ()) / Xeff
Xeff = X - Vinj/I
P. Ribeiro
June, 2002
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FACTS Implementation - UPFC
E1 / 1
P&Q
E2 / 2
I
X
Regulating Bus Voltage and Injecting Voltage
In Series With the Line
Can Control Power Flow
P1 = E1 (E2 . sin ()) / Xeff
Xeff = X - Vinj / I
Q1 = E1(E2 - E2 . cos ()) / X
P. Ribeiro
June, 2002
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FACTS Implementation - UPFC
Series Transformer
Shunt Inverter
Series
Inverter
Shunt
Transforme
r
Unified Power Flow Controller
P. Ribeiro
June, 2002
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FACTS Implementation - STATCOM + Energy Storage
E1 / 1
I
P&Q
E2 / 2
X
Regulating Bus Voltage Plus Energy Storage
Can Affect Power Flow Directly / Dynamically
Plus Energy Storage
P. Ribeiro
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FACTS Implementation - SSSC + Energy Storage
E1 / 1
P&Q
E2 / 2
I
X
Voltage Injection in Series Plus Energy Storage
Can Affect Power Flow Directly / Dynamically
and sustain operation under fault conditions
Plus Energy Storage
P. Ribeiro
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FACTS Implementation - UPFC + Energy Storage
E2 / 2
P&Q
E1 / 1
I
X
Plus Energy Storage
P. Ribeiro
Regulating Bus Voltage + Injected
Voltage + Energy Storage
Can Control Power Flow Continuously,
and Support Operation Under Severe
Fault Conditions (enhanced performance)
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FACTS Implementation - UPFC + Energy Storage
Series
Inverter
Shunt
Inverter
1000μ
F
1000μ
F
1000μ
F
1000μ
F
SMES Chopper
and Coil
Unified Power Flow Controller - SMES Interface
P. Ribeiro
June, 2002
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FACTS Implementation - UPFC + Energy Storage
MOV
UPFC
Grounding
SMES Chopper and Coil - Overvoltage Protection
P. Ribeiro
June, 2002
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FACTS Implementation - TCSC + STACOM + Energy Storage
$
Regulating Bus Voltage + Energy
Storage + Line Impedance Compensation
Can Control Power Flow Continuously,
and Support Operation Under Severe
Fault Conditions (enhanced performance)
P. Ribeiro
June, 2002
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FACTS Implementation - IPFC
E3 / 3
E1 / 1
E2 / 2
P12 = E1 (E2 . sin (1- 2)) / X
P13 = E1 (E2 . sin (1- 3)) / X
P. Ribeiro
June, 2002
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FACTS Implementation - IPFC
Series Transformer, Line 1
Series Transformer, Line 2
Series Inverter #1
Series Inverter #2
Interline Power Flow Controller
P. Ribeiro
June, 2002
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Enhanced Power Transfer and Stability:
Technologies’ Perspective
Compensation
Devices
FACTS Devices
Energy Storage
Fast
SMES Real Power Injection
and Absorption
P
P
TSSC
SSSC
UPFC
Electric Grid
Q
STATCOM
Q
2
Acceleration
Area
1.5
STATCOM
Fast
Reactive Power Injection and
Absorption
June, 2002
Increased Power
Transfer
Additio
nal
Stabilit
y
Margin
Electric Grid
Fast
Reactive Power Injection
and Absorption
P. Ribeiro
P
Power Transfer
TSSC
SSSC
UPFC
Deceleration
Area
Stability
Margin
1
0.5
0
0
0.5
1
1.5
2
2.5
3
Phase Angle
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FACTS + Energy Storage
Q
The Role of Energy Storage: real
power compensation can
increase operating control and
reduce capital costs
STATCOM
Reactive Power Only
Operates in the
vertical axis only
P
MVA Reduction
The Combination or Real
and Reactive Power will
typically reduce the Rating of
the Power Electronics front
end interface.
Real Power takes care of
power oscillation, whereas
reactive power controls
voltage.
P. Ribeiro
P - Active Power
Q - Reactive Power
STATCOM + SMES
Real and Reactive Power
Operates anywhere within the
PQ Plane / Circle (4-Quadrant)
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FACTS + Energy Storage - Location Sensitivity
Additional Power Transfer(MW)
Closer to generation
Closer to load centers
SMES Power (MW)
P. Ribeiro
June, 2002
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Enhanced Power Transfer and Stability:
Location and Configuration Type Sensitivity
No Compensation
60.
8
59.
2
time (sec)
2 STATCOMs
1 STATCOM + SMES
60.
8
60.
8
59.
2
59.
2
time (sec)
time (sec)
Enhanced Voltage and Stability Control
Voltage and Stability Control
(2 x 80 MVA Inverters)
P. Ribeiro
( 80 MVA Inverter + 100Mjs SMES)
June, 2002
43
FACTS For Optimizing Grid Investments
FACTS Devices Can Delay Transmission Lines Construction
By considering series compensation from the very beginning, power transmission between regions can be
planned with a minimum of transmission circuits, thus minimizing costs as well as environmental impact
from the start.
The Way to Proceed
· Planners, investors and financiers should issue functional specifications for the transmission system
to qualified contractors, as opposed to the practice of issuing technical specifications, which are
often inflexible, and many times include older technologies and techniques) while inviting bids for a
transmission system.
· Functional specifications could lay down the power capacity, distance, availability and reliability
requirements; and last but not least, the environmental conditions.
· Manufacturers should be allowed to bid either a FACTS solution or a solution involving the
building of (a) new line(s) and/or generation; and the best option chosen.
P. Ribeiro
June, 2002
44
Specifications
(Functional rather than Technical )
Transformer Connections
Higher-Pulse Operation
Higher-Level Operation
PWM Converter
Pay Attention to Interface Issues and Controls
Converter
Increase Pulse Number
Higher Level
Double the Number of Phase-Legs and Connect them in Parallel
Connect Converter Groups in Parallel
Use A Combination of several options listed to achieve required rating and performance
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June, 2002
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Cost Considerations
Technology
Reconductor lines
Fixed or Switched Shunt
Reactors
Fixed or Switched Shunt
Capacitors
Fixed or Switched Series
Capacitors
Static VAR Compensators
Thyristor Controlled Series
Compensation (TCSC)
STATCOM
STATCOM w/SMES
Transmission Line
Transfer Enhancement
Increase thermal capacity
Voltage reduction – Light
Load Management
Voltage support and
stability
Power flow control,
Voltage support and
Stability
Voltage support and
stability
Power flow control,
Voltage support and
stability
Voltage support and
stability
Voltage support and
stability
Cost Range
$50K to $200K per
mile
$8-$12 kVAR
$8-$10 kVAR
$12-$16 kVAR
$20-$45 kVAR
$25-$50 kVAR
$80-$100 kVAR
$150-$300 kW
Unified Power Flow
Controller (UPFC)
Operating principle
Increases thermal limit for line
Procurement
Availability
Competitive
Compensates for capacitive varload
Compensates for inductive varload
Reduces inductive line
impedance
Competitive
Compensates for inductive
and/or capacitive var-load
Reduces or increases inductive
line impedance
Competitive
Compensates for inductive and
capacitive var-load
Compensates for inductive
and/or capacitive var-load plus
energy storage for active power
SVC and TCSC functions plus
phase angle control
Limited
competition
Limited
Competitive
Competitive
Limited
competition
Power flow control,
$150-$200 kW
Sole source
Voltage support, and
Stability
Unified Power Flow
Power flow control
$250-$350 kW
SVC and TCSC functions plus
Sole source
Controller (UPFC) w/SMES Voltage support and
voltage regulator, phase angle
Stability,
controller and energy storage
Shaded area indicates technologies that are either permanently connected or switched on or off with mechanical switches. (i.e. these are
not continuously controllable)
P. Ribeiro
June, 2002
46
Cost Considerations
Hardware
Eng & Project Mgmt.
Installation
Civil Works
Commissioning
Insurance
Cost structure
The cost of a FACTS installation depends on many factors, such as power rating, type of device, system
voltage,
system requirements, environmental conditions, regulatory requirements etc. On top of this, the variety of
options available for optimum design renders it impossible to give a cost figure for a FACTS installation.
It is strongly recommended that contact is taken with a manufacturer in order to get a first idea of costs and
alternatives. The manufacturers should be able to give a budgetary price based on a brief description of the
transmission system along with the problem(s) needing to be solved and the improvement(s) needing to be
attained.
(*) Joint World Bank / ABB Power Systems Paper
Improving the efficiency and quality of AC transmission systems
P. Ribeiro
June, 2002
47
Technology & Cost Trends
$
I
$$$
$
I
additional cost savings possible
P. Ribeiro
June, 2002
48
Concerns About FACTS
Cost
Losses
Reliability
P. Ribeiro
June, 2002
49
Economics of Power Electronics
Sometimes a mix of conventional and FACTS systems has the lowest cost
Losses will increase with higher loading and FACTS equipment more lossy than conventional ones
Reliability and security issues - when system loaded beyond the limits of experience
Demonstration projects required
100% Power
Electronics
Delta-P4
Delta-P2
Delta-P3
Delta-P1
100%
Conventional
Cost of System
P. Ribeiro
Stig Nilson’s paper
June, 2002
50
Operation and Maintenance
Operation of FACTS in power systems is coordinated with operation of other items in the
same system, for smooth and optimum function of the system. This is achieved in a
natural way through the Central Power System Control, with which the FACTS device(s)
is (are) communicating via system SCADA. This means that each FACTS device in the
system can be operated from a central control point in the grid, where the operator will
have skilled human resources available for the task. The FACTS device itself is normally
unmanned, and there is normally no need for local presence in conjunction with FACTS
operation, although the device itself may be located far out in the grid.
Maintenance is usually done in conjunction with regular system maintenance, i.e.
normally once a year. It will require a planned standstill of typically a couple of days.
Tasks normally to be done are cleaning of structures and porcelains, exchanging of
mechanical seals in pump motors, checking through of capacitors, checking of control and
protective settings, and similar. It can normally be done by a crew of 2-3 people with
engineer´s skill.
Joint World Bank / ABB Power Systems Paper
Improving the efficiency and quality of AC transmission systems
P. Ribeiro
June, 2002
51
Impact of FACTS in interconnected networks
The benefits of power system interconnection are well established. It enables the participating parties to
share the benefits of large power systems, such as optimization of power generation, utilization of
differences in load profiles and pooling of reserve capacity. From this follows not only technical and
economical benefits, but also environmental, when for example surplus of clean hydro resources from one
region can help to replace polluting fossil-fuelled generation in another.
For interconnections to serve their purpose, however, available transmission links must be powerful
enough to safely transmit the amounts of power intended. If this is not the case, from a purely technical
point of view it can always be remedied by building additional lines in parallel with the existing, or by
uprating the existing system(s) to a higher voltage. This, however, is expensive, time-consuming, and calls
for elaborate procedures for gaining the necessary permits. Also, in many cases, environmental
considerations, popular opinion or other impediments will render the building of new lines as well as
uprating to ultrahigh system voltages impossible in
practice. This is where FACTS comes in.
Examples of successful implementation of FACTS for power system interconnection can be found among
others between the Nordic Countries, and between Canada and the United States. In such cases, FACTS
helps to enable mutually beneficial trade of electric energy between the countries.
Other regions in the world where FACTS is emerging as a means for AC bulk power interchange between
regions can be found in South Asia as well as in Africa and Latin America. In fact, AC power corridors
equipped with SVC and/or SC transmitting bulk power over distances of more than 1.000 km are a reality
today.
P. Ribeiro
Joint World
Bank / ABB Power Systems Paper
Improving the efficiency and quality of AC transmission systems
June, 2002
52
Power Quality Issues
1 – Background
2 – The Need For An Integrated Perspective of PQ
3 – Harmonics
4 – Imbalance
5 – Voltage Fluctuations
6 – Voltage Sags
7 – Standards, Limits, Diagnostics, and Recommendations
Flexibility, Compatibility, Probabilistic Nature, Alternative Indices
8 – Combined effects
9 – Power Quality Economics
10 – Measurement Protocols
11 – Probabilistic Approach
12 – Modeling & Simulation
13 – Advanced Techniques
(Wavelet, Fuzzy Logic, Neural Net, Genetic Algorithms)
14 – Power Quality Programs
P. Ribeiro
June, 2002
53
Compatibility: The Key Approach
P. Ribeiro
June, 2002
54
Relative Trespass Level (RTL)
 U k   Uref k  

RTL k   max  0,
Uref k 


Uk - measured or calculated harmonic voltage
Uref - harmonic voltage limit (standard or particular equipment)
k - harmonic order
8
8
8
6
6
RT Lk
RT Lk
4
0
0
2
2
P. Ribeiro
4
2
2
0
8
4
6
8
k
10
12
14
13
June, 2002
0
0
0.05
0.1
0
Uk
.1
55
Harmonic Distortion Diagnostic Index Applying Fuzzy Logic
Comparisons
Alternative Approach
Individual Harmonics (Vh)
Equipment Malfunction
Fuzzy - Color Code Criteria
No Problem
b
c
Below
NormalOver
Below
Normal
Heating
Normal
a
Caution
Possible Problems
Very
Hot
d
Imminent Problems
e
1
Normal
Levels
0
P. Ribeiro
A
B
Caution Possible Severe Dangerous
Problems Distortions Levels
C
June, 2002
D
E
F
G
RTL
56
How To Interpret This?
P. Ribeiro
June, 2002
57
How To Interpret This?
P. Ribeiro
June, 2002
58
The Total Quality Environment
Power System Value Chain
Environmental
Maintainability
Availability
Safety
Efficiency
Reliability
Performance
Price
Power Quality
Energy
INPUTS
Generation
Delivery
Conversion
Power
Processing
Communication
OUTPUTS
Light / Motion
Central
Station
T&D
AC-AC
Supplies
Motion
SMES
Batteries
FACTS
SMES
PQ Parks
UPS
Appliances
Power Electronics Systems and Components
User
Utility
P. Ribeiro
June, 2002
59
Conclusions
•
•
•
•
•
•
•
•
P. Ribeiro
Future systems can be expected to operate at higher stress levels
FACTS could provide means to control and alleviate stress
Reliability of the existing systems minimize risks (but not risk-free)
Interaction between FACTS devices needs to be studied
Existing Projects - Met Expectations
More Demonstrations Needed
R&D needed on avoiding security problems (with and w/o FACTS)
Energy storage can significantly enhance FACTS controllers performance
June, 2002
60
Conclusions
A Balanced and Cautious Application
The acceptance of the new tools and technologies will take time, due to the
computational requirements and educational barriers.
The flexibility and adaptability of these new techniques indicate that they
will become part of the tools for solving power quality problems in this
increasingly complex electrical environment.
The implementation and use of these advanced techniques needs to be done
with much care and sensitivity. They should not replace the engineering
understanding of the electromagnetic nature of the problems that need to
be solved.
P. Ribeiro
June, 2002
61
Questions and Open Discussions
P. Ribeiro
June, 2002
62