Download Mini-curso-FACTS-2001F

Mini-Curso
An Overview on FACTS Controllers
Paulo F. Ribeiro, BSEE, MBA, PHD, PE
CALVIN COLLEGE
Engineering Department
Grand Rapids, MI 49546
[email protected]
From EPRI
Phase Angle
P. Ribeiro
August, 2001
1
Outline
• Introduction - 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
• Systems Studies
• AC Transmission Fundamentals
• Voltage Source vs. Current Source
• Voltage Sources
• Static Var Compensator (SVC), STATCOM, TCSC, UPFC, SMES
• System Studies (by EMTP, ATP, Saber, EDSA, EMTDC)
• Systems Integration, Specification, Cost Considerations and Technology Trends
• Operation and Maintenance
• Impact of FACTS in interconnected networks
• Market Assessment, Deregulation and Predictions
• Conclusions - Final Words
• Questions and Open Discussions
P. Ribeiro
August, 2001
2
The reason, therefore, that some intuitive minds are not mathematical is that they
cannot at all turn their attention to the principles of mathematics. But the reason
that mathematicians are not intuitive is that they do not see what is before them,
and that, accustomed to the exact and plain principles of mathematics, and not
reasoning till they have well inspected and arranged their principles, they are
lost in matters of intuition where the principles do not allow of such
arrangement. They are scarcely seen; they are felt rather than seen; there is the
greatest difficulty in making them felt by those who do not of themselves perceive
them. These principles are so fine and so numerous that a very delicate and very
clear sense is needed to perceive them, and to judge rightly and justly when they
are perceived, without for the most part being able to demonstrate them in order
as in mathematics, because the principles are not known to us in the same way,
and because it would be an endless matter to undertake it. We must see the matter
at once, at one glance, and not by a process of reasoning, at least to a certain
degree.
1660 PENSEES by Blaise Pascal
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August, 2001
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The Concept
P. Ribeiro
X
V

P    P   P   P
X
V
tg
August, 2001
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The Concept
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. Voltage is governed by reactive power (Q). Q in its turn
depends of the physical length of the transmission circuit as well as from the flow of active
power. The longer the line and/or the heavier the flow of active power, the stronger will be the
flow of reactive power, as a consequence of which the voltage will drop, until, at some critical
level, the voltage collapses altogether.
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
P. Ribeiro
August, 2001
and fan out to take unwanted paths available
in the grid.
5
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).
P. Ribeiro
August, 2001
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Introduction: 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
P. Ribeiro
August, 2001
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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
P. Ribeiro
August, 2001
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System Architectures and Limitations
The relative importance of transmission interconnection
Interconnections in a European type system are not very important because the system is built by
providing generation close to the loads and therefore, transmission is mainly for emergency
conditions.
In the US,very large power plants far from the load centers were built to bring "coal or water by
wire". Large plants provided the best solution - economy of scale. Also, seasonal power exchanges
have been used to the economic advantage of the consumers.
Newer generation technologies favor smaller plants which can be located close to the loads and
therefore, reduces the need for transmission. Also, if distributed generation takes off, then generation
will be much closer to the loads which would lessen the need for transmission even further.
However, for major market players, once the plant is built, the transmission system is the only way to
bring power to the consumer that is willing to pay the most for the power. That is, without
transmission, we will not get a well functioning competitive market for power.
P. Ribeiro
August, 2001
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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
P. Ribeiro
August, 2001
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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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August, 2001
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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
Fixed
Compensation
Advanced Solutions
FACTS
Energy Storage
Line
Reconfiguration
Transmission
Link
Better
Protection
FACTS
Increased
Inertia
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Devices
August, 2001
Transient Stability
Damping Power Swings
Post-Contingency Voltage
Control
Voltage Stability
Subsynchronous Res.
Enhanced
Power Transfer
and Stability
SVC
STATCOM
TCSC, SSSC
UPFC
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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-Serie
P. Ribeiro
August, 2001
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)
P. Ribeiro
August, 2001
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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)
P. Ribeiro
August, 2001
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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
GTO
August, 2001
IGBT
MCT
MTO
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Planing Studies
Evaluate the technical and economic benefits of a range of FACTS alternative solutions which may allow
enhancement of power transfer across weak transmission links. Part I of this effort should concentrate on
preliminary feasibility studies to assess the technical merits of alternative solutions to correct real and
reactive power transfer ratings, system voltage profiles, operational effects on the network, equipment
configurations, etc.
A - Load flow studies will be performed to establish steady-state ratings, and identify the appropriate
locations for connection of alternative compensation devices. Load flow studies will be used to address
the following:
•System Criteria (maximum steady-state power transfers, short-term operating limits, etc.)
•Controller Enhancements (controller types, ratings, sensitivities, etc.)
•Controller Losses (based on operating points and duration)
•System Losses (system losses base on controller operating point and duration)
•Overvoltsages ((steady-state and short-term voltage insulation requirements)
•Compare technical and economic benefits of alternatives
•Identify interconnection points
•Identify critical system contingencies
•Establish power transfer capability of the transmission system
•Confirm that reliability criteria can be met
•Identify the cost of capital of equipment and losses
•Identify steady-state and dynamic characteristics of FACTS controllers
Stability Studies
P. Ribeiro
IEEE
August, 2001
17
System Studies
Study Type
LOAD FLOW
System
Planning
Power Transfer Enhancement Studies
Study Category
Performance
Design
Operational
Establish existing and future network benchmarks for
power flows, bus voltages, and phase-angles
Determine final power flow conditions and
system performance criteria.
Verify detailed design studies
Confirm network loadflow conditions are
within benchmark limits
Identify network control variables, evaluate FACTS
controller configurations, enhancements, and establish
preliminary controller steady-state ratings and
locations
Determine final steady-state ratings, control
variables, controller configurations, and
location
Establish controller equipment hardware
ratings and software requirements
Confirm FACTS controller effectiveness to
enhance network steady-state performance
Establish steady-state and short-term overvoltage
requirements for network and controllers
Determine final controller fault levels and
mitigation criteria.
Establish FACTS controller equipment
overvoltage ratings.
Setup instrumentation and obtain
measurements during staged fault tests and
evaluate on-line faults.
Establish effectiveness of alternatives to damp
network power oscillations
Determine final performance criteria and
control variables
Verify performance
Confirm performance
Voltage
Stability
Establish preliminary criteria
Finalize performance criteria
Verify performance
Confirm performance
Interaction
Establish preliminary criteria
Finalize performance criteria
Verify performance
Confirm performance
Control
Strategies
Establish preliminary criteria
Finalize performance criteria
Verify performance
Confirm performance
xxx
Establish performance criteria
Verify performance
Setup instrumentation and obtain
measurements during staged fault tests and
evaluate on-line system faults
Evaluate symmetric and unsymmetric fault duties for
system and controller, including mitigation measures
Establish performance criteria
Verify performance
Confirm performance
Frequency
TRANSIENT
Short-Circuit
xxx
Establish network performance criteria
Verify performance
Confirm performance
xxx
Establish criteria
Verify performance
Confirm performance
Post-Transient
xxx
Establish criteria
Verify performance
Confirm performance
Voltage
Instability
xxx
Establish criteria
Verify performance
Confirm performance
Identify system sensitivity issues
Evaluate mitigation measures
Verify performance
Confirm performance
xxx
Establish criteria for interaction with system
Verify system SSR models and demonstrate
damping or mitigation performance
Instrument and confirm system sensitivity
while monitoring and testing SSR
damping/mitigation performance
Controller
Overvoltages &
Short-Circuit
DYMANIC
Damping
Fault Duties
Overvoltages
System SSR
Controller SSR
P. Ribeiro
IEEE
August, 2001
18
Identify
Transmission
Systems Provide System
data and
Configuration
System Studies
Outages
and load
transfer
System data
and
configuration
Outages
and load
transfer
System
operat.
limits
Load Flow
(P,Q, V, q)
Generato
r data
Voltage
Reg.
Data
(AVR)
Governor
data
Relay
data
IEEE
P. Ribeiro
Induction
motor
data
Transient
Stability
(P,Q, V, q, time)
Fault
data
Perform Load
Flow
(P,Q, V, q)
System
operat.
limits
Identify and Size
Transfer
Enhancement
Solutions
Devices
Perform
Economic
Analysis
System
changes
Load
Shedding
Dynamic
Stability
(P,Q, V, q, w,
time)
August, 2001
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System Studies
Power Transfer Enhancement Studies (Cont’d)
Study Category
Study Type
HARMONICS
System
Planning
Performance
Design
Operational
xxx
Analyze system sensitivity and establish
criteria
xxx
Instrumentation and testing to confirm system
harmonics are within established, limits
without FACTS controller
Controller
Interaction
xxx
Analyze and identify potential system
interactions and establish performance criteria
Perform design studies and offsite tests to
verify controller can meet established
criteria
Monitor potential system interactions to
confirm performance of FACTS controller
causes no interactions
Controller
Performance
xxx
Establish harmonic current, voltage, and
communication system harmonic criteria
Perform design studies and calculations to
establish equipment performance
requirements.
Instrumentation and testing to confirm FACTS
controller performance levels
Control
xxx
Establish criteria
Verify performance
Confirm performance
Relaying
xxx
Establish criteria
Verify performance
Confirm performance
Instrumentation
RELIABILITY/
AVAILABILITY
xxx
Establish criteria
Verify performance
Confirm performance
Assess impact of FACTS controller configurations on
system criteria including cooling systems
Finalize reliability/availability criteria for
FACTS controller
Calculate expected FACTS controller
reliability/availability performance
Measure reliability/availability performance of
FACTS controller
Assess impact of system transmission network and
substation facilities
Determine impact of control, relaying, and
instrumentation requirements
Evaluate impact that alternatives have on
system and develop cost factors
xxx
Preliminary impact assessment
Final Assessment
Establish preliminary cost estimates for
various controller configurations
xxx
Analysis of controller and system losses
xxx
Determine network electrical losses and
establish value for each configuration being
investigated.
Establish operational losses algorithm
Benefits
Preliminary impact assessment
Final Assessment
Summarize technical and economic benefits
for alternatives being investigated
xxx
Risks
Preliminary impact assessment
Final Assessment
Summarize technical and economic risks
for each alternative
xxx
CR&I
COST FACTORS
System
Controller
Losses
P. Ribeiro
IEEE
August, 2001
20
AC Transmission Fundamentals
E1 / 1
E2 / 2
P&Q
I
X
E2 . sin()
(E1 - E2 . cos()
P1 = E1 . Ip1
E1
E1 - E2
E2 . cos()
E1 . sin ()
Ip1 = E2 sin() / X
I
E1 . Cos ()
Iq1 = (E1 - E2 . cos() / X
P. Ribeiro
E2
(E2 - E1 . cos()
August, 2001
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AC Transmission Fundamentals
Active component of the current flow at E1
Ip1 = (E2 . sin ()) / X
Reactive component of the current flow at E1
Iq1 = (E1 - E2 . cos ())/X
Active Power at the E1 end
P1 = E1 (E2 . sin ())/X
Reactive Power at the E1 end
Q1 = E1(E1 - E2 . cos ()) / X
P. Ribeiro
August, 2001
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AC Transmission Fundamentals (Voltage - Shunt Control)
E1 / 1
E2 / 2
P&Q
I
X
P1 = k1.E1 (E2 . sin (/k2))/X
Q/V
E1
P1 = E1 (E2 . sin ())/X
E1 - E2
I
E2
Regulating end bus voltage mostly change reactive power - Compensating at an intermediate
point between buses can significantly impact power flow
P. Ribeiro
August, 2001
23
AC Transmission Fundamentals (Voltage-Series Injection)
E1 / 1
E2 / 2
P&Q
I
X
Vinj
Injected Voltage
E1
P1 = E1 . E2 . sin () / (X - Vinj / I)
E1 - E2
I
E2
Injecting Voltage in series with the line mostly change real power
P. Ribeiro
August, 2001
24
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
P. Ribeiro
August, 2001
25
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.
P. Ribeiro
August, 2001
26
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
P. Ribeiro
August, 2001
Phase Angle 2 - fault cleared
3 - equal area
3 >crit - loss of synchronism
27
Voltage Source Vs. Current Source Converters
CSC
Adv/Dis
VSC
Adv/Dis
Device Type
Thyristor
Self-Commutation
Thyristor
Self-Commutation
Device
Characteristic
Symmetry
Symmetrical
Asymmetrical
Short-Circuit
Current
Lower
+
Higher
Rate of Rise of
Fault Current
Limited by DC Reactor
+
Fast Rise (Due to
capacitor discharge)
Losses
Higher
-
Lower
+
AC Capacitors
Required
Not Required
+
DC Capacitors
Not Required
+
Required
Valves dv/dt
Lower
(AC Capacitors)
More Complex
+
Higher
Interface with AC
System
Reactive Power
Generation
Depends on Current
Flowing through
Energy Storage
+
Less Complex
+
Independent of
Energy Storage
+
Performance
Harmonics
P. Ribeiro
AC capacitors may
produce resonances
near the characteristic
harmonics – may cause
overvoltages on valves
and transformer.
-
August, 2001
28
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
P. Ribeiro
T ran s of m
r e r el a kage
ni du c at n ce
Cs
+
+
V dc
V dc
August, 2001
29
Voltage Source Converters
Basic 6-Pulse, 2-level, Voltage-Source Converter
di c
ea
eb
ec
ai
Ta 1
D a 1 Tb 1
D b1 T c1
bi
D c1
V dc
+
Cs
V dc
ci
2
H y po the tci a l
n eu tra lp o ni t
V dc
Ta 2
D a 2 Tb 2
D b2 T c2
D c2
2
ea
Vdc
eb
Vdc
ec
Vdc
eab
[a ]
ebc
eca
P. Ribeiro
ia
ib
ic
D
Ta1
a1
Ta2
D
a2
D
b1
Tb1
D
Tb2
D
c1 b2
August, 2001
Tc 2
30
[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
August, 2001
+
31
Voltage Source Converters
Voltage-Source Converter Bridges
C
voa
voavobvo c
vdc
vdc
C
voavobvo c
Vdc
C
S ni g el -pha se ,
T h ree -pha se , w
t o -el ve l
w
t o -el ve H
l -b rdi ge
s xi -pu sl e b rdi ge
P. Ribeiro
August, 2001
C /2
Vdc
C /2
T h ree -pha se , h
t ree -el ve l
12 -pu sl e b rdi ge
32
Voltage Source Converters
Output voltage control of a two-level VSC
v =V 0
iwt
v= V s n
io
v o= V o ( ) 
wt
*
wt
 =  * 
 
v o (  )
v o (  )
 
v oF (  )= V (+  ) s n
i w tw t
(v+ v )d c
v d c nom ni a l
(v - v )d c
wt
v oF (  )= V (+  ) s n
iwt
P. Ribeiro
August, 2001
vdc
C
idc
 v d c= 1 i d c d t
C
i d c = f  
33
Voltage Source Converters
Output voltage control of a three-level VSC
iwt
v= V s n
v =V 0
io
v o= V o ( ) 
wt
*
 =  * 
wt

wt
(<  <  )
v om ax
vo
v oF = f ( , )= s n
i (w t - )
V d c= con s t

wt
m ax = 2 
3
P. Ribeiro
August, 2001
Vdc
C /2
Vdc
C /2
34
Voltage Source Converters
S ys et m B u sb a r
Multi-pulse VSC with
wave-forming magnetic circuits
C o u p lni g
T ra n s of m
r er
M agne t ci s tru c tu re
fo rm u lt i-pu sl e w a ve fo m
r syn the s si
C on ve r te r 1
C on ve r te r 2
C on ve r te r n
138 kV B u s
C oup ln
ig
T ran s fo m
r er
In te r fa ce M agne t c
is
P. Ribeiro
August, 2001
35
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
August, 2001
36
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
August, 2001
37
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
P. Ribeiro
August, 2001
38
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
August, 2001
39
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
August, 2001
40
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
August, 2001
41
FACTS Implementation - TCSC
Breaker
X
MOV
TCSC
TCSC
TCSC
TCSC
TCSC
#2
#3
#4
#5
#6
TCSC module #1
Slatt TCSC
P. Ribeiro
August, 2001
42
FACTS Implementation - TCSC
Damping
Circuit
Damping
Circuit
Breaker
X
X
Breaker
MOV
MOV
MOV
40 Ω
55 Ω
TCSC 15 to 60 Ω
Kayenta TCSC
P. Ribeiro
August, 2001
43
FACTS Implementation - SSSC
E1 / 1
P&Q
E2 / 2
I
X
P1 = E1 (E2 . sin ()) / Xeff
Xeff = X - Vinj/I
P. Ribeiro
August, 2001
44
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
August, 2001
45
FACTS Implementation - UPFC
Series Transformer
Shunt Inverter
Series
Inverter
Shunt
Transforme
r
Unified Power Flow Controller
P. Ribeiro
August, 2001
46
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
August, 2001
47
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
August, 2001
48
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)
August, 2001
49
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
August, 2001
50
FACTS Implementation - UPFC + Energy Storage
MOV
UPFC
Grounding
SMES Chopper and Coil - Overvoltage Protection
P. Ribeiro
August, 2001
51
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
August, 2001
52
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
August, 2001
53
FACTS Implementation - IPFC
Series Transformer, Line 1
Series Transformer, Line 2
Series Inverter #1
Series Inverter #2
Interline Power Flow Controller
P. Ribeiro
August, 2001
54
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
STATCOM
Fast
Reactive Power Injection and
Absorption
August, 2001
Increased Power
Transfer
Additi
onal
Stabilit
y
Margin
Electric Grid
Fast
Reactive Power Injection
and Absorption
P. Ribeiro
P
Acceleration
Area
1.5
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
55
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)
August, 2001
56
FACTS + Energy Storage - Location Sensitivity
Additional Power Transfer(MW)
Closer to generation
Closer to load centers
SMES Power (MW)
P. Ribeiro
August, 2001
57
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)
August, 2001
58
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
August, 2001
59
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
P. Ribeiro
August, 2001
60
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
August, 2001
61
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
August, 2001
62
Technology & Cost Trends
$
I
$$$
$
I
additional cost savings possible
P. Ribeiro
August, 2001
63
Concerns About FACTS
Cost
Losses
Reliability
P. Ribeiro
August, 2001
64
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
August, 2001
65
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
August, 2001
66
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
August, 2001
67
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
August, 2001
68
Final Words
Power supply industry is undergoing dramatic change as a result of deregulation and
political and economical maneuvers. This new market environment puts demands for
flexibility and power quality into focus. Also, trade between companies and countries
of electric power is gaining momentum, to the benefit of all involved. This calls for the
right solutions as far as power transmission facilities between countries as well as
between regions within countries are concerned.
FACTS Benefits included:
-An increase of synchronous stability of the grid;
-An increased voltage stability in the grid;
-Decreased power wheeling between different power systems;
-Improved load sharing between parallel circuits;
-Decreased overall system transmission losses;
-Improved power quality in grids.
•The choice of FACTS device is simple and needs to be made the subject of detailed
system studies, taking all relevant requirements and prerequisites of the system into
consideration, so as to arrive at the optimum technical and economical solution. In
fact, the best solution may often be lying in a combination of devices.
P. Ribeiro
August, 2001
69
Final Words
From an economical point of view, more power can be transmitted over existing or
new transmission grids with unimpeded availability at an investment cost and
time expenditure lower, or in cases even far lower than it would cost to achieve the
same with more extensive grids. Also, in many cases, money can be saved on a
decrease of
power transmission losses.
From an environmental point of view, FACTS enables the transmission of power
over vast distances with less or much less right-of-way impact than would
otherwise be possible. Furthermore, the saving in transmission losses may well
bring a corresponding decrease in need for generation, with so much less toll on
the environment.
All these things help to enable active, useful power to reach out in growing
quantities to growing populations under safe and favorable conditions all over the
world. Also, individual countries´ own border lines no longer constitute any limit
to power industry. With FACTS, power trade to the benefit of many can be
established to a growing extent acrossAugust,
borders,
by making more efficient use of
P. Ribeiro
2001
interconnections between countries, new as well as existing.
70
Questions and Open Discussions
P. Ribeiro
August, 2001
71
Appendix
P. Ribeiro
August, 2001
72