No Slide TitleAdvanced FACTS Devices and Applications: Performance, Power Quality and Cost Considerations
Paulo F. Ribeiro, BSEE, MBA, PHD, PE
CALVIN COLLEGE
Engineering Department
System Architectures and Limitations
Application Studies and Implementation
Market Assessment, Deregulation and Predictions
P. Ribeiro
June, 2002
The Concept
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June, 2002
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.
The Concept and Challenges
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June, 2002
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
-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).
The Concept
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June, 2002
Origin of FACTS
-Environmental Movement
-HVDC and SVCs
-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
SVC (Nebraska GE 1974, Minnesota Westinghouse 1975, Brazil Siemens 1985)
TCSC, UPFC AEP 1999
-Power sales/purchases are being
Power Flow in an AC System
Power Flow in Parallel and Meshed Paths
Transmission Limitations
System Issues (Post contingency conditions, loop flows, short-circuit levels)
Power Flow and Dynamic Stability Considerations
Controllable Parameters
System Architectures and Limitations
Power Flow in Parallel Paths
Power Flow in a Meshed Systems
What limits the loading capability?
Power Flow and Dynamic Considerations
Radial
Parallel
Meshed
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
50% Series Compensation
Line Reconfiguration
Fixed Compensation
Phase Angle Regulator (PAR)
Relative Importance of Different Types of Controllers
Shunt, Shunt-Series
Energy Storage
Energy Storage
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June, 2002
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)
Power Electronics - Semiconductor Devices
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June, 2002
Speed of Switching
Parameter Trade-off
di/dt and dv/dt capability
turn-on and turn-off time
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
Real Power Angle Curve
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.
Vx
I
Vxo
Vs
I
Vs
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Integrated voltage series injection and bus voltage regulation (unified) will directly increase or decrease real and reactive power flow.
AC Transmission Fundamentals (Voltage-Series and Shunt Comp.)
E1
E2
I
Improvement of Transient Stability With FACTS Compensation
Equal Area Criteria
A1 = Acceleration Energy
A2 = Deceleration Energy
power transfer without reducing the stability margin
AC Transmission Fundamentals (Stability Margin)
1
2
3
crit
A1
A2
Amargin
Q / V
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June, 2002
CSC
AdvDis
VSC
Adv
Dis
Limited by DC Reactor
Losses
Higher
Independent of Energy Storage
Voltage Source Converters
Voltage Source Converters
Voltage Source Converters
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.
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June, 2002
HVDC
Throughput MW HVDC 2 Terminals FACTS
2000 MW $ 40-50 M $ 5-10 M
500 MW $ 75-100M $ 10-20M
1000 MW $120-170M $ 20-30M
2000 MW $200-300M $ 30-50M
FACTS and HVDC: Complimentary Solutions
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
HVDC Projects: Applications
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June, 2002
FACTS Controller
Control Attributes
Voltage control, VAR compensation, damping oscillations, voltage stability
Static Synchronous Compensator (STATCOM with storage, BESS, SMES, large dc capacitor)
Voltage control, VAR compensation, damping oscillations, transient and dynamic stability, voltage stability, AGC
Static VAR Compensator (SVC, TCR, TCS, TRS
Voltage control, VAR compensation, damping oscillations, transient and dynamic stability, voltage stability
Thyristor-Controlled Braking Resistor (TCBR)
Static Synchronous Series Compensator (SSSC without storage)
Current control, damping oscillations, transient and dynamic stability, voltage stability, fault current limiting
Static Synchronous Series Compensator (SSSC with storage)
Current control, damping oscillations, transient and dynamic stability, voltage stability
Thrystor-Controlled Series Capacitor (TCSC, TSSC)
Current control, damping oscillations, transient and dynamic stability, voltage stability, fault current limiting
Thyristor-Controlled Series Reactor (TCSR, TSSR)
Current control, damping oscillations, transient and dynamic stability, voltage stability, fault current limiting
Thyristor-Controlled Phase-Shifting Transformer (TCPST or TCPR)
Active power control, damping oscillations, transient and dynamic stability, voltage stability
Unified Power Flow Controller (UPFC)
Active and reactive power control, voltage control, VAR compensation, damping oscillations, transient and dynamic stability, voltage stability, fault current limiting
Thyristor-Controlled Voltage Limiter (TCVL)
Thyristor-Controlled Voltage Regulator (TCVR)
Interline Power Flow Controller (IPFC)
Reactive power control, voltage control, damping oscillations, transient and dynamic stability, voltage stability
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June, 2002
E1 / 1
E2 / 2
FACTS Implementation - STATCOM
E1 / 1
E2 / 2
P&Q
X
FACTS Implementation - TCSC
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 ...
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Xeff = X - Vinj/I
P&Q
Regulating Bus Voltage and Injecting Voltage In Series With the Line
Can Control Power Flow
Xeff = X - Vinj / I
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June, 2002
E1 / 1
E2 / 2
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Plus Energy Storage
Can Affect Power Flow Directly / Dynamically
and sustain operation under fault conditions
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June, 2002
Regulating Bus Voltage + Injected Voltage + Energy Storage
Can Control Power Flow Continuously, and Support Operation Under Severe Fault Conditions (enhanced performance)
FACTS Implementation - UPFC + Energy Storage
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June, 2002
Shunt Inverter
Series Inverter
SMES Chopper and Coil
SMES Chopper and Coil - Overvoltage Protection
UPFC Grounding
Regulating Bus Voltage + Energy Storage + Line Impedance Compensation
Can Control Power Flow Continuously, and Support Operation Under Severe Fault Conditions (enhanced performance)
FACTS Implementation - TCSC + STACOM + Energy Storage
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June, 2002
E1 / 1
E3 / 3
E2 / 2
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Technologies’ Perspective
STATCOM + SMES
P
Q
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.
The Role of Energy Storage: real power compensation can increase operating control and reduce capital costs
P - Active Power
Q - Reactive Power
SMES Power (MW)
Additional Power Transfer(MW)
Closer to generation
System Frequency
System Frequency
System Frequency
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.
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June, 2002
Converter
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
Cost Considerations
Competitive
$8-$12 kVAR
Voltage support and stability
Power flow control, Voltage support and Stability
$12-$16 kVAR
Competitive
Power flow control, Voltage support and stability
$25-$50 kVAR
Limited competition
Limited competition
STATCOM w/SMES
Compensates for inductive and/or capacitive var-load plus energy storage for active power
Limited
Power flow control, Voltage support, and Stability
$150-$200 kW
Sole source
Power flow control Voltage support and Stability,
$250-$350 kW
SVC and TCSC functions plus voltage regulator, phase angle controller and energy storage
Sole source
Shaded area indicates technologies that are either permanently connected or switched on or off with mechanical switches. (i.e. these are not continuously controllable)
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June, 2002
Cost Considerations
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.
Improving the efficiency and quality of AC transmission systems
Chart2
Hardware
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
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
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June, 2002
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.
Joint World Bank / ABB Power Systems Paper
Improving the efficiency and quality of AC transmission systems
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June, 2002
3 – Harmonics
4 – Imbalance
8 – Combined effects
14 – Power Quality Programs
Uref - harmonic voltage limit (standard or particular equipment)
k - harmonic order
Alternative Approach
SMES
Batteries
FACTS
SMES
Conclusions
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
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June, 2002
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
Competitive
Limited
phase angle control
voltage regulator, phase angle
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)
stability
large dc capacitor)
and dynamic stability, voltage stability, AGC
Static VAR Compensator (SVC, TCR,
TCS, TRS
and dynamic stability, voltage stability
Thyristor-Controlled Braking Resistor
Static Synchronous Series Compensator
voltage stability, fault current limiting
Static Synchronous Series Compensator
voltage stability
voltage stability, fault current limiting
Thyristor-Controlled Series Reactor
voltage stability, fault current limiting
Thyristor-Controlled Phase-Shifting
stability, voltage stability
Active and reactive power control, voltage control, VAR
compensation, damping oscillations, transient and dynamic stability,
voltage stability, fault current limiting
Thyristor-Controlled Voltage Limiter
Thyristor-Controlled Voltage Regulator
transient and dynamic stability, voltage stability
Interline Power Flow Controller (IPFC)
Reactive power control, voltage control, damping oscillations,
transient and dynamic stability, voltage stability
P
tg
P
V
V
P
X
X
P
Current
Losses
Higher
Current
Losses
Higher