PESGM2007P-000768

6-25-07 2007 PES General Meeting 1

Overview of Transmission System Application Requirements for FACTS Controllers

Don Ramey


Flexible AC Transmission System. FACTS

Evolving technology-based solutions to help electric utilities fully utilize their transmission assets.

Alternating current transmission systems incorporating power electronic-based and other static controllers


Development of the Special Publication

Working Group 15-05-13 has been meeting since at least January 2000 to prepare this document.

More than 50 engineers have submitted written material or attended meetings.

Both the scope of the document and the pace of commercialization of FACTS Controllers changed several times.


Outline of the Special Publication

Transmission System Planning Considerations Overview of FACTS Controllers FACTS Controller Models Operational Requirements for FACTS

Controllers


Transmission System applications for FACTS Controllers

Steady state Voltage regulation and control

Steady state control of power flow on a transmission line

Transient stability enhancement Damping at transmission system

oscillation frequencies (0.2 2 Hz)


Benefits from steady state Voltage regulation and control

Reduction in transformer tap change operations and shunt capacitor switching

Better voltage profiles for customers System more prepared to withstand

contingencies


Control VoltageNon FACTS Control Methods

FACTS Controllers

Electric generators Synch. CondensersTransformer tap-changerShunt Capacitor Shunt Reactor

Static Var Compensator (SVC)Static Synchronous Compensator (STATCOM)Superconducting Energy Storage (SMES)Battery Energy Storage System (BESS)


Benefits of steady state control of power flow on a transmission line

Reduce unscheduled line flow and allow increased contract flow

Control overloads to allow higher system flow

Force current flow in cold weather conditions to prevent ice formation

Force current flow to help control over voltage


Control Power FlowNon FACTS Control Methods

FACTS Controllers

Generator schedulesTransmission line switchingConventional Phase Angle Regulator (PAR)Series Capacitor HVdc TransmissionInter-phase Power Controller (IPC)

Thyristor controlled Series Capacitor (TCSC)Thyristor controlled Phase Shifter (TCPST)Unified Power Flow Controller (UPFC)Static Synchronous Series Compensator (SSSC)Interline Power Flow Controller (IPFC)


Benefits of improved transient stability

Allow increased steady state loading Reduce need for load shedding or other

special protection measures Reduce susceptibility for system collapse

from multiple contingency events


Improve Transient Stability Non FACTS Control Methods

FACTS Products

Braking resistorExcitation Spec. Prot. SystemsFast ValvingIndependent pole trippingLine sectioningHVdc

Thyristor Controlled Braking Resistor (TCBR)Thyristor Controlled Phase Shifting TransformerSVC, STATCOM, TCSC, UPFC, BESS, SMESS, SSSC, IPFC


Benefits of enhanced dynamic stability

Allow system operation over larger range of loading profiles without power and voltage oscillations

Reduced need for special protection systems


Enhance Dynamic StabilityNon FACTS Control Methods

FACTS Products

HVdcPower System Stabilizer

TCSCSVCSTATCOMUPFCSSSC


Reactive power to maintain 1.0 pu V at both ends of a 100 mile long 500 kV transmission line

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1.0 pu = 1000 MVA




Controllers


Steady State Models

The SVC has an embedded model in the most widely used power flow (load flow) software. User defined models are often required for other controllers. Can model many of the controller functions

in load flow programs using existing models for non FACTS equipment Models must also be implemented in EMS

software


Models for Transient and Dynamic System Simulations (Transient Stability and Dynamic Simulation Programs)

Models must be compatible with the simulation tool being used. Power circuit equations solved

algebraically Inverter represented as voltage source Voltage/power change occurs at each

simulation time step Damping control functions represented

with differential equations


Models for Harmonic Analysis and Detailed Transient Analysis (EMTP)

Models must be supplied by the equipment manufacturer Models must be compatible with

EMTP or EMTDC analysis software Inverter power circuits can be

modeled as voltage sources or by detailed switching circuits




Controllers


Operational Robustness Requirements

Control based upon directly measured system dynamics Assured resources for prompt detection,

analysis and correction of anomalous controller effects Performance monitors that communicate

information to system analysts Commissioning and periodic certification tests Information exchange with major grid operators


Conclusions Transmission planning may be more

difficult in deregulated systems, but functions have not changed FACTS controllers have been designed

and installations placed in operation to perform most of the identified control functions Realization of the full benefits of FACTS

controllers requires many more installations than presently exist.


Issues that have limited the application of FACTS Controllers

Costs higher than alternatives for many applications Size of power semiconductors needs to increase Semiconductor costs have not decreased as predicted

Transient overload capability not as much as generators or other transmission equipment VSI controllers must be bypassed or blocked for close-

in faults Long term reliability and equipment life not well

established Limited number in service and technology changes

Documents

PESGM2007P-000768