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POWER ELECTRONICS PPLIC TIONS IN UTILITY SYSTEMSDr. Luis
MoranDepartment of Electrical Eng ineering
Universidad de ConcepcionCasilla 16 CEmail:
[email protected] CHILEDigest
IECON Panel Discussion)
One of the major changes associated with theoperation of power
systems is related with deregulationand power quality. The main
objective of deregulation isto facilitate the development of a
competitive electricitymarket. The main economic emphasis of a
competitivemarket is to reduce the cost of electricity, that is
tominimize the cost of electric power generation by theintroduction
of a nondiscriminatory competition. Acompetitive market allows
users to select the utilitycompany or generator that will provide
the electric powersupply. This selection is normally done based on
theprice and the quality of service. The quality of the serviceis
basically a pow er quality problem w hich is basically atechnical
issue while deregulation deals with theoperation mode and
principles of the complete powersystem, that is generation,
transmission and distribution.In order to provide technical
solutions to the newchallenges imposed in power systems, two
new.conceptshave been adopted by the technical community.
Theseconcepts are the Flexible Transmission SystemsFACTS) and the
Flexible Reliable and IntelligentElectric Energy Delivery System
FRIENDS). Theacronym FACTS identifies altemating
currenttransmission systems that incorporates power
electronics-based controllers to enhance the controllability
andincrease power transfer capability. The FACTS initiativewas
originally launched to so lve the transmission systemproblems in
the late 198 s due to restrictions ontransmission line
construction, that is to facilitate theincrease power transfer
capability of transmissionsystems, and to keep power flow over
designated routes.On the other hand, the purpose of FRIENDS is
todeveloped a desirable structure for power deliverysystems where
Distributed Generations DGs) andDistributed Energy Storage Systems
DESS) are locatednear the demand side, and to develop reliable and
energyconservation oriented operating strategies of the
powersystems. In existing radial type power distributionsystems,
these dispersed energy resources cause manyproblems in the
distribution system, such as over voltageat the end of the feeder
and fault protection problems.
Moreover, s the deregulation of the power industryproceeds,
power quality is becoming a commodity of theindustry. Namely, power
quality as well as electricalenergy can be sold to customers when
more reliable andmore qualified power is needed in the demand side
thanthose of the power transmission network. N ormally,
powerquality is defined by the following three items,
exceptfiequency: That is continuity of the power supplymomentary
power interruptions, temporary interruptionand sustained
interruption), voltage stability under overvoltage, voltage sag,
voltage swell, flicker, etc.) andvoltage waveform distortion
harmonics, unbalance).The implementation of these two new concepts
inpower systems requires the development of high powercompensators
and controllers. The technology needed forthis is based in high
power electronics with its real timeoperating control. In the near
future, power systems willlook like the one shown in Fig. 1 in
which most of thestatic power compensator develop so far has
beenincluded. The use of such devices will improve the overall
reliability and associated quality, with a significantreduction in
the operating cost. However, once asufficiently large number of
these fast compensators andcontrollers are deployed over the
system, the coordinationand overall control to provide maximum
system benefitsand prevent und esirable interactions with different
systemconfigurations and objectives, under normal andcontingency
conditions, will present a differenttechnological challenge.There
are two approaches for the realization of powerelectronics based
compensators: one employsconventional thyristor-switched capacitors
and reactors,and the other uses self-commutated switching
converters.Both schemes help to control efficiently real and
reactivepower, but only the second one can be used to
compensatecurrent and voltage harmonics. Moreover
self-commutatedswitching converters present better response time
andmore compensation flexibility. The development of
suchcompensators is one of most important challenges ofpower
electronics.
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REFERENCES [2] K. Nara, J. Hasegawa, T. Oyama, K. Tsuji, T.
Ise,l] Y. H. Song, A. T. Johns Flexible AC TransmissionSystems, The
Institution of Electrical Engineers,UK, 1999.
FRIENDS Forwarding t Future Power DeliverySystem, in IEEE Con,f.
on Harmonics and Quality ofPower, Oct. 2000, pp. 8 18.
Fig. 1. A power distribution system with different static
compensators and controllers.
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