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CIRED

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Title: Introdu o Author: Power System Group Last modified by: Chantal LACROSSE Created Date: 5/6/1999 10:42:26 AM Document presentation format – PowerPoint PPT presentation

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Title: CIRED


1
Controllability of DG helps managing
Distribution Grids
  • J. A. Peças Lopes
  • (jpl_at_fe.up.pt)

2
Exploiting DG to improve system operation
  • DG has been considered as non controllable and
    non dispatchable, since all the energy production
    has priority to be absorbed by the network
  • The increase in DG foreseen for the next years
    will require a different approach regarding the
    way how DG units will be operated
  • Concepts of controllability should be developed
    and exploited
  • Participation in reactive power control
  • Interruptability
  • Delivery of ancillary services (primary and
    secondary reserves, according to the conversion
    technology and primary energy sources)
  • Participation in system restoration strategies
  • Development of concepts related with control of
    clusters of DG and virtual power stations

3
Main characteristics of DG units and
controlability concepts
  • Three main types of energy conversion systems can
    be found among DG units
  • Conventional synchronous machines (cogeneration,
    CHP, mini-hydro)
  • Asynchronous generators (wind power, mini-hydro)
  • AC/DC/AC electronic conversion systems used
    together with synchronous or induction machines
    (micro-turbines, fuel cells, wind generators).
  • Classification (according to primary energy
    source and conversion system used)
  • Non- controllable (Ex Wind park with
    asynchronous stall generators)
  • Partially controllable (Ex Wind park with
    synchronous variable speed gen. and AC/DC/AC
    converters)
  • Controllable (Ex Mini-hydro or Cogeneration
    plant with synchronous units).

4
DG units used to optimise the distribution system
operation
  • DG can be used to optimise the operation strategy
    of distribution networks.
  • The Problem can be formulated an optimisation
    problem
  • Min (active power losses)
  • Subj. to
  • Vmax lt Vi lt Vmin
  • Sij max lt Sij
  • Qgmaxilt Qgi lt Qgmini taking into
    account the type of generator
  • Qimpor max lt Qimpor
  • Transformer tap limits are kept
  • Control variables Qg, capacitor banks and
    transformer taps
  • The need to use a motor of optimisation
  • (Evolutionary Particle Swarm Optimisation
    EPSO)

5
Some results of the participation of DG in
Voltage VAR control
  • Test System 60 kV distribution network with a
    large penetration of DG (mini-hydro and wind
    generation).

Activate control on reactive power generated in
the DG Units.
6
Some results of the participation of DG in
Voltage VAR control
  • Changes in active Losses
  • Peak load scenario
  • A clear reduction on actives losses was obtained

7
Some results of the participation of DG in
Voltage VAR control
  • Results concerning voltage in network busses

8
Dynamic Impacts
  • Dynamic behaviour impacts need to be addressed
    using adequate DG modelling and DG equivalent
    representation
  • Considering disturbances resulting from DG
    operation
  • Considering disturbances in distribution
    networks
  • Considering disturbances in the transmission
    system

9
Dynamic behavior analysis
  • Scenario Week peak with maximum dispersed
    generation
  • Disturbance Outage of Power Plant H 7,346MVA,
    production of 6,692j3,03 MVA, injection of
    2,678j1,081 MVA (tg j 0,404)
  • Voltage profile
  • 60kV bus at the substation

10
Dynamic behavior analysis
15 kV bus of the feeder where the power plant was
connected
15 kV bus of the feeder where the power plant was
not connected
11
Dynamic behavior analysis (Impact in the other
generators)
12
Relay coordination
  • Under voltage relay coordination is needed
  • Energy conversion systems need to able to
    withstand low voltages during short-circuits
    up-stream.

Frequency changes
Changes in contractual inter-area power flows
13
Impacts on Operation
  • Load flows become bi-directional
  • Voltage profiles have different patterns
  • Losses change as a function of the production and
    load levels
  • Congestion in system branches is a function of
    the production and load levels
  • Short-circuit levels increase
  • Power quality may be affected
  • Voltage transients will appear as a result of
    connection disconnection of generators
  • Risk of islanding operation
  • Reliability may be reduced
  • System dynamic behavior may be largely affected
  • Protections coordination is needed

14
Conclusions
  • The future
  • DG units should be more actively used to help in
    the management of the distribution grid
  • New DMS tools need to be developed
  • Topology processor with capabilities of
    identification of energised areas
  • Voltage and reactive power control
  • Load and current forecasting
  • Load flow including new generator models and load
    allocation algorithms to allow load flow to run
  • Optimum network reconfiguration
  • State estimation (considering that some DG units
    will not be monitored and new pseudo-measures
    need to be defined)
  • Cluster control strategies should be implemented,
    involving the development of local dispatch
    centres
  • Development of DMS training simulators for
    distribution grids with large amounts of DG
    (steady state and dynamic behaviour).
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