Application to an Italian distribution system of a multiobjective optimal VoltVar control strategy:

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Application to an Italian distribution system of
a multiobjective optimal Volt/Var control
strategy improvements and management problemsA.
Campione, S. Favuzza, E. Riva Sanseverino
DIEET Dipartimento di Ingegneria Elettrica,
Elettronica e delle Telecomunicazioni Università
di Palermo
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Table of contents
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• Introduction
• Problem formulation
• Application
• Results
• Conclusions

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Introduction
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The networks reconfiguration is a fundamental
issue in distribution systems
Reconfiguration allows to restore supply at some
of the loads in the affected area
During outages
During normal operation
Reconfiguration allows the energy losses
reduction and the improvement of voltage profiles
These objectives can be achieved together with
tie-switches, also by means ULTCs and capacitor
banks
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Introduction
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• multiobjective formulation
• presence of many constraints
• search space is quite large
• optimization problem is non linear, constrained
  and combinatorial
• impossibility to execute an exhaustive search in
  affordable calculation times

Heuristic techniques (GA, ANN, ES, SA, TS)
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Problem formulation
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problem of finding the optimal operation strategy
in normal working conditions along 24 hours
multiobjective optimization problem
The variables are mixed-integer strings
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Problem formulation
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Objectives

• the power losses minimization in the branches and
  in the HV/MV windings

• the voltage profile regularization

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Problem formulation
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Optimization string ?
mixed-integer vector of control variables

• ?s boolean string expressing the status of the
  tie-switches
• ?ULTC integer string expressing the ULTC (tap
  positions) status

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Problem formulation
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Technical constraints

• Current ampacity of the lines
• Max number of manoeuvres for tie-switches
• Max number of manoeuvres for ULTCs

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Problem formulation
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The optimization problem is non linear,
constrained and combinatorial.
Fuzzy Evolution Strategy
Solution approach
Borland Delphi 7 programming language in a
Windows environment
Implementation of the algorithm
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Application
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Studied system a part of a 20 kV MV urban system
in Sicily radially operated
Features

• 2 substations
• 3 HV/MV transformers (25 and 40 MVA) with ULTC
• 4 main MV feeders
• 159 buses
• 164 branches
• 5 possible meshes

• residential customers
• hospitals
• sport plants
• small industrial sites

Type of loads
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Application
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LOAD DIAGRAMS
Unique load diagram for each main feeder (current
values measured at the primary substation each 15
minutes)
Main feeder 1
Main feeder 2
Main feeder 3
Main feeder 4
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Application
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Hypothesis

• remotely controllable ULTCs in all the
  transformers of the two substations (17 insertion
  steps)
• remotely controllable tie-switches in all
  branches.

Constraints

• Max number of manoeuvres for ULTC 30 in 24
  hours
• Max number of manoeuvres for tie-switches 4 in
  24 hours
• The currents in all the branches do not exceed
  their ampacity.

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Results
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Optimal solution strategy along 24 hours

• Decrease of yearly energy losses

• Improvement of the voltage profile

• Yearly economic benefit.

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Results
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Optimal solution strategy along 24 hours
The implementation of the 24 hrs optimal
management strategy implies

• installation of six more remotely controlled
  tie-switches
• setting up of an adequate telecontrol center
• installation of a suitable data transmission
  system
• modification of the voltage regulation mode.

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Results
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Stable configuration (solution A)

• Decrease of yearly energy losses

• Improvement of the voltage profile

• Yearly economic benefit.

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Results
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Stable configuration (solution A)
The implementation of solution A implies

• installation of 4 more remotely controlled
  tie-switches.

Considering

• the investment costs for the remotely controlled
  tie-switches
• the economical benefit connected to the losses
  reduction

the proposed investment can be covered in,
approximately, a time-frame smaller than 3 years.
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Results
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Stable configuration (solution B)

• Decrease of yearly energy losses

• Improvement of the voltage profile

• Yearly economic benefit.

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Results
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Stable configuration (solution B)
The implementation of solution B implies

• simply the modification of the current
  configuration, with no further investment.

The solution suggested is that to adopt a
different network configuration attainable simply
by changing the statuses of some already
installed tie-switches
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Results
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Power losses course
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Conclusions
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• An innovative optimal Volt/Var control strategy
  has been applied to a real distribution system
• the economical benefit for each system
  configuration hypothesized has been calculated
• attained results suggest that sometimes real
  systems do not operate in optimal conditions
• most of the times further analysis should be
  carried out in order to better evaluate each
  situation and improve the energy efficiency.