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					     Barcelona 12-15 May 2003




 Proposal for a High Quality dc Network
      with Distributed Generation

               A. Agustoni, M. Brenna, E. Tironi
                       Politecnico di Milano – Italy
                                   G. Ubezio
                                SIEL S.p.A. – Italy


Agustoni IT Session 2 – Block 3
     Barcelona 12-15 May 2003




                            Introduction
   Need of high-quality power supply
                  
         UPS with dc section

                                           Integration in a
           Distributed Generation
                                              local dc
              Generation in dc               distribution
                                               network
              Electronic devices
                      
                  dc section

Agustoni IT Session 2 – Block 3                        2
            Barcelona 12-15 May 2003


                Comparison between ac and dc
                    distribution systems
                       dc bus                                        ac
 public                                                                   ac users
network
                                                     public
                                                    network
                                dc users                                             dc users
    ac generators
                                                    ac
                                      dc users   generators                                ac users

    dc generators
                                                                           storage
                                      ac users       dc generators

           storage                                                                                  dc users

                                                                           storage




    Agustoni IT Session 2 – Block 3                                                             3
     Barcelona 12-15 May 2003




           dc distribution advantages
  • Island operation
  • Reduction of power converters number and
    their complexity
  • Increase in power quality for
       – end users
       – public network
  • Better integration of DG

Agustoni IT Session 2 – Block 3                4
     Barcelona 12-15 May 2003




             dc system choice criteria
 Sinusoidal absorbtion                    Keep the same ac distribution
Bidirectional power flow                      systems apparatuses



Forced-commutated ac/dc                     Same MV/LV substation
    interface converter                          transformer



                            dc voltage = ±400 V


Agustoni IT Session 2 – Block 3                                   5
     Barcelona 12-15 May 2003




          Proposed network schemes
  Use existing distribution lines


                                                                          1
                                                                          2
                                                                          3
                                                                          N




                                  load   load   load   DG   storage
                                                                          PE




Agustoni IT Session 2 – Block 3                                       6
     Barcelona 12-15 May 2003




          Proposed network schemes
   Connection of the neutral to the grounding
   system of MV/LV substation

                                                                          1
                                                                          2
                                                                          3
                                                                          N




                                  load   load   load   DG   storage

                                                                          PE

Agustoni IT Session 2 – Block 3                                       7
     Barcelona 12-15 May 2003




    Control system – characteristics
  • dc bus is the only connection common to all
    converters  control system is based on dc
    voltage
  • Presence of different supply sources 
    possibility to integrate and optimize system
    management with field bus systems
  • Control system must be robust

Agustoni IT Session 2 – Block 3                8
     Barcelona 12-15 May 2003




          Control system – functions
  • Keep dc voltage within acceptable range
  • Renewable generators must supply all the
    available power, if loads, network or storage
    systems can absorb it
  • Storage systems have to be recharged as soon as
    possible and need to be discharged if necessary
  • ac/dc interface converter has to absorb or deliver
    power from or to the network

Agustoni IT Session 2 – Block 3                          9
     Barcelona 12-15 May 2003




            Control system – strategy
                  Vref ren        renewable generators
                  Vref nren       non-renewable generators
                  Vref net s
                                  public network - sale
                   Vref st c
                                  storage system – charge
             Vn
                  Vref net p      public network - purchase
                   Vref st d      storage system - discharge


  By varying the reference values is possible to adjust
  system performance
Agustoni IT Session 2 – Block 3                                10
        Barcelona 12-15 May 2003




                                    Simulation results
                              ac input currents
    500                                                                                        805
                                                                                                                               dc bus voltage
     [A]                                                                                         [V]
    375
                                                                                               795
    250
                                                                                               785
    125

                                                                                               775
       0

   -125                                                                                        765

   -250
                                                                                               755
   -375
                                                                                               745
   -500                                                                                          0.00             0.05           0.10             0.15       0.20        0.25   [s]    0.30
      0.00            0.05           0.10              0.15     0.20       0.25   [s]   0.30   (f ile lv dc03ts.pl4; x-v ar t) v :DC_POS-DC_NEG     v :POS1 -NEG1   v :POS2 -NEG2
   (f ile lv dc03ts.pl4; x-v ar t) c:CONDAM-CONDA       c:CONDBM-CONDB   c:CONDCM-CONDC        v :DCPOS1-NEU1+v :NEU1 -DCNEG1


   78.0
                renewable power delivered                                                       500
                                                                                                                 storage system current
   [kW]                                                                                           [A]
                                                                                                400
   77.7

                                                                                                300
   77.4
                                                                                                200

   77.1
                                                                                                100

   76.8
                                                                                                   0


   76.5                                                                                        -100
      0.00            0.05           0.10              0.15     0.20       0.25   [s]   0.30      0.00             0.05           0.10            0.15       0.20        0.25   [s]    0.30

Agustoni IT Session 2 – Block 3
   (f ile lv dc03ts.pl4; x-v ar t) v :DC1 -DC2*c:GEN    -DC1                                   (f ile lv dc03ts.pl4; x-v ar t) c:BATTC -BATTM
                                                                                                                                                                                      11
     Barcelona 12-15 May 2003




                             Conclusion
  • A new dc distribution system has been
    proposed
  • The system permits an increase in power
    quality both for end users and network
  • The system allows an easier integration of
    DG
  • It is possible to optimize the system
    management by means of field bus systems
Agustoni IT Session 2 – Block 3              12
     Barcelona 12-15 May 2003




Agustoni IT Session 2 – Block 3   13
           Barcelona 12-15 May 2003




                                                 Simulation results
          power absorbed from the network                                                                                ac voltages
 120                                                                                400
 *10 3                                                                               [V]
 100                                                                                300

                                                                                    200
  80
                                                                                    100
  60
                                                                                       0
  40
                                                                                   -100
  20
                                                                                   -200

    0                                                                              -300

 -20                                                                               -400
   0.00               0.05                0.10   0.15   0.20   0.25   [s]   0.30      0.00             0.05           0.10          0.15           0.20      0.25    [s]   0.30
 (f ile lv dc03ts.pl4; x-v ar t) t: PTR                                            (f ile lv dc03ts.pl4; x-v ar t) v :CARA -NEU2   v :CARB -NEU2     v :CARC -NEU2




Agustoni IT Session 2 – Block 3                                                                                                                                        14
          Barcelona 12-15 May 2003




                                                     Simulation results
  70
                                ac input currents                                                400
                                                                                                    ac input current and phase voltage
  [A]
                                                                                                 300
   44
                                                                                                 200

                                                                                                 100
   18

                                                                                                    0
   -8
                                                                                                -100

                                                                                                -200
  -34
                                                                                                -300

  -60                                                                                           -400
    0.00               0.04              0.08            0.12           0.16         [s] 0.20      0.00                0.04              0.08         0.12   0.16   [s] 0.20

  815
                                    dc bus voltage
  (f ile lv dc03ts.pl4; x-v ar t) c:CONDAM-CONDA     c:CONDBM-CONDB     c:CONDCM-CONDC          (f ile lv dc03ts.pl4; x-v ar t) c:CONDAM-CONDA

                                                                                                10
                                                                                                                     storage system current      v :CONDAM



   [V]                                                                                          [A]
  810
                                                                                                -10
  805

  800                                                                                           -30

  795
                                                                                                -50
  790

  785                                                                                           -70


  780
    0.00               0.04              0.08            0.12           0.16         [s] 0.20   -90
  (f ile lv dc03ts.pl4; x-v ar t) v :DC_POS-DC_NEG   v :POS1 -NEG1   v :POS2 -NEG2                0.00               0.04               0.08         0.12    0.16   [s] 0.20
Agustoni IT Session 2 – Block 3
  v :DCPOS1-NEU1+v :NEU1 -DCNEG1                                                                (f ile lv dc03ts.pl4; x-v ar t) c:BATTC -BATTM
                                                                                                                                                                       15
             Barcelona 12-15 May 2003




                                                  Simulation results
   40
     power absorbed from the network                                                       78.0
                                                                                                      renewable power delivered
  *10 3                                                                                    [kW]
   30
                                                                                           77.7
   20

                                                                                           77.4
   10

     0                                                                                     77.1

  -10
                                                                                           76.8
  -20

  -30                                                                                      76.5
    0.00                  0.04             0.08    0.12      0.16      [s] 0.20               0.00              0.04              0.08               0.12   0.16   [s] 0.20
  (f ile lv dc03ts.pl4; x-v ar t) t: PTR

                                                    400
                                                                           ac voltages    (f ile lv dc03ts.pl4; x-v ar t) v :DC1 -DC2*c:GEN   -DC1



                                                     [V]
                                                    300

                                                    200

                                                    100

                                                      0

                                                   -100

                                                   -200

                                                   -300

                                                   -400
                                                      0.00      0.04          0.08           0.12              0.16        [s] 0.20
Agustoni IT Session 2 – Block 3 x-v ar t) v :CARA -NEU2
                         (f ile lv dc03ts.pl4;                                       v :CARB -NEU2    v :CARC -NEU2
                                                                                                                                                                     16
     Barcelona 12-15 May 2003




    A dc distribution system realization
                 Storage system           Photovoltaic arrays




                                            DC-DC
                                           Converter




                                               DC Bus
                                                                Inverter




                                       Rectifier
                 Auxiliary generator                             Loads

Agustoni IT Session 2 – Block 3                                            17

				
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