Agustoni IT Session 2 – Block 3

Barcelona 12-15 May 2003

Proposal for a High Quality dc Network with Distributed Generation

A. Agustoni, M. Brenna, E. TironiPolitecnico di Milano – Italy

G. UbezioSIEL S.p.A. – Italy

2Agustoni IT Session 2 – Block 3

Barcelona 12-15 May 2003

Introduction

Need of high-quality power supply

UPS with dc section

Distributed Generation

Generation in dc

Electronic devices

dc section

Integration in a local dc

distribution network

3Agustoni IT Session 2 – Block 3

Barcelona 12-15 May 2003

Comparison between ac and dc distribution systems

ac generators

storage

dc users

dc bus

public network

dc users

ac users

dc generators

ac

public network

ac generators

dc generatorsstorage

storage

ac users

ac users

dc users

dc users

4Agustoni IT Session 2 – Block 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

5Agustoni IT Session 2 – Block 3

Barcelona 12-15 May 2003

dc system choice criteria

Sinusoidal absorbtion

Bidirectional power flow

Keep the same ac distribution systems apparatuses

Forced-commutated ac/dc interface converter

Same MV/LV substation transformer

dc voltage = ±400 V

6Agustoni IT Session 2 – Block 3

Barcelona 12-15 May 2003

Proposed network schemes

Use existing distribution lines

load load load

PE

DG storage

N 3 2 1

7Agustoni IT Session 2 – Block 3

Barcelona 12-15 May 2003

Proposed network schemes

Connection of the neutral to the grounding system of MV/LV substation

load load load

PE

DG storage

N 3 2 1

8Agustoni IT Session 2 – Block 3

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

9Agustoni IT Session 2 – Block 3

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

10Agustoni IT Session 2 – Block 3

Barcelona 12-15 May 2003

Control system – strategy

By varying the reference values is possible to adjust system performance

renewable generators

non-renewable generators

storage system – charge

public network - sale

public network - purchase

storage system - discharge

Vn

Vref ren

Vref nren

Vref net s

Vref st c

Vref net p

Vref st d

11Agustoni IT Session 2 – Block 3

Barcelona 12-15 May 2003

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

0.00 0.05 0.10 0.15 0.20 0.25 0.30[s]76.5

76.8

77.1

77.4

77.7

78.0

[kW]

renewable power delivered

Simulation results

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

0.00 0.05 0.10 0.15 0.20 0.25 0.30[s]-500

-375

-250

-125

0

125

250

375

500[A]

(f ile lv dc03ts.pl4; x-v ar t) v :DC_POS-DC_NEG v :POS1 -NEG1 v :POS2 -NEG2 v :DCPOS1-NEU1+v :NEU1 -DCNEG1

0.00 0.05 0.10 0.15 0.20 0.25 0.30[s]745

755

765

775

785

795

805

[V]

(f ile lv dc03ts.pl4; x-v ar t) c:BATTC -BATTM

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

0

100

200

300

400

500

[A]

ac input currents dc bus voltage

storage system current

12Agustoni IT Session 2 – Block 3

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

13Agustoni IT Session 2 – Block 3

Barcelona 12-15 May 2003

14Agustoni IT Session 2 – Block 3

Barcelona 12-15 May 2003

Simulation results

(f ile lv dc03ts.pl4; x-v ar t) t: PTR

0.00 0.05 0.10 0.15 0.20 0.25 0.30[s]-20

0

20

40

60

80

100

120

*103

(f ile lv dc03ts.pl4; x-v ar t) v :CARA -NEU2 v :CARB -NEU2 v :CARC -NEU2

0.00 0.05 0.10 0.15 0.20 0.25 0.30[s]-400

-300

-200

-100

0

100

200

300

400[V]

power absorbed from the network ac voltages

15Agustoni IT Session 2 – Block 3

Barcelona 12-15 May 2003

Simulation results

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

0.00 0.04 0.08 0.12 0.16 0.20[s]-60

-34

-8

18

44

70

[A]

(f ile lv dc03ts.pl4; x-v ar t) c:CONDAM-CONDA v :CONDAM

0.00 0.04 0.08 0.12 0.16 0.20[s]-400

-300

-200

-100

0

100

200

300

400

(f ile lv dc03ts.pl4; x-v ar t) v :DC_POS-DC_NEG v :POS1 -NEG1 v :POS2 -NEG2 v :DCPOS1-NEU1+v :NEU1 -DCNEG1

0.00 0.04 0.08 0.12 0.16 0.20[s]780

785

790

795

800

805

810

815[V]

(f ile lv dc03ts.pl4; x-v ar t) c:BATTC -BATTM

0.00 0.04 0.08 0.12 0.16 0.20[s]-90

-70

-50

-30

-10

10

[A]

ac input currents ac input current and phase voltage

dc bus voltage storage system current

16Agustoni IT Session 2 – Block 3

Barcelona 12-15 May 2003

Simulation results

(f ile lv dc03ts.pl4; x-v ar t) t: PTR

0.00 0.04 0.08 0.12 0.16 0.20[s]-30

-20

-10

0

10

20

30

40

*103

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

0.00 0.04 0.08 0.12 0.16 0.20[s]76.5

76.8

77.1

77.4

77.7

78.0

[kW]

(f ile lv dc03ts.pl4; x-v ar t) v :CARA -NEU2 v :CARB -NEU2 v :CARC -NEU2

0.00 0.04 0.08 0.12 0.16 0.20[s]-400

-300

-200

-100

0

100

200

300

400[V]

power absorbed from the network renewable power delivered

ac voltages

17Agustoni IT Session 2 – Block 3

Barcelona 12-15 May 2003

A dc distribution system realization

Inverter

Storage system

Auxiliary generator

Rectifier

Loads

DC-DCConverter

DC Bus

Photovoltaic arrays