1. 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. Tironi Politecnico di Milano – Italy G. Ubezio SIEL S.p.A. – Italy

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

3. Agustoni IT Session 2 – Block 3 Barcelona 12-15 May 2003 3 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 generators storage ac users dc users

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

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

6. Agustoni IT Session 2 – Block 3 Barcelona 12-15 May 2003 6 Proposed network schemes Use existing distribution lines load PE DG storage N 3 2 1

7. Agustoni IT Session 2 – Block 3 Barcelona 12-15 May 2003 7 Proposed network schemes Connection of the neutral to the grounding system of MV/LV substation load PE DG storage N 3 2 1

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

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

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

11. Agustoni IT Session 2 – Block 3 Barcelona 12-15 May 2003 11 renewable power delivered Simulation results ac input currents dc bus voltage storage system current

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

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

14. Agustoni IT Session 2 – Block 3 Barcelona 12-15 May 2003 14 Simulation results power absorbed from the network ac voltages

15. Agustoni IT Session 2 – Block 3 Barcelona 12-15 May 2003 15 Simulation results ac input currents ac input current and phase voltage dc bus voltage storage system current

16. Agustoni IT Session 2 – Block 3 Barcelona 12-15 May 2003 16 Simulation results power absorbed from the network renewable power delivered ac voltages

17. Agustoni IT Session 2 – Block 3 Barcelona 12-15 May 2003 17 A dc distribution system realization