The document discusses a flexible test bed being developed at the Electric Ship Research and Development Consortium (ESRDC) to validate medium-voltage direct current (MVDC) and high-frequency alternating current (HFAC) power system architectures through modeling, simulation, and experimentation. Current experimental activities involve conducting and modeling ac and dc series fault tests. Planned experimental activities will explore dc grid stability with multiple power sources and loads, as well as "smart" microgrid control systems. The test bed utilizes various power supply, converter, and load components rated from 250kW to 4MW to conduct experiments at significant power levels.

1. Flexible Test Bed for MVDC and HFAC Electric Power Systems John Herbst Program Manager 2011 Advisory Panel Presentation April 27, 2011 Electric Ship Research and Development Consortium Industry Day May 28, 2009

2. Presentation Overview Research Motivation Microgrid Architectures Major Component Descriptions Current Experimental Activities Planned Experimental Activities 2

3. Commercial Microgrids Generation Sources Active/Passive Rectifier DC-- DC Converter DC Bus User Loads Energy Storage Bi-directional DC-- DC Converter Bi-directional Converter Inverter Wind Turbine Solar Array Diesel Generator Fuel Cell Electric Utility Electric Motors Battery Storage Air Conditioner Capacitor Storage Flywheels Data Centers

4. Research Motivation Modeling and simulation play a critical role in understanding complex naval power systems Active simulation work on multiple power system architectures underway at ESRDC Universities Model validation at significant power levels needed to support large scale implementation of new power system technologies Flexible, MW scale microgrid assembled using equipment from prior power system research 4

5. Microgrid dc Block Diagram 5

6. Microgrid HFAC Block Diagram 6

7. Microgrid Power Supply Components Power supply transformers Two independent multi-tap transformers to enable evaluation of dc grid stability with multiple power sources Currently fed from 480V 3Ø utility taps 400A and 1200A breakers Provisions for feed from diesel generators to enable evaluation of “soft” grid 7

9. ARCP soft switching topology

10. Includes 1.25 MW brake chopper

11. 1.25 MW Toshiba Model HX7 VFD

12. Ac or dc input

13. 4 MW controlled rectifier

15. Microgrid Passive Loads Variety of air-cooled resistor grids Primary is 2 kV, 1.3 MW locomotive brake resistor 3x 250 kW resistors Inductor loads 750 V, 300A, 225 kVA each 10

16. Current Microgrid Experiments Series Fault Experiments Exploring impact of both ac and dc series faults on system circuit Controlled separation of electrodes 0.1 in/s slow fault 386 in/s2 fast fault Measuring voltage and current transients Paper in preparation Developing circuit model to capture behavior for use in larger system simulations Paper in preparation 11

17. Future Experiments Dc grid stability Extensive simulations of dc grid stability issues but little validation at MW power levels Multiple power sources with both passive and active rectifiers Combination of resistive/reactive dynamic loads “Soft” grid with sources and loads of comparable scale Diesel generators in place of stiff utility supplies Supervisory Control Systems “Smart” control of microgrid elements with 12

18. Grid Stability 13

19. Presentation Summary ESRDC is developing a flexible test bed at UT-CEM for validation of MVDC and HFAC power system architectures Modeling and experimentation of ac and dc series faults is currently being conducted Developing dc series fault model Future experiments will explore dc system stability with multiple power sources 14