Center for Electromechanics…it’s all about energy

Flexible Test Bed for MVDC and HFAC Electric Power Systems

Electric Ship Research and Development ConsortiumIndustry DayMay 28, 2009

John HerbstProgram Manager

2011 Advisory Panel PresentationApril 27, 2011

Presentation Overview

• Research Motivation• Microgrid Architectures• Major Component Descriptions• Current Experimental Activities• Planned Experimental Activities

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Commercial Microgrids

DC Bus

Fuel Cell

Diesel Generator

Solar ArrayElectric Utility

Active/PassiveRectifier

Wind Turbine

DC-- DC Converter

Inverter

Electric Motors

Air Conditioner

Bi-directionalDC-- DC Converter

Battery Storage

Bi-directionalConverter

Generation Sources

UserLoads

Energy Storage

FlywheelsCapacitor Storage

Data Centers

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

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Microgrid dc Block Diagram

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Microgrid HFAC Block Diagram

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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

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Microgrid Converter Components

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• 2 MW bi-directional converter• ARCP soft switching topology• Includes 1.25 MW brake chopper

• 1.25 MW Toshiba Model HX7 VFD• Ac or dc input

• 4 MW controlled rectifier• 3 MW passive rectifier

Microgrid Active Load

• High speed induction motor– 2 MW continuous duty– 7,500 – 15,000 rpm

• KAHN Model 108-080 high speed hydraulic dynamometer– Rated 4.8 MW @ 18,000 rpm– Vertical or horizontal orientation– Programmable speed/torque &

transient loading profiles

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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

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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

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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

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0 1 2 3 4 5 6 7 8 9 100

200

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600

800

1000

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Time, s

VabF

lyw

heel (b

lue),

VabT

urb

ine (

gre

en),

Vdc (

red),

RM

S

100 kW load with 2.0 MW step load at 3.0 s and turbine generator loss at 6.0 s (PF=1.0).

Grid Stability

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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

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