Intelligent Micro-Grid Demonstrator

R. E. Hebner, J. D. Herbst, A. L. GattozziCenter for ElectromechanicsUniversity of Texas, Austin

May 19, 2010

Electric ship Micro-grid

• Close similarity but with unique features • Special characteristics of ship’s power system:

– Wide variety of loads, from continuous duty to pulsed loads

– Minimal available margin of generated power over total required

– Greater reliance on energy storage to supply intermittent loads

• Many aspects are very similar

Micro-grid Technical Challenges

• Increasing incidence of power electronics• Co-existence of ac and dc sections• Presence of non-traditional energy resources• More decentralized control system• Lack of experimental data especially at MW

power levels– CEM-UT micro-grid demonstrator attempts to

bridge this gap

CEM-UT Micro-Grid Demonstrator

DC Bus:2 parallel AWG535 DLO cable2 kV, 1.6 kA, 31 m long

Preliminary Investigations

• Many components developed over time and tested individually

• Computer models of components• Models of various topologies• Comprehensive model of micro-grid being

developed• Preliminary tests on sub-assemblies• System stability issues

Stability of Common DC Bus Topology

Constant Power Load Instability

• Constant power load fed by dc source:

PP const vi P

Pi

v

2

0P

dv v

di P

2

0loadP

v v

i PR

2

12 2

1 11

e

P

e

d v L LP dvLC RC

dt R v dt

R Rv E

R v

2212

2d v dv

v fdt dt

2

1 1( )

2

Pv t

Cv

2 1( ) o

R Pf v t E

v

2 21

sin ( )tv Ve t w t

2

0Cv

P

2

1 1

2 2 P

E Ev R P

21

2P

ER

P

(16)

(21)

1 P PE i R v

P

Pi

v

Experimental Test

ConstantPowerLoadkW

StabilityCriterionper (16)

Existence ofStable states

per (21)

151,033 < 15,000

unstable23,058,824 >

15,000 ok

21.5840 < 21,500

unstable23,058,824 >

21,500 ok

15 kW

21.5 kW

Experimental verification work

• CEM has all the major building blocks of a ship’s electrical power system

• An electrical micro-grid is being assembled to collect experimental data