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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