Coupling Low Voltage Microgrids into Mid-Voltage...
Transcript of Coupling Low Voltage Microgrids into Mid-Voltage...
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Coupling Low Voltage Microgrids into
GE Energy Coupled Microgirid Project - University of Notre Dame - Oct. 21, 2011
Mid-Voltage Distribution Systems
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GE Energy Coupled Microgirid Project - University of Notre Dame - Oct. 21, 2011
Each bus connected to a microgrid;Representing typical rural distribution network;Usually with severe voltage-rise problem;
Radial system structure with buses connected to primary substation:
Distribution System Control Architecture
VoltageRegulator
microgrid microgrid microgrid
GEMEMwirelesscomm.
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VoltageRegulator switchable
capacitor banks
switchable capacitor banks
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Project Objective and Approach
GE Energy Coupled Microgirid Project - University of Notre Dame - Oct. 21, 2011
Objective: Maximize real power exported bycoupled low-voltage microgrids.
Issues:- Voltage Rise Problem;
Transient Stability;Legacy Controls.
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Approach:- Two-layer Voltage Control Architecture:
Decentralized Voltage Controler
Simulation Studies and Analysis.-
Benefits:- Minimize impact on DSO
voltage regulation policies;Maximize real power exported back to distribution network.
- Reactive Power Dispatch
VoltageRegulator
microgrid microgrid microgrid
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VoltageRegulator switchable
capacitor banks
switchable capacitor banks
MCM
MIC MIC MIC
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GE Energy Coupled Microgirid Project - University of Notre Dame - Oct. 21, 2011
Talk Outline
Distribution System Model
Voltage Rise Problem
Proposed Controller Architecture
Optimization Problem
Task Status and Schedule
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GE Energy Coupled Microgirid Project - University of Notre Dame - Oct. 21, 2011
Micro-Source
Bus 1
Bus 2 Bus 3 Bus N. . .
. . .PrimarySubstation 2PP 2Q 3PP 3Q NPP NQ
1PP 1Q
LoadMicro-Source Load
Micro-Source Load
Define voltage magnitude and phase angle of ith bus as:Distribution network is a passive system that only consumes power;
Bus 1 is reference bus with and .
System Model
Ei , δi
2E 2δ E δ3 3 E δN N
Real and reactive power injected through ith bus:Pi , Qi (i = 1,2,· · ·,N)
(i = 2,3,· · ·,N)
E = 1.0 pu1 δ = 0 rad1
Distribution Network
A microgrid can be represented as a microsource and a load;
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GE Energy Coupled Microgirid Project - University of Notre Dame - Oct. 21, 2011
Schematic diagram of a five-bus example system:
System Model
Primary Substation
B3 B4B1
Load 2
B5
Micro-Source1
Micro-Source2
B2
Load 1
A B C
A B C
A B C
A B C
powergui
Discrete,Ts = 5e-005 s.
ms_4_scope
ms_4_internal_scope
ms_4
E_req
P_req
mabc
ms_3_scope
ms_3_internal_scope
ms_3
E_req
P_req
mabc
Vab
cIa
b cP
QR
MS
(V-I )
A B C
a b c
Vab
cIa
b cP
QR
MS
(V-I )
A B C
a b c
VabcIabcPQ
RMS (V-I)
A
B
C
abc
Vab
cIa
b cP
QR
MS
(V-I )
A B C
a b c
VabcIabcPQ
RMS (V-I)
A
B
C
abc
Vab
cIa
b cP
QR
MS
(V-I )
A B C
a b c
VabcIabcPQ
RMS (V-I)
A
B
C
abc Vabc
IabcPQ
RMS (V-I)
A
B
C
abc
VabcIabcPQ
RMS (V-I)
A
B
C
abc
load_2_scope
load_2
A B C
load_1_scope
load_1
A B C
grid_scope
cable S3-S4ABC
A*B*C*
cable S2-S3ABC
A*B*C*
cable S1-S2ABC
A*B*C*
cable G-S1ABC
A*B*C*
ABC
abcSubstation
A
B
C
S4_scope
S3_scope
S2_scope
S1_scope
P_req40.6P_req3
0.6
E_req4-C-
E_req3-C-
Corresponding SimPower Model:
Z = 0.5+1j Ω Z = 0.5+1j Ω Z = 0.5+1j Ω Z = 0.5+1j Ω480 V
P = 30 kWQ = 10 kvar
P = 30 kWQ = 10 kvar
P = 0~60 kWQ = -20~20 kvar
P = 0~60 kWQ = -20~20 kvar
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GE Energy Coupled Microgirid Project - University of Notre Dame - Oct. 21, 2011
Example with farthest bus injecting real power:
Voltage Rise Problem Illustration
Primary Substation
B3 B4B1 B5B2
Bus voltage magnitudes of the distribution network:
P = 0 kWQ = 0 kvar
Z = 0.5+1j ΩZ = 0.5+1j ΩZ = 0.5+1j ΩZ = 0.5+1j Ω
Bus 1 Bus 2 Bus 3 Bus 4 Bus 50.8
0.85
0.9
0.95
1
1.05
1.1
1.15
Bus
Vol
tage
Mag
nitu
de (V
)
1.2
1
P = 200 kW
P = 100 kW
P = 20 kW
P = 0 kWQ = 0 kvar
P = 0 kWQ = 0 kvar
P > 0 kWQ = 0 kvar
2
2
3
3
4
4
5
5
5
5
5
480 V
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GE Energy Coupled Microgirid Project - University of Notre Dame - Oct. 21, 2011
Example with farthest bus 100 kW real power injection, and keep all bus voltages to be 1.0 pu:
Reactive Power Control Illustration
Primary Substation
B3 B4B1 B5B2
Reactive power support required to maintain 1.0 pu bus voltages:
Z = 0.5+1j ΩZ = 0.5+1j ΩZ = 0.5+1j ΩZ = 0.5+1j Ω
Bus 1 Bus 2 Bus 3 Bus 4 Bus 5
-100
-80
-60
-40
-20
0
20
40
60
80
100
Rea
ctiv
e P
ower
Inje
ctio
n (k
var)
P = 0 kWE = 1.0 pu
P = 0 kWE = 1.0 pu
P = 0 kWE = 1.0 pu
P = 100 kWE = 1.0 pu
2
2
3
3
4
4
5
5
Bus
Vol
tage
Mag
nitu
de (V
)
0.95
1
1.05
1.10
1.15
1.20
0.90
0.85
0.80
Q = 20 kvar
Q = -20 kvar
480 V
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GE Energy Coupled Microgrid Project - University of Notre Dame - Oct. 21, 2011
Voltage Rise Problem
Z R jX= +
E
E E
SP jQ= +
I∠φ
V0 ∠ 0° E∠δ
IR
IX
δI∠φ
V0 ∠0°
E∠δ
95%
105%
Distribution line impedance, Z=R+jXSubstation voltage V0∠ 0°Line current, I∠φInjected Power, SE = PE+ jQETerminal voltage, E∠δ
Phasor diagram shows injected power’s impact on current flows result in line voltages that exceed the 5% voltage regulation rule.
Without reactive power support: QE = 0PE > 0
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GE Energy Coupled Microgrid Project - University of Notre Dame - Oct. 21, 2011
Reactive Control of Voltage Rise Problem
Z R jX= +
E
E E
SP jQ= +
I∠φ
V0 ∠ 0° E∠δ
� Total Injected Power:SE = PE + jQE = EI∠ ( δ - φ )
� We reduce voltage rise by forcing linecurrent to lead terminus voltage
� This strategy implies= EI sin(δ φ) < 0.
� Voltage rise can be reduced by absorbingreactive power at the terminal bus.
� Reactive control mechanisms:static var compensator, voltage regulator, capacitor banks, and Q-E droop controls
I∠φ
V0 ∠ 0°
E∠δ
95%
105%IR
IX
φ δ
-QE
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GE Energy Coupled Microgirid Project - University of Notre Dame - Oct. 21, 2011
Ancillary Services
Defined by Federal Energy Regulatory Commission (FERC):“... those necessary to support the transmission of electric power from seller to purchaser given the obligations of control areas and transmitting utilities within those control areas to maintain reliable operations of the interconnected transmission system.”
Six Ancillary Services:Scheduling and Dispatch;Load Following;Operating Reserves.
Energy Imbalance;Real-power-loss Replacement;Voltage Control.
Coupled microgrids provide “voltage control” service, and become a player in the market.
Coupled microgrids can provide reactive power support, while exporting real power to the distribution network.
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GE Energy Coupled Microgirid Project - University of Notre Dame - Oct. 21, 2011
Providing Other Ancillary Services
Microgrid Consortium Manager (MCM):Predicting consortium’s overall capacity;Using the prediction to bid in ancillary service market;Distributing service bid among participating microgrids.
Maintaining set points with both P-freq & Q-E droop control;Rearranging if a microgrid’s capacity or network topology changes.
Microgrid Interface Controller (MIC):
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�
�
VoltageRegulator
microgrid microgrid microgrid
wirelesscomm. wirelesscomm.wirelesscomm.
VoltageRegulator capacitor
bankscapacitor banks
MCM
MIC MIC MIC
CERTSController
CERTSController
CERTSController
CERTSController
CERTSController
CERTSController
CERTSController
CERTSController
CERTSController
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GE Energy Coupled Microgirid Project - University of Notre Dame - Oct. 21, 2011
Objective Function
Maximizing real power exportation by downstream buses;Minimizing real power loss along the distribution line.
Cost function is accordingly defined as:
J(P, E )N�
i=2(Pcap,i � Pload ,i � Pi ) +
N�i=1
Pi =N�
i=2(Pcap,i � Pload ,i ) + P1Σ Σ- -Σ
J(P, E ) = P1 = E1N�
j=1
Ej(GBUS ,1j cos(δ1 δj) + BBUS ,1j sin(δ1 � δj))Σ - -The cost function worked on is actually:
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Bus 1
Bus 2 Bus 3 Bus N. . .
. . .PrimarySubstation 2PP 2Q 3PP 3Q NPP NQ
1PP 1Q
2E 2δ E δ3 3 E δN N
Distribution Network
=
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GE Energy Coupled Microgirid Project - University of Notre Dame - Oct. 21, 2011
Optimization Problem
E 1
N�
j=1
Ej (GBUS,1j cos(δ1- δj ) + BBUS,1j sin(δ1 � δj ))
w.r.t. Ei , Pi (i = 2, 3, · · · , N)
Pgen,i ≤ Pgen,i ≤ Pgen,iQgen,i ≤ Qgen,i ≤ Qgen,i
(i = 2, 3, · · · , N)
(j = 1, 2, · · · , N -1)
Pi = Ei
N�
j=1
Ej (GBUS,ij cos(δi- δj ) + BBUS,ij sin(δi- δj ))
i = 1, 2, · · · , N)
Qi = Ei
N�
j=1
Ej (GBUS,ij sin(δi- δj � BBUS,ij cos(δi- δj ))
Σ
Σ
Σ
Minimize
Subject to
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(
) +
E i ≤ ≤ Ei (i = 2, 3, · · · , N)E i
Pln, j ≤ ≤≤ ≤
Pln, j Pln, j
Qln, j Qln, j Qln, j
Expression of P1
Voltage Magnitude and RealPower Injected at ith Bus;
Voltage Regulation Rule at ith Bus;
Real an Reactive Power Constraints Determined by Generation Capability;
Real and Reactive Power FlowConstraints of jth Distribution Line;
Real and Reactive Power Balance Relationship at ith Bus.
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GE Energy Coupled Microgrid Project - University of Notre Dame - Oct. 21, 2011
CERTS Microsource Controller
PowerInverterDG
localcontroller
Distributed Dispatch Integrated into Inverter ControlDispatcher generates P and E set points, as inputs to the CERTS inverter controller.
DG source TerminalMeasurement
CERTS DroopController c
3
b2
a1Vpk
w
Va
Vb
Vc
Vabc
IabcA
B
C
a
b
c
v_meas
i_meas
E_req
P_req
Vpk
w
P_req2
E_req1
dispatchagent
Decentralized Inverter Controls (CERTS)-
Provide small-signal stability;Mimic P-freq & Q-E droop control;
- Interface to any DG unit.-
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Microgrid Simulation Example
simPower Simulation of UWM Microgrid Testbed- validated against UWM testbed- 42.5 kW Generation (storage, micorsource, genset) - 32 kW real load (8 kW can be automatically shed
GE Global Research Telecon - Notre Dame Microgrid Research - October 21, 2011
smartcoupler3
event connected
A
B
C
a
b
c
smartcoupler2
event connected
A
B
C
a
b
c
smartcoupler1
event connected
A
B
C
a
b
c
reset pulses
Out1
powergui
Discrete,
Ts = 2e−05 s.
microsource
E_req
P_req
PQ
V
I
RMS
freq
Pmm
a
b
c
PQ
V
I
RMS
freq
A
B
C
a
b
c
PQ
V
I
RMS
freq
A
B
C
a
b
c
main grid
A
B
C
genset
Ereq
Preq
PQ
V
I
RMS
freq
Pmm
a
b
c
external storage
E_req
P_req
PQ
V
I
RMS
freq
Pmm
a
b
c
dispatch request1
dispatch request
disconnect event2
Out1
disconnect event1
Out1
disconnect event
Out1
Switch
Step1
Step
A B C
a b c
SS
comABC
a
b
c
PC6
PQA B C
A* B * C*
PC5
PQA B C
A * B* C*
PC4
PQA B C
A * B* C*
PC3
PQA B C
A * B* C*
PC2
A
B
C
A*
B*
C*
MainGrid
MS
Line Summary
Level−2 M−fileS−Function1
dispatcher3
L6
A B C
L5
A B C L42
A B C
L4
A B C
L3
A B C
L2
A B C
L1
A B C
[PQgenMS]
[IgenMS]
[VgenMS]
[PmmES]
[PmmMS]
[PmmGS]
[PQcable31]
[PQcable43]
[freqES]
[PQcable42]
[PQcable21]
[loadshed]
[ESconnect]
[MSconnect]
[IslandState]
[RMSeb4]
[Ieb4]
[Veb4]
[PQeb4]
[PQgenES]
[EB4state]
[freqEB4]
[RMSeb3]
[Ieb3]
[RMSeb2]
[Ieb2]
[Veb2]
[PQeb2]
[RMSeb1]
[Ieb1]
[IgenES]
[Veb1]
[PQeb1]
[RMSbus]
[freqmain]
[RMSgenGS]
[RMSgenMS]
[PQgenGS]
[freqMS]
[VgenES]
[Vmain]
[reset]
[RMSgenES]
[RMSmain]
[freqbus]
[Ibus]
[Vbus]
[PQbus]
[Veb3]
[PQeb3]
[EB3state]
[freqEB3]
[Imain]
[PreqGS]
[PreqMS]
[PreqES]
[IgenGS]
[VgenGS]
[freqGS]
[EB2state]
[freqEB2]
[EB1state]
[freqEB1]
[PQmain]
[GSconnect]
Generation Summary
Gain7
−K−
Gain6
−K−
Gain5
−K−
Gain4
−K−
2/15
2/15
2/15
2/15
GS
[freqGS]
[freqES]
[PQgenGS]
[PQgenMS]
[PQgenES]
[PQcable43]
[PQcable42]
[PQcable31]
[RMSmain]
[PQcable21]
[PQcable43]
[PQcable42]
[PQcable31]
[PQcable21]
[PQgenGS]
[PQgenMS]
[PQgenES]
[freqMS]
[PmmGS]
[Vmain]
[PmmMS]
[PmmES]
[GSconnect]
[MSconnect]
[ESconnect]
[IslandState]
[PQgenGS]
[PQgenMS]
[PQgenES]
[PQmain]
[PQmain]
[loadshed]
[loadshed]
[loadshed]
[loadshed]
[loadshed]
[EB1state]
[EB4state]
[EB3state]
[EB2state]
[PQbus]
[Imain]
[Vbus]
[freqES]
[freqEB4]
[Veb4]
[PQeb4]
[Ieb4]
[EB4state]
[RMSeb4]
[freqEB4]
[Veb3]
[reset]
[PQeb3]
[Ieb3]
[EB3state]
[RMSeb3]
[freqEB3]
[Veb2]
[PQeb2]
[Ieb2]
[EB2state]
[RMSeb2]
[reset]
[freqEB2]
[Veb1]
[PQeb1]
[Ieb1]
[EB1state]
[RMSeb1]
[freqEB1]
[RMSbus]
[Vbus]
[PQbus]
[reset]
[Ibus]
[freqbus]
[RMSgenGS]
[VgenGS]
[PreqGS]
[RMSgenES]
[PQgenGS]
[IgenGS]
[freqGS]
[RMSgenMS]
[reset]
[PreqMS]
[PreqES][VgenMS]
[PQgenMS]
[IgenMS]
[freqMS]
[VgenES]
[PQgenES]
[IgenES]
[freqES]
[freqmain]
1
1
1ES
EB4
EB3
EB2
EB1
2
1
1
1
1
1
2
2
.8
.5
−.1
2
Bus SummaryBUS
2 kW e−board4
reset
priority
shed_load
w
state
PQ
V
I
RMS
A
B
C
2 kW e−board3
reset
priority
shed_load
w
state
PQ
V
I
RMS
A
B
C
2 kW e−board2
reset
priority
shed_load
w
state
PQ
V
I
RMS
A
B
C
2 kW e−board1
reset
priority
shed_load
w
state
PQ
V
I
RMS
A
B
C
Measurement Block
Computes amount of shed load
Dispatch Logic
main grid
External Storage (ES)15 kW
Microsource (MS)15 kW
Genset (GS) - 12.5 kW
Load 2 kW Load 6 kW
Load 8 kW
Load 8 kW
eboard 2 kW
eboard 2 kW
eboard 2 kW
eboard 2 kW
smartswitch
smartswitch
smartswitch
cable
cable
cablecable
eboard bus
cable
0 1 2 3 4 5 6 7 8
59
60
61ES and eBoard4 Frequency (Hz)
0 1 2 3 4 5 6 7 8−200
0
200eBoard Bus Voltage (V)
0 1 2 3 4 5 6 7 8−1
0
1
x 104 real/reactive power (W)
0 1 2 3 4 5 6 7 8−0.5
0
0.5
1
1.5Shed Load Power (pu)
dispatcherenabled
islandingevent
loss ofmicrosource
loadshedding
microsourcereconnect
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Transient Stability
GE Global Research Telecon - Notre Dame Microgrid Research - October 21, 2011
• System State equations
δ̇i = mP (Pi − P 0i )Ėi = k(E
0i − Ei −mQQi)
Pi = Ei
n∑
j=1
EjYij cos(δi − δj + αij)
Qi = Ei
n∑
j=1
EjYij sin(δi − δj + αij)
• This system interconnects two net-worked systems
– System of coupled nonlinearoscillators (δ)
– Voltage control system (E)
• Stable interconnection occurs whenthe oscillators are synchronized.
Q Calculation Low PassFilter
Q vs E Droop
VoltageControl
P vs FreqDroop
Low PassFilter
Low PassFilter
Magnitude Calculation
P Calculation
Gate PulseGenerator
InverterCurrent
Load Voltage(measured)
Line Current
Q
P
E
RequestedVoltage, Ereq
RequestedPower, Preq
Requestedfrequency, freq
δv
V
E0
δ̇i = mP (Pi(δ, E)− P 0i )
Ėi = k(E0i − Ei −mQQi(δ, E))
P0
E δ
power setpoint
voltage setpoint
coupled oscillators
voltage controllers
CERTS Controller for Fast Inverters
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GE Energy Coupled Microgirid Project - University of Notre Dame - Oct. 21, 2011
Example of Optimization Problem
P = 60 kW req,1 E = 1.0433 pureq,1 P = 60 kW req,2 E = 1.0426 pureq,2
Set points of microgrid determined by the optimization problem:
Primary Substation
B3 B4B1
Load 2
B5
Micro-Source1
Micro-Source2
B2
Load 1
Z = 0.5+1j Ω Z = 0.5+1j Ω Z = 0.5+1j Ω Z = 0.5+1j Ω480 V
P = 30 kWQ = 10 kvar
P = 30 kWQ = 10 kvar
P = 0~60 kWQ = -20~20 kvar
P = 0~60 kWQ = -20~20 kvar
P1 Q1 E2 E3 E4 E543.54 kW -55.35 kvar 0.9570 pu 0.9650 pu 1.0334 pu 1.0502 pu
P = 60 kW req,1 E = 1 pureq,1 P = 60 kW req,2 E = 1 pureq,2
For comparison, we can use set points as:
In this situation, even though more reactive power support is provided, voltages of two load buses exceed the upper and lower limits defined byvoltage regulation rule.
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GE Energy Coupled Microgirid Project - University of Notre Dame - Oct. 21, 2011
Future Work
Verification of Compatibility with Legacy Equipments:Algorithm must not contradict with current control mechanism;Must consider both automatic controller and DSO controls;Use simpower model to verify the compatibility.
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VoltageRegulator
microgrid microgrid microgrid
wirelesscomm. wirelesscomm.wirelesscomm.
VoltageRegulator capacitor
bankscapacitor banks
MCM
MIC MIC MIC
CERTSController
CERTSController
CERTSController
CERTSController
CERTSController
CERTSController
CERTSController
CERTSController
CERTSController
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Task 1 Summary
GE Project Summary - University of Notre Dame - Oct. 21, 2011
Task 1.1 - Algorithm DevelopmentAlgorithm determine “exported real power” and “voltage levels”, microgrid controllers automatically supply reactive power to maintain voltage levels.Zhao Wang currently developing algorithms for optimal power and voltage assignment.Algorithm development to be completed by mid Nov. 2011, technical report by Jan. 2012.
Task 1.2 - Simulation DevelopmentPrototype simPower models of distribution line and microgrid completed in mid-July 2011.Current simulations include UWM controllers, and use capacitor banks for voltage control.Zhao Wang currently integrating microgrid controller and optimization algorithm into MV distribution line simulation.Integration to be completed by mid Nov. 2011, technical report by Jan. 2012.
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Task 1.3 - EvaluationNot started yet, and expected start date is Jan. 2012.Goal is to integrate capacitor banks and microgrid controls into simulation, and study interaction of microgrid control with automatic capacitor bank controls.Expected completion by end of Apr. 2012, findings to be presented in project final report by May 2012.
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Task 1 Overview - Coupled Microgrid
GE Project Summary - University of Notre Dame - Oct. 21, 2011
- Task 1.1 (algorithm development) about 4 months behind schedule- Task 1.2 (simulation) to be done in parallel with task 1.1- Interim Technical Report on Task 1.1/1.2 to be completed by January 2012- Task 1.3 (evaluation) to start in November 2011 and complete in April 2012- Final Report to be finished by May 2012.
4/1/
2012
Page_1 Cover SlidePage_2 Distribution System Control ArchitecturePage_3 Project Objective and ApproachPage_4 Outline of The TalkPage_5 System ModelPage_6 SimPower Simulation ModelPage_7 Voltage Rise Problem IllustrationPage_8 Reactive Power Control IllustrationPage_9 Voltage Rise ProblemPage_10 Solution to Voltage Rise ProblemPage_11 Ancillary ServicesPage_12 Controller Architecture to Provide Ancillary ServicesPage_13 Objective FunctionPage_14 Optimization Problem DescriptionPage_15 Controller StracturePage_16 Microgrid Simulation ExamplePage_17 Transient StabilityPage_18 Example of Optimization ProblemPage_19 Future WorkPage_20 Task SummaryPage_21 Task Overview