power monitoring and control system (pmacs) neptune preliminary design review 4-5 december 2003...
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Power Monitoring And Control System (PMACS)
NEPTUNE Preliminary Design Review4-5 December 2003Chen-Ching Liu, Ting Chan, Kevin Schneider
Overview
Compliance matrix PMACS State estimation and topology error
identification Load management and emergency control Fault location
Compliance Matrix
SEF50 Voltage limit adjustable +/-10% Yes
SEF51 Current Limit adjustable down to 1A Yes
SEF52 Shore stations capable of coordinating power outputs Yes
SEF53 Power Flow direction in any segment of system is arbitrary Yes
SMA1 Fault location to within 1km without underwater intervention Yes
SPE2 Peak power delivered 100kW, 10 kV, 10A Yes
SPE15 All shore station equipment can operate off single UPS Yes
Base 46 node system
2 shore stations 46 BU’s 46 Science nodes 3000 Km of cables
93
94
1
2
3
4
47
48
49
50
51552
53
54
55
56
57
58
59
60
61
14
15
62
63
64
16
17
18
11
10
9
8
7
6 24
23
22
21 67
68
69
70
19
25
6620
75
76
78
79
32
33
4241
87
65
71
74
80
73
26 72
45
89
34
35
77
40
46
43
37
83
38 84
82
3985
86
36
91
9081
92
44
13
12
27
28
29
30
31
88
1
2
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5
7
14
13
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10
9
8
6
26
25
24
39
5049
48
47
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21
15
42
41
40
46
45
4443
30
29
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27
37
36
3534
33
32
38
31
51
59
58
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55
54
53
52
70
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68
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65
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63
62
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60
77
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83
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9585 86
90
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91
PMACS
State Estimation andTopology ErrorIdentification
Load Management andEmergency Control
Fault Location
Voltage, Current, PowerLimit Checking
Status Data and Analog Measurements
PMACS
PMACS functions are performed at two shore stations, and possibly a third control station
input signals are received from science nodes command sequences are sent to science
nodes
State Estimation and Topology Error Identification
State Estimation andTopology ErrorIdentification
Load Management andEmergency Control
Fault Location
Voltage, Current, PowerLimit Checking
Status Data and Analog Measurements
State Estimation
By using a limited number of measurements, the state of the system can be estimated
Allows for the identification of “bad” data
Reduce errors in estimated states
Unobservability Issuebackbone
backbone
up to 100 km
long “extension cord”
single-conductor spur cable to science node, 2½ water depths
branching unit
science node
up to 1 km
short “extension cord”
sensor
sensor
sensor
sensor
Instrument module
Weighted Least Square (WLS)
measZ
measTTest ZRHHRHX 111
estX
: Column vector of measured science node voltages and currents
:Column vector of estimated BU voltages
Calculated Residual
Helps to identify “bad data”
Gives an estimate of the accuracy of the estimation
n
Z
n
xZsumR i
mi
i
esti
mi
94
1
94
1_
n
Z
n
xZR
mi
esti
mi
n: number of measurements
Topology Error Identification
Allows for the possibility of a single back bone breaker being out of position
Method should also work for multiple breakers out of position, but this has not been verified
Method of Topology Error Identification
Voltage at each shore station is varied independently
Variation of residual is then examined
22
1
:,:,k SS
mm
SS V
ZkZksign
V
R
Correct Topology
0.215
0.22
0.225
0.23
0.235
0.24
0.245
0.25
0.255
0.26
8000 8500 9000 9500 10000 10500 11000 11500
Shore Station Voltage (Volts)
Ca
lcu
late
d R
es
idu
al
Voltage vaiation of SS1
Voltage variation of SS2
Incorrect topology
0
0.1
0.2
0.3
0.4
0.5
0.6
8000 8500 9000 9500 10000 10500 11000 11500
Shore Station Voltage (Volts)
Ca
lcu
late
d R
es
idu
al
Voltage variation of SS1
Voltage variation of SS2
Load Management and Emergency Control
State Estimation andTopology ErrorIdentification
Load Management andEmergency Control
Fault Location
Voltage, Current, PowerLimit Checking
Status Data and Analog Measurements
Load Management
Uses values from science nodes, shore stations, and state estimation to determine if the current system load violates any limits
Interfaces with Observatory Control System Performs traditional security assessment in a
limited manner
Power Flow with Zener Diodes
ki
n
ikk
ikiiiDGi VVYVYPPPii
1
2
Where:
PGi=Power injected at node I, source
PDi=Power removed at node I, load.
Yik=Resistance of the line between node I and k
VZ=Voltage drop of zener diodes
m=number of BU’s
Z
m
ikk
iim VVY
1
Emergency Control
If/when the load management module determines that a system limit has been violated, emergency control attempts to correct the problem
Can adjust shore station voltages Can shed load at science nodes
Adjustment of Shore Station Voltage
The sensitivity coefficients of the node(s) that have violated a limit are calculated
The shore station voltage is then adjusted by the amount calculated
SS
i
V
V
Load Shedding
The science node loads are tentatively categorized into three load classes
1) High
2) General
3) Deferrable
Load Shedding Cont.
Li
i
V
V
The sensitivity coefficients of the node(s) that have violated a limit are calculated
The load is then shed by the amount calculated
Fault Location
State Estimation andTopology ErrorIdentification
Load Management andEmergency Control
Fault Location
Voltage, Current, PowerLimit Checking
Status Data and Analog Measurements
Fault Location
Determine the location of backbone cable fault to within 1 km
Use voltage and current measurements at two shore stations
Models include cable resistances and BU voltage drops
Assumptions
• Faulted link is known based on result of state estimation
• Network topology is known and fixed (all breakers closed onto the fault)
• Resistances of cables and BU voltage drops can be calculated using state estimation
• BU voltage drops are constant assuming Zener diodes are operating in saturated region
Fault Current Characteristics
Type 1– If from each end known
Type 2– If from each end not known
Type 3– If from one end known
Nedonna beachshore station
Port AlberniShore station
Type 1
Type 2
Type 3
38
37
3635
34
27
26
25
19
20
21
22
23
24
56
7
89
1011
12
13
14
15
33
32
3140
3943 44 45
46
41
42
47
48
4
3
2
1
30 29 28
16 17 18
Fault Location Formulation
For a Zero- ground fault, multiple non-linear equations can be set up based on Ohm’s Law and Loop Analysis– VNode = VPrevious Node + ILink * RLink + BU Voltage drop
All breakers closed onto the fault Negative shore station voltage outputs
Distance Calculation
Cable resistance = 1 /km BU voltage drop = 15.2V per link
(Zener diodes in saturated region) Measurement errors = 0.01%
(voltage and current)
Voltage and Current Requirements
If faulted link is known before taking measurements
– Apply predetermined voltage levels at both shore stations– Ensure backbone currents in branches are sufficient without
causing over-current violation
If faulted link is not known before taking measurements
– Increase current outputs at both shore stations until the total current output reaches limit