Transcript Power System Monitoring And Control System (PMACS)

Power Monitoring And Control
System (PMACS)
NEPTUNE Preliminary Design Review
4-5 December 2003
Chen-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
51
38




2 shore stations
46 BU’s
46 Science nodes
3000 Km of cables
84
1
37
52
83
89
30
2
81
36
39
31
44
32
85
33
43
80
82
53
45
82
3
29
46
83
90
84
91
79
4
40
86
92
55
28
78
43
30
34
44
29
31
80
45
28
91
5
46
92
56
27
76
93
73
75
27
77
78
35
35
81
77
93
34
54
74
32
6
26
57
76
26
79
72
33
25
7
75
15
61
47
16
58
48
24
74
60
17
25
36
71
49
14
41
18
37
42
8
50
94
38
85
95
23
59
19
96
62
87
63
59
13
60
66
20
22
10
72
58
61
12
67
21
21
11
11
20
71
10
62
57
19
70
68
22
9
18
56
8
69
55
68
12
63
17
69
23
7
54
13
16
64
67
6
53
94
88
9
64
73
86
65
70
24
66
14
65
15
51
52
5
39
87
4
50
40
88
3
49
41
89
2
48
42
90
47
1
PMACS
Status Data and Analog Measurements
Voltage, Current, Power
Limit Checking
State Estimation and
Topology Error
Identification
Load Management and
Emergency Control
Fault Location
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
Status Data and Analog Measurements
Voltage, Current, Power
Limit Checking
State Estimation and
Topology Error
Identification
Load Management and
Emergency Control
Fault Location
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 Issue
backbone
branching unit
backbone
single-conductor spur
cable to science node,
2½ water depths
sensor
long “extension cord”
science
node
sensor
up to 100 km
short “extension cord”
up to 1 km
Instrument
module
sensor
sensor
Weighted Least Square (WLS)
X
est
  R  H   H  R  Z
 H
T
1
1
T
1
meas

Z meas: Column vector of measured science node voltages and currents
X est :Column vector of estimated BU voltages
Calculated Residual
Z i  xi
m

Helps to identify “bad
data”
R
n
94
R _ sum 

Gives an estimate of
the accuracy of the
estimation
n:
  Z i m
est

i 1

n
Z i  xi
m
number of measurements
n
94
est

m



Z

i
i 1
n
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
m
22
R

Z
  sign k , : Z m  k , :
VSS k 1
VSS


Correct Topology
0.26
Calculated Residual
0.255
0.25
0.245
0.24
0.235
0.23
Voltage vaiation of SS1
Voltage variation of SS2
0.225
0.22
0.215
8000
8500
9000
9500
10000
Shore Station Voltage (Volts)
10500
11000
11500
Incorrect topology
0.6
Calculated Residual
0.5
0.4
0.3
0.2
0.1
Voltage variation of SS1
Voltage variation of SS2
0
8000
8500
9000
9500
10000
Shore Station Voltage (Volts)
10500
11000
11500
Load Management and Emergency
Control
Status Data and Analog Measurements
Voltage, Current, Power
Limit Checking
State Estimation and
Topology Error
Identification
Load Management and
Emergency Control
Fault Location
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
n
m
k 1
k i
k 1
k i
Pi  PGi  PDi  Yii Vi 2   Yik Vi Vk   Yim Vi VZ
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
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
Vi
VSS
Load Shedding

1)
2)
3)
The science node loads are tentatively
categorized into three load classes
High
General
Deferrable
Load Shedding Cont.


The sensitivity coefficients of the node(s) that
have violated a limit are calculated
The load is then shed by the amount calculated
Vi
VLi
Fault Location
Status Data and Analog Measurements
Voltage, Current, Power
Limit Checking
State Estimation and
Topology Error
Identification
Load Management and
Emergency Control
Fault Location
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
38

Type 1
–

If from each end known
43
39
–
If from one end known
40
30
31
If from each end not known
Type 3
44
36
45
47
35
Type 2
–

37
29
28
46
34
Type 1
27
32
Type 2
26
33
15
16
17
14
Type 3
41
25
18
42
48
19
13
20
12
11
Port Alberni
Shore station
21
10
22
9
8
23
7
24
6
5
4
3
2
1
Nedonna beach
shore station
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