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

3

4

5

7

14

13

12

11

10

9

8

6

26

25

24

39

5049

48

47

16

17

18

19

20

23

22

21

15

42

41

40

46

45

4443

30

29

28

27

37

36

3534

33

32

38

31

51

59

58

57

56

55

54

53

52

70

69

68

67

66

65

64

63

62

61

60

77

76

75

74

73

72

71

78

83

82

81

80

79

84

9585 86

90

89

88

87

96

94

93

92

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