1. PERFORMANCE ANALYSIS OF
A NETWORK BASED, ULTRAFAST
CENTRALIZED FAULT IDENTIFICATION AND
LOCATION SYSTEM
Advisor: Dr. Ming Yu
Co-advisor: Dr. Michael Steurer
Committee member: Dr. Hui Li
7/12/2016 1
Presenter: Shravan Tamaskar
M.S. Thesis Defense: 6 June 2016

2. Outline
 Overview
– Motivation
– Objective and key contribution
 Introduction to Centralized Fault identification and Location (CFL) system
architecture
 Performance modeling of CFL system
 Analyzing the factors affecting the CFL system performance
 Validation: CFL demonstration and implementation
 Conclusion and Future work
7/12/2016 2

3. Motivation: CFL
 Fault management in
medium voltage direct
current (MVDC)
shipboard power system
(SPS) aimed to be
accomplished in 8 ms
7/12/2016 3
 A need for
fast fault
identification
system
necessary
 This led to the
development of
centralized fault
identification and
location (CFL)
system
8 ms

4. Objective
■ To develop a testbed for
an ultrafast fault
identification system for
the MVDC SPS
■ To model, analyze and
validate the performance
of the CFL system
■ To analyze the scaling
and the factors affecting
the CFL system
performance
Key Contribution
■ Modeling of
– EtherCAT Frame
– CFL decision time
■ Scaling of CFL system based on
– Frame
– Cycle time
■ Performance parameters
– Topology
– Preliminary noise analysis
■ Developed a CFL testbed and
implemented using different
system configurations
7/12/2016 4

5. 7/12/2016 5
Fault Management in MVDC SPS
Fault Management in MVDC SPS
Rapid fault identification
Fault
Identification
Fault Clearing
highly-coordinated interaction
Detect and
localize fault
Re-energize
system
De-energize
system
Isolate
faulted
segment
Detect &
locate
8 ms

6. Introduction to CFL architecture
■ CFL architecture
■ Differential protection scheme
■ CFL process description
7/12/2016 6

7. CFL architecture
7/12/2016 CAPS, FSU 7
CS- Cable Section
PGM- Power Generation Module
Disconnect Switch
CS1 CS2 CS3
CS4
CS5CS6CS7
CS8
PG
M
PG
M
Load
Load
CFL
Power System

8. No Fault
Differential protection scheme
7/12/2016 CAPS, FSU 8
Operates based on
Percentage Differential Protection (PDP) scheme
CS- Cable Section DS- Disconnect Switch
LIF test case
Slope diagram of protection scheme
DSA
DSA DS B
DS BCS
CS
Normal
Operation
During Fault
A
B
Time
msΔI
+Ia
-Ib
| 𝑛=2
𝑛
𝐼 𝑛| − 𝑆 . 𝑛=2
𝑛
|𝐼 𝑛| ≥ 𝐼𝑚𝑖𝑛

9. 7/12/2016 CAPS, FSU 9
 Main parts of CFL system
 A master unit with fault protection algorithm
 Several slave units that perform data acquisition and send digitized
current data to master unit for decision making
 A communication (EtherCAT) protocol governing master- slave
topology
Master
(Algorithm)
Line topology
Slave nSlave 1 Slave 2
Generic CFL system Architecture
EtherCAT Hardware CAPS Capability In-use
Master 1 1
I/O nodes 20 9
Slaves 6 6

10. 7/12/2016 10
Master
Condition
check
Counter
Increment
Counter
threshold
Trip
True
slave1slave n
False
EtherCAT Frame
YesNo
CFL process description
Data signal
Logic signal
Reset
counter

11.  Frame modeling
 Cycle time modeling
 Decision time
1. RTDS processing
2. Hardware sync
3. Beckhoff processing
7/12/2016 11
Performance Modeling

12. 7/12/2016 12
EtherCAT Frame

13. Frame Modeling
7/12/2016 13
𝐷𝐺 𝑝𝑙 = (𝑛 𝐹𝑂 x 𝐿 𝐹𝑂 + 𝑛 𝐴𝐼 x 𝐿 𝐴𝐼 + 𝑛 𝐷𝑂 x 𝐿 𝐷𝑂 )
𝐿 𝐷𝐺 = 𝐷𝐺=1
𝐷𝐺
(𝐷𝐺 𝐻 + 𝐷𝐺 𝑝𝑙 + 𝐷𝐺 𝑤𝑘𝑐 )
𝐿 𝐹𝑟𝑎𝑚𝑒 = 𝐸 𝑇𝑦𝑝𝑒 + 𝐿 𝑐𝑚𝑑 + 𝐸𝑐𝑎𝑡 𝐻 + 𝐿 𝐷𝐺
Description Abbreviation Size (Byte)
EtherType 𝐸 𝑇𝑦𝑝𝑒 2
Commands 𝐿 𝑐𝑚𝑑 10
EtherCAT Header 𝐸𝑐𝑎𝑡 𝐻 2
Datagram Header 𝐷𝐺 𝐻 10
No. of Slaves 𝑛 𝑠𝑙𝑎𝑣𝑒𝑠 6
No. of Analog Input
channel
𝑛 𝐴𝐼
No. of Digital Output
channel
𝑛 𝐷𝑂
No. of Fiber Optic
connecter
𝑛 𝐹𝑂
Size of Analog Input 𝐿 𝐴𝐼 4
Size of Digital Output 𝐿 𝐷𝑂 3
Size of Fiber Optic
connecter
𝐿 𝐹𝑂 2
Datagram working
counter
𝐷𝐺 𝑤𝑘𝑐 2

14. Simulated number of frames
7/12/2016 14
𝑇𝑓𝑟𝑎𝑚𝑒 =
𝐿 𝑓𝑟𝑎𝑚𝑒 × 8
𝑏𝑤
Frame transmission time
nFrame = ceiling (
𝐿𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝐹𝑟𝑎𝑚𝑒
1500
)
Time taken by the controller
to transmit the bits in the
frame

15. Cycle Time
7/12/2016 15
𝑇𝑐 = 2 × (( 𝑁 𝑇 + 1) × 𝑇𝑝+ 𝑇 𝑀
𝑓
+ (𝑁 𝑇 × 𝑇𝑆
𝑓
) + 𝑇𝑐
𝑝
)
Master
Slave
1
Slave
2
Slave
n
Defined as the time
necessary for the
exchange of input/output
data between the
controller and all
networked devices once
Simulated cycle time
Measured cycle timeMeasured cycle time
20.22 µs
16.73 µs
Number of slaves
Minimumcycletime(µs)
20.96 µs

16. Communication
System
Power System
CFL Testbed
7/12/2016 CAPS, FSU 16
RTDS
SPS
Simulation
Slaves
AI, DO
Master
(Protection
algorithm)
Analog
Signals
Digital
Signals
Simulates
Fault
Initiates fault
clearing sequence
EtherCAT Packet
Simulation timestep- 50 µs
Cycle
Time
50 µs
M ss s
CS4
CS8
PGM Load
PGM Load

17. CFL decision time-
RTDS processing
7/12/2016 17
tRTDS = nproc step x tSimulationTimeStep
Time taken by RTDS (tRTDS) to process the
simulation logic and generate a signal which
goes out of RTDS analog output
Decision time
• RTDS
processing
• Beckhoff
processing
• Synchronization
mismatch

18. CFL Decision Time-
Beckhoff Processing
7/12/2016 18
The time taken by the beckhoff (tbeckhoff)
system to read the signals and compute the
algorithm and generate a response signal.
Cycle time (tct) 50 µsCycle time (tct) 100 µs
tbeckhoff = (niter + 1) x tct
600 µs
5 iterations (niter) for fault
identification,
(n+1) 6 timesteps
fault initiation signal
fault detection by CFL
300 µs
Yellow
-
Blue-

19. CFL Decision Time-
Synchronization mismatch
7/12/2016
19
Additional time added to the system operation due to simulation
delays and delays in the logic processing and hardware interfacing
tmismatch = thsm+ tbpd
RTDS
SPS
Simulation
Slaves
AI, DOAnalog
Signals
No sync
Beckhoff
processing
delay
(tbpd)
Hardware
Synchronization
Mismatch
(thsm)
Worst timing
2 cycle time
1 cycle
time Best
timing

20. CFL Decision Time
7/12/2016 20
Decision time is the sum of all the individual timings to detect a fault in the SPS
td = tRTDS + tbeckhoff + tmismatch
Fault initialization
RTDS output to slaves
CFL decision out
RTDS trip signal
Time (µs)

21. CFL Decision Time
7/12/2016 21
0 100 200 300 400 500 600 700 800 900
Total
RTDS Processing
RTDS Processing
Hardware Sync
Beckhoff error
Cycle 1
Cycle 2
Cycle 3
Cycle 4
Cycle 5
(n+1)th cycle
RTDS Processing
time (µs)
CFL Timing Analysis- Individual Split-up
Hardware sync
Beckhoff delay

22. 1. Topology
– Line
– Ring
2. Jitter
3. Bandwidth
4. Network propagation time
5. Noise
– AWGN / SNR
– Noise on CFL System
7/12/2016 22
Performance parameters

23. Performance parameters- Topology
7/12/2016 23
Master Slave 1 Slave 2 Slave n
Ring topology
Additional/ return path
Master Slave 1 Slave 2 Slave n
Line topology
Return path
Tcycle = Tframe + Tnetwork
Advantages of Ring
topology
1. Resilient to 1
cable cut
condition
2. Additional path
for packet flow
3. Better cycle time
for large
systems
Theoretical minimum cycle time

24. Performance parameters- Jitter
7/12/2016 24
J = |Tc − Tcm|
TC - set cycle time
(eg. 50 µs)
Tcm - measured cycle time
Causes-
• Network
congestion
• Improper queuing
• Configuration
errors
Jitter can be described as latencies in the network
components which may result in the variation of the cycle
time
Jitter (simulated) per slave during the execution of the CFL
system configured at 50 µs

25. Performance parameters-
Bandwidth
7/12/2016 25
NRB =
|Tc − MCT|
Tc
× 100
MCT- Minimum cycle time
TC – set cycle time value
NRB- Non-realtime bandwidth
Line
Topology
Theoretical extrapolation showing the comparison of Fast Ethernet and gigabit Ethernet
The affect of bandwidth on
cycle time with respect to
slaves
Number of slaves
Minimumcycletime(µs)
Line
Topology
Number of slaves
Minimumcycletime(µs)
Fast Ethernet 100 Mbps
Gigabit Ethernet 1 Gbps

26. Performance parameters-
Network propagation time
7/12/2016 26
• Forwarding delays produced by slave devices
• Cable propagation delays
Theoretical network propagation time
networkpropagationtime(µs)
Number of slaves

27. Performance parameters-
Noise
7/12/2016 27
Additive White Gaussian noise SNR = 20 × log10(
𝑉 𝑠𝑖𝑔𝑛𝑎𝑙
𝑉 𝑛𝑜𝑖𝑠𝑒
)
Higher the SNR
Lower the noise in the
signal
Better the
measurement reading
Definition:
Noise is a random,
undesirable energy that
enters the
communication system
via the communicating
medium and interferes
with the transmitted
message
Preliminary analysis: Focused on
the effect of noise on the CFL
detection before the fault occurs.
Question:
Can noise create a false
identification?
Noise
Signal
Receiver
Signal +
Noise

28. Performance parameters-
Noise: CASE 1
7/12/2016 28
CASE 1:
Noise in one measurement node
measurement node
Timestep

29. Performance parameters-
Noise CASE 2
7/12/2016 29
CASE 2:
Noise in both the measurement nodes
measurement node
Timestep

30. CFL demonstration and
implementation
Norbert Doerry’s MVDC SPS architecture
7/12/2016 30

31. SPS model
7/12/2016 31
1 MW PGM is interfaced to 5 kV MVDC bus
CS1 CS2 CS3
CS4
CS5CS6CS7
CS8
F I O
FIO
F
IO
F I O
F
I
O
Master
F
I
O
LOADInput signals (Current) from RTDS to Analog Input
Output signal from Digital Output to RTDS GTDI
Master Slave Connection (Fiber)
Disconnect Switch
CS- Cable Section
I –Analog Input Terminal
O–Digital Output Terminal
F –Fiber optic converter junction
F
I
O
Slave
UnitMMC LOAD
MMC 1
PG
M
PG
M
Load
Load

32. CFL Demonstration
7/12/2016 CAPS, FSU 32
t0 – RTDS simulation
logic processing
t1 – CFL decision time
t2 – synchronization
mismatch and
simulation logic
processing
CHIL implementation
of CFL system
t0
t1 t2
750 µs
time (ms)
0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85
time (ms)
Fault Simulation
RTDS trip signal

33. Implementation
Condition Type Time (µs)
Fault impedance Low impedance fault
300
High impedance fault
Power system
configuration
Open ring
Closed ring
Loading condition 0.544 MW
0.125 MW
Operating modes VSM- CSM
VSM- VSM
7/12/2016 33
VSM- Voltage source mode
CSM- Current source mode

34. ■ Models to determine the performance and scaling of CFL
system were developed
■ Analyzed and discussed the factors affecting the CFL
performance
■ The effectiveness of the model has been verified.
■ A CFL, based on percentage differential protection,
demonstrates fault detection time of ~300 µs.
■ The CFL system was tested for various system operating
conditions and the results demonstrate its desired
performance
■ The ultrafast fault identification system paves the way to
accomplish fault management in the desired 8 ms time
frame
7/12/2016 34
Conclusion

35. ■ Hardware Implementation of a ring topology
■ Validating the system resiliency for cable cut condition
■ System level control
■ Exhaustive Noise analysis
■ Integrating multiple CFL units
7/12/2016 35
Future Work

36. References
1. Shravan Tamaskar, Harsha Ravindra, Mike Sloderbeck, Ruturaj Soman, and Michael Steurer.
"CHIL-based Demonstration of Centralized Fault Location Strategy for a MVDC Shipboard Power
System."
2. Qiu Deng, Xing Liu, Ruturaj Soman, Michael Steurer, and Roger A. Dougal. "Primary and backup
protection for fault current limited MVDC shipboard power systems." In Electric Ship Technologies
Symposium (ESTS), 2015 IEEE, pp. 40-47. IEEE, 2015.
3. Michael J. Thompson, "Percentage restrained differential, percentage of what?." In Protective
Relay Engineers, 2011 64th Annual Conference for, pp. 278-289. IEEE, 2011.
4. https://www.ethercat.org/
5. http://infosys.beckhoff.com/
6. Ziyuan Cai, and Ming Yu. "Modeling and Simulation of a Real-time Ethernet Protocol for Smart
Grids." International Journal Of Intelligent Control And Systems 17, no. 3 (2012): 69-78.
7. Mladen Knezic, Branko Dokic, and Zeljko. Ivanovic. "Topology aspects in EtherCAT networks."
In Proceedings of 14th International Power Electronics and Motion Control Conference EPE-
PEMC 2010. 2010.
8. B. P. Lathi (1968). Communication systems. New York, Wiley.
9. J. A. Betts (1970). Signal processing, modulation and noise. London, English Universities.
7/12/2016 36

37. 7/12/2016 37