PMU simulation and application for power system stability monitoring

1
PMU simulation and application for power system
stability monitoring

• Harmeet Kang
• Areva Technology Centre
• Stafford, UK

Sept. 2009 MOSCOW
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Historical Perspective

• Impossible to compare data from geographically
  different locations
• No context to the measurements
• Slow RTU data
• Technology cost prohibitive

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Why Synchrophasors

• Difficult to do post analysis if measurements
  cannot be aligned
• Very difficult to develop a pre-emptive strategy
  if the phase angles between various points in a
  system cannot be determined
• GPS and Ethernet have made it possible to have
  time aligned measurements from geographically
  different locations
• Systems are operating closer to the limit than
  they were before
• Better State Estimation

4
Comparison with traditional SCADA
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What is a Phasor
IEEE C37.118 specifies that the angle ? is 0
degrees when the maximum of the signal to be
measured coincides with the GPS pulse and -90
degrees if the positive zero crossing coincides
with the GPS pulse.
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Measurement
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Phase Angle
50 Hz
49.93 Hz

• Not constant if Frequency is constant
• 2p(ff0)T0, where f0 1/T0
• 2p(49.9350)0.02-0.504 degrees/measurement
• 25.2 degrees between two GPS pulses

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PMU device basics
GPS
Receiver
Oscillator
Microprocessors
A
/
D
Digital
Digitised
IEEE C
37
.
118
Data
Analog
Samples
Electrical
Data Frame over
signal
Serial or Ethernet
P
847
PMU
(
TCP
/
UDP
)
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PMU device basics
Small error
GPS
Receiver
Oscillator
Fixed delay in gathering data
CT/VT Mag/Angle Errors
Small error
Microprocessors
A
/
D
Digital
Digitised
IEEE C
37
.
118
Data
Analog
Samples
Phase delays /Variable
Electrical
Data Frame over
signal
Serial or Ethernet
P
847
PMU
(
TCP
/
UDP
)
10
GPS input
200ms

• Output Site 1

/- 1ms
Light ON
Leading edge is
timing point
Light OFF
Time

• Output Site 2

lt100 ns
Light ON
Light OFF
Time
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MiCOM P594

• MiCOM P594 is the universal time synchronising
  unit for the substation
• Accurate for PMU applications
• Accurate for GPS line differential
• Accurate for NCIT merging units
• Accurate for all other purposes
• Modulated IRIG-B
• Un-modulated IRIG-B
• 4 x 1 PPS fibre outputs to synchronise P54x
  relays
• P594 Status, Static Output Relays
• Visual time reference on LCD

One Device Synchronises All One Single
Investment
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Acceptable Total Vector Error (TVE)
1 TVE 0.5 degrees 26 msec _at_60Hz
Where Xr (n) and Xi (n) are the measured real and
imaginary components and Xr and Xi are the
reference values. This measurement accuracy
varies with the magnitude and frequency of the
input signal.
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Measurement Window
Filter Coefficients are chosen to provide A zero
degrees phase shift if the middle of the window
corresponds to the peak of the signal
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Filter Length

• Programmable
• 1 7 Cycles
• Default - 5 Cycles

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Impact of Filter Length
Particularly important to have good noise
rejection as inter area and local oscillations
are around 0.1 -3 Hz
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MiCOM P847 Main Functionality
Multifunctional
Phasor Measurement Function
Breaker Fail Re-trip Backtrip
Disturbance /Transient Recorder
Voltage, Current Freq. Protection
Communications
Local/Remote Control Monitoring
Fault Location, Events, Recording
Programmable Logic, I/O Marshalling
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PMUs in a System
PMU1
PMU2
PMU3
PMU4
E-terra
PDC
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Phasor Data Transfer
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IEEE C37.118 Protocol

• Configuration gt To PDC
• Header gtTo PDC
• Data gt To PDC
• Command lt From PDC

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PMU Protocol Settings
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PMU Data Config
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Communication/Data Architecture
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Why Substation PDC

• Can create a virtual PMU for a complete
  substation out of many PMU's, hence lowering
  network congestion
• Provides a reliable and persistent data storing
  environment when the communication link is down
• Can be used to make the Control Centre catch
  up data to a certain extent if the communication
  link is intermittent
• Creates a set up for the future where direct
  control actions (substation based logic or Wide
  Area Control) can be taken based on PMU data.

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Communication Issues

• Communication bandwidth can be reduced by
  combining data from multiple PMUs in one channel
• Communication bandwidth can be reduced by
  choosing integer data transfer (16 bit) over
  floating point(32 bit)
• Must be considered carefully depends on what
  applications are using phasor data
• The same channel should be capable of configuring
  a substation PDC or PMU without loss of data

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Embarking on a PMU basedWMS system
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PMU / WAMPAC roadmap
Envisaged User Requirements
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PMU Locations and Number of

• Which feeders are key to the interconnection
  between grid regions
• Which nodes exhibit large shifts in power angle
  based on a loss of generation, load and change in
  topology.
• Which areas are of interest from a load modelling
  perspective
• Which areas of the grid are known to contain
  dynamic stability issues
• Which areas can form frequency Islands
• Which areas of the grid are prone to voltage
  collapse
• Which nodes will be most beneficial for the
  current state estimator improvement and a future
  linear state estimator

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PMU Locations and Number of
Phenomena Power Angle Load Dynamics Stability
monitoring Frequency Islands Voltage
Collapse State Estimation
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System Study and Virtual PMUs
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Application of PMUs in Power System Stability
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Small Signal Stability
Ability of a power system to maintain
synchronism When subjected to small
disturbances. In todays practical power
systems, the small signal Stability problem is
usually of insufficient damping of system
oscillations
Ref Power System Stability and Control Prabha
Kundur
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Small Signal Stability
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System Oscillations
Ref UNDERSTANDING POWER SYSTEM STABILITY Michael
J. Basler and Richard C. Schaefer
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Oscillations
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Anatomy of an Oscillation
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Power Transfer Between Two Systems after a
disturbance
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PMU Data
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Modal Analysis
Oscillatory Modes and associated damping factors
for two buses in a system after a small
disturbance
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Significance of Negative Damping
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Effect of Data Transmission rate of application
Every PMU measurement
Every second PMU measurement
Every tenth PMU measurement
Every second
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Operator View of PMU data
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Conclusions

• Technology enablers have made PMUs a logical
  choice for Wide Area Applications
• PMUs can be used for variety of monitoring and
  stability applications
• The common angle reference provides context to
  the measurements
• Adaptive filter length and data rate can be used
  to match measurement to application
• PSS tuning can be done to improve system response
  to disturbances
• PMU Simulation can help in planning location ,
  number, characteristics

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Conclusions
Applications

• Real-time measurement of the power system state
• Real time monitoring of angular stability
• Real time monitoring of damping issues
• Post event analysis
• Post-Disturbance Analysis and Compliance
  Reporting
• System Operations and Planning

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Thank You