Transcript D2-01_34

A Smart Grid Application for
Dynamic Reactive Power
Compensation
A presentation by
G. Vamsi Krishna Kartheek
PRDC, Bangalore
Co-Author
SVN Jithin Sunder
BHEL, Hyderabad
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Requirement of Automatic Coordinated Control
• Modern power system are distributed over a wide geographical region.
• Voltage levels are 33kV, 132kV, 220kV, 400kV, 765kV and even 1200kV.
• Both conventional and non-conventional sources are present.
• Voltage controls are like AVR, Online tap change transformers, FACTS,
HVDC, Switchable capacitors and reactors, etc.
• All these controls to be coordinated through centralized control to achieve
optimization at higher level.
• Automation is to implement effective control in real time.
2
Steps to Implement Automatic Coordinated Control
• Network operating condition to be monitored
• Network operating state to be visualized
• Higher level control from a centralized control center
• Complete system automation
• Effective ICT
3
Technologies to be Effectively Deployed and Exploited
• Network operating condition monitoring
– Measuring devices to measure voltages, real power, reactive powers
– PMU technologies to measure voltage phase angle at all substations
• Network operating state visualization and Higher level control from a
centralized control center
– PRM control system for visualization and control in real time to
optimize the reactive power dispatch from time to time.
– Additionally various system stability analysis algorithms (non real
time) can run in back ground for visualization and analysis of operator.
4
Technologies to be Effectively Deployed and Exploited
• Automation of complete reactive power control
– Thyristor switched reactors in place of fixed shunt reactors where ever
possible.
– Dynamic reactive power support devices like SVC, STATCOM, CSR,
etc.
– Relay protection and circuit breaker control be centralized in all
substations and be monitorable/controllable from control center.
– Complete automation of substations where reactive power control is
present.
– Any substation/power plant monitoring and control system will be
centralized in itself and controllable from control center.
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Technologies to be Effectively Deployed and Exploited
• Effective ICT
– Good communication channels for communication between control
centers and entire network.
– Full-fledged SCADA system with hierarchal control system.
– Substation wise control be primary level control
– PRM control system at control center will be secondary level control.
– State of art technology hardware and software.
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Phasor Relativity based Mathematical Control System
• The PRM control system will not predict any voltage collapse.
• The control system will always try to bind the system operation within the
optimum region of operation through optimum reactive power dispatch.
• So this will enhance the voltage stability from time to time.
• The computations will be from the local measurements.
• We are proposing PRM control system for online real time control based on
the studies performed.
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WAMS Architecture proposed by [2]
Dotted Line Indicates
Data Flow
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WAMS Architecture with PRM Control System
Dotted Line Indicates
Data Flow
Solid Line Indicates
Control Flow
Secondary & Highest Level Control
Primary Level Control
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WAMS Architecture with PRM Control System
• Any disturbance will lead to change in operating state.
• New optimum reactive power dispatch will be generated for the new state.
• Incase of system islanding each island will operate as separate region.
• So the respective PRM control system in the island will be the central
control.
• Any time the controller at NLDC will be the supreme.
• Effective reactive power management helps to neutralize the post
disturbance uncertainties.
• Ultimately helps in mitigating blackout.
• No alarm will be generated to indicate voltage collapse.
• Alarms can be generated to indicate the exhausted reserves.
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Types of Controls
Control Stations
Generating Plant
Types of Controllers
AVR, Governor, Transformer tap control, bus/line
switchable reactors (if any available)
EHV/UHV substations
Transformer
tap
control,
Switchable
bus/line
reactors, switchable capacitors, FACTS
HVDC substation
Converter control, Inverter control, switchable
capacitors, switchable reactors
Non-Conventional
Sources
Energy Switchable
capacitors,
switchable
reactors,
transformer tap control, FACTS
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Case Studies Performed
• Two case studies are performed, model analysis and time domain
simulation.
• All devices are assumed to be centrally controlled.
• System operating state data comes from SCADA using PMU in WAMS
• In Model analysis performing load flow, the same data is assumed to be
reaching the PRM control system.
• The simulation demonstrates the performance of PRM control system for
functional behavior of the system.
• In the time domain simulation also similar consideration is assumed.
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Equivalent South Indian Grid Model (EHV 24 Bus
System)
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Case Study 1
• Model analysis is performed for three cases. The cases are as below.
– Case(1):- This case is with fixed shunt reactors and no control in the
system.
– Case(2):- This case is with fixed shunt reactors but PRM control system
is implemented with controls limited to generators, tap change
transformer and switched shunt capacitors.
– Case(3):- In this case along with all the controllers in the case(2) CSR
is also installed in the PRM control system.
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Studies Performed on the EHV 24 Bus System
• Load is varied from 40% of the base load to the maximum permissible limit
in each case.
• For every 10% of load variation a snapshot is collected.
• Control calculations are performed manually according to the algorithm.
• The voltages are plotted for the three cases for all the snapshots.
• Voltage stability indices plot and loss plot are drawn separately for all the
three cases.
• MATPOWER and PSAT software are used.
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Results of the Cases(1)
Maximum Network
Loading Limit
Is 100% of Base Load
Network Voltages are
between 0.82-1.10 p.u.
Voltage profile(p.u.) Vs percentage of base load
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Results of the Cases(2)
Maximum Network
Loading Limit
Is 110% of Base Load
Network Voltages are
between 0.84-1.05 p.u.
Voltage profile(p.u.) Vs percentage of base load
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Results of the Cases(3)
Maximum Network
Loading Limit
Is 145% of Base Load
Network Voltages are between
0.95-1.05 p.u. upto 140% of Base Load
Voltage profile(p.u.) Vs percentage of base load
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Eigen Value Analysis for Voltage Stability of the Three
Cases
Most predominant Eigen value (distance from Y axia) Vs percentage of
base load
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Real Power Losses of the Three Cases
Real Power losses(MW) Vs percentage of base load
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Comparison of Three Cases
No Control Case
Power Transmission 100%
Capacity
Control without
CSR
115%
This limit can be
extended to 180%
with installed shunt
capacitors
Control with CSR
145%
Voltage Limits in
p.u.
0.82-1.10
0.84-1.05
Types of Controls
No Controls
AVG, Onload
Tapchanger, Shunt
Capacitors
0.91-1.05
(0.95-1.05 upto
140%)
AVG, Onload
Tapchanger, Shunt
Capacitors, CSR.
Real power loss at
rated full load
70MW
60MW
55MW
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Case Study of Stability Maintenance under Disturbance
Condition
• The studies are performed for two cases.
• The cases are
• Case(A):- The reactors are fixed reactors.
• Case(B):- The reactors are switched reactors and PRM control system is
implemented.
• Branch between buses 23-24 is tripped at 10s.
• Voltages, rotor angles and powers are plotted for the two cases.
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Voltage and rotor angle plots of two cases
Case(B)
1.05
1.05
1
1
0.95
0.95
0.9
0.9
0.85
0.85
Voltages (V)
Voltage (V)
Case(A)
0.8
0.75
0.8
0.75
0.7
0.7
0.65
0.65
0.6
0.6
0.55
0
20
40
60
80
0.55
100
Time (s)
20
40
60
80
100
Time (s)
0.6
 Syn 1
0.4
 Syn 1
0.4
 Syn 2
0.2
 Syn 2
0.2
 Syn 3
0
 Syn 3
0
Rotor Angle
Rotor Angle
0.6
0
 Syn 4
-0.2
-0.2
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1
0
20
40
60
Time (s)
80
100
 Syn 4
-1
0
20
40
60
Time (s)
80
23
100
Explanation to the Case Study
• The network with reactors
connected wont satisfy n-1
contingency means in Alert
state.
• When any fault occurs it
goes to emergency or
extremis case.
• Network with reactors disconnected satisfies n-1 contingency so its in normal
state.
• When any fault occurs it goes to alert state.
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Explanation to the Case Study
• When the reactors are suddenly switched the system that’s in alert state will
stay in alert state for some more time.
• This time gap may be of order of 20s to 5mins.
• Some control action should taken to bring the system back to normal state.
• If not again blackout may occur or load shedding is to be performed.
• The operator or the control system has to make advantage of this time gap
to secure the system.
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Significance of PRM Control System and CSR
• System security will be improved with increased reactive power reserve.
• Reduction in dynamic over voltage limit as its no more required to limit the
reactive compensation to 60%.
• The faster response of CSR (10ms) will be primary control and PRM
control system will be secondary control with response time of 10-20s.
• System security is improved with CSR. (as system satisfies n-1
contingency)
• Coordinated control can avoid blackouts.
• Reduces the installation cost and the maintenance cost in a significant
manner.
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Intelligent Control Actions that can Save System from
Collapse
• Intelligent switching of line, bus reactors, shunt capacitors and FACTS
devices
• Using optimum tap controls
• Intelligent and controlled switching of line circuit breakers
• Optimally setting the generator terminal voltage
• Optimal load dispatch under critical situations
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Conclusion & Future Work
• In the studies performed, the local controls are not considered as it is
difficult to simulate local automatic control.
• However the future work is to simulate local automatic control at each
substation and centralized control in RTDS.
• PMUs to be present at main substations and where control is available.
• WAMS system present at control centers.
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Thank you
Questions & Discussions
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