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A Smart Grid Application for Dynamic Reactive Power Compensation
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  1. A Smart Grid Application for Dynamic Reactive Power Compensation A presentation by G. Vamsi Krishna Kartheek PRDC, Bangalore Co-Author SVN JithinSunder BHEL, Hyderabad

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. WAMS Architecture proposed by [2] Dotted Line Indicates Data Flow

  9. WAMS Architecture with PRM Control System Dotted Line Indicates Data Flow Solid Line Indicates Control Flow Secondary & Highest Level Control Primary Level Control

  10. 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.

  11. Types of Controls

  12. 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.

  13. Equivalent South Indian Grid Model (EHV 24 Bus System)

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 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

  19. Eigen Value Analysis for Voltage Stability of the Three Cases • Most predominant Eigen value (distance from Y axia) Vs percentage of base load

  20. Real Power Losses of the Three Cases • Real Power losses(MW) Vs percentage of base load

  21. This limit can be extended to 180% with installed shunt capacitors Comparison of Three Cases

  22. 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.

  23. Voltage and rotor angle plots of two casesCase(A) Case(B)

  24. 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. Explanation to the Case Study

  25. 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.

  26. 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.

  27. 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

  28. 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.

  29. Thank you Questions & Discussions