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A Smart Grid Application for Dynamic Reactive Power Compensation A presentation by G. Vamsi Krishna Kartheek PRDC, Bangalore Co-Author SVN JithinSunder BHEL, Hyderabad
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.
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
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.
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.
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.
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.
WAMS Architecture proposed by  Dotted Line Indicates Data Flow
WAMS Architecture with PRM Control System Dotted Line Indicates Data Flow Solid Line Indicates Control Flow Secondary & Highest Level Control Primary Level Control
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.
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.
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.
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.
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
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
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
Eigen Value Analysis for Voltage Stability of the Three Cases • Most predominant Eigen value (distance from Y axia) Vs percentage of base load
Real Power Losses of the Three Cases • Real Power losses(MW) Vs percentage of base load
This limit can be extended to 180% with installed shunt capacitors Comparison of Three Cases
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.
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
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.
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.
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
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.
Thank you Questions & Discussions