Distributed Voltage Support on the Smart Grid

1. Distributed Voltage Support on the Smart Grid Kate Rogers Power Affiliates Meeting May 14, 2010

2. Acknowledgements • Other Contributors • Ray Klump • HimanshuKhurana • Angel Aquino • Thomas J. Overbye • U.S. Congressman Bill Foster • K. M. Rogers, R. Klump, H. Khurana, T.J. Overbye, “Smart-Grid –Enabled Load and Distributed Generation as a Reactive Resource,” Proceedings of the 2010 IEEE PES Conference on Innovative Smart Grid Technologies, Jan. 2010. • K. M. Rogers, R. Klump, H. Khurana, A. Aquino-Lugo, T.J. Overbye, “An Authenticated Control Framework for Distributed Voltage Support on the Smart Grid,” accepted for publication, IEEE Transactions on Smart Grid.

3. Motivation • Increased PMU deployment will improve monitoring capabilities • Improved monitoring motivates improved control of resources • Inadequate reactive power supply was a factor in most previous major North American blackouts

4. Goal of this work • Improve control of resources using … • A distributed reactive power support system • A comprehensive form of control • Near real-time reactive control at residential level • Coordinating communications must be secure

5. Definitions • Q-C Buses • transmission system level buses controlled to provide an amount of aggregated reactive power support • Load Categories • Loads classified according to ability to provide support • CAT1 (most controllable) through CATN (least controllable) • Categories are not fixed

6. Definitions • Reactive Support Regions • Buses chosen a priori to help each other • One main controller in each region can be responsible for obtaining the necessary reactive support for all devices in its region • Division allows focus on a subset of the controllers • Can also help make the framework extensible to decentralized control algorithms

7. Intelligent Control Framework • The Incident Command System (ICS) helps coordinate emergency response • Can leverage other domains’ experience with this model • Members follow a chain of authority and command Central EMS Feeder Relay Feeder Relay Relay A Relay B Relay C Relay D loads

8. Overview of Proposed Framework • Centralized control – detects voltage problems • Centralized control – computes required aggregate reactive power responses • Regional controllers – receive requests for support directed to constituent Q-C Buses • Q-C Buses – receive requests for an aggregate amount of support which they must obtain from devices in the distribution system • Each party confirms its participation

9. Vision of the Proposed Framework Central Control A priori analysis Wait and detect changes Reactive Support Regions Q-C Buses Distribution System Loads Event Detected Q-C Buses communicate with the distribution system to provide the requested output Choose Q-C buses Regional controllers send messages to Q-C Buses Determine outputs to restore voltages, send messages to appropriate regions. Choose more Q-C Buses in region Support remaining in the same region? Update reserves info., a new solution is needed Q-C Buses tell regional controller amount of committed support N Y Regional controller decides -is amount sufficient ? N Y Tell Q-C Buses to execute the action Confirmation (all parties)

10. Example - Constituents of a Reactive Support Group Transmission System Distribution System Reactive-Power-Capable Devices at the Residential Level Home Monitoring and Control System PMU PHEV Smart meter * * M1 M2 Combined Heat and Power (CHP) PMU Manager of Devices ( )in Reactive Support Group Mi = Message to provide reactive power amount Qi at Q-C buses i *

11. Communications Convenient way to segregate and secure communications top layer A Realm 1 bottom layer B Realm 2 C loads

12. Communications • Digital signatures- one option • Secure communication framework to control reactive-power-capable devices at the end-user • Provides integrity, authentication, and protection against replay Mcomm| T | Sign(H(Mcomm|T)PRA B A Mresp| T | Sign(H(Mresp|T)PRB

13. Communications • HMAC - another option • No encryption step - less computational expense • Good if confidentiality is not a concern M| T |HMAC(M|T,KAB) B A

14. IEEE 24-Bus RTS Example and 5 Chosen Supporter Buses for Each Group Possible Reactive Support Groups

15. IEEE 24-Bus RTS Example Results

16. 2003 Blackout Example Power factor correction at just 5 buses results in appreciable voltage improvement Voltage (per unit) 1.02 Reconstructed pre-blackout state with low voltages 0.95 0.88 After power factor correction of 5 buses

17. . Control with Intelligent Agents (Angel Aquino) • Agent Scheme follows the ICS response structure • Central EMS Agents responsible for Feeder Relays Agents • Feeder Relay Agents responsible for Downstream Control Relays Central EMS Feeder Relay Feeder Relay Feeder Relay Feeder Relay Feeder Relay Transmission Network Central EMS (B_A) Feeder Relay SS 1 Control Relay A 2 Distribution Network 3 5 Control Relay B 6 Control Relay 7 4 10 13 8 9 12 11

18. Voltage Control by Thermal Loads(KomalShetye) • Problem: Dynamic behavior of certain loads like induction motors during faults may cause voltage stability issues on the distribution network • Possible solution: Residential thermal loads for such ‘short-term’ voltage control • Disconnection may aid voltage recovery during faults • Requires high-speed and secure communications at the distribution level

19. Thank You Kate Rogers- krogers6@illinois.edu