1. Microgrid Load Management and Operation Erich Keller G&W Electric Co. Frank Patton Jr., PE N. J. Shaum & Son, Inc.

2. Havasupai Microgrid Overview of Project System Capabilities Load Management Challenges Lessons Learned

3. Havasupai Community Just over 200 year-round residents 20,000+ visitors annually 8 mile hike or mule ride to village (or 15 minutes by helicopter) 70+ miles of overhead distribution lines to nearest substation 3

4. 4

5. Havasu Creek and Falls

6. 9 new switches, and 1 existing – G&W PVI Style with two or three load break ways and up to two tap ways – SEL-451 Relays for protection and control – Existing switch was retrofitted with new control Communicating Centralized Control – FLISR – LOV Transfer – HMI – Load Management Generator Backup Grid Connected Solar Generation 6 Microgrid Components

7. Microgrid Design 7

8. SWPV SWM SW1 SW2 SW3 SW4 SW5SW6 SW7 SW8 MEC PV Inverter Microgrid Controller Ethernet Radios + Antenna Ethernet Switch Existing Hunter RTU Ethernet Switch Serial to Fiber Ethernet Converter Weather Station Diesel GEN Communication

9. Operation 9

10. FLISR Straightforward, but critical part of project due to its remoteness Fault interrupted by nearest capable device – Controller detects trip – Performs Fault Location – Isolates faulted section – Performs Service Restoration (close tie and fault interrupter as applicable)

11. Automatic Utility Source Transfer When two or more phases of the utility source are lost: – The controller starts the generator – Sheds all non-critical loads – Transfers from the utility to generator

12. Automatic Utility Source Transfer When all three phases of the utility source are regained: – The controller transfers back from generator to the utility – Picks up all loads – Stops generator

13. Three Modes of Microgrid Operation Utility Source Transfer: Automatic Transfer Control (ATC) as above with no automatic load adding/shedding after transfer Max Generator Run: ATC with only highest priority loads picked up Load Management: ATC with all loads picked up/dropped automatically as needed

14. Load Management Most complex/interesting part of project Simplified economic dispatch of generator and solar resources – Calculate and store average power consumption of each load when connected to utility – Calculate real-time solar capacity using temperature, irradiance and wind speed – Use generator as swing bus

15. Load Management Iterations Initially allowed for wide range of generator and solar usage – Decreased generator operating band to 30-70% – Decreased solar band to 5-50% while disconnected from the utility

16. Generator Considerations The diesel generator was changed to operate within a narrow band to avoid equipment damage or unnecessary tripping – When too lightly loaded, the generator runs less efficiently and may require more maintenance – When too heavily loaded, the generator has too little margin to allow for picking up load in the event of a sudden loss of solar capacity

17. System Operation Over Time

18. Excess VAR Troubleshooting 18

19. Step 1: ID Parallel Cable Run 19

20. Step 2: Temporary Mitigation 20

21. Step 3: Addition of Reactor Banks 21

22. Lessons Learned Importance of understanding distribution system – Power quality and installation issues Understand operating range of generator Comprehensive factory acceptance testing is critical Adding remote monitoring to village allowed the serving utility to improve recloser and voltage regulator settings Distributed resources cannot be as fully utilized without storage (consider battery or flywheel)

24. Questions?

25. Communication 25

26. System Operation Over Time

27. Troubleshooting Actions As originally designed, the Auto Transfer would close the generator into the distribution network with all loop ways in their normal conditions and only the highest priority loads closed. It was found during site testing that the generator was feeding VARs in excess of its capacity when feeding the loop and highest priorities and would trip. – It is suspected that a parallel run of cables caused the excess VARs, but no formal study was performed. This was experimentally postulated after splitting the distribution loop in half to observe the VAR flow in different topologies. Before adding the reactor banks, the program was modified to segment the distribution loop and feed only the half of the loop that had the highest priority loads. A reactor was added to compensate for the effect of the capacitive VARs. This helped to improve the situation, but a second reactor bank was added for more security. 27