NERC Voltage Ride-through Follow-up Activities

Transcription

1 NERC Voltage Ride-through Follow-up Activities Robert W. Cummings Senior Director of Engineering and Reliability Initiatives MRO Reliability Conference May 24, 2017

2 Early JUNE Publish Inverter Task Force report Operating Committee review in late May Inverter Task Force Next Steps Mid June Industry Recommendation (Level 2 Alert) Loss of Solar Resources during Transmission Disturbances due to Power Inverter Settings Possible SAR for modifications to PRC 024 for clarification Current Standard language more appropriate for rotating machines Specificity of performance for inverter based resources Additional analysis on inverter blocking analyzing risk and exposure Continue working with inverter manufacturers to mitigate tripping due to erred frequency measurements Work with FERC, IEEE, UL, NFPA and state jurisdictions to harmonize regulations on voltage and frequency ride through 2

3 ITF Report Recommendations Recommendations 1a and 1b 1a Review PRC for possible revision to add clarity that outside the frequency curves is a may trip area (if needed to protect equipment) and not a must trip area 1b Review PRC for possible revision to add required delay for large over and under frequency excursions to ensure transient/distorted waveform ride through Alternative approach New standard for inverter connected resource voltage and frequency ride through Performance base Directly address inverter controls not to be confused with protective relays 3

4 Frequency Ride-Through Curve Changes May Trip Zone Extend scale to T=0 sec May Trip Zone 4

5 ITF Report Recommendations Recommendation 2a and 2b 2a Inverters that momentarily cease active power output for voltage excursions should be configured to restore output to pre disturbance levels in no greater than five seconds providing the inverter is capable of these changes 2b Review PRC for possible revision to indicate that Momentary Cessation of inverter connected resources is not allowed within the No Trip Zone of the voltage curves If Momentary Cessation is not allowed, the standard should reflect what type of current should be injected during low voltage periods 2bi Provide appropriate exceptions where existing installed equipment is not physically capable of meeting the new requirements of the revised PRC Requirement R3 5

6 Voltage Ride-Through Curve Changes May Trip Zone No Momentary Cessation May Trip Zone 6

7 Recommendations 2c and 2ci 2c Perform further, in depth analysis of Momentary Cessation to determine: If Momentary Cessation should be allowed for voltages less than 0.9 per unit or greater than 1.1 per unit If current injection is required, determine what type of current to inject o active or reactive, positive negative zero sequence o At what voltage levels? ITF Report Recommendations 2ci ERO Enterprise and affected entities perform more detailed benchmarking studies and analysis to determine: Reliability risk associated with potential resource loss events caused by momentary cessation or tripping during fault conditions, especially in highpenetration areas Whether if adjustments to the Resource Loss Protection Criteria are needed to protect interconnection frequency stability 7

8 ITF Report Recommendations Recommendation 3 3 NERC Event Analysis should develop a NERC Alert for the industry to ensure: Awareness of the risks associated with inverter based resources during fault conditions Understanding of the steps that can be taken to mitigate these risks including recommended changes to inverter settings That BAs and RCs assess the reliability risk of solar PV Momentary Cessation and take appropriate measures 8

9 ITF Report Recommendations Recommendation 4 4 NERC should work with FERC, IEEE, UL, NFPA, and state jurisdictions to eliminate potential conflicts between NERC Standards, IEEE 1547, UL 1741, National Electrical Code, Generator Interconnection Agreements, et al. 9

10 ITF Report Recommendations Recommendation 5 5 NERC should develop a standard that is pertinent to inverters for transmission connected resources addressing: the use of reactive current injection into the grid instead of Momentary Cessation while in the Voltage Ride through mode Identify method to determine amount of reactive current injection during Voltage Ride Through mode when (if) it is determined to be the preferred method of operation Maximum time to return to normal operating mode (i.e., real and reactive power injection) following Momentary Cessation or current injection during Voltage Ride Through operation Identification of allowable modes for inverter Trips Maximum allowed time to Return to Service (i.e., real and reactive power injection) a Trip Acceptability for inverters to use a counter to Lock Out the inverter following pre determined number of Trips over a specified time period 10

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