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Telemetry of HSLs for WGRs. David Maggio April 12 th , 2011. Issue. There is a flaw in the logic that QSEs are using to determine the telemetered HSL in real-time This primarily causes an issue for the period following a release from curtailment
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Telemetry of HSLs for WGRs David Maggio April 12th, 2011
Issue • There is a flaw in the logic that QSEs are using to determine the telemetered HSL in real-time • This primarily causes an issue for the period following a release from curtailment • After a release from curtailment, a WGR’s output is still affected by the curtailment instruction • Setting the HSL equal to output immediately following a release in curtailment can result in a significant underestimation of the WGR output potential The WGR is released from curtailment and the HSL was set to output immediately. The potential output from that WGR is not correctly accounted for in RLC for SCED dispatch.
Issue cont. • The compounded effect of this logic is that SCED releases too many WGRs from curtailment due to the potential aggregate WGR output not correctly being accounted for • After the full output of the WGRs is realized, SCED must again curtail WGRs to manage the congestion • The cycle continues resulting in control and response oscillations
Issue cont. • This logic is a result of the following language from Protocol Section 6.5.5.2(3) • For each Wind-powered Generation Resource (WGR), the QSE shall set the HSL equal to the current net output capability of the facility within one SCADA cycle after receiving the last SCED Base Point Dispatch Instruction from ERCOT. The HSL telemetered to ERCOT for the WGR shall not be changed until the receipt of the next Base Point. If the Base Point received from ERCOT is less than the telemetered HSL minus two MW, then the WGR shall respond to the Base Point Dispatch Instruction and shall be considered curtailed. During any curtailed SCED intervals, the WGR HSL shall be updated within one SCADA cycle after the receipt of a subsequent SCED Base Point with a value which represents the WGR’s estimated, non-curtailed output potential. This estimated, non-curtailed output potential shall be based upon turbine availability, wind speed at the WGR and application of the appropriate wind/power curves. During SCED intervals when the telemetered Base Point of the WGR exceeds the last HSL telemetered to ERCOT minus two MW, the WGR shall be considered as not curtailed. HSLs telemetered to ERCOT for WGRs that are not curtailed shall be based on the WGRs’ actual net output as stated above in this Section 6.5.5.2.
Option 1 • QSE will telemeter a MW value representing the estimated wind power output capability of the WGR • The HSL would be calculated as the larger of the estimated wind power output capability and the net real power of the WGR • This will be independent of whether or not the WGR is required to comply with the SCED Dispatch Instruction • This change in logic will provide the desired effect whether the grey-boxed language of NPRR285 has been implemented or not • The implementation of NPRR285 will only change the frequency at which the telemetered HSL is being updated • This logic should provide SCED with a more consistent and clear view of the real power capabilities of WGRs • This approach can introduce some error into the SCED solution for WGRs that are not being curtailed
Option 2 • This was the option discussed at the 4/4/11 QMWG • Still uses the detection of “curtailment” to determine whether the HSL should be set to estimated wind power output capability or the net real power of the WGR • Following a release from curtailment, the QSE would continue to telemeter an estimate of un-curtailed wind output for a set period of time • Based on the ramp rates provided, 20 minutes should be sufficient for a large majority of WGRs • A time delay doesn’t guarantee that the WGRs output is not still reduced for the curtailment • After this set period of time, if the WGR is still not being curtailed, the QSE would begin setting the telemetered HSL equal to the current net output of the WGR • This approach should reduce the error introduced by the previous proposed solution, however it is more complex