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SunSpec Model Definitions
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Model 704 WMaxLimPct and WSetPct #216

Closed FW22 closed 1 year ago

FW22 commented 3 years ago

WMaxLimPct is used to limit active power generation of DERs in general (PV and Battery inverters) - usually on request of the distribution network operator. WSetPct is used to set active power level for DERs that are able to follow a setpoint (e.g. Battery systems) - usually on request of a local energy management system. For Battery systems that support both (WMaxLimPct and WSetPct), this could lead to conflicting requirements, because, both refer to the AC output of the DER. Did you consider a prioritization between the two?

bobfox commented 3 years ago

There are a lot prioritization questions that come up across the models for active and reactive power control. In general, we have left prioritization out of the communications specification with the view that it may vary across contexts. IEEE 1547-2018 makes statements about prioritization of functions. This approach makes it possible that some decisions are device specific but the alternative of specifying them in the communications specification may not be workable. In the example you site, it seems like WMaxLimPct would limit the values that could be applied with WSetPct but I am not sure that would always be the case. In general, It is probably best for the standards and jurisdictional requirements that specify functional behavior to address these considerations. That can leave a gap in this area, however.

FW22 commented 3 years ago

You mentioned in #154 that WSetPct may be negative. What is the basis if it is negative? Is it always 702-WMax?

bobfox commented 3 years ago

Yes, all active power percentage settings are based on WMax.