Grid Interconnection Limit

Hello Team, 

As we know, in a "Net energy metering" all energy produced by the PV system is first consumed by the load and the rest is injected to the grid. Based on this, I want to limit, dynamically, the Inverters output power by measuring the load power to control/allow the inverters to generate 50 kW above the demand power by the load, see figure attached. 

Unfortunately, by limiting the power to the grid to 50 kW in SAM it does not take into account the load demand. Question, is there a way to substract the load demand from the PV generation first and then take the result as the limit to inject to the grid?

Best-
Carlos     

Hi Carlos,

It is not possible to limit power to the grid to a function of the load in the way you describe.

What is the motivation for this application? Is it part of a net metering or other policy?

Best regards,
Paul.

Hi Paul,

It is related to the  power demand policy. Here in DR the policy about the demand charge is determined either by the last highest peak or the average of the two months with the highest peak registered, whichever is larger will be taken as reference for the rest of the year as fix demand charge. 

If a residential/commercial customer install a PV system with a net metering structure, then the same policy stated above  apply or......... if the power injected from the PV system is larger then the last one is consider as the fix demand charge for the rest of the year, that's why we need to take care about the power injected to the Grid. 

My intention is to control, dynamically, the inverters power output by measuring the load (using the eGauge tool, for example). So, as an example, if at any step the load is 20 kW then the max inverters output power will be limited to 70 kW (70 - 20 = 50 kW) and then the Utility Grid will see only 50 kW injected to its system. 

Let me know if you got the idea.

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Correction...............I think the time serie "Electricity to/from grid peak (kW)" is already the result of the "System power generated (kW)" minus the "Electricity load (kW)" at least for positive values, correct me if I am wrong. So when I limit the grid interconnection to any value, the reflected result already have the "Electricity load (kW)" subtracted.   

Best-
Carlos  

 

Hi Carlos,

Thank you for that information about the net metering policy in the Dominican Republic,

And, yes, your understanding of "Electricity to/from grid" is correct. You should be able to verify that on the Data Tables tab by displaying the hourly (or subhourly) "Electricity to/from grid", "Electricity load (year 1)" on the "Hourly Data" tab (for subhourly simulations, the tab will be "15-minute Data" or "5-minute Data", etc.), and "System power generated" on the "Lifetime Hourly Data" tab. You can export the tables to Excel to verify the relationship.

It's a little confusing that some of the time series outputs are reported as "lifetime" values and others as "year 1" values. We are working on improving the way this data is reported.

Best regards,
Paul.