In PVsyst, how can I calculate aux-load loss that the grid provide to a PV plant which we should pay for the utility?

[Sang Han]

In PVsyst, how can I calculate aux-load loss that the grid provide to a PV plant which we should pay for the utility? 

Aux-load loss is generally 0.3% for the 100-200MW utility scale solar project. But that loss can be cutoff by PV plant itself during a day. 

What I want to know is the aux-load usage that utilities provide when PV plant is not operating such as nighttime loss or no-load loss for Inverters or transformers?

How can I calculate that?

[André Mermoud]

The auxiliaries and night losses may be specified for the simulation, in the "Detailed losses" part, page "Auxiliaries".

You have the opportunity of defining fixed values, with possibly a part proportional to the produced power, as the inverter losses will produce heat which has sometimes to be evacuated.

 

 

 

 

[dtarin]

Transformer losses will come from the manufacturer. If you are modeling transformers in PVsyst, ensure the no-load losses are captured there, and it will reflect in the 8760 for night hours. For MV transformers, 0.10% - 0.16% is a good range for no load losses, for MPTs, 0.04% - 0.06% is a good range. Other items you will need to determine based on plant equipment. 0.2% of POI rating for total hourly night loss at the revenue meter is a good estimate overall (utility scale SAT). Use something higher for cold-weather plants. 

Edited March 4 by dtarin

[Sang Han]

My result by PVsyst regarding the nighttime loss is 0.04% with disconnection for MV and HV transformers. 
But once I have these (MV&HV night loss) included, 0.33% of nighttime aux loss occurs.

When I contact an interconnection engineer, he said I need to include transformer night losses due to the grid stability based on interconnection agreement. 

0.33% will be used for my calculation. 

Any comments on this?

[André Mermoud]

Please give some precisions about  what you mean by "Night losses". 

You can define losses for feeding the auxiliary equipment (fans, HVAC, monitoring, etc) , which are usually drawn from the usual low-voltage grid.

The Iron loss of the transformers is a completely different kind of "night" loss. In fact this is a permanent loss, acting as soon as your transformer is connected to the grid. When producing PV energy, this is substracted from the production. This loss may be suppressed by night, by installing a switch on the HV line.

[Sang Han]

When I unchecked the "Night Disconnection" in MV and HV transformer loss input section, the more loss occur at nigh. MV and HV losses are increased when I see the 8760. 

so I think night losses connected with the grid at night is related to TX losses and fans, HVAC, and others. 

[dtarin]

Night losses are everything the plant draws at night, including transformers. The utility does not distinguish between devices. Most utility-scale plants (in my opinion) do not have nighttime disconnects on the MV equipment. The MPT is always connected to the grid. It is best to assume (unless you have a detailed design stating otherwise) that the plant will not be disconnected from the grid at night. 

The caveat here is that depending on how you are using your energy model and if it is flowing into a financial model, you may want to separate these out in case they are considered independently in the financial model. 

Edited Thursday at 10:07 PM by dtarin

[Sang Han]

@dtarin @André Mermoud, Thanks for your help!