Constant sky diffuse shading loss error.

Hello!

I am trying to model a my PV system to evaluate the power generated. I have run a couple of simulations and some results are negative power generated (-0.00101kW) and the results are much higher than real data. 
I assume that -0.00101kW is 0kW, right?
Regarding the difference between real data and SAM's, I assume that I haven't added shading losses correctly. But, whenever I change the constant sky diffuse shading loss and simulate, more numbers from the System Power Generated turn into -0.00101kW.
Do you know why this could be happening?
Please find attach my DetailPVsystem.sam 

Hi Rita,

Those negative power values at night are caused by the inverter's night time or standby power consumption, which is determined by the Power consumption at night input on the Inverter page.

The constant sky diffuse shading loss in the shading inputs reduces the amount of diffuse irradiance incident on the array. For any time steps when the direct normal irradiance (DNI) is zero, or when the array is completely shaded (beam shading loss = 100%), the only light available to the array is diffuse irradiance. If the diffuse shading loss is also 100%, then the array receives no light, and the inverter goes into standby mode and consumes power defined by the nighttime power consumption input.

Best regards,
Paul.