Designing an Stand Alone PV System in PVSol

[Johan van t Wout]

Over the past few days I’ve been working on configuring a stand-alone system in PVSol, and I must admit it hasn’t been easy to figure out the logic. I think I’m starting to understand it now, but I still have doubts and questions about certain points.

I want to design a stand-alone system based on the Morningstar SureSine inverter (1250 W, 48 Vdc) and a TriStar MPPT 45A charge controller.

When I select Stand Alone PV System as the project type, I still see “AC Mains” displayed on the screen. I don’t quite understand this—shouldn’t we be working in stand-alone mode? Or does it simply indicate that the stand-alone system provides an AC 230 V single-phase output?

What if I want to design a stand-alone system that only has a DC load circuit—how would that be handled?

As I understand it, PVSol treats an inverter as a charge controller. So I would need to enter the Morningstar TriStar MPPT 45A under Inverters in the database? PVSol then only considers the DC side of the inverter for simulation, while the AC side is ignored—is that correct?

My intended configuration is two strings with two PV modules each, connected to the Morningstar TriStar MPPT 45A. This is normally done via a combiner box, keeping the Voc within the 150 Vdc limit of the TriStar MPPT 45A, since it only has one MPPT input. However, I can’t find a way to model this in PVSol. I’ve read that PVSol doesn’t support this setup and instead forces you to use one string of four modules in series, which would push the Voc above 150 Vdc. That would mean I’m required to use a larger Morningstar charge controller (600 Vdc). Is that correct?

The Morningstar Off-Grid Inverter SureSine 1250 W 48 Vdc should be entered under Battery Inverters in the PVSol database, right? And of course, the batteries must be entered under the Battery section of the database.

I’ve configured the system this way, but I keep getting the error message: “Simulation not completed as the battery could not supply the required energy. Please verify configuration and increase the PV power or battery capacity if necessary.”

The consumption is about 3.5 kWh per 24 hours. I’ve set the PV capacity to 3.2 kWp and the storage capacity to 19.2 kWh, which should be more than sufficient for such a small system. I deliberately oversized them because I kept getting this error message.

I hope someone can help me with the above design—what am I doing wrong?

Kind regards,