PV + BESS Architecture

[Nikhil Lokhande]

Hello PVsyst Team and Forum Community,
I am currently modeling a 5.00 MWdc / 2.49 MWac utility-scale project in PVsyst 8.1.0 that utilizes a split-architecture. I am seeking guidance on how to accurately isolate storage to a specific sub-array or if this is a planned feature for future updates.
System Architecture: Our design uses two distinct paths tied to a single 2.49 MW AC Point of Interconnection (POI):

• Path 1 (DC-Coupled): 4.364 MWp PV array connected via 4x Dynapower DPS-500 DC-DC converters to a 10 MWh BESS. This path uses 4x Solectria PVS-500 (1.992 MW AC total) bi-directional inverters. The ILR on this path is high (2.18) specifically to maximize clipping recapture.
• Path 2 (PV-Only): 0.641 MWp PV array connected to 3x Solectria XGI 1500-166 inverters (0.498 MW AC total). This path has no battery and should feed the grid directly.

The Issue: In the current version (8.1.0), the Storage menu for DC-coupled systems appears to follow a "Global DC Bus" logic. I am unable to find a way to assign the battery and the DC-DC chargers exclusively to the DC bus of Sub-array 1 while treating Sub-array 2 as a standard PV-to-grid path.
As a result, the simulation assumes the battery can "see" the excess energy from the entire 5 MWdc array, which does not reflect the physical wiring of the site.

Secondary Reporting Observations:

1. SLD Visualization: Even in 8.1.0, the Single Line Diagram tool does not render symbols for the battery or the DC-DC converters (chargers), making it difficult to present the architecture to stakeholders within the report.
2. System Overview: The chargers (Dynapower DPS-500) are omitted from the primary System Overview tab, which focuses only on the grid-feeding inverters.

Questions for the Community/Developers:

• Is there a workaround to "un-assign" a specific sub-array from the DC-coupled storage bus within the same variant?
• If we must run two separate projects and combine the hourly data in Excel to respect the 2.49 MW POI limit, how can we best account for the shared "Grid Power Limitation" within PVsyst’s energy management logic?

Any insights on how to handle this "Hybrid" Path 1/Path 2 architecture would be greatly appreciated.

[Robin Vincent]

Dear Nikhil Lokhande

Thanks for your feedback! As you correctly analyzed, the battery is currently shared across the whole system, between the final MV transformer and the injection point.

You could find some very far-fetched workaround (splitting your system into two variants and upscaling your inverters so as to not clip and use a variable grid limitation to reintroduce the clipping after the battery), but I'm not sure about the reliability of the results you may obtain that way.

We have planned for more options in terms of battery connection, but it won't be before the next major version at the very least. 

 

Secondary Reporting Observations:

SLD Visualization: 

The single loss diagram is currently under heavy rework and should be available in the next major version.

 

System Overview: The chargers (Dynapower DPS-500) are omitted from the primary System Overview tab, which focuses only on the grid-feeding inverters.

As mentioned, the battery can only be set on the AC side for the moment, so it is not possible to simulate a system with DC-DC converters. 

 

Questions for the Community/Developers:

• Is there a workaround to "un-assign" a specific sub-array from the DC-coupled storage bus within the same variant? : Not for the moment (DC coupling is not possible either)

• If we must run two separate projects and combine the hourly data in Excel to respect the 2.49 MW POI limit, how can we best account for the shared "Grid Power Limitation" within PVsyst’s energy management logic?

When applying the grid limitation to individual inverters during the simulation, PVsyst is dispatching the total value based on the estimated AC power of each inverter.

You could reproduce a similar strategy if you split your system into two variants. 

• run the two variants without grid limitation
• Compute the relative production of each system
• Compute the grid limit for each system at each time step based on the total grid limit and the relative production
• Use the possibility introduced with PVsyst 8.1 to import a time series for the grid limitation

• Run the simulation again with the grid limitation activated.

You can also create alternative strategies to reflect your system behavior if needed (e.g : prioritize one side of the system for example).