search

NREL / SAM

System Advisor Model (SAM)
BSD 3-Clause "New" or "Revised" License
340 stars 142 forks source link

Add support for PV-battery with DC-connected battery and multiple MPPT inputs: #396

Closed dguittet closed 10 months ago

dguittet commented 4 years ago

Add support for PV-battery with DC-connected battery and multiple MPPT inputs:

https://sam.nrel.gov/forum/forum-general/3160

Originally posted by @cpaulgilman in https://github.com/NREL/SAM/issues/215#issuecomment-693702967

dguittet commented 4 years ago

From https://github.com/NREL/ssc/issues/250 about DC-Connected batteries, we have the configuration for a single-MPPT inverter: image

image

The simplest way to support DC-connected battery with multiple MPPT inputs may be to assume charge controllers for each PV array are connected to the battery, which can then charge from both PV arrays. Each PV array's power can charge the battery or be inverted. The power inverted is the sum of the PV arrays and battery. The rectifier shown in the first diagram is not explicitly modeled currently, but the power passing from the AC bus to the BMS is netted out of the power inverted.

Thoughts and suggestions welcome.

Mermaid markdown code for diagram:

graph LR
PV1[PV Array]-->O1[DC/DC Power Optimizer]
PV2[PV Array]-->O2[DC/DC Power Optimizer]
O1-->I[Inverter]
O2-->I
O1-->BMS[DC/DC Battery Management System]
O2-->BMS
BMS-->I
BMS-->B[Battery]
B-->BMS
I-->AC[AC Bus]
AC-->R[Rectifer]
R-->BMS
AC-->L[Load]
AC-->G[Grid]
cpaulgilman commented 2 years ago

Some additional context:

This revised diagram from help shows how SAM models BTM PV-battery DC-connected systems in a way that is more consistent with SAM's inputs than the older version of the diagram:

image

Feedback from a user (with diagram):

Most residential battery based DC Coupled systems have the DC/DC converter that steps down the 600V to 24-48V and the inverter is then 24-48V based. It would be great to be able to model these types of systems in the future more accurately. Do you think this could be a future possibility?

image

And:

The FRX can dispatch stored energy to loads or to the grid, it should have an arrow that goes both ways too. For the FRX, it is similar to the original diagram I drew. There are charge controllers (CC) , a DC bus , that combines theCC outputs and batteries. The inverter have the capability to provide power to backed-up loads if there was a power outage. Here is a wiring diagram that shows the wiring better:

https://outbackpower.com/downloads/documents/integrated_systems/flexpower_two_fxr/fp2_qsg_na.pdf#page=4

Skybox is similar, but it incorporates the CC into the inverter so that the PV can land within the inverter instead of having a separate CCs:

https://outbackpower.com/downloads/documents/skybox/skybox_qsg.pdf#page=3

cpaulgilman commented 11 months ago

See also https://github.com/NREL/SAM/issues/215