Limit PV during negative import rates

[mpi]

Hi all,

I’m trying to implement the following scenario and could use some guidance.

In Poland, on certain holidays, we occasionally get negative import electricity prices (while export prices remain at zero). My goal is to take advantage of this by prioritizing grid consumption during those windows instead of using PV or battery.

So far, I’ve managed to adjust the SolaX Remote Control Mode 8 script to limit PV output (via maxPvPower var) during the negative price window, which works as expected. However, I’m running into a problem earlier in the day:

By the time the negative price window starts, my battery is already fully charged from morning PV generation. As a result, I can’t take advantage of cheap (negative-priced) grid energy because there’s no capacity left in the battery.

What I’m looking for is a way for Predbat to:

• anticipate a future negative price window
• limit or delay PV charging earlier in the day
• keep battery capacity available so it can be charged from the grid during that negative price period

Below is an example plan for such a day. As you can see, the battery reaches 100% before the negative price slot begins.

Has anyone implemented a similar strategy, or is there a recommended way to achieve this behavior in Predbat?

Thanks in advance!

[gcoan]

One gap in predbat's planning functionality is that it plans all solar charging will be at full rate. You can set a slow rate charge (e.g. for overnight grid charging) but this isn't used for solar charging unfortunately.

I manage similar things in the UK, in my case to slow down/stop charging the battery until later in the day to reduce clipping

There's a few things you can do in an automation alongside predbat which is how I handle it

1. turning switch.predbat_set_freeze_export_during_demand on will overwrite any planned demand slots and turn them to freeze export, thus exporting all solar. I use this overnight to stop the inverters cross charging but also at the start of the day to prevent early battery charging

2. set the battery charge rate using select.predbat_manual_api to a low value. I use zero to stop charging or a low value to trickle charge the battery

3. use select.predbat_manual_xxx to manually overwrite the planned behaviour for certain slots, e.g. to freeze export