Why Does My HMS-2000-4T Inverter Limit Each PV Module to a fixed value?

[moritzabcde]

Hi everyone!

I'm new to OpenDTU and I'm not sure if this is intended behavior. I have an HMS-2000-4T, with a 460 W PV module connected to each of its four strings/MPPTs. The entire system is limited to 800 W. Two modules are oriented towards the southeast, and two towards the southwest.

At midday, the system reaches 800 W. However, I thought that even in the morning and afternoon, with two well-illuminated PV modules, 800 W could still be generated, as they could theoretically produce 920 W together. But the inverter limits each module to a maximum of 215 W. The power curve rises as sunlight increases but then caps at 215 W per module (see attached picture).

Did I misconfigure the DTU? Is there any way to change this behavior?

Thanks a lot for your help!

[ms49434]

What you see is the default behaviour of the Hoymiles inverter. If the inverter is limited to 800 W, the Hoymiles throttles each string to 800 W / 4 + 2 % = 204 W. You can solve the issue with PDL (Power Distribution Logic) which is available from firmware version 1.1.12 onwards. You need a Hoymiles DTU and an installer account to be able to request a firmware update of your inverter at Hoymiles.

[Anton-Le]

Thanks for the info! I've been wondering about the same thing with my HM600 where I have a 430W module on one strand and 2 fairly bad flexible ones that should reach 300 Wp on the other but never reach even 200 W.

But applying your suggested formula should limit the input per string to 600 / 2 + 0,02*300 = 306 W, whereas the cutoff appears to actually be 320.4 W sharp (or 74.51 % irradiation).

As for the FW version: Is there a way of checking it without getting the HM DTU?

[ms49434]

OpenDTU can show the firmware version. On the Live View page, select the inverter and click on button "Show Inverter Info".
DC input power is not the same as AC output power due to conversion and operating losses. It should only give you an indication of what you can expect from the inverter.
Please check the voltage and current specification of your flex modules. It could be that these modules are low voltage models and therefore don't play nice with the Hoymiles.

[moritzabcde]

Thank you for your help!
It took some time for support to upgrade my firmware to 2.0.4, but it worked in the end. The Power Distribution Logic is now marked as supported, and my inverter delivers a much more consistent output—reaching the 800W maximum more reliably.

However, it still seems a bit slow when switching between strings. I've attached another screenshot to illustrate the issue (The red string does not increase as the green and yellow strings decline). It looks like this is a firmware-related problem, rather than something caused by openDTU.

[Humbatze]

Hi,
I'm new to the group and recently became the proud owner of an openDTU. First of all, a big thank you to the developers of openDTU.
I'm also struggling with the issue of power reduction. I understand that it's not customizable with OpenDTU, but I wanted to investigate this further, since you can actually do this in the "limit setting" screen. But unfortunately, it doesn't work at all??
Thanks in advance

[ms49434]

Hi, I'm new to the group and recently became the proud owner of an openDTU. First of all, a big thank you to the developers of openDTU. I'm also struggling with the issue of power reduction. I understand that it's not customizable with OpenDTU, but I wanted to investigate this further, since you can actually do this in the "limit setting" screen. But unfortunately, it doesn't work at all?? Thanks in advance

§1: Do not hijack somebody else's discussion.
The answer to your question is that you can throttle the power output of a supported hoymiles inverter with OpenDTU, temporarily or permanently.

[Humbatze]

Thank´s for the info.
I always got the info in the status line after permanently adjusting to 100 % "Aktuelles Limit: 800 W | 50,0 %"
("Aktuelles Limit: 1600 W / 100 %" popped up for a short time only)
Today (sunny wether) I jumped over the 50 % power output and it seems to work. But the 50 % is still displayed ?