we have a small solar plant on our workshop that only for self-consumption. The system consists of 17.05kW solar panels, SG20RT inverter, COM1000D logger and a DTSD1352-C/1 (6A) smart meter.
The problem is that when there small loads in the workshop, the inverter feeds energy into the grid. We are forbidden to feed-in any energy. The amount of fed energy is about 0.5-1 kWh per day. And this energy is considered purchased from the grid, as if we consumed because the grid meter is one way only.
I set export control to on - Total Phase Power Control and the Active Power Control to -0.3kW in the logger i.e. to always pull that amount of power from the grid but still the inverter feeds energy into the grid.
Does anyone have experience with this kind of issue?
Hi Konstantin — That is quite annoying, thanks for flagging this, seems like an issue with the hardware on a multi phase install.
I looked into it, my understanding is that the inverter only limits total export across all three phases, not each phase on its own. If your workshop loads are uneven, it can export a little on one phase even when the overall reading looks fine — and on a one-way meter that still counts as bought energy. Leading to small daily exports, like yours, even when settings look correct.
Worth having your installer check meter placement, CT ratio, and that the COM1000D is using closed-loop control with the meter. If phase readings show export on one phase and import on another, that’s likely the cause — and there isn’t a simple fix on this inverter alone.
You could install a third party zero export device, however I doubt it would be worth it. Of course a battery is another option, but does not sound like the direction you want to go.
thank you for your response. By the way I installed and commissioned the photovoltaic system myself. I checked the CTs a few time and everything seems ok with them.
Actually, the SUNGROW support told me that Feed Limitation On Each Phase works only on hybrid inverter but I am allowed to choose it from the data logger device. And it actually works as the inverters produces power using the phase that has the lowest load.
But it still feeds-in some energy into the grid. And it sums to about 15kWh fed into the grid per month, not that low of value, I think.
Do you think that the problem might be in the smart meter device? SUNGROW support assured me that with the COM1000D device, zero-export can be fully achieved.