Increase of self-consumption and zero feed-in export

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arianitz asked Jun 30, '20

Increase of self-consumption and zero feed-in export

Hi,

I have a solar kit which is supposed to increase self-consumption of energy and to supply the electricity in grid failure, which contains:

1x PV On-Grid (3-phase) inverter Solax X3 MIC 10.0

1x Multi Plus II 48/3000

4x Polyontech US2000 2.4kWh lithium batteries

1xCCGX Victron energy

1x patch cable for connecting battery with ccgx

1xInterface MK3-USB (VE.Bus to USB)

1xRS485 to USB interface

1xRJ45 3m patch cable

1xRJ45 10m patch cable

1xET340 energy meter

36 Trina PV modules of 280Wp

DC cables, dc breakers, mounting construction etc.

I wanted to know if I can use the system for the increase of self-consumption and as a back-up supply, where the PV on-grid inverter and the battery inverter does not feed into the grid.

I'm confused because we have only one energy meter and I don't know how to connect the Multi Plus II and the Solax On-Grid inverter to that energy meter.

Can someone help?

Multiplus-II ESS

2 |3000

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Modifications Space

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Answer 1 · 2020-07-02T05:45:40Z

dayandnight answered · Jul 02, 2020 at 05:45 AM

Hello @arianitz,

is the energy meter ET340 now already used for communication with the inverter system? I don't know this inverter. What is it doing / controlling in combination with the ET340? To help any way further it is necessary to know more about your current installation. This listed components are installed? How?

To guess a little bit: The components you listed looks like for an ESS system which is able to do exactly what you intend to do. Based on the few infos knowing now, I am afraid that your inverter / ET340 is setup in the same sense as zero feed-in. In combination with an ESS to do the same, there will be conflicts. Who is the master?

Normally an system for zero feed-in checks and controls the flow of energy

from / to the grid
from / to the batteries
from / to the PV system

and regulate that all available PV energy is used by consumers or be used to charge the batteries. In case there is more energy available from the PV system as being used for consumers and charging batteries it has to control down and up the PV system.

So when there are two controlling units doing quite the same, this will be not possible in sense of parallel controlling. There must be only one master controller!

DayAndNight

2 |3000

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Answer 2 · 2020-07-02T14:17:47Z

arianitz answered · Jul 02, 2020 at 02:17 PM

Dear @DayAndNight,

Thank you for your reply.

I have not yet installed the system. These goods were as the scope of delivery of a client of mine, where he has bought them as a complete solar kit.

The only thing that makes me confused is that in this scope of delivery is an on-grid inverter that I can't find any example on the internet with that (Solax inverter).

So, to make more clearer, my confusion is that these two inverters can also feed into the grid, thus to prevent this I have to set zero feed-in conditions in both inverters. The inverter regulates the power limit based on the information that he takes from the energy meter. In the delivery, there is only one energy meter ET340 and before going to install I wanted to make clear all things because the location is much far from my office.

Can I connect in one port of the two existing communication ports at the energy meter an ethernet cable from the Solax inverter to the meter, and one from the meter to the CCGX such that the two inverters have information about the load consumption?

or

Is it possible that the Solax inverter can be connected with CCGX, also the Multiplus II and the energy meter such way that the Solax inverter and the other inverter can take the information about the load consumption?

1

2 |3000

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dayandnight commented · Jul 03, 2020 at 07:50 PM

Hi @arianitz,

I understood what are you want to do. My advice: You need a Victron dealer or another specialist who is on site and is able to give you all neccessary details and help you with a solution. I am not the real "deep" specialist and I can give you here only my personal opinion on your idea, based on my understanding. Here my five cents! ;-)

It is not possible to have two controllers which check how much energy is feed in to the grid. For example when the controller from your inverter get the information there is a feed in to grid it regulates the PV harvest down, it lowers the amount of energy which is produced by PV until there is no more feed in to grid. The Victron GX controller works completely different. In case it detects a feed in to the grid it rises charging the batteries, so it consumes all available energy until there is no longer a feed in to the grid. But it needs all energy what your PV system is able to produce in this moment. But when the controller of your inverter lowers or stops PV harvest there is no energy which can be used for charging the batteries. So one controller directs we go to South the other controller wants to go for North!

Trust me! The only master in an ESS system can be the Victron GX device, not your inverter. The Victron unit has two possibility to control the PV inverter. One is by network communication with the inverter, one is by frequency shift.

I don't know if there is an implementation that the GX device can communicate with your inverter by network. But I am afraid it is not possible!

Frequency shift work somehow like this: In case the batteries are fully charged and your grid consumers need less energy as PV is able to do in this moment the GX device will rise the grid frequency. With higher grid frequency the inverters lowers energy what it is to be feed in direction grid. As higher the grid frequency is as fewer energy is produced from PV. At a certain frequency the PV systems stops completely.

But to do frequency shift it is necessary to do a special installation. The PV system needs to be connected to the AC-Out of the Victron and of course it has to be setup according to the specs. And your inverter has to work with frequency shift.

End of the story: You have to go into all details for such an ESS system and do all necessary investigation on your own and design afterwards a new and different system based on Victrons ESS specs or you look for somebody who can help you locally in front on your location.

Wish you success!

DayAndNight

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