Limiting your grid feed-in with the zero-export functionality
Feeding your surplus solar power back into the grid is becoming less and less self-evident. Until recently, the net metering system ensured that all generated solar power had the same value, whether it was used in the home or not. But that system is starting to change bit by bit, due to things like feed-in costs or negative electricity prices. In addition, in some places the power grid is saturated, which means that grid operators don't allow feed-in on their grids at those locations. How does limiting feed-in power work and what are the options that Zonnefabriek can offer?
Feedback loop
In order to be able to limit your feed-in to the grid, the inverter(s) must know what is happening at the grid connection point, in other words: at the main connection in the distribution board. As long as all generated power is used within the home or business, there is no feed-in at the grid connection point, and nothing needs to be regulated. But as soon as there is a risk of power being fed back into the grid at the grid connection point, the inverter(s) must immediately receive a signal to adjust their production. If there are batteries in the installation, the excess power can be pumped into them, but if there are no batteries or the batteries are full, the inverter must reduce generation. A constant feedback loop between the grid connection point and the inverter ensures that the inverter's production ramps down very quickly to match consumption, in order to avoid any energy leaking towards the grid.
Constant feedback of information between the grid connection point and the inverter(s) ensures that solar power production never exceeds consumption in the home
It would be useful if the inverters could communicate directly with the grid operator's smart meter: after all, that one is situated at the grid connection point and measures consumption and feed-in at all times. However, it turns out that the information from the smart meter (via the so-called 'P1 port') is not fast enough for many systems to adjust the inverter(s) in time. That's why an extra kWh meter is almost always necessary just behind the main breaker in the distribution board, that communicates with the inverter(s).
In SMA systems, it's usually a Sunny Home Manager that fulfils the role of meter at the grid connection point. The Sunny Home Manager is the 'boss' in the system, and can ramp the power from the inverter(s) in the home up or down if necessary. For SolarEdge systems, a separate RS485 kWh meter or 'inline' meter is required.
How can you set up zero-export (no grid feed-in) for your solar panels yourself?
For SMA systems, the feed-in limitation is set via the monitoring platform ennexOS or via the classic Sunny Portal (but not via the SMA Energy App). Don't forget that a Sunny Home Manager or SMA Energy Meter must be present in the installation in order to use this functionality. For SolarEdge systems, the SolarEdge 'SetApp' is used. Below, we explain the steps for each type of system.
Go to ‘Configuration’ by clicking on the cog wheel icon, and then to ‘Grid management service’. The option ‘User-defined limitation of active power’ appears. This is usually still set to ‘Off’. Click on the pencil icon to change the setting. You can choose ‘zero export’, i.e. no grid feed-in at all, or else a limitation to a certain upper limit (in kiloWatts). Don’t forget to click on ‘save’.
N.B.: If the system continues to feed in to the grid despite this setting, the inverter probably still needs to be ‘told’ that the Sunny Home Manager can control it. First check whether the parameter in question is set correctly by clicking on Configuration in ennexOS and then on ‘Device management’. You will then see a list of your SMA products. The Sunny Home manager is usually at the top and 1 or more inverters are hanging below it. Click on the inverter. You will now end up in the dashboard of the inverter. Click on Configuration again and then on ‘Parameters’. In the search bar you can search for the parameter we are looking for: it is called ‘Operating mode active power setting’. If all is well, it is set to ‘External active power setpoint’. However, if this value is set to ‘Off’, the inverter cannot be controlled properly by the Sunny Home Manager. In that case, follow these steps.
Click on ‘Configuration’ and then on ‘PV system properties’. Then click on the 'parameters' tab. You will immediately see the heading ‘Limiting of the active power feed-in’. This is usually set to ‘no limiting of the active power feed-in’.
To change this, scroll all the way down on the page to the ‘edit’ button. You can then adjust feed-in limitation to, for example, 0 kW or 0 %. Don’t forget to scroll down again and click ‘save’.
N.B.: If the system still feeds back into the grid despite this setting, the inverter probably needs to be ‘told’ that the Sunny Home Manager can control it. Especially in the STPSE, it may happen that the setting ‘Operating mode active power setting’ is set to ‘Off’ ; in that case, the inverter cannot be controlled properly by the Sunny Home Manager. To fix that, try following these steps.
To enable zero-export with SolarEdge, either an RS485-connected meter must be installed at the grid connection point, or the SolarEdge inline meter which can also communicate wirelessly. Setting up zero-export is done via SetApp, a special SolarEdge app for installers. More information can be found in this document and in this YouTube video.
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In ennexOS
Go to ‘Configuration’ by clicking on the cog wheel icon, and then to ‘Grid management service’. The option ‘User-defined limitation of active power’ appears. This is usually still set to ‘Off’. Click on the pencil icon to change the setting. You can choose ‘zero export’, i.e. no grid feed-in at all, or else a limitation to a certain upper limit (in kiloWatts). Don’t forget to click on ‘save’.
N.B.: If the system continues to feed in to the grid despite this setting, the inverter probably still needs to be ‘told’ that the Sunny Home Manager can control it. First check whether the parameter in question is set correctly by clicking on Configuration in ennexOS and then on ‘Device management’. You will then see a list of your SMA products. The Sunny Home manager is usually at the top and 1 or more inverters are hanging below it. Click on the inverter. You will now end up in the dashboard of the inverter. Click on Configuration again and then on ‘Parameters’. In the search bar you can search for the parameter we are looking for: it is called ‘Operating mode active power setting’. If all is well, it is set to ‘External active power setpoint’. However, if this value is set to ‘Off’, the inverter cannot be controlled properly by the Sunny Home Manager. In that case, follow these steps.
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In the 'classic' Sunny Portal
Click on ‘Configuration’ and then on ‘PV system properties’. Then click on the 'parameters' tab. You will immediately see the heading ‘Limiting of the active power feed-in’. This is usually set to ‘no limiting of the active power feed-in’.
To change this, scroll all the way down on the page to the ‘edit’ button. You can then adjust feed-in limitation to, for example, 0 kW or 0 %. Don’t forget to scroll down again and click ‘save’.
N.B.: If the system still feeds back into the grid despite this setting, the inverter probably needs to be ‘told’ that the Sunny Home Manager can control it. Especially in the STPSE, it may happen that the setting ‘Operating mode active power setting’ is set to ‘Off’ ; in that case, the inverter cannot be controlled properly by the Sunny Home Manager. To fix that, try following these steps.
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SolarEdge
To enable zero-export with SolarEdge, either an RS485-connected meter must be installed at the grid connection point, or the SolarEdge inline meter which can also communicate wirelessly. Setting up zero-export is done via SetApp, a special SolarEdge app for installers. More information can be found in this document and in this YouTube video.
With the above steps you can make sure that your solar power system only produces power for your own consumption. In most cases this is a bit of a waste, because you throw away some of your yield. It is nice to know that it is possible, and how to set it up, but in most cases we do not recommend setting it up this way!
Explainer: How is an inverter able to reduce the solar power generation?
The fact that inverters can reduce their production is due to the ‘MPP trackers’ in the devices. By slightly increasing the voltage on the strings, the inverter pushes the power slightly away from the ‘Maximum Power Point’ (MPP); as a result, slightly less energy is extracted from the solar panels. The result is that hopefully no more feed-in is measured at the grid connection point; if there is still too much production or if there is suddenly extra consumption in the home, the feedback loop ensures that the inverter power can be ramped up or down very quickly.
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