With the energy transition underway, the number of photovoltaic installations is rising all the time. This is excellent news, to the point of saturating the electricity grid in certain districts and causing what is known as "stalling" of certain inverters. We tell you all about it.
Le décrochage des onduleurs : Un but de protection
The inverter is the device that links your solar panels to your home's electricity grid. Its main role is to transform the electricity arriving from the panels in the form of "direct" current into "alternating" current that can be used in the house. During this transformation, the inverter checks that the alternating current complies with a series of parameters to avoid disrupting the electricity grid and damaging your electrical appliances. It is mainly for this purpose of protection that the inverter may decouple.
In Belgium, electrical devices are designed to operate at 230 volts. The aim of the grid operators is to keep the grid as close as possible to this value at all times. In practice, with or without a solar panel, this value fluctuates constantly and is never exactly 230 volts, but it is never very close either. If the voltage fluctuates significantly, the risk would be that your electrical appliances could be damaged or even put out of service.
Let the sun shine 🎶
Let's get back to the panels now: when the sun shines, current is generated, the inverter converts it and now has to feed it into the grid. This stage requires a certain amount of "effort": the inverter must succeed in injecting its current into the grid and not the other way round. It must therefore be "stronger", i.e. have a slightly higher voltage to ensure that it is its current that goes to the grid. As long as there is only one photovoltaic installation on the grid, this increase remains very moderate. But when there are 5? 10? 15? That's when problems generally appear.
With a large number of installations on the grid, the voltage can rise significantly. As we saw earlier, if the voltage rises uncontrolled, damage can occur. Standards have therefore been created and incorporated into the operation of inverters: they must constantly measure the network voltage and comply with these 2 conditions :
- Maximum instantaneous voltage: 264.5 volts
- Maximum average voltage over 10 minutes: 253 volts
As soon as one of these two limits is reached, the inverter must disconnect from the grid and stop producing. This is the famous " decoupling ".
Decoupling is therefore ultimately a protective measure, which is normal and useful. Unfortunately, it also undermines the profitability of producers. Find out here in our article dedicated to network overvoltages.
Do you have a question about decoupling inverters ?