Inverters are essential components of PV systems which convert DC electricity produced by panels to AC electricity to power appliances. They come in various types; central, string and micro.
Individual solar panels are connected in series to form strings in order to get a higher voltage rating. DC power from these strings is then taken to central or string inverters for conversion. Central and String Inverters have been around for a long time. Micro-Inverters made their entry to the solar industry recently.
String Inverters: They are mostly seen in residential PV applications. Depending on the size of the installation, more than one string inverter may be present. When using string inverters, there are multiple smaller inverters for several strings, so the DC power from a few strings runs directly into a string inverter rather than a combiner box and is converted to AC. String inverters are best applicable for systems whose solar arrays have different angles or orientation. Residential rooftops usually don’t have the structural support needed for central inverters. The major advantage of string inverters is that it ensures that the entire system won’t shut down if just a few solar panels are affected.
Central Inverters: Here DC power is taken from each string into a combiner box and from there power is taken to the central inverter to be converted into AC power. Central inverters are usually used for large-scale industrial applications and have larger capacities than string inverters. The initial cost for central inverters is lesser than a system based on string inverters and also has fewer component connections. The disadvantage here is that if the performance of one solar panel connected to a string is affected, the performance of the entire system is affected. It’s more or less like a single point of failure.
Micro Inverters: These are inverters that are attached to each and every solar panel of the PV system. It is a relatively new technology and is expensive when compared to the other inverters. Here they optimize performance for each panel alone, unlike the central inverters. Micro-Inverters are yet to go really popular because of the cost it comes at. The economics of micro-inverters are currently being looked into and it is believed that soon micro-inverters will take over from central inverters in terms of usage.
Thus, as you can see from the above details, which type of inverter is best for you depends on the type of solar power plant you have, the type of performance you are looking for and the costs you are willing to afford.