Solar inverters are electronic devices that act as the brain of solar energy systems. Their original and main function is to take the direct current (DC) generated by solar panels and convert it into alternating current (AC), to either be fed into the grid or used in the home.
The second important function of the inverter is the maximum power point tracking (MPPT). This function is basically an algorithm that is responsible for finding the point at which the maximum amount of power can be generated from all the PV panels in a single string. However, over the years, the inverter’s role has expanded and today they are responsible for many other functions, such as safety, communications, monitoring, smart energy management, and more.
There are three basic types of inverters: basic string inverters, micro-inverters, and DC-optimised inverters.
String inverters were the industry standard for residential solar energy systems until recently. True to their name, string inverters track the maximum power point function at the string level. This means that if one panel has decreased performance, it will pull down the performance of all the other panels in that string.
Micro-inverters are shrunken down inverters and placed behind each panel. With micro-inverters both the DC/AC conversion and MPPT take place at the panel level. This allows the harnessing of more solar energy, increased safety, some more design flexibility, and panel-level monitoring. The drawback to this option is that it requires placing sensitive electronics that are needed for DC/AC conversion on the roof, which can increase the need for maintenance.
DC-optimised inverters were introduced to the market a bit under ten years ago and are quickly becoming the new industry gold standard. This type of system separates the inverter's functionality. The DC/AC conversion is kept at the system level, but the MPPT tracking is moved to panel level. This means that each panel can perform at its highest possible point.
By moving the MPPT to the panel level, DC optimized inverters offer a number of advantages:
- There is a lot more flexibility in how the system can be designed (more panels can be added on the roof and more roof types can support solar).
- High definition monitoring down to the panel level.
- Increased safety as the DC voltage can be decreased to safe levels during maintenance or during emergency situations.