Before learning the working principle of a grid-tied PV inverter, you need to learn the basic function of a PV inverter. What is it? It functions to convert direct current into alternating current. Where does the direct current come from? It comes from the solar panels that absorb sunlight and turns it to direct current which a common family using alternating current cannot use. Thus, an inverter comes into use. The principle of a grid-tied inverter is similar to that of a common inverter.
The direct current generated by these solar panels is fed to an inverter. In daytime the solar modules generate solar electricity and keep feeding the inverter. As this happens the solar inverter directs the generated electricity to the household electrical loads or is fed to the grid.
The amount of electricity generated depends on the quality of sunlight. If your system produces more electricity than you need, the remained electricity will be directed to the utility grid. If you require more power than the power produced, the extra electricity will be drawn from the utility grid. Thus the utility grid serves as an infinite battery back-up for your system.
At the DC side of the system the power output of a module depends on the voltage. So by varying the voltage and the current the maximum power point can be found. Therefore, most inverters grid- tied or off-grid include a Maximum Power Point Tracking system.
At the AC side the grid interactive inverter supplies power in the sinusoidal form. The frequency of the power generated must be synchronized with the grid frequency. The feed in voltage must not be greater than that of the grid voltage.
On the occurrence of a power outage in the electricity grid, the grid-tied inverter is shut down. This shut-down ensures the safety of the service personnel who is responsible for the problem of power outage. Each grid interactive inverter must have this feature as mentioned in the National Electricity Code (NEC). This feature of autonomy is a key differentiating factor between solar inverters and grid tied PV inverters.
The quality of an inverter is essentially decided by its efficiency, which guarantees how much electricity can be finally generated and how much money one can finally earn by using the solar power system. The highest conversion efficiency is 98.5%, and the highest conversion efficiency of a micro grid-tied inverter is 96.5% or so.