A solar inverter is the box that converts the DC electricity from solar panels into the AC electricity that homes and the grid use. It also reports how much power the panels are producing.
Panels give out direct current, which moves in one direction. Homes and the grid use alternating current, which completes 50 full cycles a second in India. So the current reverses 100 times a second. The inverter switches the current electronically to make it alternate at that rate, and it matches the grid's voltage so that the two can be connected safely. This is the main use of the idea explained in AC and DC. Inside the box are power semiconductors, which do the switching.
An inverter also protects people. If the grid fails, the inverter must stop feeding power within a moment. Otherwise a roof system could send power into a line that a lineman believes is dead. For this reason an ordinary rooftop solar system goes off during a power cut, even in bright sun.
For instance, a flat in Hyderabad has a 3-kilowatt rooftop system. The inverter takes DC from the panels, converts it, and feeds the flat's wiring. If the flat uses less power than the roof produces, the extra goes to the grid. The power passes through a smart meter, which counts how much power goes out to the grid and how much comes in from it. The electricity company then credits the exported units on the bill. The inverter can also exchange data with a smart electrical panel inside the home.
Large solar parks use big inverters that each serve hundreds or thousands of panels. The grid operator's energy management system can send them a command to reduce output. Installers use solar design software to choose the size of the inverter. A smaller variant is the microinverter, one for each panel.