What is a power inverter?
A power inverter or inverter is a device that can transform Direct Current (DC) to Alternating Current (AC) using switching, transformers and control circuits. And this is the basic purpose of any inverter: be it solar or normal inverter. A home UPS or normal inverter takes the DC power from the batteries and converts it to AC power used by appliances. A solar inverter also works same if it is an ‘Off Grid’ solar power system. In case of ‘Grid Connected’ the DC power is from the solar panels and AC power is given to the grid.
Operation of a Home UPS/ Inverter
A normal home inverter system has a system of inverter and batteries that is connected to the home power connection. When the power is coming from the grid or network, the inverter scheme charges the batteries using the power coming from the grid or network. When the power is cut off, the inverter takes the DC power from the batteries and converts it into AC used by appliances. There is an automatic control in the system that intellects if the grid is not supplying power and switches the UPS or inverter into battery mode.
Operation of an Off Grid Solar Powered system
The assembly used for an off grid solar powered systems are solar panels, charge controller, batteries, inverter and load which is shown in the figure. The batteries are charged by solar panels and the inverter converts DC to AC. It can also have an automatic control to sense if grid is not supplying power that can change the power source of the connected home from grid to batteries.
Depending on the need the system can be designed to:
1) To fully depend on solar power
2) Charge the batteries from solar power when sun is available and use power from the grid when power is not available from solar.
A present home Inverter system can be converted to be used with an off grid powered system by just adding a switch which can control the change source: solar or grid (based on accessibility).
Operation of a Grid Connected Solar Power System
A grid connected solar power system furthermore supplies additional electricity to the grid. If there is enough space to install solar powered system, we go for this kind of system and they can retail the extra electricity generated back to the electricity distribution company.
The function of the inverter in this kind of system is also to convert DC (produced from Solar Panel) to AC. But it furthermore wants a MPPT (Maximum Power Point Tracking) feature to be built in it. As the voltage produced by Solar Panel varies depending on the temperature and obtainability of sun, MPPT allows solar inverters to draw maximum power from the solar panels. The solar inverter used for grid-connected result also comprises an anti-islanding functionality to prevent risks to grid in case there is power failure in the grid.