In all grid-connected solar systems, the PV module array is connected to a PV inverter which converts direct current (DC) electricity from the PV modules into alternating current (AC) electricity.
PV inverters convert the DC electricity from PV modules to AC electricity. This AC electricity is then either consumed directly in the building or fed into the national electric grid.
The power (W) rating of the inverter needs to match the peak power rating (Wp) of the PV module array to which it is connected. However, many other parameters also need to be taken into consideration.
If the grid is ‘off’ (down or not available), the PV inverter stops producing electricity. This is for safety reasons. When the gird comes back ‘on’ (available again), the system automatically starts producing electricity again (during the day).
The inverter output is usually connected to a meter which records the amount of energy being fed into the grid. PV inverter efficiencies are very high, greater than 90%.
There are two general categories of PV inverters:
- String inverters, which are connect to individual PV module arrays. Larger solar systems will have several of these inverters.
- Central inverters, which are connected to many large PV arrays. These are used on large solar power plants.
Since inverters incorporate electronic components they can fail.