What is a Power Inverter?

A power inverter, or inverter, is an electronic device or circuitry that changes direct current (DC) to alternating current (AC).[1]
The function of an Inverter is to change the Dc input to a symmetrical AC voltage of desired magnitude and frequency. The output voltage could be fixed or variable at a fixed or variable frequency. A variable output can be obtained by varying the DC input voltage and maintaining the gain of the inverter constant.[2]
Voltage and current waveforms produced by inverters are never perfect sinusoids (even for sine wave inverters); therefore some harmonic currents are expected during normal system operation. Total harmonic distortion (THD) is a measure of the harmonic content in current and voltage waveform. The type of inverter used will depend on the load that it will serve. Resistive loads could tolerate square wave inverters which are cheaper and easier to develop. Motors and sensitive electronics will need inverters that are able to produce almost perfect sinusoidal voltage and current waveforms in order to operate correctly. These tend to be more expensive and difficult to design. The designer should choose inverters according to load types and power requirements.
In the photovoltaic industry, inverters can be classified into two broad categories:

1) Stand-Alone Inverters
These inverters are meant to operate isolated from the electrical distribution network (off-grid) and require batteries for proper operation. The batteries provide a constant voltage source at the DC input of the inverter.

2) Grid-Tied Inverters
These inverters operate coupled to the electrical distribution network and therefore must be able to produce almost perfect sinusoidal voltages and currents.

In our project, the PV System...

... middle of paper ...

... which potentially leads to low manufacturing cost and low retail prices. This technology is also very appropriate for residential applications with low power requirements and where partial shading is a critical issue. This type of inverter is also designed with a “plug and play” feature so that it can be installed without a deep electrical knowledge. However, if implemented by a big number for industrial applications, due to the distributed installation, the maintenance requirements can increase the cost and discourage wide usage. To keep inverter boxes watertight and use components that have large temperature ambient is major concerns. It will be necessary to develop a system that can detect failure of any micro-inverter and isolate it immediately. This type of inverter has recently become emerging product and promised a remarkable market share in future.