How can DC power be converted into AC power?

Photovoltaic modules produce DC power, but almost all the appliances we use in daily life are designed for AC power, so we have to convert DC power to AC power through an inverter. An inverter is the core of the PV system, controlling the efficiency of the PV power plant. So, how does an inverter do this job?

What is DC and AC?

First of all, we need to understand what is DC and AC.

Direct current (DC): An electric current whose electromotive force, voltage, or direction of current does not change periodically with time.

Alternating current (AC): An electric current whose electromotive force, voltage, or direction of current varies periodically with time.

Direct current

How is DC converted to AC?

The working principle of the inverter can be divided into three parts: 1)DC can be changed into AC through the oscillating circuit; 2)the AC obtained is then boosted through the coil; 3)the boosted AC is rectified to obtain a sine wave.

Schematic diagram

electric current

When the green switch is pressed, the waveform is as follows.

DC power

A waveform in the opposite direction is obtained when the yellow switch is pressed.


If you keep switching on and off, DC becomes AC, but this is square-wave AC. It can’t carry capacities and inductive loads because its waveform is not smooth and the voltage keeps changing abruptly, which will seriously affect the life of the appliances.

Photovoltaic modules

So you need to convert the square-wave AC to sinusoidal AC by adding more switches, at which point its average value is close to sinusoidal AC.

PV system

Finally, a simple way to smooth the waveform is to add capacitors. A capacitor is equivalent to a reservoir, which can store the intermittent flow of water, and then smoothly release it so that the square-wave AC becomes sinusoidal AC.

DC power

Different inverters have different conversion efficiencies
Inverters convert DC power into AC power, but the conversion efficiency varies.
In most cases, factors such as power loss may affect the conversion efficiency of the inverter, which may lead to changes in the power generation revenue of the PV plant.

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