What is the working principle of photovoltaic inverters?

Update:2020-09-10
Abstract:

Photovoltaic inverters are also called power regulators […]

Photovoltaic inverters are also called power regulators. According to their use in photovoltaic power generation systems, they can be divided into independent power supplies and grid-connected ones. According to the waveform modulation mode, it can be divided into square wave inverter, step wave inverter, sine wave inverter and combined three-phase inverter. The inverters used in grid-connected systems can be divided into transformer-type inverters and transformer-less inverters according to the presence or absence of transformers. An inverter is a power adjustment device composed of semiconductor devices, which is mainly used to convert DC power into AC power. Generally consists of a boost circuit and an inverter bridge circuit. The boost circuit boosts the DC voltage of the solar cell to the DC voltage required by the inverter output control; the inverter bridge circuit converts the boosted DC voltage into an AC voltage of common frequency equivalently. The inverter is mainly composed of switching elements such as transistors, and the switching elements are regularly turned on-off (ON-OFF) to turn the DC input into an AC output. Of course, such an inverter output waveform generated purely by an on and off loop is not practical. Generally, it is necessary to use high-frequency pulse width modulation (SPWM) to narrow the voltage width near the two ends of the sine wave, widen the voltage width at the center of the sine wave, and always make the switching element move in one direction at a certain frequency within a half cycle. A pulse wave train (quasi-sine wave). Then let the pulse wave pass through a simple filter to form a sine wave.
power inverter