Output Waveform Classification Of Solar Inverters

(1) Square wave inverter
The AC voltage waveform output by the square wave inverter is a square wave. The inverter circuits used in this type of inverter are not entirely the same, but the common feature is that the circuit is relatively simple and the number of power switches used is very small. The design power is generally between 100 watts and kilowatts. The advantages of square wave inverters are: simple circuit, cheap price, and convenient maintenance. The disadvantage is that the square wave voltage contains a large amount of higher-order harmonics, which will generate additional losses in load appliances with iron core inductors or transformers, causing interference to radios and certain communication equipment. In addition, this type of inverter also has drawbacks such as insufficient voltage regulation range, incomplete protection function, and high noise.
(2) Stepped wave inverter
The AC voltage waveform output by this type of inverter is a stepped wave, and there are also various circuits for the inverter to achieve stepped wave output, with significant differences in the number of steps in the output waveform. The advantage of a stepped wave inverter is that the output waveform is significantly improved compared to a square wave, and the content of higher harmonics is reduced. When the number of steps reaches 17 or more, the output waveform can achieve quasi sine wave. When using transformer free output, the overall efficiency is very high. The disadvantage is that the stepped wave superposition circuit uses more power switches, and some circuit forms also require multiple sets of DC power inputs. This brings trouble to the grouping and wiring of the solar cell array and the balanced charging of the battery. In addition, the stepped wave voltage still has some high-frequency interference on radios and certain communication devices.
(3) Sine wave inverter
The AC voltage waveform output by the sine wave inverter is a sine wave. The advantages of a sine wave inverter are good output waveform, low distortion, low interference with radios and equipment, and low noise. In addition, the protection function is complete and the overall efficiency is high. The disadvantage is that the circuit is relatively complex, requires high maintenance techniques, and is expensive.
The classification of the three types of inverters mentioned above is beneficial for designers and users of photovoltaic and wind power generation systems to identify and select inverters. In fact, inverters with the same waveform still have significant differences in circuit principles, components used, and control methods.