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Solar inverters can be divided into square wave inverters, ladder wave inverters and sine wave inverters according to different output waveforms.

(1) Square wave inverter

The AC voltage waveform output by the square wave inverter is a square wave. The inverter circuit used by this type of inverter is not exactly the same, but the common feature is that the circuit is relatively simple and the number of power switch tubes used is very small. The design power is generally between 100 watts and 1000 watts. The advantages of the square wave inverter are: simple circuit, cheap price, and easy maintenance. The disadvantage is that because the square wave voltage contains a large number of high-order harmonics, additional losses will occur in load appliances with iron core inductors or transformers, which will interfere with radios and some communication equipment. In addition, this type of inverter has the disadvantages of not wide enough voltage regulation range, not perfect protection function, and relatively large noise.

(2) Ladder wave inverter

The AC voltage waveform output by this type of inverter is a step wave, and there are many different lines for the inverter to realize the step wave output, and the number of steps of the output waveform varies greatly. The advantage of the ladder wave inverter is that the output waveform is significantly improved compared with the square wave, and the content of high-order harmonics is reduced. When the ladder reaches more than 17, the output waveform can achieve a quasi-sine wave. When using transformerless output, the efficiency of the whole machine is very high. The disadvantage is that the ladder wave superposition circuit uses more power switch tubes, and some of the circuit forms also require multiple sets of DC power input. This brings troubles to the grouping and wiring of the solar cell phalanx and the balanced charging of the storage battery. In addition, the ladder wave voltage still has some high-frequency interference to radios and some communication equipment.

(3) Sine wave inverter

The AC voltage waveform output by the sine wave inverter is a sine wave. The advantage of the sine wave inverter is that the output waveform is good, the distortion is very low, the interference to the radio and equipment is small, and the noise is low. In addition, the protection function is complete, and the efficiency of the whole machine is high. The disadvantages are: the circuit is relatively complicated, the maintenance technology is high, and the price is relatively expensive.

The classification of the above three types of solar inverters is helpful for photovoltaic system and wind power system designers and users to identify and select inverters. In fact, inverters with the same waveform still have great differences in circuit principles, devices used and control methods.