Comparison of sine wave inverter and modified wave inverter

【Abstract】：

  In the solar power generation system, the inverter is one of the important components. Simply put, an inverter is a device that converts low voltage (12V/24V/48V) DC into 220V AC. In fact, the inverter output waveform can be divided into modified wave inverter and sine wave inverter. The following compares the modified sine wave inverter and the sine wave inverter in order to distinguish their differences:

【Main body】：

1. Comparison of output waveforms from modified sine wave inverter and sine wave inverter:

     The traditional modified wave inverter is produced by stepwise superposition of square wave voltage. This method has complicated control circuits, more power switch tubes used in superimposed lines, and larger volume and weight of the inverter. Many problems. In recent years, with the rapid development of power electronics technology, the PWM pulse width modulation method has been widely used to generate the corrected wave output.

     The output waveform of the sine wave inverter is a complete sine wave with low distortion rate, so there is no interference to radio and communication equipment, the noise is also very low, the protection function is complete, and the overall efficiency is high. The reason why the sine wave inverter can output a complete sine wave is because it adopts SPWM technology, which is more advanced than PWM technology.

2. Compare the internal circuits of the modified wave inverter and the sine wave inverter:

The sine wave inverter and the modified wave inverter also differ greatly in their internal circuits. First of all, the sine wave inverter must require software control and inductance and capacitance modulation due to the problem of waveform modulation. Therefore, a single-chip microcomputer and an inductor are required in the sine wave inverter, which is obvious at a glance. The technical difficulty is far higher than that of the modified sine wave inverter. As a result, the price of sine wave inverters is much higher than that of modified wave inverters.

3. Compare the advantages of modified wave inverter and sine wave inverter:

Modified Sine Wave Inverter:

① The output waveform is significantly improved compared to the square wave, and the content of higher harmonics is reduced. When the number of steps reaches more than 17, the output waveform can realize a quasi-sine wave.

②When using transformerless output, the efficiency of the whole machine is very high.

Sine wave inverter:

①The output waveform is good, and the distortion is very low. The output waveform is basically the same as the AC waveform of the mains power grid. In fact, the AC power provided by a fine sine wave inverter is higher in quality than the grid.

②The sine wave inverter has little interference to radios, communication equipment and precision equipment, low noise, strong load adaptability, and can meet all AC load applications

③Complete protection functions, high efficiency of the whole machine.

4. Compare the shortcomings of the modified sine wave inverter and the sine wave inverter:

Modified Sine Wave Inverter:

① There are many power switch tubes used in stepped wave superposition lines, some of which require multiple sets of DC power inputs. This brings trouble to the grouping and wiring of the solar cell array and the equalization of the battery.

②The step wave voltage still has some high-frequency interference to the radio and some communication equipment.

Sine wave inverter:

①The line is relatively complicated

②High requirements for maintenance technology

③The price is more expensive.

【Conclusion】：

  In general, the modified sine wave inverter and the sine wave inverter each have their own advantages and disadvantages, and they need to be purchased according to their actual needs. Modified sine wave inverters have been widely used in user systems in remote areas, because these user systems do not require high power quality, and modified inverters are suitable for resistive electrical loads. The AC power provided by the sine wave inverter is of higher quality than the grid. In the solar power generation system, in order to avoid power pollution to the public grid, a sine wave inverter must also be used. For equipment with high quality and requirements, of course, sine wave inverters are used.