Application range classification
(1) Ordinary inverter
DC 12V or 24V input, AC 220V, 50Hz output, power from 75W to 5000W, some models have AC and DC conversion, ie UPS function.
(2) Inverter / charging integrated machine
In this type of inverter, the user can use various forms of power to supply the AC load: when there is AC power, use the AC to power the load through the inverter, or charge the battery; when there is no AC, use the battery to supply the AC load . It can be combined with a variety of power sources: batteries, generators, solar panels and wind turbines.
(3) Special inverter for post and telecommunications
Provide high-quality 48V inverter for post and telecommunications, with good quality, high reliability, modular (module 1KW) inverter, and N+1 redundancy function, expandable (power from 2KW to 20KW ).
(4) Aviation and military special inverters
These inverters are 28Vdc input and offer the following AC outputs: 26Vac, 115Vac, 230Vac, with output frequencies of 50Hz, 60Hz and 400Hz, and output power from 30VA to 3500VA. There are also DC-DC converters and inverters for aviation.
Output waveform classification
(1) Square wave inverter
The AC voltage waveform output by the square wave inverter is a square wave. The inverter circuits used in such inverters are also not identical, but the common feature is that the lines are relatively simple and the number of power switches used is small. The design power is typically between one hundred watts and one kilowatt. The advantages of the square wave inverter are: simple circuit, low price and convenient maintenance. The disadvantage is that due to the large number of higher harmonics in the square wave voltage, additional losses will occur in the load consumers with core inductors or transformers, which will interfere with the radio and some communication equipment. In addition, this type of inverter has the disadvantages that the voltage regulation range is not wide enough, the protection function is not perfect, and the noise is relatively large.
(2) Step wave inverter
The AC voltage waveform output by such an inverter is a step wave, and the inverter realizes a step wave output also has a plurality of different lines, and the number of steps of the output waveform varies greatly. The advantage of the step wave inverter is that the output waveform is significantly improved compared with the square wave, and the higher harmonic content is reduced. When the step reaches more than 17, the output waveform can realize the quasi-sine wave. When using a transformerless output, the overall efficiency is high. The disadvantage is that the step wave superposition line uses more power switch tubes, and some of the line forms also require multiple sets of DC power input. This causes trouble for the grouping of the solar cell array and the balanced charging of the wiring and the battery. In addition, the step wave voltage still has some high frequency interference on the radio 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 whole machine is efficient. The disadvantage is that the line is relatively complicated, the maintenance technology is high, and the price is relatively expensive.
The classification of the above three types of inverters is beneficial to the identification and selection of inverters by designers and users of photovoltaic systems and wind power generation systems. In fact, inverters with the same waveform are still very different in terms of line principle, device and control methods, etc.
Other classification methods
1. According to the output AC energy frequency classification, it can be divided into power frequency inverter, intermediate frequency inverter and high frequency inverter. The frequency of the power frequency inverter is 50-60 Hz; the frequency of the intermediate frequency inverter is generally 400 Hz to more than ten kHz; the frequency of the high frequency inverter is generally more than ten kHz to MHz.
2. According to the number of phases of the inverter output, it can be divided into single-phase inverter, three-phase inverter and multi-phase inverter.
3. According to the direction of the output of the inverter, it can be divided into active inverter and passive inverter. The inverter that transmits the electric energy output from the inverter to the industrial power grid is called an active inverter; the inverter that outputs the power output from the inverter to a certain electric load is called a passive inverter. Device.
4. According to the form of the main circuit of the inverter, it can be divided into single-ended inverter, push-pull inverter, half-bridge inverter and full-bridge inverter.
5. According to the type of inverter main switch device, it can be divided into thyristor inverter, transistor inverter, field effect inverter and insulated gate bipolar transistor (IGBT) inverter. It can be classified into two categories: "half-controlled" inverter and "full control" inverter. The former does not have the self-shutdown capability, and the components lose control after being turned on. Therefore, the “half-controlled” common thyristor belongs to this category; the latter has self-shutdown capability, ie, no device. The turn-on and turn-off can be controlled by the control electrode, so it is called "full control type", and the power field effect transistor and the insulated gate dual-weight transistor (IGBT) belong to this category.
6. According to the DC power supply, it can be divided into voltage source inverter (VSI) and current source inverter (CSI). In the former, the DC voltage is nearly constant, and the output voltage is an alternating square wave; the latter, the DC current is nearly constant, and the input current is an alternating square wave.
7, according to the inverter control method, can be divided into frequency modulation (PFM) inverter and pulse width (PWM) inverter.
8. According to the working mode of the inverter switching circuit, it can be divided into resonant inverter, fixed frequency hard switching inverter and fixed frequency soft switching inverter.
9. According to the inverter commutation method, it can be divided into load commutating inverter and self-converting inverter.