Generally, the process of converting AC electrical energy into DC electrical energy is called rectification, the circuit that completes the rectification function is called the rectifier circuit, and the device that realizes the rectification process is called the rectifier equipment or rectifier. Correspondingly, the process of converting direct current energy into AC power is called inverter, the circuit that completes the inverter function is called the inverter circuit, and the device that realizes the inverter process is called the inversor equipment or inverter.
● According to the inverter output phase can be divided into:
(1) single-phase inverter
(2) three-phase inverter
(3) polyphase inverter
● According to the direction of the inverter output power can be divided into:
(1) Active inverter
(2) Passive inverter
● According to the form of the inverter main circuit can be divided into:
(1) Single-ended inverter
(2) push-pull inverter
(3) Half bridge inverter
(4) Full bridge inverter
● According to the type of inverter main switch device can be divided into:
● According to DC power supply can be divided into:
(1) Voltage Source Inverter (VSI)
(2) Current Source Inverter (CSI)
● According to the inverter control mode can be divided into:
(1) Frequency modulation (PFM) inverter
(2) Pulse width modulation (PWM) inverter
● According to the inverter switching circuit working mode can be divided into:
(1) resonant inverter
(2) fixed frequency hard switching inverter
(3) fixed frequency soft switching inverter
According to the inverter output voltage or current waveform can be divided into:
(1) Square wave inverter
The output voltage waveform of square wave inverter is square wave, and the inverter circuit used by such inverters is not exactly the same, but the common feature is that the line is relatively simple and the number of power switches used is small. The design power is generally between hundreds of watts and kilowatts.
The advantages of square wave inverter are: simple line, convenient maintenance and cheap price.
The disadvantage is that the square wave voltage contains a large number of higher harmonics, which will produce additional losses in load appliances with core inductors or transformers, and interfere with radios and some communication equipment. In addition, this type of inverter has the disadvantages of not wide enough voltage regulation range, imperfect protection function, relatively large noise and so on.
(2) Step wave inverter
The output voltage waveform of this inverter is a stepped wave. There are also many different circuits for inverters to achieve stepped wave output. The number of steps in the output waveform varies greatly.
The advantages of the step-wave inverter are: the output waveform is significantly improved, the high-order harmonic content is reduced, and the output waveform can achieve quasi-sine wave when the step reaches more than 17, and the efficiency of the whole machine is very high when the transformer-free output is used.
The disadvantage is that the stepped wave superposition line uses more power switches, of which some line forms also require multiple sets of DC power input. 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 to the radio and some communication equipment.
Several inverter technology analysis
1. Low frequency link inverter technology
This technology can be divided into: Square wave inverter, step synthesis inverter and pulse width modulation inverter, but the common denominator of these three inverters is that the working frequency of the transformer used to achieve electrical isolation and adjust the transformer ratio is equal to the output voltage frequency, so it is called the low frequency link inverter. The circuit structure is composed of power frequency or high frequency inverter, power frequency transformer and input and output filter, as shown in Figure 1. It has the advantages of simple circuit structure, single-stage power conversion and high conversion efficiency, but it also has the disadvantages of large volume and weight of transformer and loud audio noise…….
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