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All switch input and output ports of the inverter are isolated by photoelectric couplers. In addition to photoelectric coupler isolation for the trigger pulse output circuit of the thyristor, transformer isolation is also used to prevent the reverse interference of the higher voltage of the main circuit. The 01 circuit is also used to improve its anti-interference ability. In order to ensure the normal operation of the microcomputer floating on the ground, the ground wire of the analog input port should also be isolated from the microcomputer ground wire. Although the isolation amplifier can be used to isolate the internal and external ground wires, the anti-interference ability of this type of amplifier module is limited due to the transformer coupling technology. In the test, it is found that there is a narrow spike interference that can enter the sampling and conversion loop of the microcomputer. Control errors. For this reason, before entering the microcomputer after the analog quantity is converted into a digital quantity, each digital quantity is isolated with a photoelectric coupler.

Because the optocoupler is a current-type device, it has better suppression of narrow spike interference signals, and can obtain better anti-interference ability and higher conversion accuracy. Power supply anti-interference: The power supply of the microcomputer adopts the power supply mode of ferromagnetic AC voltage stabilizer, super isolation transformer, two-wire low-pass filter, and anti-interference type microcomputer switching power supply. Experiments show that this system has good anti-interference performance, which can ensure that the microcomputer is not interfered by AC power. The power supply of the peripheral circuit is drawn from the AC voltage stabilizer and realized through another super isolation transformer to prevent the communication between the peripheral circuit and the microcomputer. Of mutual interference. Other anti-interference measures include: signal input filter network, digital filter program, trap program, the use of integrated circuits, separate wiring of power lines and control lines, and use of shielded wires for microcomputer signal lines.