Most of the auxiliary generators in thermal power plants are provided with frequency converter, but the frequency converter is easily affected by the input side voltage drop ,which triggers the low voltage protection of the frequency converter, blocks the output pulse, leads to production interruption and even major accidents.
It is impossible to eliminate the problem of "interference electricity" from the grid side, but the frequency converter used in the power plant can be modified from the perspective of application. The original AC service power supply is the only power supply of the frequency converter. Through the rectifier circuit, the alternating current is changed into direct current, which is provided to the frequency converter for power output. By adding DC power supply as the backup power supply of the frequency converter, the main and backup power supplies are respectively connected to the AC input end and the DC bus of the frequency converter and the two power supplies are put into operation at the same time in normal operation. In case of AC power supply interruption or the voltage drop, the DC power supply will supply power to the DC bus of the frequency converter to maintain the normal operation of the frequency converter.