Harmonics refer to the amount of electricity contained in a current with a frequency that is an integer multiple of the fundamental frequency. Generally, it refers to the Fourier series decomposition of periodic non sinusoidal electricity. In addition to the electricity at the fundamental frequency, the electricity at currents with frequencies greater than the fundamental frequency is called harmonics.The harmonic frequency is the ratio of the harmonic frequency to the fundamental frequency....

Power grid shaking refers to the phenomenon of significant voltage fluctuations or short-term power outages that occur during the operation of the power system due to lightning strikes, short circuits to ground, fault reclosing, backup automatic switching, external and internal power grid failures of the enterprise, and the start-up of large equipment.

With the rapid development of modern power industry and significant changes in the power load structure of the system, the dependence of factories and office automation on electronic equipment is growing rapidly. For power users, voltage sag is becoming a major issue. During the whole process of power generation and use, it must span a wide geographical area, where the entire transmission system generally encounters lightning, rainstorm, gale, construction, personnel misoperation and other accidents, which cause voltage sag caused by short circuit fault, some of which are enough to affect the normal operation of sensitive equipment....