This method is still widely used. The harmonic problem of power system has attracted people's attention as early as the 1920s and 1930s. At that time, in Germany, the voltage and current waveforms were distorted due to the use of static mercury arc converters. J.C.Read's paper on converter harmonics published in 1945 is a classic paper on early harmonic research.
In 1950s and 1960s, due to the development of HVDC transmission technology, a large number of papers were published on the harmonic problems of power system caused by converters. Since 1970s, due to the rapid development of power electronic technology, various power electronic devices have been widely used in power system, industry, transportation and home, and the harm caused by harmonics has become increasingly serious. The problem of harmonics has attracted great attention from all countries in the world. Many international academic conferences have been held on the issue of reconciliation, and many countries and international academic organizations have formulated the issue of reconciliation.
The significance of harmonic research lies in the serious harm of harmonic. Harmonics reduce the efficiency of production, transmission and utilization of electric energy, overheat electrical equipment, produce vibration and noise, age insulation, shorten service life, and even fail or burn out. Harmonic will cause local parallel resonance or series resonance of power system, amplify harmonic content, and cause capacitors and other equipment to burn out. Harmonics will also cause misoperation of relay protection and automatic devices, which will confuse the electric energy measurement. For the outside of the power system,