The characteristics of power electronic devices have been improved significantly. The power electronic devices with high-voltage rating, high-current rating, and high switching speed have been developed due to the improvement of semiconductor manufacturing technique. But the electric power equipment may generate a large amount of harmonic current due to their nonlinear characteristic. The harmonic current will pollute the power system, and it results in the problems such as overheat, shorten battery life, degrading voltage quality, electric power components destruction, etc…

Therefore, how to solve the harmonic problem is an important topic in the power system today