1) When pure capacitors are used for compensation, if the system contains harmonic components, they will form a parallel resonance point with the system, which may lead to harmonic parallel resonance.

2) Connecting a reactor in series at the front end of the capacitor can effectively shift the parallel resonance point away from the characteristic harmonics of the load. In addition, it can also suppress the magnitude of the inrush current when the capacitor is switched on.