An improved method of SAPF for harmonic compensation and resonance damping with current detection of power capacitors and linear/nonlinear loads

This paper presents a hybrid compensation system with shunt active power filter(SAPF) and power capacitors. Firstly, two different load current detection points are introduced. With traditional method, hybrid compensation system is stable when capacitor current is not included in the detected load current. But, when capacitor current is included, the resonance frequency would be shifted to higher frequency which leads to SAPF self-oscillation and controller saturation. Then, an improved method that reversing part of SAPF controller current references whose spectra higher than resonance frequency is proposed. The objective of this improved method is to prevent SAPF out of control. However, harmonic mitigation is a welcome “by-product” which comes from this reversal of current reference. Terminal voltage is also detected for resonance damping which is helpful to mitigate harmonic distortion. At last, experiments results are presented to verify the proposed method.