Direct AC Main Current Control of Shunt Active Power Filters – Feasibility and Performance

Harmonic and reactive current control is a critical technique in the conventional shunt Active Power Filter (APF) control. Recently years, another control scheme – the direct ac main current control is emerging, where the harmonic and reactive current detection module is no longer needed. This paper proves theoretically that the current controllability of the direct ac main current scheme (DCS) is the same as that of the conventional control scheme (CCS) that employs a sophisticated harmonic and reactive current detection module. Based on this finding, a simple and high performance direct ac main current scheme has been developed. Further theatrical analysis shows the harmonic and reactive current detection module in the conventional module just functioning as a forward feeding in the proposed DCS APF control, and the fluctuation of the compensated load is just a disturbance in dc voltage control loop of the proposed control schemes. The simulation results show that discarding the harmonic and reactive current detection module does not sacrifice the steady-state control accuracy. A prototype was developed to demonstrate the feasibility and performance of the proposed APF control scheme, and the above findings are well supported by the experimental results.