Adaptive control of a current-fed active filter

This paper proposes a simple and practical method for improving the performance of DSP-controlled active power filters (AF). The transfer function of a DSP-controlled AF has a phase-lag property because there is a calculation time delay in the control output, and the converter used for AF has first order lag characteristics. As AF has to generate high frequency compensation currents, the phase-lag property causes a serious deterioration in the filter performance. In the proposed system, an adaptive digital filter (ADF) operates as a series compensator and it compensates for the time-lag property of AF. ADF requires no additional hardware but only slight additional software. It was confirmed by experimental results that a simple two-tap ADF is very effective to improve the AF compensation performance.