A novel control strategy of active filter for suppressing background harmonic voltage magnification in power distribution system

The dramatic growth of power electronics applications have led to serious harmonic pollutions in the power system. Due to the changeable feature of system characteristic impedance, a curious phenomenon referred to the ‘whack-a-mole’ may occur when using the resistive active power filter (R-APF) to suppress the harmonic in a long distance distribution line. This paper proposes a new approach by installing an APF at the end of the line which is equivalent to the approximate infinitely long transmission line (I-APF, infinite active power filter), to eliminate the reflected wave and mitigate the background harmonic voltage in power distribution systems. The I-APF is able to maintain equivalent to infinitely long transmission line while system characteristic impedance varies under certain conditions that compensation factors of the APF are great enough. Simulations and experiments have been performed to verify the theoretical analysis and demonstrate the effectiveness of the proposed strategy.