Selective compensation of harmonics of unidentified nonlinear loads as ancillary function of grid inverters

This paper presents the inverter control of a shunt active power filter (APF) for the mitigation of harmonics caused by multiple low power Harmonic Generating Loads (HGLs) in a Low Voltage (LV) grid. The shunt APF acts as adjustable admittance for each individual harmonic frequency in accordance with the harmonic voltage and the grid admittance at its installation point. The aim of the compensation is to maintain the harmonic voltages under the standard threshold and to collect the harmonic currents from the HGLs installed close to the shunt APF by shaping an optimal compensation current. The harmonic detection method and the controller strategy are described and experimental result on a prototype attests the performances of the harmonics compensation.