Merus active harmonic filters are connected in parallel with the loads to be compensated. They measure the current of the non-linear load and inject the same harmonics, but with opposite phase angle. The current of the active harmonic filter thus cancels out the harmonic currents of the load, and only fundamental frequency current component is left to be supplied from the power system.
In addition to current and voltage profile smoothing by harmonic current mitigation, the active filters also provide fast fundamental frequency reactive power compensation and balance loads in three-phase systems. Reactive power compensation stabilizes voltage, mitigates flicker, releases additional capacity for transferring more active power in the existing electrical network and improves the power factor.