A system and a method for compensating harmonic components or a reactive power of an electrical network. The system comprises a measurement unit (1) configured to measure an electrical quantity to be compensated, a control unit (2) configured to determine harmonics contents or a reactive power need of the measured electrical quantity to be compensated as well as to determine, as relative values, desired values corresponding with the harmonics to be compensated or the reactive power to be compensated, one or more compensation units (5, 6) configured, responsive to the desired values provided by the control unit (2), to generate harmonic components or a reactive current according to the desired values given as relative values, and a communications connection (3) configured to communicate the desired values determined by the control unit (2) to the compensation units (5, 6).