Compensation of reactive power via a frequency converter

A method and an apparatus for compensating reactive power and/or harmonic currents in an alternating-current network by means of a frequency converter (1) feeding an alternating-current load (3), which frequency converter has a mains bridge (10) and at least one load bridge (11), said bridges being provided with controllable semiconductor switches. In the method, the reactive power and/or harmonic currents in the alternating-current network are measured, the load of the mains bridge of the frequency converter is measured, and the reactive power and/or harmonic currents in the alternating-current network are compensated by means of the frequency converter when the mains bridge is running at less than full capacity or has no load.