In order to feed to the converter on the load side of an intermediate-link frequency converter a frequency control signal (fI(S)*) which is formed by means of an angle controller (RW) from the difference of an angle reference value (wi(F)*) and a corresponding actual value (wI(F)), an actual value of the phase current is required which, for stable operation, must not contain heavy harmonics in stable operation nor must not be damped excessively dynamically by smoothing. Therefore, the measured actual angle value (wI(S)) is fed as the reference value of a servo controller (RS), to the output of which the integral (wI(S)*) of the frequency control quantity is added and the output of which is fed back to the input of the servo controller (RS).