Abstract: A space-vector pulse-width modulation method for a frequency converter provided with a voltage intermediate circuit, said frequency converter comprising a mains bridge (10) to be connected to an alternating current source (UU, UV, UW), a direct-voltage intermediate circuit and a controlled load bridge (11) for supplying a variable-frequency alternating voltage (US, UR, UT) to a load (12), and in which method the modulator performing the modulation is given a reference. The load bridge modulator is given a reference consisting of the references for the flux linkage changes produced by the voltage vectors, the flux linkage change is calculated on the basis of measured intermediate-circuit voltage, and the currently active voltage vector is kept turned on until the reference value is reached.

Abstract: A space-vector pulse-width modulation method for a frequency converter provided with a voltage intermediate circuit, said frequency converter comprising a mains bridge (10) to be connected to an alternating current source (UU, UV, UW), a direct-voltage intermediate circuit and a controlled load bridge (11) for supplying a variable-frequency alternating voltage (US, UR, UT) to a load (12), and in which method the modulator performing the modulation is given a reference. The load bridge modulator is given a reference consisting of the references for the flux linkage changes produced by the voltage vectors, the flux linkage change is calculated on the basis of measured intermediate-circuit voltage, and the currently active voltage vector is kept turned on until the reference value is reached.

Abstract: A method for starting an open-loop vector control of a synchronous machine by determining a stator inductance model of the machine; measuring the stator iductance in a plurality of directions; arranging the measured inductances in the model to form model parameters resulting in minimum error; checking the polarity of rotor magnetization to verify the direction thereof; initializing flux linkages of the open-loop vector control according to the model parameters and the direction of rotor magnetization; and starting the machine by the open-loop vector control method.

Abstract: A method of minimizing errors in a rotor angle estimate in a synchronous machine the method comprising the steps of determining the stator flux (&PSgr;ssest) of the synchronous machine on the basis of the current model of the synchronous machine, determining the stator flux (&PSgr;ssu′) on the basis of the voltage integral and initial value (&PSgr;ssu(n-1)) of the stator flux, and determining the rotor angle (&thgr;est(n)) of the synchronous machine. The method also comprises the steps of determining an angle correction term (&thgr;k(n)) on the basis of the determined stator fluxes (&PSgr;ssest, &PSgr;ssu′), and adding the angle correction term (&thgr;k(n)) to the determined rotor angle (&thgr;est(n)) of the synchronous machine to obtain a rotor angle estimate (&thgr;(n)).