Patent ID: 6956352

Claim:
A method in connection with an inverter, the inverter comprising a direct voltage intermediate circuit, an optimum switching table and output power switches, characterized by the method comprising the steps of defining a synchronous rectangular dq coordinate system; measuring the phase currents (i A , i C ) of the inverter outputs; converting the phase currents (i A , i C ) of the inverter to a synchronous dq coordinate system in order to achieve synchronous rectangular current vector components (i d , i q ); low-pass-filtering the synchronous current vector components (i d , i q ) in order to achieve low-pass-filtered current vector components (i d,lpf , i q,lpf ); generating a current reference (i q,ref ) in the direction of the q axis of the dq coordinate system; generating a current reference (i d,ref ) in the direction of the d axis of the dq coordinate system; generating a torque (t e,ref ) reference by comparing the current reference (i q,ref ) in the direction q with a low-pass-filtered current vector component (i q,lpf ) in the direction q; generating an absolute value reference (|{overscore (ψ)}| ref ) of the flux linkage by comparing the current reference (i d,ref ) in the direction d with a low-pass-filtered current vector component (i d,lpf ) in the direction d; and forming switching commands of the power switches on the basis of the torque reference (t e,ref ) and the flux reference (|{overscore (ψ)}| ref ) by using an optimum switching table (5).