Method for determining a rotational angle position of a rotor of a multiphase electrical machine, and frequency converter

A frequency converter for actuating a multi-phase electrical machine, the frequency converter comprising:

• an inverter configured to generate phase voltages for the multi-phase electrical machine via pulse-width modulation;
• a current sensor unit configured to measure phase currents generated by the inverter;
• a torque regulator that controls a torque generated by the electrical machine, wherein the torque regulator delivers a target current vector as a control variable output;
• a current controller configured to adjust a value and phase of a current vector obtained from the measured phase currents to the target current vector, wherein the drive voltage vector is employed as a control variable of the current controller;
• a test voltage vector generation unit, which is configured to generate temporally sequential test voltage vectors;
• a vector addition unit configured for vectorially adding an instantaneous drive voltage vector and a corresponding test voltage vector to form a sum vector;
• a PWM unit configured to generate actuation signals for the inverter based on the sum vector, and
• a rotational angle estimation unit configured to estimate a rotational angle position of the rotor, in accordance with a variation in the current vector which is generated by the test voltage vectors.