Method for determining a correction value which describes an angular difference between an assumed and an actual position of a d-axis, control device and inverter

Method for determining a correction value for a control device for an electric machine, the correction value describing an angular difference between a position of a d-axis of the electric machine assumed in an initial configuration of the control device on a basis of rotor position information of a rotor position sensor and an actual position of the d-axis, a zero current being impressed in stator windings of the electric machine and the correction value being determined in a rotating state of a rotor of the electric machine as a function:

• of a d-voltage value describing a d-component of a stator voltage specified by the control device in the initial configuration,
• of a q-voltage value describing a q-component of the stator voltage specified by the control device in the initial configuration,
• of a flux value describing a magnetic flux of the rotor,
• of a speed value describing a speed of the rotor in the rotating state, and
• of a calibration value describing a speed-dependent voltage error of the d component of the stator voltage,
• wherein the following equation is evaluated to determine the correction value:
• Δγ=γ tan(ωel·Ψ·ud−Δud·uq, Δud·ud+ωel·Ψ·uq),
• where
• α tan(x, y) describes an arc tangent function or an arc cotangent function, in particular
• arctan
• ⁡
• (
• x
• y
• )
• ⁢
• ⁢
• or
• ⁢
• ⁢
• arccot
• ⁡
• (
• y
• x
• )
• or α tan 2(x, y) or α cot 2(y, x),
• ud describes the d-voltage value,
• uq describes the q-voltage value,
• Ψ describes the flux value,
• ωel describes the speed value, and
• Δud describes the calibration value.

A control device for an electric machine, which is arranged to impress a zero current into stator windings of the electric machine, and to determine a correction value describing an angular difference between a position of a d-axis of the electric machine assumed in an initial configuration of the control device on a basis of rotor position information of a rotor position sensor and an actual position of the d-axis in a rotating state of a rotor of the electric machine in dependence

• of a d-voltage value describing a d-component of a stator voltage specified by the control device in the initial configuration,
• of a q-voltage value describing a q-component of the stator voltage specified by the control device in the initial configuration,
• of a flux value describing a magnetic flux of the rotor,
• of a speed value describing the speed of the rotor in the rotating state, and
• of a calibration value describing a speed-dependent voltage error of the d-component of the stator voltage, and
• wherein the flux value is determined as a function of the d-voltage value and the q-voltage value and the speed value as an additional function of the calibration value.