Controller device controlling a power converter device of an electrical generator during rotation of the electrical generator, the controller device comprising: - a feedback input receiving a current feedback; - a demand input (210, 212) receiving a current demand (214, 216), the current demand comprising a first, d-axis demand for a current on a d-axis defined by the direction of the rotor flux of the electrical generator and a second, q-axis demand for a current on a q-axis defined by the direction of a stator back electromotive force generated by a flux in the electrical generator; - a signal converter receiving an angle signal and in response hereto transposing the current feedback onto two axes (101, 102) of a rotating reference frame, wherein the rotation angle of the reference frame is defined by the angle signal, the two axes being the d-axis and the q-axis, and the transposing of the current feedback resulting in a d-axis feedback and a q-axis feedback; - a current controller matching the d-axis feedback to the d-axis demand and matching the q-axis feedback to the q-axis demand, the current controller having a d-axis regulator receiving the d-axis feedback and the d-axis demand and providing in response hereto a d-axis response operative in reducing the difference between the d-axis feedback and the d-axis demand; characterized by - an error unit providing an error signal indicative of an angle error of the rotating reference frame on the basis of the d-axis response of the d-axis regulator; - an angle feedback unit receiving the error signal and providing in response hereto the angle signal to the signal converter; - wherein the error unit comprises ∘ an emf input receiving an estimated stator back electromotive force signal indicative of a magnitude of an estimated stator back electromotive force; and ∘ a divider providing the error signal by dividing the d-axis response or a quantity derived therefrom by the magnitude of the estimated stator back electromotive force. - a feedback input receiving a current feedback; - a demand input (210, 212) receiving a current demand (214, 216), the current demand comprising a first, d-axis demand for a current on a d-axis defined by the direction of the rotor flux of the electrical generator and a second, q-axis demand for a current on a q-axis defined by the direction of a stator back electromotive force generated by a flux in the electrical generator; - a signal converter receiving an angle signal and in response hereto transposing the current feedback onto two axes (101, 102) of a rotating reference frame, wherein the rotation angle of the reference frame is defined by the angle signal, the two axes being the d-axis and the q-axis, and the transposing of the current feedback resulting in a d-axis feedback and a q-axis feedback; - a current controller matching the d-axis feedback to the d-axis demand and matching the q-axis feedback to the q-axis demand, the current controller having a d-axis regulator receiving the d-axis feedback and the d-axis demand and providing in response hereto a d-axis response operative in reducing the difference between the d-axis feedback and the d-axis demand; - an error unit providing an error signal indicative of an angle error of the rotating reference frame on the basis of the d-axis response of the d-axis regulator; - an angle feedback unit receiving the error signal and providing in response hereto the angle signal to the signal converter; - wherein the error unit comprises ∘ an emf input receiving an estimated stator back electromotive force signal indicative of a magnitude of an estimated stator back electromotive force; and ∘ a divider providing the error signal by dividing the d-axis response or a quantity derived therefrom by the magnitude of the estimated stator back electromotive force. ∘ an emf input receiving an estimated stator back electromotive force signal indicative of a magnitude of an estimated stator back electromotive force; and ∘ a divider providing the error signal by dividing the d-axis response or a quantity derived therefrom by the magnitude of the estimated stator back electromotive force.