A controller device for controlling a power converter device of an electrical generator during rotation of the electrical generator includes a signal converter which is configured to receive an angle signal and in response hereto transposes a current feedback onto two axes of a rotating d, q-reference frame. Further, a current controller has a regulator receiving a d-axis feedback and a d-axis demand and provides 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 provides 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.