Abstract: A method and arrangement for determining leakage inductances of a double fed induction generator, DFIG, (10) wherein, in response to the stator current of the DFIG being equal to or below a first predetermined threshold, values of a stator voltage, a rotor voltage and a rotor current of the DFIG are determined, and a rotor leakage inductance of the DFIG is calculated on the basis the determined values, and, in response to the rotor current of the DFIG being equal to or below a second predetermined threshold, values of the stator voltage, the rotor voltage and the stator current of the DFIG are determined, and a stator leakage inductance of the DFIG is calculated on the basis of the determined values.

Abstract: A method and arrangement in connection with an electric drive system are provided. The electric drive system includes an intermediate circuit with two or more supply units and two or more inverter units connected thereto, and an electric machine having two or more three-phase windings galvanically separated from each other. Two or more inverter units are connected to the three-phase windings. The arrangement also includes first main circuit switches to galvanically separate each supply unit from a supply, second main circuit switches to galvanically separate each supply unit from the intermediate circuit, first intermediate circuit switches to galvanically separate each inverter unit from the intermediate circuit, and second intermediate circuit switches to galvanically separate each inverter unit from the electric machine.

Abstract: Exemplary embodiments provide a method of controlling a doubly-fed electric generator using a frequency converter having a torque and flux controller. The frequency converter is connected to a rotor of the generator. The frequency converter calculates a stator flux positive sequence component from a stator flux. A rotor flux amplitude reference and an estimated torque is then calculated by using the stator flux positive sequence component. The frequency converter selects a voltage vector to steer the rotor flux by using the rotor flux amplitude reference and the estimated torque.

Abstract: A method and apparatus are provided for controlling a cascade-fed asynchronous generator in connection with a voltage dip of a network fed by the generator. A frequency converter is connected between the rotor of the asynchronous generator and the network. The method includes measuring the magnitude of the voltage in the network, calculating, on the basis of the voltage in the network, a base value for reactive current to be fed to the network, generating reactive current in the network by the generator, measuring the stator current, determining the actual value of the reactive current in the network, calculating the difference between the base value and the actual value of the reactive current, providing the calculated difference to the frequency converter to serve as an instruction in reactive current, and generating reactive current in the network by the frequency converter in accordance with the instruction in reactive current.

Abstract: Exemplary embodiments provide a method of controlling a doubly-fed electric generator using a frequency converter having a torque and flux controller. The frequency converter is connected to a rotor of the generator. The frequency converter calculates a stator flux positive sequence component from a stator flux. A rotor flux amplitude reference and an estimated torque is then calculated by using the stator flux positive sequence component. The frequency converter selects a voltage vector to steer the rotor flux by using the rotor flux amplitude reference and the estimated torque.

Abstract: A method and arrangement in connection with an electric drive system are provided. The electric drive system includes an intermediate circuit with two or more supply units and two or more inverter units connected thereto, and an electric machine having two or more three-phase windings galvanically separated from each other. Two or more inverter units are connected to the three-phase windings. The arrangement also includes first main circuit switches to galvanically separate each supply unit from a supply, second main circuit switches to galvanically separate each supply unit from the intermediate circuit, first intermediate circuit switches to galvanically separate each inverter unit from the intermediate circuit, and second intermediate circuit switches to galvanically separate each inverter unit from the electric machine.