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: A frequency converter assembly including an input for supplying electric power having an input frequency into the frequency converter assembly from a supply network, a direct voltage intermediate circuit having capacitor component, and at least one controllable switch. The switch being electrically positioned between the input and the direct voltage intermediate circuit. The assembly also includes an output for supplying electric power having an output frequency from the frequency converter assembly, and control component arranged to control the at least one controllable switch. The control component provides a recovery function to recover the capacitor component by supplying restricted recovery current from the supply network to the capacitor component through the at least one controllable switch, the control means also prevents supply of electric power from the direct voltage intermediate circuit towards the output during the recovery function.

Abstract: An arrangement for controlling frequency converter modules of an electric drive. In the arrangement, the frequency converter modules are arranged to control alternatively a first motor or several motors having less power than the first motor.

Abstract: A method and an arrangement for determining the rotation speed of a motor fed by an inverter, the arrangement comprising means for determining the rotation speed of the motor in at least two alternative manners, whereby the means for determining the rotation speed of the motor comprise one of the at least two alternative manners of performance: means for measuring the frequency of the voltage fed to the motor by the inverter; and means for estimating the rotation speed of the motor on the basis of the measured frequency.

Abstract: A frequency converter assembly including an input for supplying electric power having an input frequency into the frequency converter assembly from a supply network, a direct voltage intermediate circuit having capacitor component, and at least one controllable switch. The switch being electrically positioned between the input and the direct voltage intermediate circuit. The assembly also includes an output for supplying electric power having an output frequency from the frequency converter assembly, and control component arranged to control the at least one controllable switch. The control component provides a recovery function to recover the capacitor component by supplying restricted recovery current from the supply network to the capacitor component through the at least one controllable switch, the control means also prevents supply of electric power from the direct voltage intermediate circuit towards the output during the recovery function.

Abstract: An exemplary electric drive system has a plural number of electric drive subsystems. Each subsystem having a fault diagnostics arrangement, where the arrangement includes a respective control board for each subsystem. Event data of each subsystem is recorded on the respective control board, and one of the respective control boards of the electric drive system is a main control board of the electric drive system. Event data of a subsystem is transferred from the respective control board to the main control board through a data transfer medium.

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: An arrangement for controlling frequency converter modules of an electric drive. In the arrangement, the frequency converter modules are arranged to control alternatively a first motor or several motors having less power than the first motor.

Abstract: A method and an arrangement for determining the rotation speed of a motor fed by an inverter, the arrangement comprising means for determining the rotation speed of the motor in at least two alternative manners, whereby the means for determining the rotation speed of the motor comprise one of the at least two alternative manners of performance: means for measuring the frequency of the voltage fed to the motor by the inverter; and means for estimating the rotation speed of the motor on the basis of the measured frequency.

Abstract: An electric drive system comprising several electric drives, each of which comprises an electric motor, and a control system which is arranged to control said several electric drives and comprises a first outer controller and a first speed controller. A signal supplied to the input of the first speed controller is generated by using the output signal of said first outer controller, and the first speed controller is arranged to generate an output torque signal at its output. The control system further comprises a torque controller per each electric drive, which torque controller is arranged to control the torque of the corresponding electric motor. A signal supplied to the input of each torque controller is generated by using the output torque signal of the first speed controller.

Abstract: A method in connection with a network converter, and a network converter, the network converter comprising two or more network converter modules coupled in parallel, and first control means for controlling the network converter modules. The method comprises the steps of controlling the network converter modules by the first control means, preventing or allowing use of one or more network converter modules in order to reconfigure the network converter during operation of the network converter.

Abstract: An electric drive system comprising several electric drives, each of which comprises an electric motor, and a control system which is arranged to control said several electric drives and comprises a first outer controller and a first speed controller. A signal supplied to the input of the first speed controller is generated by using the output signal of said first outer controller, and the first speed controller is arranged to generate an output torque signal at its output. The control system further comprises a torque controller per each electric drive, which torque controller is arranged to control the torque of the corresponding electric motor. A signal supplied to the input of each torque controller is generated by using the output torque signal of the first speed controller.

Abstract: A method for preventing mechanical oscillation in a wind power plant includes determining wind speed, controlling a generator of the power plant with speed control when the wind speed is below a predefined limit to maintain the rotation speed of the generator below a predefined first limit, detecting the increase of wind speed above the predefined limit, controlling the electric drive of the wind power plant generator to torque control by using a predefined crossover torque in response to the wind speed increasing above a predefined limit, maintaining the crossover torque as the reference torque for the electric drive until the rotation speed of the generator has increased above a predefined second limit, and controlling the electric drive of the wind power plant generator with torque control while the rotation speed of the generator remains above the predefined second limit.

Abstract: A method for operating a doubly-fed machine by determining its rotational speed (nact), forming a rotational speed reference (nref), measuring network voltage and current, and calculating network active power (Pact) and reactive power (Qact). Thereafter, calculating shaft torque (T) based on active power (Pact) and rotating speed (nact), forming a frequency reference (Fref) for the inverter based on machine rotating speed (nact), rotating speed reference (nref), shaft torque (T), and the known pole pair number and network frequency, forming a reactive power reference (Qref) for the machine.

Abstract: A method for preventing mechanical oscillation in a wind power plant, the method comprising the steps of determining wind speed, controlling a generator of the power plant with speed control when the wind speed is below a predefined limit to maintain the rotation speed of the generator below a predefined first limit, detecting the increase of wind speed above the predefined limit, controlling the electric drive of the wind power plant generator to torque control by using a predefined crossover torque in response to the wind speed increasing above a predefined limit, maintaining the crossover torque as the reference torque for the electric drive until the rotation speed of the generator has increased above a predefined second limit, and controlling the electric drive of the wind power plant generator with torque control while the rotation speed of the generator remains above the predefined second limit.

Abstract: A method for operating parallel-connected inverter modules, wherein two or more inverter modules (A, B, C) are connected in parallel to feed the same load. Each inverter module has two or more output phases (u, v, w) for supplying electric power into a two or more phase load by determining the temperature (TAu, TAv, TAw, TBu, TBv, TBw, TCu, TCv, TCw) of each output phase (Au, Av, Aw, Bu, Bv, Bw, Cu, Cv, Cw) in each inverter module, comparing the temperatures of the output phases in each inverter module with the temperatures of the same output phase in other parallel-connected modules, and generating an alarm signal if the temperature of the output phase in an inverter module differs from the temperatures of the same output phase of the other inverter modules more than allowed by a predetermined limit.

Abstract: A method for operating parallel-connected inverter modules, wherein two or more inverter modules (A, B, C) are connected in parallel to feed the same load. Each inverter module has two or more output phases (u, v, w) for supplying electric power into a two or more phase load by determining the temperature (TAu, TAv, TAw, TBu, TBv, TBw, TCu, TCv, TCw) of each output phase (Au, Av, Aw, Bu, Bv, Bw, Cu, Cv, Cw) in each inverter module, comparing the temperatures of the output phases in each inverter module with the temperatures of the same output phase in other parallel-connected modules, and generating an alarm signal if the temperature of the output phase in an inverter module differs from the temperatures of the same output phase of the other inverter modules more than allowed by a predetermined limit.

Abstract: A method for operating a doubly-fed machine by determining its rotational speed (nact), forming a rotational speed reference (nref), measuring network voltage and current, and calculating network active power (Pact) and reactive power (Qact). Thereafter, calculating shaft torque (T) based on active power (Pact) and rotating speed (nact), forming a frequency reference (Fref) for the inverter based on machine rotating speed (nact), rotating speed reference (nref), shaft torque (T), and the known pole pair number and network frequency, forming a reactive power reference (Qref) for the machine.

Abstract: A method and an arrangement for stopping sectional drive controllably in connection with a fault situation in the supplying mains, the sectional drive comprising a plurality of inverters (4) which are supplied by a DC intermediate circuit (3) supplied by the mains (1), a plurality of electric motors (5) which are controlled by inverters with speed and/or torque control and which are used for implementing speed and tightness reference values of the strip in the sectional drive system, the tightness reference value being predetermined motor-specifically or motor-group-specifically.

Abstract: A method and an arrangement for stopping sectional drive controllably in connection with a fault situation in the supplying mains, the sectional drive comprising a plurality of inverters (4) which are supplied by a DC intermediate circuit (3) supplied by the mains (1), a plurality of electric motors (5) which are controlled by inverters with speed and/or torque control and which are used for implementing speed and tightness reference values of the strip in the sectional drive system, the tightness reference value being predetermined motor-specifically or motor-group-specifically.