Woodward Kempen Gmbh

Woodward Seg Gmbh & Co. Kg

Andrzej Geniusz

Stephan Engelhardt

Holger Wrede

The invention relates to a method for operating a wind energy plant having a double-fed asynchronous machine, at least one inverter and at least one control device, wherein electrical energy is at least partly supplied into a grid via the inverter, the inverter comprises per phase at least one power semi-conductor module with at least two transistor circuits and at least two free-wheeling diodes and the inverter by using the control device is actuated at least at times via a pulse width modulation (PWM). The object, namely of providing a generic method for operating a wind energy plant in which an improved power output is effected even in the low-noise rotational speed range of the rotors, is achieved in that, at frequencies of the current to be impressed by the inverter on the machine side of less than 10 Hz, preferably less than 6 Hz, the switching-on duration and/or the switching frequency of the transistor circuits and/or of the free-wheeling diodes of the inverter are altered via the control device by taking their thermal heating into account.

Method for operating a wind energy installation

In a method for the compensation of rotor torque oscillations upon the occurrence of mains asymmetries in relation to a double-fed asynchronous machine () it is provided that at least one respective currently prevailing machine parameter is measured and/or derived, the at least one machine parameter is respectively decomposed by calculation into a positive and a negative sequence system component and optionally a DC component, and for the positive sequence system component, the negative sequence system component and optionally for the DC component of the at least one machine parameter, there are respective separate control members for controlling an adjusting value, to which the respective components of the machine parameters are fed as input components and the output values of which are additively superposed. In that case the control members are so adapted for controlling the adjusting value in such a way that the torque oscillations are counteracted. Alternatively there is provided a control member to which the cross-product of the positive sequence system components and negative sequence system components as well as the cross-product of the negative sequence system components and positive sequence system components are fed as an input value, the control member being so adapted for controlling the adjusting value in such a way that second-order torque oscillations are counteracted.

Method of and apparatus for compensation of oscillation effects in the event of mains asymmetry in a double-fed asynchronous machine

A method for operating a wind turbine that includes a generator device for outputting electric energy to a network, the generator device having a stator, and a controller device for controlling the generator device. To ensure sufficient protection of the wind turbine even during network fluctuations, a network voltage is determined using a network model at least as a function of a stator voltage measured with a first measuring apparatus and a network power measured with a second measuring apparatus, and the determined network voltage and a predeterminable maximum phase angle present between the stator voltage and network voltage are used to determine the maximum effective power of the wind turbine that can be output, and the output effective power is regulated as a function of the determined maximum effective power that can be output and a target effective power predetermined by the control device.

Method for operating a wind turbine

In a method and an apparatus for controlling the output or drawn active and reactive power of a double-fed asynchronous machine (), the maintenance of a maximum permissible current () of the machine&#x2014;without the use of a subordinate current controller&#x2014;is ensured by virtue of the fact that, during the operation of the double-fed asynchronous machine, a maximum permissible desired value for the active power () to be output or to be drawn and a maximum permissible desired value for the reactive power () to be output or to be drawn are calculated with the aid of a model of the asynchronous machine from the maximum permissible current (), preferably corrected at least using the actual value of the current to be limited of the machine, in such a way that the maximum permissible current () is not exceeded. The predetermined active and reactive power desired values are then limited to the calculated maximum permissible values.

Current limitation for a double-fed asynchronous machine

Regulation of the active and reactive power of an induction machine in a coordinate system fixed on the winding, wherein a first regulator output variable is generated using a first regulator as a function of a setpoint variable deviation of the active power and a second regulator output variable is generated using a second regulator as a function of a setpoint variable deviation of the reactive power, feedback variables are added to each of the first and second regulator output variables, which are functions of at least one chronologically changing system variable of the induction machine, and a voltage or a current of the induction machine is determined as a manipulated variable without further regulation at least from the first and second regulator output variables added to the feedback variables. The feedback variables may linearize the regulation path and then allow restriction to only two simple regulators, e.g., two PI regulators. The regulation may be used in double-fed asynchronous machines.

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Mulheim an der Ruhr, Germany

Andrzej Geniusz