Wind Turbine Power Train Torsional Oscillation Control
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Solution Overview
Problem
Existing methods for controlling wind turbines during grid loss are complex, expensive, and ineffective in reducing torsional oscillations, which can significantly damage the gearbox and reduce its lifetime.
Innovation Solution
A method that applies a braking torque to the power train for a duration determined by the torsional resonance frequency and delay after grid loss, using the aerodynamic torque and wind speed to calculate the optimal braking period and torque, thereby minimizing torsional oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If prior art methods (multiple braking stages, hydraulic control, pitch regulation) are used to deal with grid loss, then the wind turbine can be slowed down, but the methods are complicated and expensive, and torsional oscillations are not effectively reduced
Solution Approach 1:
The invention extracts and isolates the critical function of reducing torsional oscillations from the complex multi-stage braking systems. By applying a single mechanical brake on the high-speed shaft with precisely controlled duration based on torsional frequency, it separates the oscillation reduction function from other braking functions, achieving effectiveness without complexity
Solution Approach 2:
The invention performs preliminary calculation of the optimal braking duration based on the torsional resonance frequency of the power train before grid loss occurs. This pre-determined timing allows the brake to be applied during the critical unwinding phase, preventing torsional oscillations before they can damage the gearbox
2Reliability
If mechanical brakes are applied on the high speed shaft during grid loss, then torsional oscillations can be reduced, but the braking must be precisely timed to avoid increasing oscillations
Solution Approach 1:
The system uses the power train's own torsional resonance frequency characteristics to determine the optimal braking duration. By calculating the braking time based on the inherent mechanical properties of the power train components, the system makes the control strategy self-adapting and eliminates the need for complex external sensing and adjustment mechanisms
Solution Approach 2:
The invention applies the brake for a specific duration that corresponds to a fraction of the torsional oscillation period. This periodic timing ensures the brake acts during the unwinding phase when it is most effective, and automatically stops before the winding phase would increase oscillations
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Significantly reduces torsional oscillations, extending the lifespan of the gearbox by applying the braking torque during the power train's unwinding phase, optimizing the braking period and torque to ensure effective shutdown and reduced damage.
Implementation Method 1
a braking torque is applied to the power train
Implementation Method 2
The components of the power train (rotor shaft or slow speed shaft, gearbox, high speed shaft, generator) elastically deform under the influence of the aerodynamic torque acting on the rotor and the magnetic torque acting on the generator. Potential energy is stored in this elastic deformation.
Implementation Method 3
When a grid loss occurs, the magnetic torque at the generator is very suddenly lost, and the potential energy of the power train is converted into kinetic energy. As a result, the power train suffers from torsional oscillations.
Implementation Method 4
the power train will start to oscillate with a frequency that is its torsional resonance frequency
Data Source
AI summary
The present invention refers to a method of reducing torsional oscillations in the power train of a wind turbine in the event of grid loss. According to the method, after the grid loss, a braking torque is applied to the power train during a period of time and said period of time is determined as a function of the torsional resonance frequency of the power train.