Wind Turbine Control Upsampling for Alias-Free Actuation
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Solution Overview
Problem
Conventional upsampling techniques for wind turbine control systems often result in aliasing and phase delay, which are undesirable in dynamically changing systems, as they fail to accurately convert low-rate control signals from control units to the higher rates required by actuator systems.
Innovation Solution
A wind turbine control system that incorporates an upsampling module capable of generating a higher frequency control signal based on both the current control sample value and a predicted control trajectory, using interpolation functions to calculate additional control sample values, thereby avoiding the limitations of conventional methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional upsampling techniques (zero-order hold or zero-stuffing) are used to convert low-rate control signals to high-rate signals, then the signal rate is increased, but aliasing occurs and phase delay is introduced
Solution Approach 1:
The control trajectory is predicted in advance using a model-based approach (MPC or LQR) before upsampling. This preliminary prediction of future control values allows the upsampler to generate accurate intermediate samples without introducing aliasing or phase delay, as the trajectory information is already computed ahead of time
Solution Approach 2:
A trajectory predictor acts as an intermediary between the low-rate controller and high-rate actuator system. This intermediary component uses model predictions to generate the missing intermediate samples, bridging the frequency gap without requiring aggressive filtering that would cause phase delay
2Reliability
If low-pass post-filtering is applied to smooth discontinuities in upsampled signals, then aliasing is reduced, but phase delay in the control signal increases
Solution Approach 1:
The control trajectory is predicted in advance using a model-based approach (MPC or LQR) before upsampling. This preliminary prediction of future control values allows the upsampler to generate accurate intermediate samples without introducing aliasing or phase delay, as the trajectory information is already computed ahead of time
Solution Approach 2:
A trajectory predictor acts as an intermediary between the low-rate controller and high-rate actuator system. This intermediary component uses model predictions to generate the missing intermediate samples, bridging the frequency gap without requiring aggressive filtering that would cause phase delay
3Measurement precision
If the control signal rate is increased to match actuator system requirements, then control accuracy is improved, but the control module computational load increases
Solution Approach 1:
The control system is segmented into two functional parts: a low-rate control module that computes control decisions at reduced computational load, and a trajectory predictor that generates intermediate samples at high rate using lightweight interpolation based on the control trajectory, thus distributing computational effort efficiently
Solution Approach 2:
A trajectory predictor acts as an intermediary between the low-rate controller and high-rate actuator system. This intermediary component uses model predictions to generate the missing intermediate samples, bridging the frequency gap without requiring aggressive filtering that would cause phase delay
Data Source
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AI summary
A wind turbine control unit comprising a control module configured to control an actuator system by outputting a first control signal, wherein the first control signal includes a current control sample value and a predicted control trajectory; the control unit further comprising an upsampling module configured to receive the first control signal from the control module, and to output a second control signal for controlling the actuator system, the second control signal having a higher frequency that the first control signal. The upsampling module calculates the second control signal in dependence on the current control sample value and the predicted control trajectory. The embodiments provide a more accurately reproduced control signal at a higher frequency that is suitable for onward processing which does not suffer from the problems of aliasing and delay that exist with conventional upsampling techniques. The dynamic response of the actuator system is improved such that it exhibits lower overshoot and is more optimally damped. Embodiments of the invention also relate to a wind turbine control system including such a control unit, a method for operating a control unit, and a computer program product adapted for implementing the method.