Wind Turbine Generator Control via Dual-Loop Dynamics
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Solution Overview
Problem
Wind turbine generators face challenges in responding quickly to changes in power reference signals due to the presence of slow outer control loops, which also make them sensitive to high-frequency disturbances and require mode changes during low voltage events.
Innovation Solution
A control method using two controllers with different dynamics, where a first controller with slower dynamics acts as a low-pass filter for high-frequency disturbances and a second controller with faster dynamics quickly responds to changes in the power reference signal by receiving a feed-forward of the output power reference value, allowing for improved tracking of power speed curves and reduced disturbances in the generator shaft power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a slow outer control loop is used to filter high-frequency disturbances, then the wind turbine generator becomes less sensitive to high-frequency disturbances, but the response speed to changes in power reference signal deteriorates
Solution Approach 1:
The control system is divided into two separate control loops: an outer control loop with slow dynamics that filters high-frequency disturbances, and an inner control loop with fast dynamics that responds quickly to power reference changes. Each loop handles different frequency ranges and control objectives, resolving the contradiction between filtering disturbances and responding quickly to reference changes.
Solution Approach 2:
The outer control loop acts as an intermediary that processes the power reference signal and feedback, filtering out high-frequency disturbances before passing the processed signal to the inner control loop. This intermediary structure allows the fast inner loop to respond to reference changes without being directly affected by high-frequency noise.
2Object-affected harmful factors
If a slow outer control loop is used, then high-frequency disturbances are filtered, but the control structure complexity increases due to mode change requirements during low voltage events
Solution Approach 1:
The dual-loop control structure is designed to operate universally across different operating conditions including normal operation and low voltage events. The outer loop consistently filters disturbances while the inner loop handles fast responses, eliminating the need for mode changes and simplifying the control structure during abnormal conditions.
3Speed
If a fast controller is used to respond quickly to power reference changes, then the response speed improves, but the controller becomes sensitive to high-frequency disturbances
Solution Approach 1:
The control functions are segmented into two loops with different dynamics. The outer loop with slow dynamics handles disturbance filtering, while the inner loop with fast dynamics handles quick response to reference changes. This segmentation allows each loop to optimize for its specific function without suffering from the drawbacks of the other.
Data Source
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AI summary
A method for controlling a wind turbine generator is disclosed. The method comprises: comparing an output power reference value and an actual output power value in a first control block with a first controller having a first control dynamics, comparing the output from the first control block with an actual generator shaft power value in a second control loop with a second controller having a second control dynamics, to determine a generator control signal, wherein the output power reference value is fed-forward and summed with the output of the first controller in the first control block. The disclosed method allows for fast reactions to changes in the output power reference value by the second controller regardless of the speed of the first controller.