Wind Turbine Grid Fault Control via Oscillation Damping
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Solution Overview
Problem
Wind turbines face challenges in maintaining connection and synchronization with the utility grid during faults, such as short circuits, which can lead to excessive aerodynamic power and generator speed increases, violating Low Voltage Ride Through (LVRT) grid codes if they trip offline or pitch blades inappropriately.
Innovation Solution
A method for controlling wind turbines that involves detecting grid status and mechanical oscillations, adjusting rotor blade pitch to return to normal operational settings, and reapplying thrust in counter phase to existing oscillations and loads, ensuring safe and efficient transition back to normal grid mode without causing constructive interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the blade pitch angle is varied to maintain rotor speed below over speed trip limit during low voltage, then generator speed control is improved, but mechanical oscillations and loads increase when returning to operational settings
Solution Approach 1:
The control system performs preliminary detection of mechanical oscillations and loads before returning the blade pitch angle to operational settings. By detecting the current oscillation state and load conditions in advance, the system can plan the pitch angle variation to avoid exacerbating existing oscillations, thus preventing excessive mechanical loads while maintaining speed control.
Solution Approach 2:
The system continuously monitors mechanical oscillations and loads during the transition from low voltage ride through mode back to normal operation. This feedback mechanism allows the control system to adjust the blade pitch angle variation in real-time, ensuring that oscillations are not significantly added to and mechanical loads remain within acceptable limits.
2Productivity
If the wind turbine returns to operational settings immediately after grid fault recovery, then productivity is improved, but constructive interference of oscillations may cause excessive loads exceeding damage limits
Solution Approach 1:
Before returning to full operational settings, the system performs preliminary detection of mechanical oscillations and loads to assess the turbine's current state. This preliminary assessment allows the control system to determine the safe timing and manner of returning to operational pitch angles, preventing constructive interference that could cause excessive loads.
Solution Approach 2:
The system dynamically adjusts the transition process back to operational settings based on real-time detection of mechanical oscillations and loads. Rather than a fixed immediate return, the control parameters are adapted according to the detected oscillation state, allowing safe recovery when oscillations are damped or when returning thrust is in counter phase to existing oscillations.
3Loss of time
If blade pitch angle is rapidly adjusted during grid fault, then response time is improved, but mechanical oscillations and loads are significantly increased
Solution Approach 1:
The control system performs preliminary detection of mechanical oscillations and loads before initiating blade pitch angle adjustment. This preliminary step ensures that rapid pitch changes are only executed when mechanical conditions are favorable, preventing excessive loads while maintaining responsive control during grid faults.
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
This approach allows wind turbines to maintain connection during grid faults, reduce oscillations and loads, and prevent damage by damping mechanical oscillations and loads, ensuring compliance with LVRT requirements and reliable power supply.
Implementation Method 1
the aerodynamical power must be reduced drastically throughout the period of utility grid fault
Implementation Method 2
detecting mechanical oscillations and/or loads of the wind turbine
Implementation Method 3
reapplying of thrust in counter phase to said mechanical oscillations and/or loads of the wind turbine
Data Source
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AI summary
The invention relates to methods for controlling a wind turbine connected to the utility grid by detecting status of the utility grid, and controlling one or more rotor blades and/or emitted power to the grid when returning to the operational wind turbine settings of normal grid mode. The invention also relates to a wind turbine and a wind park comprising at least two wind turbines.