Wind Turbine Drive Train Damping During Voltage Dip
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Solution Overview
Problem
Wind turbines face mechanical load issues during voltage dips, leading to drive train oscillations and potential disconnection from the grid, as existing control methods fail to effectively manage torque changes and overshoot, impacting both electrical and mechanical performance.
Innovation Solution
A method involving a wind turbine controller and converter control unit that applies optimized pitch references and controlled ramped power references with different rates to minimize oscillations, avoid overspeed, and enhance drive train damping, ensuring continued operation and rapid recovery after a voltage dip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If generator torque is decreased rapidly to reduce power production during voltage dip, then electrical restrictions are satisfied, but drive train oscillations are excited and generator speed increases
Solution Approach 1:
The control system dynamically adjusts generator torque based on the phase of drive train oscillations. The torque reference is modified using a damping term that changes with the oscillation phase, allowing the system to respond adaptively to the dynamic conditions rather than applying a static torque reduction. This dynamic control reduces torque overshoot while maintaining compliance with electrical restrictions.
Solution Approach 2:
The control method uses feedback from the drive train oscillation phase to adjust the torque reference. By monitoring the oscillation phase and using it to modulate the damping term in the torque reference calculation, the system creates a closed-loop control that actively suppresses oscillations. The feedback mechanism allows the controller to counteract oscillations in real-time, reducing drive train instability caused by rapid torque changes.
2Speed
If generator torque is decreased to avoid overspeed during voltage dip, then generator speed is limited, but torque overshoot occurs during recovery
Solution Approach 1:
The control system prepares for recovery by gradually increasing the torque reference after the voltage dip ends, rather than applying full torque immediately. The ramped torque reference with different rates for increasing and decreasing torque prevents sudden torque changes that would cause overshoot. This preliminary action of controlled torque increase ensures smooth transition back to normal operation without exceeding torque limits.
Solution Approach 2:
The control method applies periodic modulation to the torque reference using a damping term that oscillates in opposition to the drive train oscillations. This periodic action counteracts the natural oscillations of the drive train, reducing the amplitude of torque variations during recovery. By applying torque adjustments at the right frequency and phase, the system minimizes torque overshoot while maintaining speed control.
3Productivity
If torque reference is increased rapidly to recover power production after voltage dip, then power production recovery is accelerated, but drive train oscillations are excited
Solution Approach 1:
The control system uses dynamic torque reference adjustment based on the real-time phase of drive train oscillations. Instead of applying a fixed ramp rate, the torque reference is modulated dynamically to counteract oscillations. The damping term in the torque reference calculation changes continuously with the oscillation phase, allowing the system to accelerate power recovery while simultaneously suppressing drive train oscillations through phase-dependent torque adjustments.
Solution Approach 2:
The control method employs feedback from drive train oscillation measurements to adjust the torque reference in real-time. By monitoring the oscillation phase and using it to modulate the damping term, the system creates a feedback loop that actively suppresses oscillations during power recovery. This feedback mechanism allows the controller to increase power production speed without exciting drive train oscillations, as the torque adjustments are continuously adapted to counteract oscillatory behavior.
Data Source
AI summary
The present invention is directed to a method of reducing a mechanical load on the occurrence of voltage dip in the wind turbines. The wind turbine generator controller and the converter control unit work in combination to control the oscillation generated due to voltage dip in the wind turbine 100. The method applies a ramp in power recovery to allow the enhanced DTD damp oscillations before the peak in torque happens. The method involves the step of: delivering a maximum active power value by the converter control unit to the wind turbine generator controller. Next step is setting a saturation value for the set points to enhance the drive train limits. In the next step, ramping is applied to the power set points of the wind turbine generator. And finally an enhanced drive train damping s applied to the ramped value of the power in order to reduce the mechanical load in the wind turbine and to damp the oscillation in the wind turbine generator.