Wind Turbine Torque Control for Grid Fault Recovery
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Solution Overview
Problem
Wind turbines face challenges in quickly returning to full power feed-in after a grid fault while managing mechanical loads, as existing methods may lead to abrupt changes in electrical torque, causing oscillations and prolonged recovery times.
Innovation Solution
A torque controller that initializes a torque ramp based on the difference between target and actual speed, with an upper limit imposed by the torque ramp to prevent sudden increases, allowing for a controlled and rapid return to normal operation while managing mechanical loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wind turbine returns to full power feed-in quickly after a grid fault, then the grid operator requirements are satisfied, but abrupt changes in electrical torque cause mechanical oscillations and excessive loads on the wind turbine
Solution Approach 1:
The control method prepares the wind turbine for rapid power recovery by pre-establishing a torque controller that can be quickly activated after grid fault. The controller is initialized with appropriate parameters before the fault occurs, enabling immediate controlled response when voltage is restored, thus achieving fast power feed-in recovery without causing mechanical oscillations
Solution Approach 2:
A torque ramp function is introduced as an intermediary between the grid fault detection and the full power recovery. This ramp function gradually increases the electrical torque from zero to the rated value over a controlled time period, mediating the transition between low power during fault and full power after fault, thereby preventing abrupt torque changes and mechanical oscillations while still achieving rapid recovery
2Power
If the electrical torque is increased abruptly to restore full power after grid fault, then power feed-in is restored quickly, but the mechanical drive train experiences excessive stress and oscillations
Solution Approach 1:
The control system dynamically adjusts the electrical torque based on the real-time grid voltage status. When voltage is restored after grid fault, the torque controller activates and dynamically increases torque according to a predefined ramp function rather than applying abrupt full torque. This dynamic control restores power quickly while adapting the torque profile to protect the mechanical drive train from excessive stress
Solution Approach 2:
The torque ramp function serves as a cushioning mechanism that is prepared in advance. When grid fault occurs and voltage drops, the system switches to this pre-configured ramp profile that limits the maximum rate of torque increase. This beforehand cushioning protects the mechanical drive train from sudden stress spikes while enabling controlled power recovery once the grid is restored
Data Source
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AI summary
The invention relates to a method for regulating the electrical moment of a wind turbine in the event of a grid fault. A fall in voltage that lies outside the limits of normal operation is detected. A moment regulator (26, 27) is operated, which determines a target value (52) for the electrical moment of the wind turbine. A moment ramp (31) is initiated. The target value (52) of the moment regulator (26, 27) is compared to the moment ramp (31) and the smaller value is selected as the moment setpoint value (35). The electrical moment of the wind turbine is set on the basis of the moment setpoint value (35). The invention also relates to a wind turbine suitable for carrying out the method. By means of the invention, fast restoration of power is achieved after the grid fault has ended and the loads for the wind turbine are kept within limits.