Active Damping of Synchronous Generator Torsional Oscillations
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Solution Overview
Problem
Synchronous generators in mechanical drivetrains often experience undesirable torsional oscillations due to lightly damped engine gearboxes, leading to mechanical failures, and existing solutions require additional mechanical components for damping, increasing weight and cost.
Innovation Solution
A controller system that includes a speed sensing circuit, detection circuit, and voltage regulator to actively dampen torsional oscillations by varying the excitation voltage of the synchronous generator at the frequency of the oscillations, using electrical means to provide positive damping without additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical damping components are added to offset negative damping and dampen torsional oscillations, then torsional oscillations are reduced, but system weight and cost increase
Solution Approach 1:
The patent replaces mechanical damping components with an electrical control system. The controller modifies the excitation voltage to the synchronous generator based on detected torsional oscillations, creating an electrical damping effect that substitutes for mechanical damping hardware, thereby reducing system weight while maintaining oscillation damping performance
Solution Approach 2:
The patent introduces an intermediary control system between the mechanical drivetrain and the synchronous generator. The controller acts as a mediator that senses torsional oscillations and adjusts the generator's electrical characteristics to provide damping, avoiding direct mechanical damping components
2Reliability
If mechanical damping components are added to dampen torsional oscillations, then torsional oscillations are reduced, but system cost increases
Solution Approach 1:
The patent substitutes expensive mechanical damping components with a controller that uses existing electrical systems. By modifying excitation voltage based on oscillation detection, the system achieves damping functionality without additional mechanical parts, reducing manufacturing cost
Solution Approach 2:
The synchronous generator itself provides the damping function through controlled modification of its excitation voltage. The generator serves its primary power generation function while simultaneously providing torsional oscillation damping, eliminating the need for separate damping components and reducing overall system cost
3Length of moving object
If the shaft is made relatively long to meet mechanical design considerations, then mechanical compliance increases, but this creates distributed spring-mass system with torsional resonances
Solution Approach 1:
The patent implements a feedback control system that detects torsional oscillations in the shaft and responds by adjusting the excitation voltage to the synchronous generator. This closed-loop feedback creates active damping that counteracts the torsional resonances inherent in the long shaft design, maintaining stability despite the mechanical compliance
Solution Approach 2:
The patent changes the electrical parameters of the synchronous generator dynamically in response to detected oscillations. By modifying excitation voltage based on real-time oscillation detection, the system alters the generator's mechanical characteristics to provide damping, compensating for the resonant effects of the long shaft
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
The system effectively reduces torsional oscillations in the mechanical drivetrain by dynamically adjusting the torque of the synchronous generator, eliminating the need for mechanical damping components and maintaining a constant output voltage, thus preventing mechanical failures while minimizing system weight and cost.
Implementation Method 1
a voltage regulator circuit that varies an excitation voltage provided to the synchronous generator based, in part, on the detected torsional oscillations
Implementation Method 2
the speed sensing circuit indirectly measures the speed of the synchronous generator by detecting zero crossings of the monitored AC voltage to estimate the time period between each successive zero crossing
Data Source
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AI summary
A generator control unit (GCU) (16) provides active damping of a synchronous generator (20) by monitoring the speed of the synchronous generator (20) and detecting oscillations in the monitored speed. The oscillations are indicative of torsional oscillations within the mechanical drivetrain including the synchronous generator or generators (20). In response to detected oscillations in the monitored speed, the GCU (16) generates a varying set-point value that is used to control the excitation voltage provided to the synchronous generator (20). Varying the excitation voltage provided to the synchronous generator (20) causes a variation in synchronous generator torque. By selectively varying the torque in the synchronous generator (20), the GCU (16) provides active damping in the synchronous generator (20) that decreases or dampens the torsional oscillations.