Variable Frequency Generator Torque Ripple Reduction
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Solution Overview
Problem
Conventional methods are inadequate for controlling and reducing torque ripple and load ripple in high voltage DC electrical power generation systems, leading to reduced system reliability and efficiency.
Innovation Solution
A system comprising two variable frequency generators connected to rectifiers, a speed correcting gearbox, and control units to align generator frequencies and reduce voltage ripple, with independent DC busses for power distribution, specifically designed for aircraft engine control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional single generator systems are used, then device complexity is reduced, but torque ripple and voltage ripple increase leading to reduced system reliability
Solution Approach 1:
The system divides the power generation function into two separate variable frequency generators (VFGs), each connected to different engine spools (low-pressure and high-pressure). This segmentation allows each generator to operate independently at its optimal speed, reducing torque ripple and voltage ripple while improving overall system reliability. The dual-generator architecture eliminates the harmful effects of single-generator systems by distributing the power generation load across multiple independent sources.
Solution Approach 2:
The system changes the operating parameters by allowing each VFG to operate at different frequencies corresponding to their respective engine spool speeds. The control system dynamically adjusts the frequency of each generator to maintain optimal operation points, transforming the fixed-frequency operation of conventional systems into variable-frequency operation that adapts to engine conditions, thereby reducing ripple effects.
2Reliability
If generator frequencies are not aligned, then each generator can operate independently, but voltage ripple and load ripple increase
Solution Approach 1:
The control system continuously monitors the frequency and output of each VFG and provides feedback to adjust their operation. By measuring the actual frequency deviations and load conditions, the control system dynamically adjusts the generator speeds to maintain frequency alignment, reducing voltage ripple and load ripple while preserving the independence of each generator's operation.
Solution Approach 2:
The system transitions from static frequency operation to dynamic frequency adjustment. Each VFG's speed is dynamically controlled based on real-time conditions, allowing the system to adapt to changing load demands while maintaining frequency synchronization. This dynamic control enables the generators to operate independently in terms of physical connection but cooperatively in terms of frequency management.
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 solution effectively reduces torque and load ripple, enhancing system reliability and stability while maintaining economic viability.
Implementation Method 1
a first rectifier configured to convert alternating current from the VFG to direct current
Data Source
Figure 1
AI summary
A system including a variable frequency generator (VFG) (102) including a generator (110) configured to conduct alternating current to a first rectifier (104) configured to convert alternating current from the VFG (102) to direct current and drive it to an HVDC Bus Network (106), a variable frequency second generator (103) including a second generator (111) configured to conduct alternating current to a second rectifier (105) configured to convert alternating current from the second generator (111) to direct current and conduct it to the HVDC Bus Network (106), a speed correcting gearbox operatively connected to the VFG (102) configured to align generator frequency to the second generator frequency, and a VFG control unit (112) operatively connected to the generator configured to control the VFG (102), and a second generator control unit (113) operatively connected to the second generator and the HVDC Bus Network configured to control the second generator.