Six-Phase PMG Rectifier Segmentation for Torque Pulsation
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Solution Overview
Problem
Conventional DC power generating systems using 3-phase permanent magnet generators require large passive components and are sensitive to torque pulsation due to phase current harmonics, while multilevel topologies offer high power density but are complex and expensive.
Innovation Solution
A 6-phase permanent magnet generator system with passive rectifiers and an output voltage regulation section using pulse width modulation to selectively couple rectifier outputs, eliminating the need for a generator position sensor and reducing harmonic distortion and torque pulsation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional 3-phase active rectifier is used, then DC power generation is achieved, but large passive components (dc link capacitor and output power quality filter) are required
Solution Approach 1:
The patent divides the rectification process into two separate 6-pulse rectifiers processing two sets of 3-phase windings independently, then combines their outputs. This segmentation allows each rectifier to operate at lower voltage stress and enables more efficient power density utilization, reducing the overall size of passive components required compared to a single high-voltage rectifier system.
Solution Approach 2:
The six-phase PMG system provides multiple functions: it generates DC power while simultaneously eliminating sixth harmonic torque pulsation and reducing the need for large passive filtering components. The dual rectifier configuration serves both power conversion and harmonic cancellation purposes, improving power quality without requiring additional bulky filters.
2Power
If multilevel topologies (unidirectional Vienna Rectifier or bi-directional neutral diode clamped multilevel converter) are used, then high power density with low harmonic distortion is achieved, but device complexity and cost increase
Solution Approach 1:
Instead of implementing a complex multilevel converter topology, the patent segments the system into two independent 6-pulse rectifiers processing separate winding sets. This approach achieves similar power density and harmonic performance without requiring the complex switching arrangements and control algorithms of multilevel topologies.
Solution Approach 2:
Rather than using a single complex multilevel converter to achieve low harmonic distortion, the patent inverts the approach by using two simpler 6-pulse rectifiers with phase-shifted windings. The harmonic cancellation emerges from the phase relationship between the two rectifier outputs rather than from complex multilevel switching, simplifying the overall device architecture.
3Power
If a 3-phase PMG is used, then power generation is achieved, but torque pulsation sensitivity to phase current harmonics increases
Solution Approach 1:
The patent segments the electrical system into two independent 6-pulse rectifier paths processing two sets of windings. This segmentation, combined with the 6-phase configuration, eliminates the sixth harmonic torque pulsation that plagues 3-phase systems, resulting in smoother torque delivery and improved reliability.
Solution Approach 2:
The patent converts the potential harm of harmonic currents into a benefit by configuring the six-phase system with two sets of windings connected to 6-pulse rectifiers. The phase relationships cause harmonic components that would normally cause torque pulsation to cancel each other out, transforming what would be a harmful effect into a torque-smoothing mechanism.
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 achieves high power density with reduced losses and low torque pulsation, improving power quality and minimizing the size of output power quality filters by controlling voltage ripple through PWM.
Implementation Method 1
a six-phase permanent magnet generator (PMG) that includes first and second sets of windings... generating alternating current (AC) voltage produced by the six-phase PMG
Implementation Method 2
a rectifier section that converts alternating current (AC) voltage produced by the six-phase PMG into a DC output. The rectifier section includes: a first six-pulse rectifier... and a second six-pulse rectifier
Implementation Method 3
an output voltage regulation section... that is coupled between the first rectifier positive output and the second rectifier positive output. The output voltage regulation section selectively coupling the first rectifier positive output or the second rectifier positive output to the positive rail of the output bus. The unit also includes a controller that provides a pulse width modulated (PWM) signal
Data Source
AI summary
An aircraft power generation unit to generate direct current (DC) power provided to a load includes a six-phase permanent magnet generator (PMG) and a rectifier section that converts alternating current (AC) voltage produced by the six-phase PMG into a DC output. The rectifier section includes a first six-pulse rectifier and a second six-pulse rectifier connected to the second set of windings. The unit also includes an output bus configured to be connected to the load and including a positive rail and a negative rail connected to the second rectifier and an output voltage regulation section that provides an output voltage to the output bus. The unit also include a controller that provides a pulse width modulated (PWM) signal to the output voltage regulation section to vary the output voltage provided to the output bus.