Frequency Converter Harmonic Reduction via Rotor Feedback
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Solution Overview
Problem
Alternating current electric machines with frequency converters experience harmonic distortions in line current due to non-sinusoidal rotor magnetization and discrete winding placements, leading to irregular power supply and grid inefficiencies.
Innovation Solution
A method and frequency converter system that includes a controllable machine bridge and line bridge, with a feedback channel for measuring rotor pole position, calculating and updating a compensation term to remove harmonics, and incorporating this term into control signals to reduce harmonic effects on line current and motor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional frequency converter control is used, then the electric machine can operate with variable speed and torque, but line current distortion occurs due to harmonics caused by non-sinusoidal rotor magnetization and discrete winding placement
Solution Approach 1:
The patent implements feedback by measuring or estimating rotor pole position and using this information to dynamically adjust control signals. The system continuously monitors the electric machine's operation and modifies the frequency converter output based on actual rotor position, enabling precise control that reduces harmonic distortion while maintaining variable speed capability
Solution Approach 2:
The patent changes control parameters by calculating machine bridge control signals as functions of rotor pole position and updating these signals when pole position changes. This dynamic parameter adjustment allows the system to optimize the control strategy based on real-time operating conditions, reducing harmonics without sacrificing productivity
2Power
If harmonics are present in the electric machine, then power can be supplied to the machine, but irregular power supply causes distortion in line current which reduces power grid efficiency
Solution Approach 1:
The system uses feedback from rotor pole position measurement to continuously adjust the control signals, ensuring that power is supplied efficiently while minimizing harmonic generation. This closed-loop control enables the frequency converter to adapt to changing load conditions and maintain optimal power transfer with reduced grid losses
Solution Approach 2:
The patent converts the harmful effect of harmonics into a beneficial control mechanism by using rotor pole position information to pre-compensate for harmonic distortion. The control system deliberately adjusts the output signals to counteract the expected harmonic effects, transforming what would be a harmful distortion into a controlled parameter that improves overall system efficiency
Data Source
AI summary
Invention is related to a method for controlling an alternating current electric machine with a frequency converter including a controllable machine bridge and a controllable line bridge, and a corresponding frequency converter. The method comprises calculating a line bridge control signal, controlling line current through the line bridge using the line bridge control signal, measuring or estimating rotor pole position of the electric machine, calculating a machine bridge control signal as a function of the rotor pole position, updating the machine bridge control signal when the rotor pole position changes, and controlling current of the electric machine through the machine bridge using the machine bridge control signal.