Three-Phase Machine Controller Harmonic Peak Reduction
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Solution Overview
Problem
Existing three-phase rotating machine controllers face challenges in minimizing phase current peak while superimposing harmonic components with a fundamental component, particularly in reducing heat and losses, especially for electric power steering devices with limited mounting space and heat dissipation requirements.
Innovation Solution
A controller configuration that includes two three-phase winding sets with electric power converters outputting alternating currents with the same amplitude and a phase difference of (30±60*n) degrees, and a control unit that superimposes phase current 5th and 7th order components with the 1st order component to reduce phase current peak, with specific amplitude ranges for the 5th and 7th order components to optimize peak reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If harmonic components are superimposed with the fundamental component to improve motor output, then the motor output is improved, but the phase current peak increases leading to increased heat and losses
Solution Approach 1:
The patent applies parameter changes by optimizing the amplitude ratios of harmonic components (5th order: 8.1-16.1%, 7th order: 0.6-11.1%) superimposed on the fundamental component. This specific parameter optimization reduces phase current peak while maintaining motor output, thereby reducing heat and losses in the electric power steering device.
2Loss of energy
If the amplitude of harmonic components is increased to further reduce phase current peak, then phase current peak is reduced, but torque ripple increases
Solution Approach 1:
The patent uses parameter changes by precisely controlling the amplitude ratios of 5th and 7th order harmonic components within specific ranges (5th order: 8.1-16.1%, 7th order: 0.6-11.1%). This optimization achieves the dual goal of reducing phase current peak while minimizing torque ripple, unlike conventional methods that only focus on peak reduction.
Solution Approach 2:
The patent converts the potentially harmful effect of harmonic components (which can cause torque ripple) into a beneficial effect by carefully selecting specific amplitude ratios. The harmonic components that would normally increase torque ripple are instead used to reduce phase current peak, achieving heat reduction without excessive torque ripple when amplitudes are optimized.
3Loss of energy
If conventional harmonic superimposition methods are used to reduce phase current peak, then some peak reduction is achieved, but the reduction is insufficient and heat generation remains high
Solution Approach 1:
The patent achieves superior peak reduction by optimizing parameters of both harmonic order selection (5th and 7th orders) and their amplitude ratios (5th order: 8.1-16.1%, 7th order: 0.6-11.1%). This dual-parameter optimization produces a synergistic effect that reduces phase current peak more effectively than conventional single-parameter methods, thereby significantly reducing heat generation in the electric power steering device.
Data Source
AI summary
A three-phase rotating machine controller includes electric power converters that output, to the winding sets of a three-phase rotating machine, alternating currents having a same amplitude and a phase difference of (30 ±60*n) degrees from each other, n being an integer, and a control unit that reduces a peak of a phase current 1st order component applied to the rotating machine by superimposing therewith a phase current 5th order component and a phase current 7th order component, which have 5 times and 7 times the frequency of the phase current 1st order component, respectively. The control unit superimposes the phase current 5th and 7th order components having an optimum combination of amplitudes such that a peak reduction amount of the phase current 1st order component exceeds 5%, the amplitudes of the phase current 5th and 7th order components being with respect to the amplitude of the phase current 1st order component.