Three-Phase Rotary Machine Control Reducing Torque Ripple
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Solution Overview
Problem
Existing control devices for three-phase rotary machines fail to effectively reduce torque ripple when magnetic saturation occurs, leading to increased heat generation and performance deterioration.
Innovation Solution
A control device for a three-phase rotary machine that generates torque as a sum of magnet torque and reluctance torque, using two power converters to supply alternating currents with specific phase differences to two sets of three-phase windings, and a control unit that calculates d-axis and q-axis currents to superimpose harmonic components on dq coordinates, adjusting the high-order dq amplitude ratio based on fundamental wave current amplitude to minimize torque ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large current is supplied to increase output torque, then the output torque is increased, but the heat generation becomes large and magnetic saturation occurs causing performance deterioration
Solution Approach 1:
The invention changes the control parameters by calculating and superimposing sixth-order dq-axis current components on the fundamental wave. By adjusting the amplitude ratio of d-axis to q-axis current components and the phase difference, the patent modifies the current waveform characteristics to reduce peak values while maintaining average torque output, thereby reducing heat generation without sacrificing power output
2Power
If a large current is supplied to increase output torque, then the output torque is increased, but magnetic saturation occurs causing torque ripple increase
Solution Approach 1:
The invention addresses torque ripple by introducing sixth-order current components with specific amplitude ratios and phase differences. This parameter modification smooths the torque waveform by compensating for harmonics generated during magnetic saturation, maintaining stable torque composition even at high current levels
3Stability of the object's composition
If d-axis current amplitude is increased to reduce torque ripple in magnetic saturation region, then torque ripple is reduced, but the control complexity increases
Solution Approach 1:
The control device uses feedback by calculating the actual current amplitude and comparing it with reference values. Based on this feedback, the control unit dynamically adjusts the amplitude ratio of d-axis to q-axis current components, enabling automatic optimization of torque ripple reduction without requiring complex manual intervention or additional hardware
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 heat generation and torque ripple across various current levels, ensuring the three-phase rotary machine operates efficiently without performance deterioration, particularly in electric power steering applications where both heat and noise reduction are critical.
Implementation Method 1
calculating a d-axis current and a q-axis current of a 6(2k+1)th component to be superimposed on a fundamental wave component on dq coordinates
Implementation Method 2
configured to generate torque being a sum of magnet torque and reluctance torque when alternating currents with different phases are supplied to the two sets of three-phase windings
Implementation Method 3
when a large current is supplied, the heat generation becomes large, and there is a possibility of the performance deterioration or failure generation of the three-phase rotary machine due to magnetic saturation
Data Source
AI summary
A control device is provided for a three-phase rotary machine including two three-phase-winding sets. The control device includes two power converters for outputting alternating currents with a same amplitude and a phase difference of (30±60×n) degrees to the two three-phase-winding sets and a control unit for controlling energization of the three-phase rotary machine by calculating a d-axis current and a q-axis current of a 6(2k+1)th component to be superimposed on a fundamental wave component on dq coordinates so as to reduce a phase current peak value. The control unit calculates currents so that a high-order dq amplitude ratio is 0 when a fundamental wave current amplitude is a first threshold or less, and the high-order dq amplitude ratio is 1 when the fundamental wave current amplitude is larger than a second threshold.