Motor Control Pulse Shift PWM Duty Signal Ripple Reduction
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Solution Overview
Problem
Existing motor control systems face accuracy issues in current detection due to current ripples generated by pulse shifts, leading to reduced accuracy in current detection, especially when instruction voltage values of phases are close to each other.
Innovation Solution
Implementing a motor control apparatus with a pulse shift control mechanism that adjusts the switching timings of PWM duty signals between phases to ensure a predetermined difference, and using a phase switching subsequent correction amount calculation unit to set correction amounts for PWM duty signals, thereby minimizing current ripples and improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulse shift control is performed to correct instruction voltage values, then current detection accuracy is improved, but current ripples are generated due to instantaneous voltage changes
Solution Approach 1:
The patent applies preliminary action by performing pulse shift control in advance before current detection. The instruction voltage values are corrected beforehand to ensure that voltage differences between phases are sufficient, allowing accurate current detection without requiring instantaneous corrections that would generate ripples during the detection moment itself
Solution Approach 2:
The patent converts the potentially harmful current ripples into beneficial effects by carefully timing the pulse shift control. The voltage corrections are applied in a controlled manner during PWM cycles where they create the necessary voltage differences for detection, and the resulting current changes are utilized to improve detection accuracy rather than being treated as pure noise
2Stability of the object's composition
If instruction voltage values of phases are close to each other, then system stability is improved, but current detection accuracy deteriorates due to insufficient voltage difference
Solution Approach 1:
The patent applies local quality by performing pulse shift control selectively on specific phases rather than uniformly adjusting all phases. When voltage differences between certain phases fall below a threshold, pulse shift control is applied locally to those phases to create sufficient voltage differences for detection, while maintaining the overall stability of the three-phase system
Solution Approach 2:
The patent changes the parameter of instruction voltage values dynamically through pulse shift control. When voltage differences between phases become too small, the instruction voltage values are adjusted by adding or subtracting correction amounts, thereby changing the voltage parameters to ensure sufficient differences for accurate current detection while maintaining system stability
Data Source
AI summary
The present invention performs pulse shift control in such a manner that a difference between switching timings of PWM duty signals can reach or exceed a second predetermined value when the difference between the switching timings of the PWM duty signals of phases falls below the first predetermined value, and determines a correction amount for the phase by the pulse shift control in such a manner that a correction amount after switching becomes smaller than a correction amount before the switching of a phase on which the pulse shift control is performed in pulse shift phase switching control.