Dynamic Switching Frequency Control for Multi-Phase Machine PWM
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Solution Overview
Problem
Existing methods for operating multi-phase electrical machines, such as those in electric vehicles, often result in significant switching losses due to a fixed switching frequency for pulse width modulation, which does not optimize power efficiency.
Innovation Solution
A method that dynamically adjusts the switching frequency based on the difference between modulation function curves, allowing for periods of modified switching frequency to reduce power losses, particularly by determining specific time segments where the provisional switching frequency can be lowered.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a fixed switching frequency is used for pulse width modulation, then the modulation function curves can be implemented with acceptable precision, but significant switching losses occur reducing power efficiency
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed switching frequency to a dynamically adjustable switching frequency that varies over time. The control device determines time segments where the switching frequency can be modified based on the modulation function profiles, allowing the system to adapt the switching frequency to operational conditions rather than maintaining a constant value throughout operation.
Solution Approach 2:
The patent implements parameter changes by modifying the switching frequency parameter of the pulse width modulation. The control device determines a modified switching frequency for specific time segments based on the modulation function profiles, thereby changing this critical parameter dynamically to reduce switching losses while maintaining modulation precision when needed.
2Manufacturing precision
If the switching frequency is increased to reduce deviations from desired modulation function curves, then modulation precision improves, but switching losses increase
Solution Approach 1:
The patent applies segmentation by dividing the modulation function profiles into distinct time segments. The control device determines specific time segments where modified switching frequencies can be applied without compromising overall modulation precision. This segmentation allows the system to optimize switching frequency locally in different time periods rather than using a uniform frequency throughout.
Solution Approach 2:
The patent implements local quality by applying different switching frequency characteristics to different time segments. Instead of using a uniform switching frequency across all operations, the control device determines modified switching frequencies for specific time segments based on local conditions in the modulation function profiles, allowing optimization at local levels while maintaining overall system performance.
3Loss of energy
If the switching frequency is decreased to reduce switching losses, then power efficiency improves, but deviations from desired modulation function curves increase
Solution Approach 1:
The patent applies dynamics by implementing a time-varying switching frequency that adapts to operational needs. The control device dynamically determines time segments and modified switching frequencies based on the modulation function profiles, allowing the system to reduce switching losses during appropriate periods while maintaining modulation precision when required by the specific operational context.
Data Source
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AI summary
The present invention relates to a method and device for operating a multi-phase electric machine. The method comprises the steps of: determining a working point; determining a provisional switching frequency for a pulse width modulation for each of the electrical phases of the multiphase electric machine; determining a respective modulation function curve (m1, m2, m3) for the pulse width modulation for each of the electrical phases of the multiphase electric machine; determining at least one time period (Tmod) in the modulation function curves (m1, m2, m3) as a function of the values of the provisional modulation function curves in the time period (Tmod); changing the provisional switching frequency of the pulse width modulation towards a modified switching frequency in the at least one determined time period (Tmod); and generating a switching signal for each of the electrical phases by pulse width modulation based upon the determined modulation function curves (m1, m2, m3) using the modified switching frequency in the at least one determined time period (Tmod).