Random Position PWM for Inverter Noise Reduction

Solution Overview

Problem

Existing random PWM schemes, such as RFPWM, require complex calculations and increased programming considerations due to changing triangle wave frequencies, leading to increased calculation time and noise in inverter systems.

Innovation Solution

The implementation of a random position PWM (RPPWM) method using MinMaxPWM operation, which generates random offset values to change the position of active vectors within a fixed switching frequency, simplifying the generation of random PWM signals and reducing electromagnetic noise in inverters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If random frequency PWM (RFPWM) is used to vary the triangle wave frequency, then electromagnetic noise is reduced, but calculation time increases and programming complexity increases

Engineering Contradiction:

Improveelectromagnetic noiseVSAvoidcalculation time

Core Design Contradiction:

Object-affected harmful factorsVSLoss of time

Solution Approach 1:

The patent changes the parameter being randomized from triangle wave frequency (RFPWM) to active vector position (RPPWM). By keeping the triangle wave frequency fixed and randomizing only the active vector position within the PWM period, the calculation complexity is reduced while still achieving noise reduction through position variation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent segments the randomization process into a fixed component (triangle wave frequency) and a variable component (active vector position). This segmentation allows the system to maintain a constant sampling frequency for calculations while introducing randomness only where needed for noise reduction, thereby reducing overall computational burden.

Inventive Principle:

Principle #1Segmentation

2Object-affected harmful factors

If random frequency PWM (RFPWM) is used to vary the triangle wave frequency, then electromagnetic noise is reduced, but device complexity increases

Engineering Contradiction:

Improveelectromagnetic noiseVSAvoidprogramming complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent changes the parameter being randomized from triangle wave frequency (RFPWM) to active vector position (RPPWM). By keeping the triangle wave frequency fixed and randomizing only the active vector position within the PWM period, the calculation complexity is reduced while still achieving noise reduction through position variation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent segments the randomization process into a fixed component (triangle wave frequency) and a variable component (active vector position). This segmentation allows the system to maintain a constant sampling frequency for calculations while introducing randomness only where needed for noise reduction, thereby reducing overall computational burden.

Inventive Principle:

Principle #1Segmentation

3Loss of time

If fixed switching frequency is used, then calculation time is reduced and programming is simpler, but electromagnetic noise increases

Engineering Contradiction:

Improvecalculation timeVSAvoidelectromagnetic noise

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

The patent changes the parameter being randomized from triangle wave frequency (RFPWM) to active vector position (RPPWM). By keeping the triangle wave frequency fixed and randomizing only the active vector position within the PWM period, the calculation complexity is reduced while still achieving noise reduction through position variation.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3208932B1Method and apparatus for generating PWM signal

Publication Date: 2019.09.04 LSIS CO LTD

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Figure 3(a)~3(c)

AI summary

Disclosed herein are a method and an apparatus for generating a random PWM voltage reference signal for driving an inverter, which can more simply generate random position PWM (RPPWM) in which a position of an active vector is changed to achieve the same effect as when a switching frequency is changed.