Multi-Level Power Converter EMI Reduction via Random PWM
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Multi-level power converters using pulse-width modulation (PWM) suffer from output waveform distortions, leading to electromagnetic interference (EMI) due to fixed switching frequencies, which are not effectively mitigated by existing technologies.
Innovation Solution
A multi-level power converter system that generates PWM signals by varying the period of carrier signals randomly, using a controller with a random value generator to add random values to a nominal period, thereby reducing EMI by spreading high-frequency noise components across a wider frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If pulse-width modulation (PWM) with fixed switching frequency is used to control multi-level power converter, then the converter can synthesize multiple DC voltages into AC output voltage, but electromagnetic interference (EMI) noise is generated due to the fixed switching frequency
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The controller dynamically adjusts the switching frequency within a range around a nominal value, allowing the system to adapt and avoid fixed-frequency EMI while maintaining power conversion capability.
Solution Approach 2:
The patent changes the frequency parameter of the PWM signals. By varying the switching frequency within a specified range instead of maintaining a constant frequency, the system reduces EMI noise while preserving the ability to synthesize AC output voltage from multiple DC voltages.
2Manufacturing precision
If multi-level converter topology is used to synthesize three or more voltages, then less distorted waveforms are produced compared to two-level converters, but PWM still causes some distortion in the output waveform
Solution Approach 1:
The patent uses dynamic switching frequency adjustment to further reduce waveform distortion. By varying the frequency rather than keeping it fixed, the system minimizes PWM-induced distortion while maintaining the low-distortion advantage of multi-level topology.
Solution Approach 2:
The patent modifies the frequency parameter of the PWM control signals to optimize waveform quality. By changing the switching frequency within an optimal range, the system achieves minimal distortion in the synthesized AC output voltage.
Data Source
Figure 1
Figure 2A~2E
Figure 3
AI summary
A multi-level power converter system includes a multi-level power converted 12 configured to synthesize at least three direct current (DC) voltages into an alternating current (AC) output voltage, and includes a plurality of transistors Q. A controller 14 generates pulse-width modulation (PWM) signals used to control a state of the plurality of transistors of the multi-level converter by comparing first and second carrier signals to a reference signals, wherein a period of the first and second carrier signals is randomly varied from a nominal period.