Multi-Level Converter Center-Aligned PWM Common-Mode Elimination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multi-level converters, such as three-level converters, face challenges in preventing common mode voltage at AC terminals, leading to distortion in line-to-neutral voltages, which existing controllers using space vector modulation fail to fully address.
Innovation Solution
A system and method that generates center-aligned pulse-width modulated (PWM) patterns for multi-level converters by switching one phase at twice the frequency of the other two phases, ensuring no common mode voltage is produced at AC terminals, utilizing space vector modulation to selectively control solid-state switches and regulate AC terminal voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If switches are controlled to provide desired voltages at AC terminals, then voltage regulation is achieved, but thermal stress on semiconductors increases
Solution Approach 1:
The center-aligned PWM approach creates periodic switching patterns that distribute thermal stress more evenly across semiconductor devices. By aligning switching events symmetrically around the modulation period midpoint, the patent reduces peak thermal stress while maintaining effective voltage regulation at AC terminals
Solution Approach 2:
The patent changes the switching frequency parameter by switching one phase at twice the frequency of other phases during specific portions of the fundamental period. This parameter modification optimizes the balance between voltage regulation performance and thermal stress reduction on semiconductor devices
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A multi-level converter, 10, includes a plurality of alternating current (AC) terminals connected to an AC source or load, at least three direct current (DC) terminals connected to a multi-level DC source or load, and plurality of solid-state switches that are selectively turned On and Off to connect each of the plurality of AC terminals to one of the DC terminals, A controller, 12, provides PWM control signals to the solid-state switches. The controller, 12, utilizes space vector modulation to organize the various switching state configurations, and increments the switching states during a first half of the switching period and decrements the switching states during a second half of the switching period to center-align the PWM signals provided about the center of the switching period. The switching states utilized during the switching period dictate the PWM control signals provided to the plurality of switches employed in the three-level converter.