Multi-Level Converter Switching Frequency Segmentation
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Solution Overview
Problem
Conventional multi-level converters are complex and costly due to the large number of switches operating at high frequencies, leading to increased switching losses, heat generation, and maintenance challenges, which affects efficiency and longevity.
Innovation Solution
A multi-level converter system with a DC link and phase circuits that include flying capacitors and switching devices, where the first set of switching devices operates at a lower frequency than the second set, reducing the overall number of switches and switching operations while maintaining performance through a controller that generates gating signals for efficient phase signal generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional multi-level converters use a large number of switches operating at high frequencies to achieve multi-level power conversion, then power quality and voltage levels are improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent divides the switching function into two separate sets of switches: first set switches (S1-S6) that operate at line frequency to connect DC sources to flying capacitors, and second set switches (S7-S12) that operate at higher frequency to connect flying capacitors to output nodes. This segmentation allows each switch set to be optimized for its specific function, reducing the total number of switches required while maintaining multi-level power conversion capability.
Solution Approach 2:
The patent implements dynamic switching frequency control where the first set of switches operates at a lower frequency (line frequency) and the second set operates at a higher frequency. This dynamic frequency assignment optimizes the switching operations by matching each switch set's operating frequency to its functional requirements, thereby reducing overall switching losses and device complexity.
2Productivity
If switches operate at high frequencies to maintain power quality, then conversion efficiency is improved, but switching losses and heat generation increase
Solution Approach 1:
The patent implements dynamic switching frequency control where the first set of switches operates at line frequency (lower frequency) to minimize switching losses during DC source connection, while the second set operates at higher frequency only when needed for output node connection. This dynamic frequency assignment maintains conversion efficiency by optimizing switching operations rather than continuously operating all switches at high frequency.
Solution Approach 2:
The patent uses periodic switching patterns where the first set of switches operates periodically at line frequency to charge/discharge flying capacitors, and the second set operates periodically at higher frequency to transfer energy to output nodes. This periodic action ensures that high-frequency switching occurs only when necessary, reducing overall switching losses while maintaining power quality.
3Device complexity
If the number of switches is reduced to lower cost and complexity, then device simplicity is improved, but maintaining power quality becomes difficult
Solution Approach 1:
The patent introduces flying capacitors as intermediary energy storage elements between the DC sources and the output nodes. These flying capacitors act as mediators that can be charged from DC sources through the first set of switches and then discharged to output nodes through the second set of switches, enabling multi-level voltage generation with fewer switches than conventional direct conversion topologies.
Solution Approach 2:
The patent changes the operating parameters of different switch sets, with the first set operating at line frequency and the second set operating at higher frequency. This parameter differentiation allows the system to maintain power quality by using high-frequency switching only where necessary (second set), while reducing overall switching complexity by using lower frequency for the first set.
4Duration of action of stationary object
If switching frequency is reduced to lower costs and heat generation, then operational longevity is improved, but power output quality may deteriorate
Solution Approach 1:
The patent implements dynamic frequency assignment where the second set of switches operates at higher frequency to maintain power output quality, while the first set operates at lower frequency to reduce heat generation and extend lifespan. This dynamic differentiation ensures that high-frequency switching occurs only when necessary for power quality, optimizing both longevity and performance.
Solution Approach 2:
The patent segments the switching function into two frequency domains: line frequency for DC source connection (first set) and higher frequency for output node connection (second set). This segmentation allows the system to maintain power output quality through targeted high-frequency switching while minimizing overall heat generation and extending converter lifespan.
Data Source
AI summary
A multi-level converter is provided. The multi-level converter may include a plurality of direct current (DC) sources coupled in series to form a DC link, and at least one phase circuit coupled in parallel to the DC link. The phase circuit may include at least one flying capacitor, at least one output node, a first set of switching devices selectively coupling the flying capacitor to one or more of the DC sources at a first frequency, and a second set of switching devices selectively coupling the flying capacitor to the output node at a second frequency.