Modular Multilevel Converter Bypass Circuit Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power conversion apparatuses with modular multilevel converters face high costs and size issues due to the need for bypass circuits with high current resistance and explosion-proof capabilities to handle short circuit inrush and circulation currents, which are essential for continuous operation but increase the overall cost and size of the system.
Innovation Solution
The power conversion apparatus incorporates a bypass circuit that allows self-feeding drive power to be supplied from other cell converters within the same cell block, reducing the number of bypass circuits needed and utilizing a low-cost, simple configuration that can withstand short circuit currents, while also providing a mechanism to protect the cell converters during DC short circuit accidents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bypass circuits with high current resistance and explosion-proof capabilities are provided for each cell converter, then continuous operation during failures and protection during short circuit accidents is achieved, but cost and device size significantly increase
Solution Approach 1:
The power conversion apparatus is divided into multiple cell blocks, each containing several cell converters. The bypass circuit is provided at the cell block level rather than for each individual cell converter, segmenting the protection function to reduce overall system complexity while maintaining reliability through hierarchical organization
Solution Approach 2:
The bypass circuit is designed to perform multiple functions: it provides continuous operation capability during cell converter failures and offers protection during DC short circuit accidents. This multi-functional design eliminates the need for separate protection circuits for different failure modes, reducing overall device complexity and cost
2Reliability
If bypass circuits with sufficient current capacity are provided for each cell converter, then protection against short circuit circulation current is achieved, but cost increases due to high current resistance and explosion-proof requirements
Solution Approach 1:
Multiple cell converters within the same cell block share a common bypass circuit. This merging approach consolidates the protection function, allowing the bypass circuit to handle short circuit circulation currents for the entire cell block rather than requiring separate high-capacity circuits for each cell converter, thereby reducing cost while maintaining protection capability
Data Source
Figure 1
Figure 2(a)~2(e)
Figure 3(a)~3(d)
AI summary
A cell block (30) including a plurality of cell converters (10) connected in cascade and each including switching elements (11) and a capacitor (13) is provided. The cell block (30) includes external connection terminals (X31, 32) for connecting to another cell block in cascade, and a bypass circuit (20) is connected to the external connection terminals (X31, 32).