Multilevel Converter Voltage Balancing via Sub-Module Extraction
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Solution Overview
Problem
Existing multilevel converter systems face inefficiencies in voltage balancing due to the time-consuming process of sorting and arranging sub-module voltages, especially as the number of sub-modules increases, leading to prolonged processing times and increased computational demands.
Innovation Solution
A method that efficiently reduces the arrangement time for sub-module values by extracting the maximum and minimum voltage sub-modules, determining state variations, and adjusting their states based on current direction and variations, allowing for rapid control without the need for extensive sorting operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sorting operation is performed to arrange sub-module voltage values in order, then voltage balancing is achieved, but processing time increases significantly
Solution Approach 1:
The patent extracts only the essential information needed for voltage balancing (number of ON sub-modules and current direction) rather than processing all sub-module voltage values. This selective extraction eliminates the time-consuming sorting operation while maintaining voltage balancing functionality.
Solution Approach 2:
The patent segments the voltage balancing process into two independent parts: (1) counting the number of ON sub-modules, and (2) determining current direction. This segmentation allows the system to avoid processing individual voltage values and their arrangement, significantly reducing computational time.
2Power
If the number of sub-modules is increased for large capacity electric power devices, then converter capacity is improved, but processing time increases infinitely
Solution Approach 1:
The patent segments the control process to depend only on the count of ON sub-modules and current direction, making the processing time independent of the total number of sub-modules. This allows large capacity converters with 150-200+ sub-modules to operate without proportional increases in processing time.
Solution Approach 2:
The patent extracts only the necessary control parameters (ON sub-module count and current direction) from the system state, eliminating the need to process individual voltage values from each sub-module. This extraction approach makes processing time constant regardless of the number of sub-modules.
3Reliability
If extensive sorting operations are performed on sub-module voltage values, then voltage distribution is equalized, but computational complexity increases
Solution Approach 1:
The patent extracts only the count of ON sub-modules and current direction from the complex system state, eliminating the need for sorting operations. This reduces computational complexity from O(n log n) sorting to simple counting and sign detection operations.
Solution Approach 2:
The patent changes the control parameters from individual sub-module voltage values to aggregate parameters (count of ON sub-modules and current direction). This parameter transformation simplifies the computational requirements while maintaining voltage balancing effectiveness.
Data Source
AI summary
A method of controlling a multilevel converter is provided. In the method of controlling a multilevel converter according to an embodiment, a sub-module having the maximum voltage and a sub-module having the minimum voltage respectively are extracted from among a plurality of sub-modules. An amount of state variation of each of the plurality of sub-modules is determined. When the amount of state variation is not determined to be 0, a direction of a current flowing through the plurality of sub-modules is detected. A subsequent state of at least one sub-module is determined according to at least one of the amount of the state variation and current direction. Subsequently an arrangement time for sub-module values can be efficiently reduced while the number of the sub-modules increases in the voltage balancing.