Multilevel Converter Control via Power Module Grouping
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Solution Overview
Problem
Multilevel converters face abnormal operation and signal interference due to common mode current caused by large transitions in common mode voltage, which existing methods attempt to mitigate with hardware additions or shielding, resulting in complex circuits and increased costs with limited effectiveness.
Innovation Solution
A control method for multilevel converters that classifies power modules into groups and controls them to start, update, or stop working simultaneously or sequentially, with a preset time interval, to minimize the change in output level and reduce common mode interference without adding hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If power modules are controlled to switch on/off or update output state simultaneously, then the output level changes rapidly improving response speed, but common mode voltage transitions become large causing severe common mode current and signal interference
Solution Approach 1:
The patent segments the n power modules into m power module groups (n≥m≥1). Each group contains a limited number of power modules such that when they switch simultaneously, the output level change remains within a preset value. This segmentation prevents large common mode voltage transitions while maintaining coordinated switching within each group, thereby reducing common mode current and signal interference while preserving adequate response speed.
2Object-affected harmful factors
If power modules are switched sequentially with preset time intervals, then common mode interference is reduced, but the response speed and update efficiency decrease
Solution Approach 1:
The patent divides power modules into multiple groups that can switch simultaneously within each group, maintaining high update efficiency. Sequential switching is applied at the group level rather than individual module level, with preset time intervals between group switchings. This approach reduces common mode interference compared to individual sequential switching while preserving better update efficiency than complete sequential switching of all modules.
Solution Approach 2:
The patent merges multiple power modules into groups where they switch on/off or update output states simultaneously. By coordinating the switching of multiple modules within each group at the same time, the system achieves faster update efficiency while controlling the total output level change to remain within preset limits, thus balancing productivity and interference reduction.
3Device complexity
If the number of power modules in each group is unlimited, then grouping simplifies control, but large output level changes cause severe common mode voltage transitions and interference
Solution Approach 1:
The patent segments power modules into groups with a limited number of modules per group, specifically controlling that the number of modules in each group does not exceed a preset value. This limitation ensures that when modules within a group switch simultaneously, the output level change remains within a preset value, preventing severe common mode voltage transitions. The grouping structure simplifies control compared to individual module management while avoiding the interference problems of unlimited group sizes.
Data Source
AI summary
A control method of a multilevel converter includes: classifying power modules that start working, need to update an output state or stop working to form m power module groups; and controlling power modules in a same one of the power module groups to start working, update the output state or stop working at the same time, and sequentially controlling the m power module groups to start working, or update the output state or stop working, according to a preset time interval. The number of power modules in each power module group is less than or equal to a preset value, causing a change value of an output level of the each power module group to be less than or equal to a preset voltage value.