Multilevel Inverter Submodule Segmentation with Inductive Decoupling
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Solution Overview
Problem
Existing multilevel converters are prone to submodule destruction due to abrupt capacitor discharge when switches are incorrectly switched on, leading to a chain reaction of failures and mechanical damage, which is mitigated by using stable housings or reduced capacitance, but these solutions increase weight and material usage or reduce load handling capacity.
Innovation Solution
The submodule design includes two submodules connected galvanically with an inductive element, allowing electrical behavior but decoupling them to limit current flow during failures, ensuring that if one submodule fails, others are minimally affected by using inductive elements with high inductance and ohmic resistance to isolate and protect the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stable submodule housings are used to prevent bursting, then reliability is improved, but weight and material usage increase significantly
Solution Approach 1:
The submodule is divided into two galvanically connected submodules, each with its own capacitor. The inductive element creates electrical decoupling between them, so that if one submodule fails, the other is protected from the full impact current. This segmentation allows using lighter housing materials while maintaining reliability.
2Reliability
If capacitor capacitance is reduced to prevent housing bursting, then reliability is improved, but load handling capacity is reduced
Solution Approach 1:
The total capacitance is distributed across two submodules, each with its own capacitor. The inductive element limits current flow between them during faults, allowing each capacitor to be sized for lower individual stress while maintaining total system power capacity.
Solution Approach 2:
The inductive element acts as an intermediary between the two submodules, limiting the discharge current that can flow during a short-circuit event. This mediator protects the submodules from destructive currents without requiring reduced capacitance values.
3Reliability
If submodule capacitance is reduced to limit short-circuit current, then reliability is improved, but material usage decreases which is beneficial
Solution Approach 1:
The total capacitance is split into two separate capacitors in galvanically connected submodules. The inductive element limits current flow between them, allowing the system to maintain adequate energy storage while limiting fault currents through the segmented architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively prevents submodule destruction and chain reactions while maintaining efficient load handling and reducing material usage by limiting discharge currents through inductive and ohmic impedance, ensuring adequate electrical isolation and protection of remaining submodules.
Implementation Method 1
the galvanic connection between the two sub-modules comprises at least one inductive element
Data Source
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AI summary
The invention relates to a multilevel inverter (10) having a plurality of series-connected submodules (SB), which each have at least one first switch, one second switch and one capacitor, and output current by means of the capacitor during discharging phases and receive current for charging the capacitor during charging phases. According to the invention, at least one of the submodules (SB) has two part-modules (TM1, TM2) that are galvanically connected to each other or are formed by two part-modules (TM1, TM2) that are galvanically connected to each other, which each have a first switch (S1), a second switch (S2) and a capacitor (C1, C2), and a first and a second part-module terminal (A1, A2), and the galvanic connection (V1, V2, V3, V4) between the two part-modules (TM1, TM2) comprises at least one inductive element (I1, I2, I3, I4).