Modular Multilevel Converter Submodule Topology for Loss Reduction

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Solution Overview

Problem

Conventional modular multilevel converters face challenges in scalability, complexity, and semiconductor losses, particularly with traditional half bridge submodules, which increase semiconductor losses and complexity.

Innovation Solution

A submodule topology featuring two electronic switches connected in series with capacitors and a bidirectional switch, allowing for reduced semiconductor losses and complexity, with the ability to achieve three voltage levels using fewer submodules compared to standard half bridge configurations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional half bridge submodules are used to achieve multilevel voltage, then the converter can be scaled to any number of voltage levels, but the semiconductor losses increase and device complexity increases

Engineering Contradiction:

Improvescalability to any voltage levelVSAvoidsemiconductor losses

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The converter is divided into modular submodules, each capable of independent operation. The proposed topology segments the conventional half-bridge structure into a parallel configuration with two capacitors and two switches, allowing flexible combination to achieve any voltage level while reducing losses in each modular unit

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention introduces dynamic switching control where the bidirectional switch dynamically connects or disconnects the parallel capacitor-switch combination based on operating conditions. This dynamic operation allows the converter to adaptively minimize semiconductor losses while maintaining scalability across different voltage levels

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If conventional half bridge submodules are used to achieve multilevel voltage, then the converter can be scaled to any number of voltage levels, but the device complexity increases

Engineering Contradiction:

Improvescalability to any voltage levelVSAvoiddevice complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The complex multilevel voltage generation is segmented into identical, simple modular units. Each submodule uses the same parallel capacitor-switch configuration, reducing overall device complexity through standardization while maintaining the ability to scale to any voltage level by simply adding more identical modules

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The proposed submodule topology serves multiple functions: it can generate different voltage levels, provide fault tolerance, and enable bidirectional power flow. The universal parallel capacitor-switch configuration can be used in any voltage level requirement, simplifying the overall device design while achieving scalability

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If clamp double submodule is used to improve fault handling capability, then fault handling capability is improved, but semiconductor losses increase due to additional switches and diodes

Engineering Contradiction:

Improvefault handling capabilityVSAvoidsemiconductor losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The invention extracts the essential fault handling capability from the complex clamp double submodule structure and implements it in a simplified parallel configuration. By removing unnecessary switches and diodes while retaining the core fault protection mechanism through the bidirectional switch and parallel capacitors, the topology achieves improved fault handling with reduced semiconductor losses

Inventive Principle:

Principle #2Taking out (Extraction)

4Device complexity

If fewer submodules are used to reduce device complexity, then device complexity is reduced, but achieving the same number of voltage levels becomes more difficult

Engineering Contradiction:

Improvedevice complexityVSAvoidvoltage level achievement

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The bidirectional switch enables dynamic reconfiguration of the parallel capacitor-switch combination, allowing a single submodule to effectively contribute multiple voltage levels through different switching states. This dynamic operation reduces the total number of submodules needed while maintaining the ability to achieve any required voltage level

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS10069430B2Modular converter with multilevel submodules

Publication Date: 2018.09.04 REGENTS OF THE UNIVERSITY OF MINNESOTA

AI summary

One aspect of the disclosure includes a submodule topology for a modular multilevel converter. The submodule topology includes two electronic switches connected together with a first series connection terminal connecting the electronic switches in series, the series connected switches being connected in parallel with two capacitors connected together with a second series connection terminal connecting the capacitors in series. A bidirectional electronic switch connects the first series connection terminal with the second series connected terminal. An output voltage is obtained across the first series connected terminal and a common terminal formed by the parallel connection of the series connected switches with the series connected capacitors.