Parallel Switch Modules for Stable MMC Short-Circuit Failure Mode
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Solution Overview
Problem
Existing modular multilevel converters (MMC) face operational disruptions due to semiconductor failures, which are not adequately addressed by current solutions that incur additional costs and complexity without enhancing operational resilience.
Innovation Solution
Implementing parallel semiconductor modules with a DC crowbar and free-wheeling diodes to enable stable shorting of AC terminals, allowing continued operation even with failed chips, eliminating the need for additional AC shorting devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated AC-terminal shorting devices are added to module-based chain-link and MMC converters to maintain operation after semiconductor failure, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The healthy parallel semiconductor modules automatically assume the function of the failed module by taking over its current path, eliminating the need for external shorting devices. The system uses its own redundant components to handle the failure condition internally.
Solution Approach 2:
The parallel semiconductor modules are designed to perform multiple functions: normal switching operation and failure compensation. The same modules that provide switching functions also serve as backup paths when failures occur, eliminating the need for dedicated failure handling devices.
2Reliability
If mechanical or pyrotechnical shorting devices are installed between AC terminals for failure tolerance, then reliability is improved, but ease of manufacture and device complexity worsen
Solution Approach 1:
The patent replaces mechanical shorting devices (mechanical switches, springs, pyrotechnical actuators) with an electronic solution using parallel semiconductor modules. The healthy modules electronically assume the current path that would otherwise require mechanical shorting, eliminating complex mechanical failure handling systems.
3Reliability
If parallel semiconductor modules are used to provide backup current paths, then reliability is improved, but device complexity and space requirements increase
Solution Approach 1:
The semiconductor switching function is divided into multiple parallel modules, each capable of independent operation. This segmentation allows the system to tolerate failures in individual modules while maintaining overall functionality through the remaining parallel paths.
Data Source
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AI summary
The application discloses an arrangement of switches for a voltage source converter cell, the voltage source converter cell having two AC terminals, wherein the arrangement of switches forms a number of parallel series circuits (branches, current paths), wherein the switches in each of the series circuits paths are being controlled by external signals to alter a conductivity status of the switches between an "ON"-state and an "OFF"-state. The external signals are generated by one or more control units, and the two AC terminals are each connected to subsets of the series circuits of the switches. The control units comprises failure detection means, the failure detection means being adapted to determine a defective switch in the series circuits by predetermined conditions. The control units are further configured to output a control signal to alter a conductivity condition of each of the switches in the series circuits in such a manner, that a short circuit between the two AC terminals is created, if one of the switches is determined as being defective according to the predetermined conditions.