Modular Multilevel Converter Hard-Parallel Output Synchronization
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Solution Overview
Problem
Conventional modular multilevel converters with sub-modules in series configurations face increased costs, higher failure likelihood, and space inefficiencies due to the need for intermediary components in soft-parallel configurations, which complicate power management and synchronization.
Innovation Solution
A modular multilevel converter with sub-modules connected in a hard parallel configuration without impedance, utilizing a controller to synchronize outputs by transmitting synchronizing signals in opposite directions to ensure synchronized operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sub-modules are connected in soft-parallel configuration with intermediary inductors, then current sharing is forced equal, but device complexity and cost increase
Solution Approach 1:
The patent removes the intermediary inductors from the sub-module connections, transitioning from soft-parallel to hard-parallel configuration. This extraction of unnecessary components simplifies the system while maintaining current sharing through active control of switching devices rather than passive impedance matching.
Solution Approach 2:
The patent replaces the passive mechanical/electrical impedance-based current sharing mechanism (inductors) with an active control system that uses switching devices and control circuits to regulate current distribution, thereby reducing hardware complexity.
2Power
If sub-modules are connected in series configuration, then power handling capability is increased, but failure likelihood and cost increase
Solution Approach 1:
The patent divides the power handling function across multiple sub-modules connected in parallel, where each sub-module operates independently. This segmentation allows the system to achieve high power capability without the reliability penalties of series connections, as failure of one sub-module does not necessarily cause system-wide failure.
Solution Approach 2:
The patent changes the connection topology parameter from series to hard-parallel configuration, fundamentally altering how power is handled. In hard-parallel connection, power capability scales with the number of sub-modules while maintaining independent failure modes, unlike series connections where power capability increases but reliability decreases.
3Device complexity
If sub-modules are directly connected in hard parallel configuration, then device complexity and space are reduced, but synchronization of outputs becomes challenging
Solution Approach 1:
The patent introduces synchronizing signals as an intermediary control mechanism that coordinates the switching devices of directly connected sub-modules. These signals mediate the synchronization requirement without requiring physical intermediary components, allowing hard-parallel connection to maintain both simplicity and synchronized operation.
Solution Approach 2:
The patent implements a feedback control system where synchronizing signals monitor and adjust the operation of switching devices in real-time. This feedback mechanism ensures that directly connected sub-modules operate in synchronization, resolving the control challenge while maintaining the simplicity of hard-parallel configuration.
Data Source
AI summary
Provided is a modular multilevel converter and a method for synchronizing outputs of sub-modules of the converter. The modular multilevel converter includes sub-modules connected in parallel, and each sub-module generates an output. The modular multilevel converter also includes a controller that is communicatively coupled to the sub-modules. The controller controls a flow of one or more synchronizing signals between the plurality of sub-modules, such that each sub-module receives the synchronizing signals in opposite directions simultaneously, thereby controlling a synchronization of the outputs generated by the sub-modules.