Modular Multi-Level Converter Voltage Balancing
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Solution Overview
Problem
In modular multi-level converters, varying capacitor voltages across submodules lead to uneven switching frequencies, reducing the lifespan of Insulated Gate Bipolar Transistors (IGBTs) due to differing capacitance values, especially when submodules from different manufacturers are used.
Innovation Solution
A method and system for controlling voltage balancing by grouping submodules, calculating weight information to maintain uniform switching frequencies across submodules, and adjusting switching states based on state information and arm currents to extend the life of submodules and IGBTs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If selective switching control is performed on sub modules with different capacitance values, then voltage balancing can be achieved, but switching frequency becomes uneven across sub modules leading to reduced IGBT lifespan
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the switching control parameters based on the capacitance values of individual sub modules. The control unit modifies switching frequencies and duty cycles to compensate for capacitance differences, ensuring that sub modules with lower capacitance do not experience excessively high switching frequencies while maintaining overall voltage balancing across all sub modules.
2Power
If a large number of sub modules from different manufacturers are used to increase processing capacity, then converter capacity is improved, but capacitance variation increases making voltage balancing control more difficult
Solution Approach 1:
The patent implements feedback control by continuously monitoring the voltage and capacitance values of each sub module and using this information to adjust switching control signals. The control unit receives real-time data from sensors on each sub module and dynamically modifies switching parameters to maintain voltage balancing, automatically compensating for capacitance variations without requiring manual intervention or complex external control systems.
3Ease of manufacture
If capacitance of sub module capacitors varies due to manufacturing differences, then manufacturing flexibility is improved, but switching frequency uniformity deteriorates reducing sub module life
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the switching control parameters based on the capacitance values of individual sub modules. The control unit modifies switching frequencies and duty cycles to compensate for capacitance differences, ensuring that sub modules with lower capacitance do not experience excessively high switching frequencies while maintaining overall voltage balancing across all sub modules.
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 approach enhances the reliability and lifespan of submodules and IGBTs by uniformly maintaining switching frequencies, thereby improving the overall performance and longevity of the converter.
Implementation Method 1
Each sub module includes two insulating gate bipolar transistor (IGBT) and a capacitor
Data Source
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AI summary
A method of controlling voltage balancing of a modular multi-level converter is provided. The method includes receiving state information on each of n sub modules in an arm module, grouping the n sub modules into m sub module groups, receiving first state information on each of sub modules in a first one of the m sub module groups, among the state information on each of the n sum modules, receiving second state information on each of sub modules not included in the first sub module group, among state information on each of the n sum modules previously stored in a memory, controlling switching of a sub module by using the first state information and the second state information, and updating the memory with the first state information.