Switched-Capacitor Multilevel Converter Topology for Voltage Scaling
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Solution Overview
Problem
Conventional multilevel converters face challenges in efficiently expanding the number of voltage levels due to exponential increases in component count, and they struggle with balancing capacitor voltages across sub-modules, which is crucial for multiphase systems.
Innovation Solution
A modular multilevel converter circuit topology is introduced, which allows for easy expansion to a predetermined number of voltage levels using low-voltage capacitors. This topology includes a controller and sub-modules with semiconductor switches and intermediate circuit capacitors, featuring a specific arrangement of half bridges and capacitors that enables automatic balancing of capacitor voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional multilevel converter topologies are used to expand the number of voltage levels, then the output voltage levels increase, but the number of components (semiconductor switches, gate drivers, capacitors) increases exponentially
Solution Approach 1:
The converter is divided into multiple identical sub-modules, each contributing a fixed number of voltage levels. By segmenting the system into reusable building blocks, the overall voltage level expansion becomes linear rather than exponential. Each sub-module contains a standardized set of semiconductor switches and capacitors that can be replicated to achieve the desired number of voltage levels.
Solution Approach 2:
The patent implements a hierarchical structure where sub-modules are nested within phases, and phases are nested within the overall converter system. This nested arrangement allows for systematic expansion of voltage levels by adding more sub-modules at appropriate hierarchical levels, maintaining component efficiency while achieving high voltage levels.
2Adaptability or versatility
If conventional multilevel converters are used, then voltage levels can be achieved, but capacitor voltage balancing becomes complex and requires monitoring controllers
Solution Approach 1:
The patent designs the sub-modules with inherent self-balancing capabilities through symmetric circuit topologies and balanced switching patterns. The capacitor voltages automatically equalize themselves through the circuit's natural operation without requiring external monitoring or control intervention. This self-service mechanism eliminates complex balancing controllers while maintaining stable operation across multiple voltage levels.
Solution Approach 2:
The circuit topology is designed to create equipotential conditions for capacitor voltages through symmetric arrangement of components and balanced current paths. By ensuring that all capacitors experience equivalent electrical conditions during normal operation, the system naturally maintains voltage balance across all sub-modules without requiring active control.
3Reliability
If the number of phases is expanded in multiphase machines, then power distribution and error tolerance improve, but the DC/AC converter complexity increases
Solution Approach 1:
The patent creates a universal sub-module design that can be applied to any number of phases. Each sub-module serves multiple functions: it contributes to voltage level generation, provides current paths for multiple phases, and maintains capacitor balance. This multi-functional design allows the same basic building block to support expanded phase configurations without proportionally increasing overall system complexity.
Solution Approach 2:
The converter topology is designed to be dynamically adaptable to different phase configurations. The modular structure allows the system to dynamically adjust its operation to accommodate varying numbers of phases and load conditions, maintaining efficiency and simplicity across different operational scenarios through flexible switching patterns.
Data Source
AI summary
A method for arranging a generalized multilevel converter switching topology with switched capacitors for converting DC current into AC current, wherein the arrangement can be configured with regard to predetermined output voltage levels. With the same number of semiconductor switches, a higher number of voltage levels can be achieved in comparison to previous methods. Depending on the given problem, a maximum output voltage of the AC current may vary from significantly lower values than the input voltage of the DC current up to a multiple of these values. The generalized circuit topology may be adapted to a desired number of voltage levels by a repeatable arrangement of voltage level units that can be arranged in a row and to a multiphase load by a corresponding selection of a number of sub-modules. Furthermore, a modular multilevel converter configured with the circuit topology is described.