Differential Modular Multilevel Converter With Reduced Capacitance
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Solution Overview
Problem
Traditional modular multilevel power converters require bulky capacitance for high-voltage applications, leading to increased energy storage needs and limited reliability, while existing topologies face challenges such as complexity, voltage balancing issues, and incompatibility with advanced semiconductor switches.
Innovation Solution
The design of ultra-dense modular multilevel power converters using half-bridge and full-bridge modules with fully differential pole voltages, where switches are synchronized to isolate pole voltages from capacitors in a zero state, allowing for reduced capacitance requirements and efficient high-voltage power conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional modular multilevel power converters are used for high-voltage applications, then voltage conversion capability is achieved, but capacitance requirements increase significantly
Solution Approach 1:
The power converter is divided into multiple independent modules connected in series, where each module contains its own capacitor. This segmentation allows the total capacitance to be distributed across modules rather than requiring one large capacitor, reducing the capacitance burden on individual components while achieving the required high-voltage output through series connection of module voltages.
Solution Approach 2:
The patent introduces a fully differential pole voltage configuration where voltages are referenced differentially between poles rather than to ground. This dimensional change in voltage reference architecture enables reduced capacitance requirements by utilizing the differential voltage swing more efficiently, allowing high-voltage operation with smaller energy storage elements.
2Quantity of substance
If capacitance is reduced in modular multilevel power converters, then energy storage needs are reduced, but reliability may be compromised
Solution Approach 1:
By segmenting the power converter into multiple independent modules with individual capacitors, the system achieves redundancy and improved reliability. If one module or capacitor fails, other modules can continue operating, preventing complete system failure. This modular architecture with distributed capacitance simultaneously reduces individual component stress and enhances overall system reliability.
Solution Approach 2:
The modular design with multiple capacitors provides built-in protection and cushioning against failures. The distributed capacitance architecture ensures that the system has backup energy storage capacity in other modules, cushioning against the failure of any single capacitor and maintaining reliable operation under fault conditions.
3Power
If traditional converter topologies are used, then power conversion is achieved, but complexity and voltage balancing issues arise
Solution Approach 1:
The complex power conversion function is segmented into multiple identical or similar modules, each performing a portion of the overall power conversion. This modular segmentation simplifies the design and control of each individual module compared to a monolithic converter, while the collective operation of all modules achieves the required power conversion capability with reduced voltage balancing complexity.
Solution Approach 2:
The fully differential pole voltage configuration changes the dimensional reference framework from single-ended to differential mode. This architectural change simplifies voltage balancing by creating symmetric voltage relationships between poles, reducing the complexity of control algorithms needed to maintain voltage equilibrium across the converter stages.
Data Source
AI summary
Various embodiments of an ultra-dense modular multilevel power converter are provided. In one example, a power converter includes a capacitor, and a circuit comprising a first switch and a second switch, wherein a switch throw of the first switch is coupled to a first terminal of the capacitor and a switch throw of the second switch is coupled to a second terminal of the capacitor, wherein a pole voltage is fully differential between a first pole of the first switch and a second pole of the second switch, and wherein the first pole and the second pole are isolated from the capacitor when the circuit is in a zero state. In this way, several such modules may be connected in series to form multilevel power converters with reduced capacitance requirements for coupling high-voltage sources.