Self-Balanced Hybrid Modular DC-DC Converter for Medium Voltage Grids
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Solution Overview
Problem
High-voltage DC-DC converters face challenges in achieving efficient operation and insulation requirements, particularly in high-power applications, where switches with high voltage ratings are needed, and existing solutions struggle with insulation and capacitor voltage balancing.
Innovation Solution
A self-balanced, bidirectional hybrid modular non-isolated DC-DC converter is proposed, utilizing half-bridge sub-modules and series-connected IGBTs for high-voltage switches, with a proportional integral controller to manage duty cycles and achieve efficient power flow between different voltage levels, enabling self-balancing of capacitors without the need for voltage measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If series-connected IGBTs are used to meet high voltage requirements, then the voltage rating is improved, but the device complexity and insulation challenges increase
Solution Approach 1:
The converter is divided into multiple half-bridge sub-modules, each operating at lower voltage levels. These modular units are then series-connected to achieve the required high voltage output, distributing the voltage stress across individual components rather than requiring a single high-voltage switch
Solution Approach 2:
The half-bridge sub-modules serve multiple functions: they provide voltage transformation, enable bidirectional power flow, and inherently balance capacitor voltages through their modular structure and control strategy, eliminating the need for separate insulation and balancing systems
2Strength
If multi-module DC-DC converters are employed to meet high voltage requirements, then the voltage handling capability is improved, but insulation challenges worsen
Solution Approach 1:
The control strategy maintains equal voltage distribution across all half-bridge sub-module capacitors by sequentially connecting them to the low-voltage side for charging/discharging. This equipotential operation eliminates voltage imbalances that would otherwise require complex insulation coordination between modules
Solution Approach 2:
The low-voltage side acts as an intermediary charging/discharging path for the half-bridge sub-module capacitors. By sequentially connecting capacitors to this common low-voltage node, the system achieves automatic voltage balancing without requiring direct high-voltage insulation between individual capacitor banks
3Productivity
If conventional DC-DC converters are used, then the basic power conversion function is achieved, but capacitor voltage balancing becomes difficult
Solution Approach 1:
The half-bridge sub-module capacitors are sequentially connected to the low-voltage side in periodic intervals during each switching cycle. This periodic sequential connection ensures that each capacitor undergoes equal charging and discharging cycles, automatically maintaining voltage balance across all capacitors without requiring voltage measurement or active control
Solution Approach 2:
The modular architecture and sequential switching strategy enable the capacitors to self-balance their voltages through identical operational patterns. Each capacitor naturally equalizes its voltage through the periodic connection to the common low-voltage node, eliminating the need for external voltage measurement and active balancing control systems
Data Source
AI summary
An electrical converter is provided, comprising a first half-bridge sub-module, a switch, and a first capacitor. The half-bridge sub-module is connected to the first capacitor, and the switch is connected to a terminal of the first half-bridge sub-module. The switch includes a plurality of insulated-gate bipolar transistors. The insulated-gate bipolar transistors are serially connected with each other.