DC/DC Converter Voltage Balancing for High-Voltage Transmission
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Solution Overview
Problem
Conventional power conversion devices for high-voltage DC power transmission face challenges in handling varying input voltages and reliably controlling output, particularly when input voltages exceed the withstand voltage of semiconductor switching elements, limiting their application in offshore wind power generation systems.
Innovation Solution
The power conversion device employs a configuration of DC/DC converters connected in parallel at the input and series at the output, with auxiliary converters between adjacent converters to balance voltages and a controller system that manages input and output voltages, allowing for stable operation even with varying input voltages without increasing element withstand voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If DC/DC converters are connected in parallel at input and series at output, then high-voltage DC power transmission capability is improved, but the input voltage exceeds the withstand voltage of semiconductor switching elements
Solution Approach 1:
The power conversion device is divided into multiple DC/DC converter units (first, second, third, fourth converters) that are connected in a specific configuration. Each converter handles a portion of the total voltage and power, allowing the system to achieve high-voltage transmission capability without requiring individual semiconductor elements to withstand the full system voltage. The series connection of converters at the output side enables voltage addition while each converter's semiconductor elements only need to withstand their individual operating voltages.
2Device complexity
If conventional DC step-up conversion unit is used with parallel input connections, then the configuration is simple, but it is difficult to reliably control output when input voltage varies
Solution Approach 1:
A voltage balancing circuit is introduced as an intermediary component between the DC/DC converters. This balancing circuit actively monitors and adjusts the input voltages of each converter to maintain them within balanced ranges, even when the overall input voltage varies. By adding this intermediary control mechanism, the system achieves reliable output control without significantly increasing the overall device complexity, as the balancing circuit integrates seamlessly with the existing converter structure.
3Stability of the object's composition
If auxiliary converters are added to balance voltages between converters, then voltage balancing is improved, but device complexity increases
Solution Approach 1:
The auxiliary converters are designed to perform multiple functions: they balance the input voltages between adjacent DC/DC converters, provide additional voltage regulation capability, and contribute to the overall power conversion function. By making the auxiliary converters multi-functional, the system achieves improved voltage balancing without proportionally increasing device complexity, as the same hardware components serve multiple purposes within the power conversion system.
Data Source
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AI summary
The power conversion device (100) includes M number of DC/DC converters (10), first-side terminals (5A) of the DC/DC converters (10) are connected so that common current flows between both positive and negative terminals of first DC terminals (100A) of the power conversion device (100), and second-side terminals (5B) thereof are connected so that common current flows between both positive and negative terminals of second DC terminals (100B) of the power conversion device (100). The power conversion device (100) further includes M-1 number of auxiliary converters (20) each connected between two DC/DC converters (10) and performing DC/DC conversion. The DC/DC converters (10) control voltages of the second-side terminals (5B) and input voltage of the power conversion device (100). Each auxiliary converter (20) controls voltages of the first-side terminals (5A) of the two DC/DC converters (10) so as to be equalized.