DC-Bus Pre-Charging via Segmented Auxiliary Units
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Solution Overview
Problem
Existing power conversion systems for medium-voltage applications face challenges such as large size, high cost, and reliability issues due to the need for medium-voltage elements in pre-charging circuits, which also restrict hot-plugging and lead to unbalanced capacitor voltages and increased complexity.
Innovation Solution
A power conversion system with a pre-charging unit connected to each power module, utilizing auxiliary power sources to independently pre-charge DC-Bus capacitors, allowing for modular design, reduced size, and lower power consumption, while enabling hot-plugging and balancing capacitor voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If medium-voltage elements are used in pre-charging circuits, then pre-charging function is achieved, but device size and cost increase
Solution Approach 1:
The pre-charging circuit is segmented into multiple independent pre-charging units, each responsible for charging a specific DC-Bus capacitor. This segmentation allows each unit to use lower-voltage elements rather than requiring a single medium-voltage pre-charging circuit, thereby reducing device size and cost while maintaining the pre-charging function.
Solution Approach 2:
The patent introduces auxiliary power sources as intermediaries to provide pre-charging current independently of the main medium-voltage power circuit. These auxiliary power sources act as mediators that enable pre-charging without requiring medium-voltage elements in the pre-charging circuit itself, thus reducing size and cost.
2Reliability
If medium-voltage elements are used in pre-charging circuits, then pre-charging function is achieved, but system cost increases
Solution Approach 1:
By segmenting the pre-charging circuit into multiple independent units operating at lower voltages, the system avoids the high cost of medium-voltage pre-charging elements. Each pre-charging unit can use cheaper, lower-voltage components, thereby reducing overall system cost while maintaining pre-charging reliability.
Solution Approach 2:
The patent employs auxiliary power sources that can be simpler and less expensive than medium-voltage pre-charging elements. These auxiliary sources provide the necessary pre-charging function using more economical components, reducing the overall system cost.
3Reliability
If pre-charging circuit is integrated into main power circuit, then pre-charging is achieved, but hot-plugging is restricted and system complexity increases
Solution Approach 1:
The pre-charging function is segmented into independent pre-charging units that are separate from the main power circuit. This independence allows power modules to be hot-plugged without affecting the pre-charging function, as each pre-charging unit can operate autonomously using its auxiliary power source.
Solution Approach 2:
The pre-charging circuit is extracted from the main power circuit and implemented as separate pre-charging units with independent auxiliary power sources. This extraction enables hot-plugging of power modules without disrupting the pre-charging function, thereby improving adaptability while maintaining pre-charging reliability.
4Reliability
If pre-charging circuit is integrated into main power circuit, then pre-charging is achieved, but circuit complexity increases
Solution Approach 1:
By segmenting the pre-charging function into independent units with dedicated auxiliary power sources, the circuit complexity is distributed and modularized. Each pre-charging unit is a self-contained module, making the overall system easier to design, implement, and maintain compared to a single integrated medium-voltage pre-charging circuit.
Solution Approach 2:
Each pre-charging unit is self-sufficient with its own auxiliary power source, eliminating the need for complex coordination and control between pre-charging and main power circuits. This self-service approach reduces overall circuit complexity by making each unit independent and autonomous.
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
The system effectively pre-charges DC-Bus capacitors in a compact and energy-efficient manner, ensuring reliable operation and balancing capacitor voltages, while allowing for hot-plugging and reducing the risk of system failure.
Implementation Method 1
a pre-charging unit electrically connected to the charging input end for receiving direct current and electrically connected to the DC-Bus capacitor for pre-charging the DC-Bus capacitor
Data Source
AI summary
A power conversion system comprises a plurality of power modules, each including a power input end; a charging input end; a power output end; at least one power conversion unit, each including an AC/DC conversion unit and at least one DC-Bus capacitor and being connected to the power input end and the power output end; and a pre-charging unit connected to the charging input end for receiving direct current and connected to the DC-Bus capacitor. The pre-charging unit starts to charge the DC-Bus capacitor of one of the power modules when said power module breaks down or the load of the power conversion system is light so that no current flows through the AC/DC conversion unit. The power input ends of the power modules are connected in series and then connected to an AC power source, and the power output ends of the power modules are connected in parallel.