DC Power System Split DC Link Diode Fault Isolation
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Solution Overview
Problem
Subsea and marine power supply systems face significant protection challenges due to the risk of short-circuit faults, particularly with the discharge of energy from capacitors in DC power systems, which requires costly and bulky components to prevent damage, and existing solutions do not adequately address the need for a compact and reliable system.
Innovation Solution
The system employs split DC links with small and large capacitors connected in parallel, where diodes block reverse current flow from the common DC bus to AC/DC power converter bridges during faults, isolating faulty converters and limiting energy discharge, thus preventing damage and ensuring system continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DC circuit breakers are used to interrupt DC fault current, then system protection is improved, but device complexity and cost increase
Solution Approach 1:
The DC link is segmented into multiple independent sections, each with its own capacitor and diode protection. This segmentation isolates faults to specific segments, preventing system-wide failures and eliminating the need for complex DC circuit breakers while maintaining system protection.
Solution Approach 2:
Diodes are introduced as intermediary components between the DC bus and individual loads. These diodes act as automatic fault isolation mechanisms, blocking reverse current flow during faults and protecting the system without requiring complex active protection devices.
2Reliability
If overdesigned sub-systems are used to withstand capacitor discharge energy, then protection is improved, but device complexity and space requirements increase
Solution Approach 1:
The system divides the total capacitance into multiple smaller capacitors distributed across different segments. Each segment handles only its local energy discharge, allowing the use of smaller capacitors that fit within space constraints while collectively providing the same level of protection as a single large capacitor would require.
Solution Approach 2:
The harmful discharge energy is extracted and redirected through diodes to safe paths rather than forcing sub-systems to withstand the full energy. This extraction approach protects components without requiring them to be overdesigned, reducing space requirements.
3Use of energy by moving object
If multiple capacitors are connected to the common DC bus, then energy storage is improved, but protection problems are exacerbated due to large discharge energy
Solution Approach 1:
Multiple capacitors are segmented into isolated groups, each protected by its own diode. This segmentation maintains the total energy storage capacity while preventing the harmful effect of uncontrolled discharge by directing energy through diodes during faults.
Solution Approach 2:
The diodes convert the potentially harmful reverse current flow into a beneficial protection mechanism. During normal operation, the capacitors store energy as needed; during faults, the same capacitors discharge energy but the diodes redirect this discharge safely, turning the harmful discharge effect into a protected operation.
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
This configuration allows for a compact, reliable, and fault-tolerant power transmission system that minimizes component costs and space constraints while maintaining system availability by isolating faulty components and limiting energy discharge during faults, ensuring continuous operation with minimal disturbance.
Implementation Method 1
The common DC bus also includes a plurality of capacitors
Implementation Method 2
each DC link includes at least one diode to block an instantaneous current flow from the common DC bus to the respective AC/DC converter bridge in case of a fault
Data Source
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AI summary
A direct current (DC) power system includes a common DC bus (12) configured to supply power to a plurality of loads (14). A plurality of alternating current (AC)/DC converter bridges (16 18) supply DC power to the common DC bus (12). Each of the AC/DC converter bridges (16, 18) is connected to the common DC bus (12) by at least one split DC link (32, 34). Each split DC link (32, 34) includes a first capacitor (20, 22) connected across output terminals of the respective AC/DC converter bridge (16, 18) and a second capacitor (24, 26) connected across the split DC link (32, 34). The split DC links (32, 34) are connected to the common DC bus (12) in parallel. At least one diode (28, 30) is coupled between the first capacitor (20, 22) and the second capacitor (24, 26) to block an instantaneous current flow from the common DC bus (12) to the respective AC/DC converter bridge (16, 18) in case of a fault in the AC/DC converter bridge.