DC Power Converter Fault Isolation via Bypass Switches
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Solution Overview
Problem
Existing DC power transmission systems with a multipolar configuration face challenges in quickly detecting and clearing faults on the DC power transmission line, particularly in preventing fault currents from affecting the entire system and restarting converters efficiently.
Innovation Solution
A self-excited power conversion device with a controller that rapidly detects faults by monitoring current and voltage thresholds, uses bypass switches to divert fault currents, and controls AC breakers and neutral line breakers to isolate the faulted pole, allowing the system to continue operating on unaffected poles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fault occurs in a DC power transmission line, then the faulted pole must be stopped and isolated, but the system loses the ability to continue operation on unaffected poles
Solution Approach 1:
The DC power transmission system is divided into multiple independent poles, each with its own rectifier and inverter. When a fault occurs in one pole, only that specific pole is isolated while other poles continue to operate, maintaining system continuity and power transmission capacity.
2Reliability
If conventional fault detection methods are used, then the system can detect faults, but the detection speed is insufficient for rapid fault clearance
Solution Approach 1:
The system pre-configures bypass switches and control circuits for each pole before faults occur. When a fault is detected, the control device can immediately activate the bypass switch to isolate the faulted pole without delay, enabling rapid fault clearance.
Solution Approach 2:
The control device continuously monitors the operating state of each pole and receives feedback signals indicating fault conditions. Based on this real-time feedback, the control device automatically activates bypass switches to isolate faulted poles, achieving fast and automatic fault response.
3Reliability
If high-response breakers are used to quickly clear faults, then fault clearance speed improves, but system cost increases significantly
Solution Approach 1:
Instead of using expensive high-response breakers, the system employs relatively simple bypass switches that can be quickly activated to isolate faulted poles. These bypass switches provide sufficient fault clearance capability at a much lower cost than high-response breakers would require.
4Reliability
If the entire system is stopped for fault clearance, then safety is ensured, but operational continuity is lost
Solution Approach 1:
The system is segmented into independent poles with separate control. When a fault occurs in one pole, the bypass switch isolates only that pole while other poles continue to operate normally, ensuring both safety through fault isolation and operational continuity through parallel operation of unaffected poles.
Data Source
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AI summary
A power conversion device (5) used in a DC power transmission system having a multipolar configuration includes: a self-excited AC/DC converter (20) configured to convert electric power between an AC system and a main line (9); and a controller (100). The controller (100) is configured to: receive an input of a current value between a neutral point (13) and a DC terminal (41n to 43n) of the AC/DC converter (20); control an operation of the AC/DC converter (20); and control a switch (12) to be opened and closed, the switch (12) being provided between the DC terminal (41n to 43n) and the neutral point (13). When the current value is equal to or greater than a predetermined threshold value, the controller (100) stops a plurality of cells (L1 to L12) and subsequently closes a bypass switch. When the current value is equal to or greater than a predetermined threshold value, the controller (100) opens the switch (12).