HVDC Breaker Using Segmented Semiconductor and Mechanical Switches
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Solution Overview
Problem
High voltage DC breaker apparatuses with solid state semiconductor devices suffer from high power transfer losses due to the large number of devices required to handle protective voltage levels, and mechanical DC breakers are too slow to respond to fault currents in high voltage DC conductors.
Innovation Solution
Incorporating a mechanical DC breaker in series with a current limiting arrangement of semiconductor devices, allowing the semiconductor devices to focus on current limiting rather than breaking, reducing the number of devices needed and incorporating a mechanical switch that can break fault currents, thereby reducing power transfer losses and response time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large number of semiconductor devices are connected in series to handle protective voltage levels, then the breaker can limit fault currents effectively, but power transfer losses increase significantly during normal operation
Solution Approach 1:
The patent divides the breaker function into two independent parts: a current limiting arrangement with semiconductor devices and arresters for fault current limitation, and a mechanical DC breaker for fault current breaking. This segmentation allows the semiconductor devices to operate at lower voltage levels during normal operation, reducing power losses while maintaining fault current limiting capability.
Solution Approach 2:
The patent extracts the fault current breaking function from the semiconductor devices and assigns it to a mechanical DC breaker. This extraction allows the semiconductor devices to focus solely on current limiting with reduced voltage stress, thereby reducing power transfer losses during normal operation while the mechanical breaker handles the high-voltage breaking operation.
2Loss of energy
If mechanical DC breakers are used to break fault currents, then power transfer losses are reduced, but the response time becomes too slow (10-20 ms) for high voltage DC conductors
Solution Approach 1:
The patent implements preliminary action by having the current limiting arrangement with semiconductor devices and arresters ready to immediately limit fault currents upon detection. This preliminary current limiting action occurs within microseconds, much faster than mechanical breaker operation, and creates conditions that enable the subsequent mechanical breaker to operate successfully with reduced time requirements.
Solution Approach 2:
The patent introduces the current limiting arrangement with semiconductor devices and arresters as an intermediary between the fault current and the mechanical breaker. This intermediary immediately limits the fault current magnitude, creating favorable conditions for the mechanical breaker to operate more quickly and efficiently, bridging the gap between fast semiconductor response and mechanical breaking capability.
3Loss of time
If semiconductor devices are used for both current limiting and fault current breaking, then fast response time is achieved, but the number of devices and system complexity increase significantly
Solution Approach 1:
The patent extracts the fault current breaking function from the semiconductor devices and assigns it to a mechanical DC breaker. This extraction reduces the number of semiconductor devices required, as they only need to handle current limiting at lower voltage levels rather than full breaking capability at high voltage, thereby reducing system complexity.
Solution Approach 2:
The patent replaces the need for complex high-voltage semiconductor breaking devices with a mechanical DC breaker for the breaking function. This substitution allows the use of simpler, lower-voltage-rated semiconductor devices for current limiting, reducing overall device complexity while maintaining fast response capability through the semiconductor control system.
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 reduces power transfer losses by approximately 40% during normal operation while maintaining the ability to break fault currents quickly, lowering costs and simplifying control schemes.
Implementation Method 1
The voltage across the section is given, almost independent of the fault current, by the protective level of that arrester or arrester bank
Implementation Method 2
Turning off the IGBT:s 3 of an individual section 2 during a fault inserts the corresponding arrester 4 into the line
Data Source
AI summary
A high voltage DC breaker apparatus configured to break a fault current occurring in a high voltage DC conductor includes a current limiting arrangement having at least one section with at least one semiconductor device of turn-off type and at least one arrester connected in parallel therewith, and a mechanical DC breaker connected in series with the current limiting arrangement and including a mechanical switch. The mechanical DC breaker is configured to enable breaking of a fault current in said DC conductor once said semiconductor devices of said arrangement have been turned off.