DC Voltage Switch Segmentation for Fault Protection
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Solution Overview
Problem
Existing DC voltage switches for meshed DC voltage networks are unable to quickly and reliably switch off short-circuit currents, leading to potential damage from high inrush currents when connecting faulty network sections, and existing solutions suffer from high transmission losses or inefficient energy management.
Innovation Solution
A DC voltage switch with a mechanical switch and a switch-off current path featuring power semiconductor switches that can be switched on and off, where the switch-off current path has greater electrical resistance than the operating current path, allowing controlled switching and gradual voltage increase, enabling early detection and mitigation of faults, and incorporating submodules with energy stores for efficient energy management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical switch is used to connect DC voltage network sections, then the structure is simple and cost-effective, but it cannot quickly switch off short-circuit currents leading to potential damage
Solution Approach 1:
The DC voltage switch is segmented into two distinct paths: an operating current path with a mechanical switch for normal operation, and a switch-off current path with power semiconductor switches for fault conditions. This segmentation allows each path to be optimized for its specific function - the mechanical switch for simplicity and the power semiconductors for fast switching capability.
Solution Approach 2:
The power semiconductor switches act as an intermediary between the mechanical switch and the short-circuit current. When a fault occurs, the power semiconductor switches in the switch-off current path quickly interrupt the current before it can damage the system, while the mechanical switch remains closed for normal operation.
2Reliability
If power semiconductor switches are used in the operating current path, then short-circuit currents can be switched off quickly, but transmission losses increase significantly
Solution Approach 1:
The current path is segmented into an operating current path using mechanical switches for low loss normal operation, and a switch-off current path using power semiconductor switches for fast fault interruption. This segmentation allows the system to benefit from both mechanical switch efficiency and power semiconductor speed without the drawbacks of either.
Solution Approach 2:
The system dynamically switches between different current paths based on operating conditions. During normal operation, current flows through the mechanical switch path with low transmission losses. During fault conditions, the power semiconductor path is activated for rapid current interruption, accepting the higher losses only when necessary for safety.
3Reliability
If DC voltage is applied to a faulty network section, then high inrush currents occur causing damage, but without controlled switching there is no way to detect faults early
Solution Approach 1:
Before connecting a DC voltage network section, the switch-off current path is prepared and ready to interrupt current if a fault is detected. The mechanical switch closes first to establish the connection, and if a fault occurs, the power semiconductor switches immediately interrupt the current, preventing damage from inrush currents.
Solution Approach 2:
The system incorporates monitoring that detects faults in real-time during the switching process. When a fault is detected in the network section, the control system activates the power semiconductor switches in the switch-off current path to interrupt the current, providing feedback-based protection against damaging inrush currents.
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
Enables safe and efficient connection of DC voltage network sections by preventing damage from short-circuit currents and reducing transmission losses through controlled switching and energy management, allowing for early fault detection and intervention.
Implementation Method 1
When the mechanical switches open, an arc occurs. The voltage drop across the arc ignites the power semiconductor switch
Implementation Method 2
When the mechanical switches open, an arc occurs
Data Source
Figure 1~4
Figure 5~7
Figure 8~9
AI summary
The invention relates to a method for connecting a DC voltage network section by means of a DC voltage switch (1) having two connection terminals (2,3), which comprises an operating current path (4) with a mechanical switch (7) and a turn-off current path (9) bridging the mechanical switch (7) and in which power semiconductor switches (10) that can be switched on or off are arranged. The turn-off current path (9) has a greater electrical resistance than the bridged section of the operating current path (9). According to the invention, the mechanical switch (7) opens and a current flow via the turn-off current path (9) is blocked. The first connection terminal (2) is then connected to a DC voltage source and the second connection terminal (3) to the DC voltage network section. Finally, a controlled voltage is applied to the DC voltage network section by actuating the power semiconductor switch (10), and the mechanical switch (7) is subsequently closed.