DC Grid Node Switching Using Shared Commutation Branch
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Solution Overview
Problem
The existing devices for switching direct currents in DC voltage network nodes are cost-intensive, particularly when configured as bidirectional switches, due to the requirement of multiple power electronics units, which increases costs further in redundant double busbar systems.
Innovation Solution
The solution involves providing only one shutdown branch with multiple operating current branches connected in parallel, using a mechanical switch and commutation means to redirect fault currents to the shutdown branch, reducing the need for multiple power switching units and lowering costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple power switching units are provided in each branch of a DC voltage network node, then the switching capability and reliability are improved, but the device complexity and cost increase significantly
Solution Approach 1:
The patent merges multiple power switching units into a single shared power switching unit that serves all operating current branches. The shutdown branch contains this single power switching unit, which handles fault current commutation for all branches, eliminating the need for separate power switching units in each branch while maintaining switching capability and reliability.
Solution Approach 2:
The single power switching unit in the shutdown branch performs multiple functions: it commutates fault current from any operating current branch, provides backup switching capability, and works with any of the multiple operating current branches. This multi-functional design replaces what would traditionally require multiple specialized switching units.
2Reliability
If multiple power switching units are provided in redundant double busbar systems, then the system reliability is improved, but the cost increases significantly
Solution Approach 1:
The patent combines the switching functionality needed for redundant double busbar systems into a single power switching unit located in the shutdown branch. This shared unit provides the necessary reliability for redundant operations without requiring separate expensive power switching units for each busbar configuration, significantly reducing system cost.
3Device complexity
If mechanical switches are used in operating current branches, then the device complexity is reduced, but the switching speed may be insufficient for fast fault current interruption
Solution Approach 1:
The patent replaces the need for fast mechanical switches in each operating current branch with a combination of simple mechanical switches and a single power switching unit. The power switching unit, using power semiconductor switches, provides the fast switching capability needed for fault current interruption, while the mechanical switches in operating current branches can be simpler and slower since they only handle normal current routing, not fault interruption.
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 efficient and cost-effective switching of currents in DC voltage network nodes by utilizing fewer power switching units and cheaper mechanical switches, enabling quick and reliable commutation of fault currents while maintaining high power handling capabilities.
Implementation Method 1
commutation means for commutating the direct current from the operating current branch to the shutdown branch
Implementation Method 2
at least one power semiconductor switch that can be switched on and off
Implementation Method 3
a mechanical switch is arranged and which can be connected to a branch of the DC voltage network node
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
In order to provide an apparatus (13) for switching direct currents in branches of a DC voltage grid node with a first disconnection branch (14) in which a power switching unit (18) is arranged which has a series circuit comprising two-pole submodules comprising at least one power semiconductor switch (9) which can be switched on and off, an operating current branch (15a) which can be connected in parallel with the disconnection branch (8) and in which a mechanical switch (5) is arranged and which is connectable to a branch of the DC voltage grid node, and commutation means (6) for commutating the direct current from the operating current branch into the disconnection branch, which apparatus can be used, inexpensively, in particular in branches of a DC voltage grid node, it is proposed that at least one further operating current branch (15b) is provided, which can be connected in parallel with the first disconnection branch (15a), wherein each operating current branch (15) can be connected in parallel with the disconnection branch (14) via a paralleling switch (16).