HVDC Disconnecting Assembly with Hybrid Switching
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Solution Overview
Problem
Current high-voltage direct current network disconnection arrangements face inefficiencies and reliability issues due to high losses and potential destruction of semiconductor switches during fault conditions, as they require constant current flow through semiconductor switches and are prone to damage from excessive short-circuit currents.
Innovation Solution
A disconnection arrangement featuring a first semiconductor switching unit and a second isolating device with a mechanical switching unit and an auxiliary switching device in series, where the auxiliary device includes a parallel connection of semiconductor and mechanical switches, allowing for efficient current commutation and reduced losses, with a control device managing the switching units to minimize arcing and prevent semiconductor switch destruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If semiconductor switches are used in the auxiliary switching device, then current commutation is enabled, but permanent cooling effort is required due to constant current flow and losses
Solution Approach 1:
The patent applies dynamics by making the current path configurable: during normal operation, current flows through the mechanical switch; during fault conditions, current is dynamically commutated to the semiconductor branch. This dynamic switching of current paths eliminates the need for permanent cooling while maintaining commutation capability when needed.
Solution Approach 2:
The semiconductor switches operate periodically rather than continuously - they are activated only during fault conditions for a brief period to commutate the current, then deactivated. This periodic operation eliminates continuous energy losses and the need for permanent cooling infrastructure.
2Ease of operation
If semiconductor switches are used in the auxiliary switching device, then current commutation is enabled, but the switches can be destroyed by excessive short-circuit currents
Solution Approach 1:
The patent implements beforehand cushioning by using the mechanical switch as a protective element that can withstand high short-circuit currents. The mechanical switch serves as a first line of defense, and only when it needs to open does the semiconductor branch get activated for current commutation. This prior protection prevents semiconductor destruction from excessive currents.
Solution Approach 2:
The mechanical switch acts as an intermediary between the high-voltage DC network and the semiconductor switches. It provides isolation and protection, allowing the semiconductor switches to operate only under controlled conditions with limited current exposure, thus preventing destruction from excessive short-circuit currents.
3Productivity
If multiple mechanical switches are connected in series, then high-voltage direct current can be switched off, but the arc voltage is too low to overcome the threshold voltage of semiconductor switches
Solution Approach 1:
The patent segments the switching function into two distinct branches: a mechanical switch branch for high-voltage isolation and a semiconductor switch branch for current commutation. This segmentation allows each component to perform its optimized function - mechanical switches handle the high-voltage breaking while semiconductor switches provide the necessary voltage for commutation.
Solution Approach 2:
The patent merges two different switching technologies (mechanical and semiconductor) into a hybrid arrangement. The mechanical switches provide high-voltage isolation while the semiconductor switches provide controlled commutation capability. By combining these two technologies, the system achieves both high-voltage switching and adequate commutation voltage.
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 solution reduces energy losses, eliminates the need for permanent cooling, and ensures reliable operation by minimizing arcing and protecting semiconductor switches from overvoltages and overcurrents, enabling efficient and safe disconnection of high-voltage direct current networks.
Implementation Method 1
the arc voltage that usually occurs at the contacts of the mechanical switch is too low compared to the driving mains voltage
Implementation Method 2
140 semiconductor switches in the form of IGBTs with a respective blocking voltage of 3.3 kV must be connected in series in order to be able to build up an adequate blocking voltage
Implementation Method 3
These mechanical switches are usually designed as vacuum interrupters
Data Source
AI summary
The invention relates to a disconnecting assembly (10) for a high-voltage direct-current network, having a first disconnecting device (12), which comprises a first semiconductor switching unit (16), and a second disconnecting device (14), which is connected parallel to the first disconnecting device (12) and which comprises a first mechanical switching unit (18) and an auxiliary switching device (20) connected in series with the first mechanical switching unit (18), wherein the auxiliary switching device (20) comprises a second semiconductor switching unit (22) and wherein the auxiliary switching device (20) comprises a second mechanical switching unit (24), which is connected parallel to the second semiconductor switching unit (22).