Hybrid Power Switching Apparatus for HVDC Current Interruption
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Solution Overview
Problem
Conventional semiconductor-based switches and vacuum interrupters face challenges in efficiently switching high voltage direct current (HVDC) due to high forward losses, sensitivity to transients, and poor performance in interrupting DC currents, with complex and costly solutions required for DC current interruption.
Innovation Solution
A power switching apparatus comprising parallel-connected switching assemblies, where a vacuum interrupter assembly with a control unit increases the voltage drop to match the forward voltage drop of a pulsed power switch, allowing controlled current interruption and minimizing adverse effects on contact electrodes, and an electrical device enhances arc voltage to facilitate current transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If semiconductor-based switches are used for HVDC switching, then switching speed and fault current interruption capability are improved, but forward losses and sensitivity to transients increase
Solution Approach 1:
The patent combines a vacuum interrupter (providing mechanical isolation and low forward losses) with a semiconductor switch (providing fast switching capability) in a hybrid configuration. The vacuum interrupter handles the main current interruption with its arc-quenching capability, while the semiconductor switch provides rapid pre-switching or post-switching actions, thus achieving both fast switching and low energy losses.
Solution Approach 2:
The patent introduces an auxiliary circuit with a capacitor and spark gap as an intermediary mechanism. When DC current interruption is needed, the spark gap ignites to introduce an oscillatory current that forces the main current through a zero crossing point, enabling the vacuum interrupter to successfully interrupt DC current without direct semiconductor switching.
2Device complexity
If conventional vacuum interrupter is used for DC current interruption, then mechanical simplicity is maintained, but interruption capability for high magnitude DC current deteriorates
Solution Approach 1:
The patent introduces an auxiliary circuit with a capacitor and spark gap as an intermediary mechanism. When DC current interruption is needed, the spark gap ignites to introduce an oscillatory current that forces the main current through a zero crossing point, enabling the vacuum interrupter to successfully interrupt DC current without direct semiconductor switching.
Solution Approach 2:
The patent changes the electrical parameters (introducing oscillatory current with zero crossing) to enable the vacuum interrupter to handle DC current interruption. By transforming the DC current into an oscillating current with zero crossings, the vacuum interrupter can utilize its natural arc extinction capability at current zero points.
3Reliability
If auxiliary circuit with spark gap is added to enable DC current interruption, then DC current interruption capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces an auxiliary circuit with a capacitor and spark gap as an intermediary mechanism. When DC current interruption is needed, the spark gap ignites to introduce an oscillatory current that forces the main current through a zero crossing point, enabling the vacuum interrupter to successfully interrupt DC current without direct semiconductor switching.
4Productivity
If voltage drop across vacuum interrupter is increased to enable current transfer, then current interruption efficiency is improved, but stress on contact electrodes increases
Solution Approach 1:
The control unit creates the voltage or magnetic field in advance, before the vacuum interrupter contacts fully separate, to progressively increase the voltage drop across the second switching assembly. This preliminary action prepares the conditions for smooth current transfer, reducing sudden stress on the contact electrodes when interruption occurs.
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 improves current interruption efficiency, reduces manufacturing and installation costs, and provides flexibility in design, enabling effective switching of AC and DC currents in high voltage applications while extending the lifetime of vacuum interrupter components.
Implementation Method 1
a control unit configured to control the electrical device to create a voltage or magnetic field which increases the voltage drop across the second switching assembly so that the voltage drop across the second switching assembly matches or exceeds the forward voltage drop of the first switching assembly
Implementation Method 2
an electrical device coupled with the vacuum interrupter assembly; and a control unit configured to control the electrical device to create a voltage or magnetic field which increases the voltage drop across the second switching assembly
Data Source
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AI summary
A power switching apparatus is for switching an AC or DC current. The power switching apparatus comprises first and second switching assemblies (12,14) connected in parallel, wherein the first switching assembly (12) includes at least one switching element (20), the first switching assembly (12) conducting and carrying current only in its closed state, the first switching assembly (12) being controllable to switch to its closed state only when a voltage drop across the first switching assembly (12) matches or exceeds its forward voltage drop, wherein the or each switching element (20) is controllable to modify, in use of the power switching apparatus, a current flowing through the second switching assembly (14), and the second switching assembly (14) includes: a vacuum interrupter assembly (25) including at least one vacuum interrupter (26); an electrical device (28) coupled with the vacuum interrupter assembly; and a control unit (16); wherein, in use of the vacuum interrupter assembly (25) to interrupt current, the control unit (16) controls the electrical device (28) to create a voltage or magnetic field which increases the voltage drop across the second switching assembly (14) so that the voltage drop across the second switching assembly (14) matches or exceeds the forward voltage drop of the first switching assembly (12).