HVDC Switching Apparatus Self-Powered Control
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Solution Overview
Problem
Conventional switching apparatuses for high voltage direct current applications face complexity and cost issues due to the need for external power sources to power switching control units, especially when multiple switching elements are involved, as there is no voltage available across turned-off switching elements to drive control units in parallel configurations.
Innovation Solution
A switching apparatus with parallel-connected first and second switching branches, where the second branch includes series-connected switching assemblies with impedance elements and a shunt impedance forming a permanent connection to a third node, allowing leakage current to generate a voltage across second switching elements, which powers the switching control units internally.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple switching elements are connected in parallel to handle high voltage direct current, then the switching apparatus can control line voltage effectively, but the complexity and cost increase due to the need for external power sources to power switching control units
Solution Approach 1:
The switching control units are powered by leakage current that naturally flows through the switching apparatus during normal operation. The control units draw power from the voltage present across the switching elements themselves, eliminating the need for separate external power sources. This self-powered approach reduces device complexity while maintaining the ability to handle high voltage direct current.
Solution Approach 2:
The switching elements serve dual functions: they control the main power flow and simultaneously provide power to their own control units. The leakage current that would otherwise be wasted serves as the power source for control circuits, making the system more self-sufficient and reducing overall complexity.
2Device complexity
If switching control units are powered from voltage across turned-off switching elements, then external power sources are eliminated, but there is no voltage available across turned-off switching elements in parallel configurations to drive control units
Solution Approach 1:
The leakage current, which is typically considered a harmful or wasted effect in high voltage switching apparatus, is converted into a useful resource to power the control units. By utilizing this small leakage current that naturally flows through the impedance elements, the system generates sufficient voltage to drive control circuits without requiring external power sources.
Solution Approach 2:
Impedance elements are introduced as intermediary components that facilitate the generation of control voltage from leakage current. These impedance elements create a voltage drop from the small leakage current, which then serves as the power source for control units. This intermediary mechanism bridges the gap between the main power circuit and control circuits.
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 operational complexity and cost by providing a passive means of powering switching control units within the apparatus, eliminating the need for external power sources and enabling efficient voltage measurement and control in high voltage direct current systems.
Implementation Method 1
the or each impedance element arranged in the corresponding switching assembly to combine with the shunt impedance so as to define a current path which extends between the corresponding first or second node and the third node
Data Source
Figure 1~2
Figure 3~4
AI summary
There is provided a switching apparatus (30,130)comprising: first and second nodes (32,34) operably connectable to a line voltage (44); first and second switching branches (38,40) connected in parallel between the first and second nodes (32,34), the first switching branch (38) including at least one first switching element (46,60); and the second switching branch (40) including a pair of switching assemblies connected in series between the first and second nodes (32,34), the second switching branch (40) further including a junction (48) between the pair of switching assemblies, each switching assembly including at leastone second switching element (50), at least one of the switching assemblies further including at least one impedance element (52), wherein the switching apparatus (30,130) further includes a shunt impedance (42) and a third node (36), the shunt impedance(42) arranged to form a permanent electrical connection between the junction (48) and the third node (36), the third node (36) operably connectable to a voltage that is different in magnitude to the line voltage (44), the or each impedance element (52) arranged in the corresponding switching assembly to combine with the shunt impedance (36) so as to define a current path which extends between the corresponding first or second node (32,34) and the third node (36).