DC Voltage Switch Reclosing for Selective Fault Isolation
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Solution Overview
Problem
DC voltage switches with semiconductor-based switching devices face challenges in achieving selectivity during faults, often resulting in unnecessary shutdowns due to saturation current limitations, leading to inefficiencies and increased costs.
Innovation Solution
A DC voltage switch with a semiconductor-based, electronically controllable switching device, equipped with voltage and current sensors, and a control device that determines current direction and level, interrupts current flow when thresholds are exceeded, and switches back on if the voltage difference between the DC bus and branch is within a certain value, ensuring selective shutdown and minimizing power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If semiconductor-based switching devices are used in DC voltage switches, then the switching speed and electronic controllability are improved, but the saturation current limitation causes unnecessary shutdowns during faults, reducing reliability
Solution Approach 1:
The patent introduces an intermediary electromechanical switching device that works in conjunction with the semiconductor-based switching device. The electromechanical device acts as a mediator that can handle high fault currents without saturation, allowing the semiconductor device to maintain selective shutdown capability while the electromechanical device provides robust fault current interruption support
Solution Approach 2:
The switching function is segmented into two independent switching devices: a semiconductor-based switching device for selective electronic control and fast switching, and an electromechanical switching device for robust fault current interruption. This segmentation allows each device to optimize its specific function without the limitations of the other
2Reliability
If the saturation current of semiconductor switching elements is increased to handle fault currents, then the current handling capability is improved, but the cost and device complexity increase significantly
Solution Approach 1:
The patent merges two different switching technologies (semiconductor and electromechanical) into a single DC voltage switch assembly. This combination allows the system to achieve high fault current handling capability by leveraging the strengths of both technologies rather than attempting to over-engineer a single semiconductor device
3Reliability
If DC switches are oversized to prevent unnecessary shutdowns, then the fault current handling capability is improved, but the cost and device complexity increase
Solution Approach 1:
The patent implements dynamic control where the semiconductor-based switching device can rapidly respond to fault conditions and selectively open only the affected branch. This dynamic selective shutdown capability eliminates the need for oversized switches, as the system can quickly isolate faults rather than relying on excessive current handling capacity
Data Source
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AI summary
The invention relates to a DC voltage switch for coupling a DC voltage branch to a DC voltage bus. In a forward direction, the electric current flows from the positive conductor of the DC voltage bus to the positive conductor of the DC voltage branch via the DC voltage switch. In a reverse direction, the electric current flows from the positive conductor of the DC voltage branch to the positive conductor of the DC voltage bus via the DC voltage switch and from the negative conductor of the DC voltage bus to the negative conductor of the DC voltage branch via the DC voltage switch. The DC voltage switch has: a semiconductor-based electronically controllable switching device, a DC voltage bus-side voltage sensor provided upstream of the switching device for determining the DC voltage bus-side voltage level, a DC voltage branch-side voltage sensor provided downstream of the switching device for determining the DC voltage branch-side voltage level, a current sensor for determining the current level and the current direction, a control device that is connected to the switching device, the voltage sensors and the current sensor, wherein the control device is designed such that the direction of the current and the current level are determined, the flow of current is interrupted by the switching device when a first threshold value of the current level is exceeded, when the first threshold value of the current level is exceeded in the reverse direction: after the flow of current is interrupted, the DC voltage bus-side voltage level is compared with the DC voltage branch-side voltage level, and the switching device is switched into the on state in the event of a voltage difference that is less than a voltage difference value.