DC Grid Switch Testing via Sub-Millisecond Conductivity Pulses
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Solution Overview
Problem
Existing switching devices for DC voltage grids struggle to identify defective semiconductor switches, especially when they are in the on state, as the build-up of blocking voltage is prevented by freewheeling diodes, making it difficult to detect defects during normal operation.
Innovation Solution
The implementation of a switching device with a controller that uses a control pulse to reduce the conductivity of the semiconductor switch for a short time, allowing for a function test irrespective of the current direction, by applying a current to a test circuit and ascertaining voltage values to determine switch functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If semiconductor switches are permanently activated during normal operation, then the switching device can maintain continuous current conduction, but defects that prevent voltage build-up remain undetected
Solution Approach 1:
The controller performs preliminary function tests of the semiconductor switches at predetermined intervals by applying test control signals before actual faults occur. This allows detection of defects that would prevent voltage build-up, while maintaining continuous operation during normal conditions.
Solution Approach 2:
The controller periodically activates test circuits and applies control signals to semiconductor switches at predetermined intervals to perform function tests. This periodic testing enables continuous monitoring of switch health without affecting normal continuous operation.
2Adaptability or versatility
If freewheeling diodes are used in parallel with semiconductor switches, then the circuit can handle reverse current flow, but voltage build-up across defective switches is prevented making defects undetectable
Solution Approach 1:
During function tests, the controller temporarily extracts or overrides the influence of freewheeling diodes by applying control signals that force the semiconductor switches into specific states. This allows voltage build-up to occur across the switches for testing purposes, enabling defect detection despite the presence of parallel diodes during normal operation.
Solution Approach 2:
The controller performs preliminary testing by applying control signals to create conditions where voltage can build-up across switches even with parallel diodes present. This preliminary test action occurs before actual load operation, allowing defect detection without compromising the bidirectional current handling capability during normal operation.
3Reliability
If function tests are performed during ongoing operation, then defects can be identified early, but the testing process may interfere with normal current conduction
Solution Approach 1:
The controller performs function tests at predetermined intervals rather than continuously, allowing normal current conduction to proceed undisturbed between tests. This periodic approach enables early defect identification while minimizing interference with productivity and continuous operation efficiency.
Solution Approach 2:
The function tests apply control signals only to specific semiconductor switches being tested, rather than affecting the entire switching device. This partial action approach allows testing of individual components without interfering with overall system operation and current conduction through other switches.
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 enables reliable functionality testing of semiconductor switches during ongoing operation, independent of current direction, thereby identifying defects early and preventing potential failures, which increases the availability and reduces maintenance intervals of the electrical installation.
Implementation Method 1
actuating the first semiconductor switch (151, 155) using a control pulse that, in the case of a functional semiconductor switch (151, 155), causes the electrical conductivity of the semiconductor switch (151, 155) to reduce for a time period of less than 1 ms
Implementation Method 2
ascertaining a first value representing the voltage or the change in voltage across the first semiconductor switch (151, 155) as a result of the control pulse and the application
Data Source
AI summary
Various embodiments of the teachings herein include a switching device for a DC voltage grid. The device may include: a first controllable semiconductor switch with a control contact and two load contacts; and a controller for the first switch using a control signal at the control contact. The controller is configured to: actuate the first switch using a control pulse that causes the electrical conductivity of the semiconductor switch to reduce for less than 1 ms; apply a current to a test circuit including the first switch; ascertain a first value representing the voltage or the change in voltage across the first switch as a result of the control pulse and the applied current; analyzing the first value; and generating a signal that represents the functionality of the first semiconductor switch.