Diagnosing Y-Capacitor Disconnect Switch Faults via Dynamic Voltage
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Solution Overview
Problem
The existing systems for diagnosing switching elements that selectively connect Y-capacitors to ground face challenges in distinguishing between opening and closing faults due to constant voltage readings at both terminals, regardless of the switching element's state, when Y-capacitors are connected in common to a DC link.
Innovation Solution
A system that includes a first and second Y-capacitor group connected in series between the positive and negative terminals of a DC link, a Y-capacitor disconnect switch with one terminal connected to ground, and a power conversion circuit with a controller to adjust the switching device states, forming different voltages at the switch's terminals to diagnose faults by comparing these voltages during opening and closing operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If Y-capacitors are connected in common to a DC link, then the system structure is simplified, but the voltage at both terminals of the switching element becomes constant making fault diagnosis impossible
Solution Approach 1:
The patent applies the Dynamics principle by making the voltage conditions dynamic rather than static. The controller dynamically adjusts the switching states of power conversion circuit devices to create varying voltage conditions at the switching element terminals during different time periods, enabling fault diagnosis that was previously impossible under constant voltage conditions.
Solution Approach 2:
The patent implements Periodic action by alternating between different switching states in a periodic manner. The controller periodically switches between a first state (where first Y-capacitor connects to first potential, second Y-capacitor connects to second potential) and a second state (where connections are reversed), creating time-varying voltage conditions that enable diagnostic measurements.
2Ease of operation
If the same potential is applied to both Y-capacitors, then the system operation is simplified, but opening and closing faults cannot be distinguished
Solution Approach 1:
The patent applies the Asymmetry principle by creating asymmetric voltage conditions at the terminals of the switching element. Instead of applying the same potential to both Y-capacitors, the system applies different potentials (first potential and second potential) to different Y-capacitors during different time periods, creating the voltage difference necessary to distinguish between opening and closing faults.
Solution Approach 2:
The patent implements Parameter changes by varying the voltage parameters applied to the Y-capacitors. The controller changes the potential assignments dynamically - switching between connecting first Y-capacitor to first potential/second Y-capacitor to second potential, and vice versa - thereby creating measurable voltage variations for accurate fault diagnosis.
Data Source
AI summary
A system for diagnosing switching element selectively connecting Y-capacitors to ground is provided. The state of a switching device in a power conversion circuit is adjusted such that voltages of different levels are applied to the Y-capacitors, respectively. Therefore, a Y-capacitor disconnect switch which connects a plurality of Y-capacitors connected in common to a DC link to chassis ground is diagnosed.