AC Capacitor Failure Detection During Inverter Synchronization
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Solution Overview
Problem
Existing power conversion apparatuses fail to detect AC capacitor failures during voltage matching operations, leading to the transmission of harmonics to the system and potential spread of failure to normal capacitors.
Innovation Solution
A control apparatus that includes a current component extractor, failure evaluator, and failure information notifier to detect AC capacitor malfunctions by comparing the magnitude of a current component synchronized with the inverter's output frequency during synchronization control, and issue failure information to stop the power conversion apparatus before system interconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage matching operation is performed before system interconnection, then the power conversion apparatus can synchronize output voltage with system voltage, but AC capacitor failure cannot be detected and harmonics are transmitted to the system
Solution Approach 1:
The patent performs failure detection during the voltage matching operation (synchronization control) before system interconnection. By extracting the current component at the inverter output frequency and comparing it with the evaluation value during this preliminary stage, the system detects AC capacitor failures before the AC switch is turned on, preventing harmful harmonic transmission to the system while maintaining reliable operation.
2Productivity
If AC switch is turned on after voltage matching operation, then system interconnection operation starts, but failure detection is delayed causing spread of failure to normal capacitors
Solution Approach 1:
The patent implements failure detection during the voltage matching operation that occurs before system interconnection. By evaluating the current component during synchronization control (when AC switch is open), the system identifies AC capacitor failures in advance, allowing normal capacitors to be protected from overload and failure spread while maintaining the planned startup sequence and productivity.
3Reliability
If current component extraction is performed during synchronization control, then AC capacitor failure can be detected early, but additional processing complexity is introduced
Solution Approach 1:
The control apparatus utilizes existing components (current detection means already present for synchronization control) to perform dual functions: both the synchronization control and the AC capacitor failure detection. By extracting the current component at the inverter output frequency from the same current measurements used for voltage matching, the system achieves early failure detection without adding separate detection hardware, thus minimizing complexity while improving reliability.
Data Source
AI summary
A control apparatus is a control apparatus for a power conversion apparatus including at least one AC capacitor disposed on the output side of an inverter and disconnected from a circuit when the AC capacitor malfunctions and including a current component extractor that acquires current values of the current flowing through the AC capacitor during synchronization control that synchronizes the output voltage from the inverter with a system voltage of a system, the synchronization control performed during activation of the power conversion apparatus with an AC switch on the side facing the system open, and extracts the value of a current component having a frequency synchronized with the frequency of the output voltage from the inverter out of the current values.