AC Voltage Waveform Anomaly Detection for Grid Inverters
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Solution Overview
Problem
Solar panel systems face issues with improperly injecting AC current onto the commercial power grid due to irregular AC grid voltage zero-crossings, leading to potential damage to the distributed generation system.
Innovation Solution
A method and apparatus that utilize a threshold generator to create time-variant thresholds based on AC voltage waveform information, allowing a threshold detector to identify anomalies in AC grid voltage zero-crossings, thereby preventing damage by temporarily shutting down the inverter during anomalies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the DG system uses zero-crossings of AC grid voltage for phase alignment, then the injected AC current and AC grid voltage are phase-aligned, but irregular zero-crossings cause improper injection and potential damage to the DG system
Solution Approach 1:
The patent applies preliminary action by detecting and identifying irregular zero-crossings before the DG system attempts to synchronize and inject power. The anomaly detection mechanism proactively identifies problematic zero-crossings in advance, allowing the system to prevent synchronization attempts during irregular conditions, thereby avoiding potential damage while maintaining reliable phase alignment during normal operation
Solution Approach 2:
The patent introduces an intermediary anomaly detection mechanism that sits between the grid voltage input and the phase-lock synchronization process. This intermediary layer analyzes zero-crossing patterns and determines whether conditions are suitable for synchronization, acting as a mediator that protects the DG system from harmful irregular zero-crossings while enabling safe operation during normal grid conditions
2Reliability
If the system continuously monitors AC voltage waveform to detect anomalies, then damage prevention is improved, but device complexity increases due to additional detection mechanisms
Solution Approach 1:
The patent applies self-service by utilizing the existing AC voltage waveform data that the DG system already receives for phase-lock synchronization. The anomaly detection mechanism processes this existing signal through analysis of zero-crossing patterns and waveform characteristics, eliminating the need for separate dedicated sensing hardware and reducing overall system complexity while maintaining effective damage prevention
Solution Approach 2:
The patent implements multi-functionality by designing the anomaly detection mechanism to perform multiple functions: it analyzes zero-crossing patterns, evaluates waveform characteristics, determines synchronization suitability, and provides protection decisions. This single detection apparatus handles various aspects of grid anomaly detection and protection, reducing the need for multiple separate components and simplifying the overall system architecture
Data Source
AI summary
A method and apparatus for determining AC voltage waveform anomalies. The apparatus comprises a threshold generator for generating at least one time-variant threshold based on information regarding an AC voltage waveform. The apparatus further comprises a threshold detector for comparing a sample of the AC voltage waveform to the at least one time-variant threshold to identify an AC voltage waveform anomaly.