PV Inverter Arc Detection via DC/DC Circuit Isolation
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Solution Overview
Problem
Existing methods for detecting arcing in photovoltaic systems misdiagnose arc faults due to changes in sunlight and communication interference, leading to incorrect shutdowns and reduced current supply.
Innovation Solution
A method involving stopping the control signal to a suspected DC/DC conversion circuit, allowing other circuits to operate normally, and gradually decreasing the voltage at the power supply side to detect if current exceeds a preset threshold, thereby distinguishing between false and real arcs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all DC/DC conversion circuits are turned off when a suspected electric arc is detected, then safety is improved, but system productivity deteriorates due to unnecessary shutdowns
Solution Approach 1:
The system segments the DC/DC conversion circuits and allows individual isolation. When an arc fault is detected in one circuit, only that specific circuit is disconnected while other circuits continue to operate normally, preventing system-wide shutdowns and maintaining productivity.
Solution Approach 2:
The system performs preliminary verification by decreasing voltage to a target voltage before confirming arc faults. This preliminary action distinguishes between real arc faults and false alarms caused by communication interference or sunlight changes, preventing unnecessary shutdowns.
2Speed
If the inverter is rapidly started to output voltage after shutdown, then system response speed is improved, but measurement precision deteriorates due to misdiagnosis
Solution Approach 1:
Before confirming an arc fault and initiating shutdown, the system performs preliminary verification by decreasing voltage to a target voltage and monitoring current. This preliminary action prevents misdiagnosis of false alarms, ensuring that rapid restart is only triggered for genuine arc faults.
Solution Approach 2:
The system uses feedback from current monitoring during the voltage decrease process to verify whether an arc fault truly exists. If current exceeds the preset threshold during verification, the system confirms the arc fault; otherwise, it treats it as a false alarm and maintains normal operation.
3Measurement precision
If voltage is decreased to verify arc faults, then detection accuracy is improved, but energy loss increases during the verification process
Solution Approach 1:
The system applies partial action by decreasing voltage only to a target voltage (not complete shutdown) for verification purposes. This partial voltage decrease is sufficient to detect arc faults while minimizing energy loss compared to complete system shutdown.
Solution Approach 2:
The system rapidly decreases voltage to the target voltage and quickly completes the verification process. By rushing through the verification phase, the system minimizes the duration of reduced power output, thereby reducing energy loss while maintaining detection accuracy.
Data Source
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AI summary
A method for detecting arcing, an inverter (100) and a photovoltaic (31) system are provided. The inverter (100) includes an inverter circuit (10) and DC/DC conversion circuits (20). The method includes: stopping outputting a control signal to a first DC/DC conversion circuit that is currently being suspected of having an electric arc and operating other DC/DC conversion circuits connected to the inverter circuit normally (S3015); decreasing a voltage at a power supply side of the first DC/DC conversion circuit immediately after a first preset period of time elapsed (S302); and determining that no arc fault occurs, and restoring the voltage at the power supply side of the first DC/DC conversion circuit to a first voltage that the first DC/DC conversion circuit receives before the stopping outputting the control signal, if a current at the power supply side is greater than or equal to a first preset current during the decreasing the voltage (S303).