PV Panel Rapid Shutdown via Continuity Test Signal
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Solution Overview
Problem
Photovoltaic (PV) panels continue to generate hazardous voltages even when disconnected from the electrical grid, posing a safety hazard and requiring safe shutdown and reconnection methods to comply with electrical safety codes.
Innovation Solution
A method and apparatus using a continuity test source and Rapid Shutdown Devices (RSDs) to monitor and control the connection of PV panels to an inverter, applying a test signal to ensure electrical safety by disconnecting panels during shutdown and reconnecting only when safe conditions are met, utilizing a controller and switches to manage the connection state based on the presence of the test signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If PV panels are disconnected from the electrical grid during shutdown, then safety hazard is reduced, but electrical continuity cannot be verified and safe reconnection cannot be ensured
Solution Approach 1:
The system performs a preliminary continuity test using a test signal source before allowing reconnection of PV panels. The controller activates the test signal source to apply a test signal through the disconnect switch to verify electrical continuity exists in the circuit before panels are reconnected, ensuring safe reconnection conditions are met in advance
Solution Approach 2:
The controller monitors the response of the PV panel string to the applied test signal to determine whether electrical continuity exists. Based on this feedback information, the controller automatically controls the disconnect switch to either connect or disconnect the PV panels, ensuring reconnection only occurs when safety conditions are confirmed
2Reliability
If PV panels remain connected to verify electrical continuity, then safe reconnection can be ensured, but hazardous voltages continue to be generated
Solution Approach 1:
The system introduces a test signal source as an intermediary device that can be coupled to the PV panel string through the disconnect switch. This intermediary applies a test signal to verify electrical continuity without requiring the PV panels to be fully connected and generating hazardous voltages. The test signal serves as a safe mediator to check circuit integrity
Solution Approach 2:
The system changes the electrical parameter being tested by using a low-voltage test signal instead of the high-voltage operating conditions. The controller activates the test signal source to apply a test signal at safe voltage levels to verify continuity, allowing safety verification without exposing the system to hazardous operating voltages
3Device complexity
If manual inspection of electrical continuity is performed, then equipment complexity is reduced, but safety and accuracy of reconnection cannot be ensured
Solution Approach 1:
The system performs self-verification of electrical continuity automatically through the controller that monitors the response of the PV panel string to the test signal. The disconnect switch and control system work together to automatically determine continuity status and control connection state without requiring manual inspection, ensuring both safety and operational simplicity
Data Source
AI summary
A test signal is applied from a continuity test source to a photovoltaic (PV) panel string, to test electrical continuity in the PV panel string and between the PV panel string and an inverter that is coupled to the PV panel string. If the test signal is detected at a PV panel disconnect switch that is separate from the continuity test source and switchably couples one or more Direct Current (DC) PV panels in the PV panel string, then the PV panel disconnect switch is controlled to connect the one or more DC PV panels in the PV panel string. Otherwise, the PV panel disconnect switch is controlled to disconnect the one or more DC PV panels from the PV panel string. The test signal could be, for example, an Alternating Current (AC) signal tuned to a PV installation that includes the PV panel string and the inverter.