PV Combiner Fault Detection for Reverse-Connected Strings
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Solution Overview
Problem
Conventional photovoltaic systems face challenges in accurately determining reverse connection faults in photovoltaic strings due to misjudgment caused by voltage mismatches and cable issues, leading to potential damage from overcurrents.
Innovation Solution
A combiner device equipped with current, voltage, and insulation impedance detection circuits, along with a controller, to accurately assess reverse connection faults by analyzing current direction, voltage levels, and insulation impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current detection is used to determine reverse connection faults, then fault detection capability is provided, but misjudgment occurs due to voltage mismatches and cable issues
Solution Approach 1:
The fault detection function is segmented into three independent detection circuits: current detection circuit, voltage detection circuit, and insulation impedance detection circuit. Each circuit independently monitors a specific parameter, allowing the system to analyze multiple parameters separately and comprehensively determine reverse connection faults, thereby eliminating misjudgments caused by single-parameter detection limitations
Solution Approach 2:
The detection approach transitions from single-dimensional current detection to three-dimensional parameter detection by adding voltage and insulation impedance detection dimensions. This multi-dimensional detection space enables the system to distinguish reverse connection faults from other anomalies by analyzing the combined pattern of all three parameters, significantly improving determination reliability
2Power
If multiple photovoltaic strings are connected in parallel to combine currents, then system power output is increased, but reverse connection faults cause overcurrent damage
Solution Approach 1:
The system performs preliminary detection of current, voltage, and insulation impedance parameters before overcurrent damage can occur. By continuously monitoring these parameters and identifying reverse connection faults in advance, the system can trigger protective actions to prevent overcurrent damage to photovoltaic modules, enabling preventive protection rather than reactive response
Solution Approach 2:
The detection circuits provide continuous feedback on the operational status of parallel-connected photovoltaic strings. When reverse connection faults are detected through abnormal parameter patterns, the feedback mechanism enables the system to adjust or isolate affected strings, preventing overcurrent propagation and protecting the overall system while maintaining optimal power output from healthy strings
Data Source
AI summary
The present application discloses a combiner device, a photovoltaic system and a fault detection method. The combiner device comprises at least two photovoltaic strings connected in parallel; and further comprises a current measurement circuit, a voltage measurement circuit, an insulation resistance measurement circuit and a controller. The current measurement circuit is used for measuring the current of each photovoltaic string; the voltage measurement circuit is used for measuring the voltage of the photovoltaic strings connected in parallel; the insulation resistance measurement circuit is used for measuring the insulation resistance of the photovoltaic strings connected in parallel; and the controller determines, according to the current, the voltage and the insulation resistance, whether the photovoltaic strings have a reverse connection fault.