PV String Fault Detection via Aggregated Current Sensor
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Solution Overview
Problem
In large-scale photovoltaic systems, the existing fault detection methods require a high number of current sensors, leading to increased costs due to the need for multiple sensors and accompanying devices and wiring lines.
Innovation Solution
A fault detecting apparatus that reduces the number of current sensors by using a configuration where current sensors are placed on all but one string's positive or negative electrodes and a single sensor on the aggregated wire, allowing for fault detection based on current flow and direction analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current sensors are provided at positive and negative sides of all strings to detect faults at all PV arrays, then fault detection capability is improved, but the number of current sensors increases
Solution Approach 1:
The patent extracts the current sensing function from individual string level to a centralized location. Instead of placing sensors at every string, the invention uses a single current sensor at the aggregated positive or negative electrode wire to detect faults across all parallel-connected strings, thereby reducing the number of sensors while maintaining fault detection capability
Solution Approach 2:
The single current sensor at the aggregated wire serves multiple strings simultaneously, making the sensing system universal. The sensor detects currents from all parallel-connected strings through the common aggregated conductor, allowing one sensor to perform the function that would otherwise require multiple sensors distributed across different strings
2Reliability
If the number of current sensors is increased, then fault detection coverage is improved, but devices and wiring lines accompanying the current sensors are increased
Solution Approach 1:
The patent merges multiple sensing functions into a single sensing point. By combining the current detection of all parallel strings into one measurement location (the aggregated wire), the system reduces the number of associated devices such as A/D converters and signal processing units, as well as reducing wiring complexity
Solution Approach 2:
The invention extracts the sensing function from distributed locations to a centralized location, thereby eliminating the need for multiple accompanying devices and wiring lines that would be required at each distributed sensor location
3Measurement precision
If current sensors are provided at all strings, then detection accuracy is improved, but system cost is increased
Solution Approach 1:
The patent extracts the current measurement function from individual string level to the aggregated wire level, reducing the quantity of current sensors required while maintaining the ability to detect faults. This extraction directly reduces system cost by minimizing the number of sensors, A/D converters, and associated components
Data Source
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AI summary
There is a fault detecting apparatus 1 for detecting a fault in an electric circuit including two strings STa and STb connected parallel to respectively connect PV arrays 2a and 2b with an inverter 5 and including wires Lp and Ln that aggregates two strings STa and STb and to connect the aggregated strings STa and STb with the inverter 5. The fault detecting apparatus 1 includes detecting a current Iap flowing through a wire STap of the string STa, detecting a current Ip flowing through the aggregating wire Lp, and detecting the fault when it is detected that the current Iap flows in the string STa and it is detected that the current Ip does not flow in the aggregating wire Lp.