PV Ground Fault Detection via Intra-String Current Differences
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Large PV arrays face challenges in detecting ground faults and potential ground faults, which can lead to safety hazards and fires due to leakage currents and unintended gaps in conductors, masking individual issues within the system.
Innovation Solution
The use of distributed DC/DC converters with precise current measurement capabilities to detect intra-string current differences, allowing for the identification of leakage paths and faulty modules, and employing circuit architecture changes to isolate faults and prevent ground faults through current interrupters and rail grounding techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current measurement methods are used in large PV arrays, then the system structure remains simple, but individual ground faults are masked by normal leakage currents
Solution Approach 1:
The patent divides the PV array into multiple strings and further segments each string into individual module measurements. By measuring current at each module level rather than at the array level, the system can identify ground faults in specific modules without being masked by overall leakage currents from other modules.
Solution Approach 2:
The patent introduces current measurers as intermediary devices between the PV modules and the monitoring system. These measurers capture individual module current data, which is then processed to detect ground faults. The intermediary measurement system enables precise fault detection without requiring direct intervention in the power flow path.
2Measurement precision
If distributed DC/DC converters are deployed at each module for current measurement, then ground fault detection precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent integrates current measurement functionality into the DC/DC converters that are already present in the PV modules for power optimization. By making the converters multi-functional (both power conversion and current measurement), the system achieves precise leakage current detection without adding separate measurement devices to each module.
Solution Approach 2:
The patent combines the power conversion function and measurement function into a single integrated system at each module. The DC/DC converter serves dual purposes: optimizing power output and providing accurate current measurement for ground fault detection. This merging reduces overall system complexity compared to having separate converter and measurement devices.
3Object-affected harmful factors
If small gaps between conductors are monitored continuously, then fire safety is improved, but energy consumption and system complexity increase
Solution Approach 1:
The patent implements continuous current measurement and comparison at the module level to detect ground faults before they can cause fires. By measuring current at each module and comparing it with expected values, the system identifies potential hazards (small gaps) early in their development, allowing preventive action before fire risk materializes.
Solution Approach 2:
The patent establishes a feedback loop where current measurements from each module are continuously compared against expected values, and deviations trigger alerts or automatic responses. This feedback mechanism enables real-time monitoring of conductor gaps and ground faults, allowing the system to respond to developing hazards before they become fire risks.
Data Source
AI summary
One aspect of the inventive technology disclosed herein, in certain embodiments, may involve the determination of at least one measured, instantaneous intra-string current difference for each of the power generating string, and the use of such determinations to assess the existence of leakage current, a frequent ground fault predecessor, thereby enabling preclusion of a ground fault that would otherwise result. Certain methods and detection architecture may enable precise abnormality location, e.g., enabling the identification of which solar module assembly in particular is faulty. Another aspect relates generally, in certain embodiments, to detection circuit architecture operable to sequentially impress a leakage current inducing voltage upon each rail of a photovoltaic system. Another relates generally, in certain embodiments, to the use of at least one current interrupter at each end of a string to preclude flow therethrough in the event of e.g., unintended field reversal.