PV String Insulation Fault Detection by Grounded Current Reversal
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Solution Overview
Problem
Conventional insulation fault detection in photovoltaic power generation systems fails to accurately identify the specific photovoltaic string where an insulation fault occurs, leading to inefficiencies in troubleshooting.
Innovation Solution
A photovoltaic power generation system with a switch and controller that grounds the negative electrodes of all strings and uses current detection devices to determine the string with an insulation fault based on current magnitude and direction, forming a current path between the faulted string and ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulation impedance detection is performed on the photovoltaic power generation system, then insulation fault detection capability is improved, but the ability to locate the specific faulty photovoltaic string deteriorates
Solution Approach 1:
The patent divides the photovoltaic power generation system into multiple independently detectable photovoltaic strings. By grounding the negative electrodes of all strings through a switch and detecting current in each string separately, the system can identify which specific string has an insulation fault. This segmentation transforms a system-level detection problem into string-level detection, resolving the contradiction between detecting insulation faults and locating the specific faulty string.
2Ease of operation
If conventional insulation detection method is used, then detection simplicity is improved, but troubleshooting efficiency deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where current detection results from each photovoltaic string are fed back to identify the faulty string. The controller detects currents in all strings, compares the results, and provides feedback to determine which string has the insulation fault. This feedback approach maintains operational simplicity while significantly improving troubleshooting efficiency by directly identifying the problematic string.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Accurately locates the insulation fault by detecting current direction and magnitude, enabling precise identification of the faulty string and facilitating efficient troubleshooting.
Implementation Method 1
negative electrodes of all the photovoltaic strings are grounded through the switch
Implementation Method 2
determine a photovoltaic string where an insulation fault occurs based on a magnitude and a direction of a current of each of the n photovoltaic strings
Data Source
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AI summary
A photovoltaic power generation system and an insulation detection method are provided. The system includes a switch, a DC-AC circuit, a controller and at least one DC-DC circuit. An input end of each of the at least one DC-DC circuit is configured to connect n photovoltaic strings, n is an integer greater than or equal to two, and an output end of the at least one DC-DC circuit is connected to an input end of the DC-AC circuit. Negative electrodes of all the photovoltaic strings are grounded through the switch. The controller is configured to close the switch and determine a photovoltaic string where an insulation fault occurs based on a magnitude and a direction of a current of each of the n photovoltaic strings, if the insulation fault occurs at a positive electrode of the photovoltaic power generation system to ground. If an insulation fault occurs at the positive electrode of the photovoltaic power generation system, the negative electrodes of all the photovoltaic strings are controlled to be grounded, and a short circuit occurs between a positive electrode of a photovoltaic string where the insulation fault occurs and the ground. As a result, a current path is formed between the positive electrode of the photovoltaic string and the ground, and currents of other photovoltaic strings flow into the photovoltaic string where the insulation fault occurs, in a direction opposite to a direction of a current of the photovoltaic string where the insulation fault occurs, so that the photovoltaic string where the insulation fault occurs can be determined.