PV String Insulation Fault Detection by Current Direction
Find Innovative SolutionsGenerate Solutions
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 difficulties in on-site troubleshooting.
Innovation Solution
A photovoltaic power generation system with a switch and controller that grounds the positive electrodes of all photovoltaic strings, allowing for the determination of the faulty string based on current magnitude and direction, using current detection devices to pinpoint the fault at the negative electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulation fault detection is performed by detecting insulation impedance to ground, then safety hazards can be identified, but the specific photovoltaic string where the fault occurs cannot be determined
Solution Approach 1:
The patent divides the photovoltaic power generation system into multiple independent photovoltaic strings for separate current detection. By segmenting the system into individual string units and measuring current in each string separately, the fault location can be precisely identified to a specific string, resolving the contradiction between system-level safety detection and component-level fault localization.
2Object-affected harmful factors
If conventional insulation detection methods are used, then safety monitoring is achieved, but on-site troubleshooting becomes difficult due to inability to pinpoint the faulty string
Solution Approach 1:
The patent implements a feedback mechanism where current detection devices continuously monitor each photovoltaic string and provide real-time data to the controller. When an insulation fault is detected, the system immediately identifies and reports the specific faulty string through current direction analysis, enabling rapid on-site troubleshooting and repair by providing precise feedback on the fault location.
3Measurement precision
If the switch connects positive electrodes to ground, then a current path is formed for detection, but system operation may be affected
Solution Approach 1:
The patent employs periodic action by controlling the switch to connect the positive electrodes to ground only during designated detection periods rather than continuously. The controller activates the switch at specific intervals to perform insulation detection, then disconnects it to restore normal system operation. This periodic grounding approach enables accurate current detection while maintaining system operational stability during non-detection periods.
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
Enables precise identification of the photovoltaic string with an insulation fault by forming a current path and detecting current direction, facilitating effective troubleshooting.
Implementation Method 1
positive electrodes of all the photovoltaic strings are grounded through the switch
Data Source
Figure 1
Figure 2
Figure 3
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. Positive 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 negative electrode of the photovoltaic power generation system to ground. If an insulation fault occurs at the negative electrode of the photovoltaic power generation system, the positive electrodes of all the photovoltaic strings are controlled to be grounded, and a short circuit occurs between a negative electrode of a photovoltaic string where the insulation fault occurs and the ground. As a result, a current path is formed between the negative 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.