PV String Earth Fault Detection Using Terminal Voltage Disturbance

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Solution Overview

Problem

Current photovoltaic power generation systems face inefficiencies in detecting and locating earth faults in photovoltaic strings, requiring manual and time-consuming checks, which can lead to safety risks and reduced system performance.

Innovation Solution

A photovoltaic power generation system and method that involves a controller to detect earth faults by measuring terminal voltages before and after a voltage disturbance, allowing for automatic identification of faulty strings and panels using proportional relationships between terminal and output voltages, without the need for additional hardware.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If manual checking of photovoltaic strings is performed to locate earth faults, then detection accuracy is improved, but detection time and labor cost increase significantly

Engineering Contradiction:

Improvefault location detection accuracyVSAvoiddetection time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces manual mechanical inspection with an automated electrical measurement system. The controller automatically measures terminal voltages of photovoltaic strings and uses voltage disturbance techniques to locate earth faults, eliminating the need for manual checking while maintaining detection accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system enables self-diagnosis of earth faults by automatically measuring and analyzing terminal voltages of photovoltaic strings. The controller performs voltage disturbance and calculates fault locations without external intervention, allowing the system to detect and locate its own faults independently.

Inventive Principle:

Principle #25Self-service

2Productivity

If additional detection hardware is added to automatically locate earth faults, then detection efficiency is improved, but system complexity and cost increase

Engineering Contradiction:

Improvedetection efficiencyVSAvoidsystem complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent makes the existing controller perform multiple functions: it not only controls the photovoltaic system but also serves as the detection device for earth faults. The controller uses its existing voltage measurement capabilities to measure terminal voltages and perform fault location, eliminating the need for separate detection hardware.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The existing controller serves itself by performing earth fault detection and location using its built-in voltage measurement functions. No external detection device is needed as the controller leverages its own capabilities to detect and locate faults in the photovoltaic strings.

Inventive Principle:

Principle #25Self-service

3Reliability

If traditional insulation resistance detection is used, then earth fault detection is achieved, but fault location cannot be determined requiring manual string-by-string checking

Engineering Contradiction:

Improveearth fault detection capabilityVSAvoidfault location determination

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent introduces terminal voltage measurement as an intermediary parameter to locate earth faults. By measuring the terminal voltages of photovoltaic strings and analyzing voltage disturbances, the system can determine fault locations without manual inspection, making the fault location process as easy as reading voltage values.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces manual string-by-string checking with automated voltage measurement and analysis. The controller automatically measures terminal voltages, performs voltage disturbance, and calculates fault locations based on voltage changes, eliminating the need for operators to manually check each string.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This approach enables rapid and efficient detection of earth faults, reducing manual effort and improving safety by automatically locating faults within photovoltaic strings, thereby enhancing system reliability and efficiency.

Implementation Method 1

obtain a terminal voltage of each photovoltaic string before voltage disturbance... perform voltage disturbance on each photovoltaic string and obtain a terminal voltage of each photovoltaic string after the voltage disturbance... obtain a photovoltaic panel with an earth fault by using the terminal voltage and an output voltage of the photovoltaic string

Methodology Applied

Scientific EffectVoltage measurement and proportional relationship: Ohm's Law

Data Source

PatentUS12199567B2Photovoltaic power generation system and method and device for detecting earth fault of photovoltaic string

Publication Date: 2025.01.14 HUAWEI DIGITAL POWER TECH CO LTD

AI summary

A photovoltaic power generation system and a method and a device for detecting an earth fault of a photovoltaic string. The controller obtains a terminal voltage of each photovoltaic string before voltage disturbance, where the terminal voltage is a voltage to earth of a positive electrode or negative electrode of the photovoltaic string; performs voltage disturbance on each photovoltaic string and obtains a terminal voltage of each photovoltaic string after the voltage disturbance; determines a photovoltaic string with an earth fault based on the terminal voltage of each photovoltaic string before and after the voltage disturbance; obtains a photovoltaic panel with an earth fault by using the terminal voltage and an output voltage of the photovoltaic string before the voltage disturbance, or obtains a photovoltaic panel with an earth fault by using the terminal voltage and an output voltage of the photovoltaic string after the voltage disturbance.