PV String Overcurrent Protection for Reverse Current Isolation

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Solution Overview

Problem

Conventional direct current overcurrent protection devices in photovoltaic systems fail to protect against reverse currents, leading to damage of strings and high costs due to the need for individual circuit breakers for each string.

Innovation Solution

A photovoltaic system with a direct current overcurrent protection apparatus comprising electromagnetic apparatuses and switch-on/off devices that disconnect loops between direct current modules when reverse currents exceed a preset amplitude, reducing the number of required devices and simplifying the system structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a direct current circuit breaker is connected in series with each string to provide overcurrent protection, then overcurrent protection is achieved, but the cost increases and system complexity increases

Engineering Contradiction:

Improveovercurrent protectionVSAvoidsystem structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the protection functions for multiple strings into a single direct current circuit breaker. The circuit breaker is configured to protect multiple strings simultaneously by detecting reverse currents from the converter and disconnecting the affected strings, eliminating the need for individual circuit breakers on each string.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The direct current circuit breaker is designed with multi-functionality to handle protection for multiple strings and detect reverse currents from the converter. It serves as a universal protection device that can identify and isolate faulty strings without requiring dedicated breakers for each string, thereby reducing overall system complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If a direct current circuit breaker is used for each string, then overcurrent protection is provided, but the cost increases

Engineering Contradiction:

Improveovercurrent protectionVSAvoidnumber of devices

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent combines multiple protection functions into a single direct current circuit breaker that can protect multiple strings. By merging the protective role that would otherwise require separate breakers for each string into one device, the total number of components is reduced and cost is lowered.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The circuit breaker is designed as a universal protection device capable of monitoring and protecting multiple strings simultaneously. Its ability to detect reverse currents and isolate faulty strings makes it a multi-functional device that replaces what would traditionally require multiple individual breakers, thereby reducing the quantity of devices needed.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If conventional overcurrent protection is used, then forward current protection is achieved, but reverse current protection is not provided leading to string damage

Engineering Contradiction:

Improveforward current protectionVSAvoidreverse current damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The direct current circuit breaker is configured to detect reverse currents from the converter before they can cause damage to the strings. By identifying the presence of reverse currents and disconnecting the affected strings promptly, the system prevents harmful effects from occurring in the first place.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The circuit breaker incorporates feedback mechanisms to monitor current flow direction and magnitude. It detects reverse currents flowing from the converter to the strings and uses this information to trigger disconnection of the affected strings, thereby protecting them from damage caused by reverse current flow.

Inventive Principle:

Principle #23Feedback

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

Effectively protects against reverse currents, preventing damage to direct current modules while reducing costs by minimizing the number of electromagnetic apparatuses and switch-on/off devices.

Implementation Method 1

an electromagnetic apparatus configured to trigger an action of the direct current switch-on/off apparatus

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS12362591B2Photovoltaic system and direct current overcurrent protection apparatus

Publication Date: 2025.07.15 HUAWEI DIGITAL POWER TECH CO LTD

AI summary

A photovoltaic system includes at least one first direct current module, an electromagnetic apparatus, a direct current switch-on/off apparatus, and a second direct current module. First connection ends of all first direct current modules in the at least one first direct current module are connected in parallel and then connected to a first connection end of the electromagnetic apparatus, a second connection end and a third connection end of the electromagnetic apparatus are connected to a first connection end of the second direct current module by using the direct current switch-on/off apparatus, and second connection ends of all the first direct current modules are connected in parallel and then connected to a second connection end of the second direct current module. The electromagnetic apparatus is configured to control the direct current switch-on/off apparatus to disconnect a loop between each first direct current module and the second direct current module.