Power Conversion Device Islanding Detection via Server Communication

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Solution Overview

Problem

Existing islanding detection methods in power conversion systems for distributed energy resources often result in false detection, reducing the reliability of preventing islanding states, as these methods rely on devices within the distributed energy resources to detect changes in AC characteristics.

Innovation Solution

A power conversion device with a communication unit that receives information on system accidents and initiates an islanding determination process only when no information is received for a predetermined period, using a server to manage disconnection and reduce false detection by injecting reactive power to detect AC changes, thereby reducing the frequency of islanding determination processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If islanding detection is performed by devices on the distributed energy resource side, then the detection can be performed locally, but false detection occurs reducing reliability

Engineering Contradiction:

Improveislanding detection reliabilityVSAvoidislanding state detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent introduces a communication unit that receives information from a server about system accidents as an intermediary mechanism. Instead of relying solely on local AC characteristic detection by the power conversion device, the system uses server-provided accident information to trigger islanding determination processes, reducing false detections while maintaining reliable local detection capability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The server performs preliminary detection of system accidents and communicates this information to power conversion devices before islanding determination is needed. This preliminary action allows the power conversion device to know when to initiate islanding detection, avoiding unnecessary detections and reducing false positives

Inventive Principle:

Principle #10Preliminary action

2Reliability

If islanding determination process is frequently performed to ensure detection accuracy, then reliability improves, but voltage flicker occurs and system stability deteriorates

Engineering Contradiction:

Improveislanding detection reliabilityVSAvoidvoltage flicker

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements periodic reception of server information at predetermined intervals and triggers islanding determination processes only at these periodic intervals or when server information indicates system accidents. This periodic approach ensures adequate detection coverage while avoiding excessive frequency that causes voltage flicker

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system uses feedback from server information about system accidents to control when islanding determination processes are initiated. The power conversion device receives feedback about system status and adjusts its detection frequency accordingly, performing determinations only when necessary based on server feedback, thus avoiding unnecessary voltage flicker

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

This approach enhances the reliability of islanding detection by reducing false positives and minimizing the frequency of islanding determination processes, thereby preventing voltage flicker and improving system stability.

Implementation Method 1

a communication unit configured to periodically receive, via communication, reception information indicating whether an accident has occurred in the power system

Methodology Applied

Scientific EffectCommunication:

Implementation Method 2

The islanding determination process may determine whether the distributed energy resource is in an islanding state by detecting a change in AC characteristics in the power system when reactive power is injected into the power system

Methodology Applied

Scientific EffectReactive power injection:

Data Source

PatentUS11728676B2Power conversion device, control device, server and system

Publication Date: 2023.08.15 FUJI ELECTRIC CO LTD

AI summary

A power conversion device which converts electrical power generated by a distributed energy resource into electrical power corresponding to a power system is provided, comprising a communication unit which periodically receives, via communication, reception information indicating whether an accident has occurred in the power system, a disconnection unit which disconnects the distributed energy resource from the power system when the communication unit receives the reception information indicating accident occurrence, and a control unit which starts an islanding determination process for determining whether the distributed energy resource is in an islanding state by detecting a change in AC characteristics in the power system, when the communication unit does not receive the reception information for a predetermined first period.