Relay Abnormality Detection in Grid-Connected Power Conditioners

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Solution Overview

Problem

Existing grid interconnection devices face challenges in accurately detecting relay abnormalities during grid independent operation due to power cuts, leading to potential reverse charge and asynchronous input issues, and require additional costly circuit elements and prone to erroneous detection.

Innovation Solution

A relay abnormality detection device that determines commercial power system voltage and checks for input or output currents in the power conditioner, using mathematical expressions to assess relay abnormalities without additional current detection circuits, ensuring accurate detection and preventing reverse charge and asynchronous input.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If additional current detection circuits are added to detect relay abnormalities during grid independent operation, then measurement precision is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improverelay abnormality detection accuracyVSAvoidcircuit element quantity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent makes existing circuit elements (current detection units already present for normal operation) serve multiple functions: they detect both normal operating currents and abnormal currents during grid independent operation. This eliminates the need for separate dedicated detection circuits for relay abnormality detection, resolving the contradiction between measurement precision and device complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses its own existing current detection capabilities to detect relay abnormalities without requiring external or additional specialized detection circuits. The current detection units already integrated into the power conditioner are utilized to serve the dual purpose of normal operation monitoring and relay abnormality detection

Inventive Principle:

Principle #25Self-service

2Reliability

If relay abnormality detection is implemented during grid independent operation, then reliability is improved, but device complexity increases due to additional control logic

Engineering Contradiction:

Improveprevention of reverse charge and asynchronous inputVSAvoidcontrol unit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the relay abnormality detection function with the existing control unit that manages grid connected and grid independent operations. The control unit integrates multiple functions: normal operation control, grid status monitoring, and relay abnormality detection. This merging approach improves reliability without significantly increasing device complexity, as the control unit already handles complex switching operations between different operating modes

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If traditional methods are used to detect relay contact welding, then measurement precision may be sufficient, but object-generated harmful factors increase due to reverse charge and asynchronous input

Engineering Contradiction:

Improverelay contact status detectionVSAvoidreverse charge and asynchronous input

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent performs relay abnormality detection during grid independent operation, which is a preliminary check before potentially harmful effects can occur. By detecting contact welding abnormalities early, when the relay is opened to separate from the commercial power system, the system prevents reverse charge to the commercial power system and asynchronous input, thereby eliminating the harmful factors before they can manifest

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the potentially harmful situation of relay contact welding into a detectable and manageable condition. By using the natural operating conditions (voltage and current during grid independent operation) to detect abnormalities, the system transforms what could be a harmful undetected fault into a beneficial early warning mechanism that prevents reverse charge and asynchronous input

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS9970988B2Relay abnormality detection device and power conditioner

Publication Date: 2018.05.15 DIAMOND&ZEBRA ELECTRIC MFG CO LTD

AI summary

A relay abnormality detection device to detect an abnormality of a grid interconnection relay upon switching to grid independent operation and includes an abnormality detector to execute commercial power system voltage for determining whether or not there is a commercial power system voltage, if there is commercial power system voltage through the commercial power system voltage determination, first current determination of abnormality determination as to the specific relay according to whether or not there is an input current to the power conditioner in a state where a contact of the specific relay is controlled to open, and if there is no commercial power system voltage through commercial power system voltage determination, second current determination of abnormality determination as to the specific relay according to whether or not there is an output current from the power conditioner in the state where the contact of the specific relay is controlled to open.