IBR Transformer Energization Using Remanent Flux Phase Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Inrush current during transformer energization can be as high as ten times the rated current, causing mechanical and thermal stresses and delaying power recovery after blackouts.

Innovation Solution

The use of inverter-based resources (IBRs) with a switching-cycle-based direct current (DC) feedback loop to regulate the inverter current to zero, estimate the remanent flux, and determine the initial voltage phase angle for instant transformer energization without inrush current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional transformer energization is performed, then the transformer can be energized, but inrush current reaches up to ten times the rated current causing mechanical and thermal stresses

Engineering Contradiction:

Improvetransformer energization reliabilityVSAvoidinrush current

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary estimation of remanent flux in the transformer before energization by analyzing current samples during a pre-energization period. This preliminary action allows the controller to determine the optimal voltage phase angle in advance, ensuring that energization occurs at the precise moment when inrush current is minimized, thereby resolving the contradiction between reliable energization and inrush current suppression.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system changes the voltage phase angle parameter of the inverter based on the estimated remanent flux. By dynamically adjusting this parameter, the controller ensures that the voltage applied to the transformer at energization moment is optimized to prevent core saturation and minimize inrush current, thus resolving the contradiction between achieving reliable energization and avoiding harmful inrush current effects.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If transformer energization is performed with traditional methods, then the transformer can be energized, but the process causes delays in power recovery after blackouts

Engineering Contradiction:

Improvepower system recoveryVSAvoidpower recovery time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary estimation of remanent flux and determination of optimal voltage phase angle before energization. This preliminary action enables the system to execute energization instantly without requiring gradual ramp-up or waiting periods, thereby significantly reducing power recovery time after blackouts while ensuring reliable transformer energization.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system replaces traditional mechanical switch-based energization with inverter-based controlled energization. The inverter can instantly apply voltage at the precise optimal phase angle determined by the remanent flux estimation, eliminating the delays inherent in traditional mechanical switching methods and enabling rapid power system recovery.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Strength

If transformers are designed to handle inrush current, then they can withstand energization stresses, but transformers become bigger, heavier, and more expensive

Engineering Contradiction:

Improvetransformer withstand capabilityVSAvoidtransformer weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The system converts the potentially harmful remanent flux in the transformer into a useful piece of information. By estimating the remanent flux and using it to determine the optimal voltage phase angle for energization, the system transforms what was previously a source of inrush current problems into a tool for achieving transient-free energization, thereby eliminating the need for oversized transformers designed to withstand inrush stresses.

Inventive Principle:

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

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

Achieves instant or essentially instant transformer energization with minimal inrush current (less than 0.1 mA) and rapid power recovery after blackouts, utilizing existing IBRs without additional circuit components.

Implementation Method 1

The inrush current is caused by the direct current (DC) component in the core flux (initialized from the integration of primary side voltage) and transformer saturation

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS20250141231A1Method of transient-free transformer energization and black start using inverter based resources

Publication Date: 2025.05.01 FLORIDA STATE UNIV RES FOUND INC

AI summary

Systems and methods for energizing transformers with inverter-based resources (IBRs) are provided. IBRs can pick up local critical loads after blackout and ultimately support the bulk power system recovery. The transformer energization process can be achieved by controlling IBRs without any inrush current, and the duration of the process can be instant or essentially instant.