Transformer Charging Device for Wind Turbine Inrush Current Protection

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Solution Overview

Problem

Wind turbines experience high inrush currents when the utility grid recovers from an outage, leading to unwanted protection relay tripping, mechanical loading of transformer windings, and reduced transformer lifetime due to resonances and oscillations in the power distribution system.

Innovation Solution

A wind turbine system with a charging device that charges the low-voltage side of a transformer after grid recovery before reconnecting the high-voltage side to the grid, thereby avoiding inrush currents and reducing mechanical loads and oscillations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If transformers are energized simultaneously after grid outage, then grid recovery is achieved, but high inrush current peaks occur causing protection relay tripping and mechanical loading

Engineering Contradiction:

Improvegrid recovery speedVSAvoidinrush current

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by charging the transformer core and windings with a charging device before main energization. This pre-charging process establishes the magnetic flux in the transformer core and energizes the windings gradually, preventing the sudden inrush current that would occur with direct simultaneous energization of all transformers after grid outage.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements periodic action through a two-stage energization process: first, the charging device operates to charge the transformer (period 1), then the main breaker closes for full grid connection (period 2). This staged, periodic approach replaces the single simultaneous energization action, allowing the system to recover grid connectivity while avoiding inrush current peaks.

Inventive Principle:

Principle #19Periodic action

2Reliability

If transformers are energized simultaneously after grid outage, then grid connectivity is restored, but mechanical loading and oscillations increase reducing transformer lifetime

Engineering Contradiction:

Improvegrid connectivityVSAvoidtransformer lifetime

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The charging device performs preliminary action by establishing the magnetic field and energizing transformer components before full grid connection. This pre-conditioning of the transformer reduces mechanical stress and oscillations during the subsequent main energization, thereby extending transformer lifetime while maintaining grid connectivity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The charging device acts as a cushioning mechanism by gradually building up the magnetic flux and voltage in the transformer before main energization. This beforehand cushioning absorbs and mitigates the mechanical shocks and oscillations that would otherwise occur during sudden simultaneous energization, protecting the transformer from excessive mechanical loading.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 effectively reduces inrush currents and extends transformer lifespan by buffering energy and synchronizing the high-voltage side with the grid before reconnection, minimizing mechanical loads and oscillations in the power distribution system.

Implementation Method 1

A charging device of the wind turbine is connected to the low-voltage side of the transformer and configured to charge the low-voltage side of the transformer when the electrical power generating unit does not feed ac-power to the low-voltage side of the transformer

Methodology Applied

Scientific EffectElectrical energy transfer: Conduction (electrical)

Data Source

PatentUS9745959B2Inrush current protection for wind turbines and wind farms

Publication Date: 2017.08.29 GE INFRASTRUCTURE TECH LLC

AI summary

A wind turbine is provided. The wind turbine includes a transformer having a low-voltage side and a high-voltage side. The transformer is configured to step up a voltage of the low-voltage side of the transformer to a voltage of an external grid. The wind turbine further includes an electrical power generating unit which is connected to the low-voltage side of the transformer and configured to feed an ac-power to the low-voltage side of the transformer. A charging device of the wind turbine is connected to the low-voltage side of the transformer and configured to charge the low-voltage side of the transformer when the generator does not feed ac-power to the low-voltage side of the transformer.