Wind Turbine Generator Short Circuit Mitigation

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Solution Overview

Problem

Unbalanced short circuits in wind turbine generators cause high amplitude torque oscillations, leading to mechanical stress and potential damage, as existing countermeasures like passive dump loads are ineffective in mitigating these oscillations.

Innovation Solution

A method and system that detect unbalanced short circuits in polyphase permanent magnet generators and control switches to create a balanced short circuit, altering the torque response and preventing high amplitude oscillations by selectively shorting phase legs at the switch-point between the generator and converter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If passive dump load is applied to counteract unbalanced short circuit, then energy dissipation is improved, but torque oscillation mitigation is worsened (no substantial effect)

Engineering Contradiction:

Improveenergy dissipationVSAvoidtorque oscillation

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a controlled short-circuit path as an intermediary mechanism between the unbalanced short circuit fault and the dump load. By creating a balanced short circuit condition first, the harmful torque oscillations are eliminated before energy dissipation through the dump load occurs, making the short-circuit path the mediating element that resolves the contradiction between energy management and oscillation mitigation

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If wind turbine is shut down to counteract unbalanced short circuit, then generator protection is improved, but drive train resonance risk is worsened (high risk of exciting resonances)

Engineering Contradiction:

Improvegenerator protectionVSAvoiddrive train resonance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by creating a balanced short circuit condition immediately upon detecting an unbalanced short circuit, before initiating any shutdown procedures. This preliminary transformation of the fault condition eliminates torque oscillations at their source, preventing the subsequent resonance problem that would occur during shutdown while still protecting the generator

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If unbalanced short circuit occurs in generator, then electrical fault is detected, but mechanical stress is worsened (high amplitude torque oscillations)

Engineering Contradiction:

Improvefault detectionVSAvoidmechanical stress

Core Design Contradiction:

Measurement precisionVSStrength

Solution Approach 1:

The patent converts the harmful unbalanced short circuit condition into a beneficial balanced short circuit condition through controlled switching. By deliberately creating a symmetric short-circuit path, the fault condition is transformed from a source of damaging torque oscillations into a controlled state that protects the mechanical system, turning the electrical fault into a protective mechanism

Inventive Principle:

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

Data Source

PatentEP2923441B1Methods and systems for reducing the impact of a generator short circuit in a wind turbine

Publication Date: 2019.01.09 VESTAS WIND SYSTEMS AS

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AI summary

A method is provided for reducing an impact of an unbalanced short circuit event that occurs in a polyphase permanent magnet generator of a wind turbine. According to the method, an unbalanced short circuit event is detected in the generator of the wind turbine, and, in response to detecting the unbalanced short circuit event, at least one phase of the generator is shorted at a switch-point between the generator and a converter of the wind turbine to create a balanced short circuit in the generator. By doing so, the torque response of the generator is altered to avoid high amplitude torque oscillations that would otherwise occur as a result of the unbalanced short circuit event.