Full-Bridge Cell Fault Current Blocking in Wind Turbine Converters

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Solution Overview

Problem

Wind turbines face high fault currents due to failures like short circuits, which can damage converters, necessitating expensive machine-side and line-side circuit breakers to protect them, increasing manufacturing costs.

Innovation Solution

Incorporating full bridge cells in the power converter's phase legs to block fault currents from both the generator and transformer, eliminating the need for circuit breakers between the rectifier and generator and inverter and transformer, respectively, by using fault current detectors and controllers to deactivate switches and prevent damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If machine-side circuit breaker and line-side circuit breaker are used to block fault current, then converter protection is improved, but manufacturing cost increases

Engineering Contradiction:

Improveconverter protectionVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent extracts the fault current blocking function from external circuit breakers and relocates it to the full-bridge cells within the power converter itself. Each full-bridge cell is equipped with switches that can be individually controlled to block fault currents, eliminating the need for separate machine-side and line-side circuit breakers while maintaining converter protection

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The full-bridge cells in the power converter are designed to perform multiple functions: normal power conversion operation and fault current blocking. By integrating the protection function into the existing power converter structure, the system achieves both power processing and protective capabilities without requiring additional dedicated protection devices

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Ease of manufacture

If full bridge cells are used to block fault current, then manufacturing cost is reduced, but device complexity increases

Engineering Contradiction:

Improvemanufacturing costVSAvoidpower converter structure

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The power converter uses its own internal full-bridge cell switches to block fault currents, making the system self-protecting. The control system activates the appropriate switches within the existing full-bridge structure to create blocking paths, allowing the converter to protect itself without external intervention or additional protection circuitry

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS11146166B2Modular multi-level converter with full-bridge cell fault current blocking for wind-turbines

Publication Date: 2021.10.12 VESTAS WIND SYSTEMS AS

AI summary

Embodiments herein describe a power converter in a wind turbine that includes a rectifier and an inverter. The rectifier includes a plurality of phase legs where each phase leg includes a plurality of full bridge cells configured to block fault current from flowing from a generator through the rectifier. Moreover, the wind turbine does not have any circuit breaker between the rectifier and the generator. The inverter also includes a plurality of phase legs where each phase leg includes a plurality of full bridge cells configured to block fault current from flowing from a transformer through the inverter. Moreover, the wind turbine does not have any circuit breaker between the inverter and the transformer.