Double-Fed Wind Turbine Isolation Layout Without Main LV Breaker
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Solution Overview
Problem
Existing wind turbines with doubly fed asynchronous generators require complex and expensive isolation concepts involving multiple circuit breakers, which are costly and inefficient, especially for power classes above 5 MW, and do not adequately protect against overvoltages and short circuits.
Innovation Solution
A doubly fed wind turbine design with a stator path and rotor path connected via a medium-voltage transformer, incorporating stator contactors and circuit breakers, and overvoltage protection devices to safeguard against overvoltages, eliminating the need for a low-voltage side main circuit breaker, thus reducing costs and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-voltage side main circuit breaker with 6300 A rating is provided for the entire electrical power path, then protection against overload and short circuit is ensured, but costs and device complexity increase significantly
Solution Approach 1:
The patent divides the electrical power path into separate stator path and rotor path, each with its own protective devices. The stator path has a stator contactor and stator circuit breaker, while the rotor path has a rotor circuit breaker. This segmentation eliminates the need for a single high-rated main circuit breaker, reducing overall device complexity and cost while maintaining protection reliability.
Solution Approach 2:
The invention extracts the main circuit breaker function from the low-voltage side and replaces it with separate protective devices in the stator and rotor paths. The medium-voltage switchgear on the high-voltage side provides the main isolation function, while the low-voltage side uses path-specific breakers and contactors, eliminating the need for the expensive 6300 A main breaker.
2Reliability
If multiple protective devices including low-voltage and high-voltage circuit breakers are provided, then operational safety is ensured, but total disconnect current rating reaches 12300 A resulting in high costs
Solution Approach 1:
The patent segments the protection system into path-specific protective devices rather than using multiple high-rated breakers for the entire power path. The stator contactor (4000 A) and rotor circuit breaker (2000 A) handle their respective paths independently, reducing the total disconnect current rating from 12300 A to a more manageable level while maintaining operational safety.
Solution Approach 2:
The medium-voltage switchgear acts as an intermediary that provides the main isolation function at the high-voltage side, eliminating the need for a high-rated main circuit breaker at the low-voltage side. This intermediary device redistributes the protection functions, reducing the total disconnect current rating and associated costs.
3Ease of operation
If a low-voltage side main circuit breaker is used as safe disconnect device, then maintenance work can be performed safely, but the breaker must be opened which disconnects the own power supply affecting essential functions
Solution Approach 1:
The patent segments the power paths so that the stator path contains the main isolation function through the stator contactor and medium-voltage switchgear, while the rotor path has its own circuit breaker. This allows the rotor path to remain energized through the grid-side converter during maintenance, preserving essential functions powered by the own power supply while enabling safe maintenance work on the stator side.
Solution Approach 2:
The invention extracts the safe disconnect function from the low-voltage main circuit breaker and places it in the stator contactor and medium-voltage switchgear. This extraction allows the rotor path to remain independently energized, maintaining availability of the own power supply for essential functions during maintenance operations.
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
The design reduces costs and space requirements by eliminating the need for a 6300 A low-voltage side circuit breaker, ensuring safe operation and maintenance while minimizing downtime and maintaining essential functions during faults.
Implementation Method 1
a medium-voltage transformer, with the stator path and the rotor path feeding together on the low-voltage side of the transformer's low-voltage winding
Implementation Method 2
a first overvoltage protection device being provided between the medium-voltage transformer and the stator contactor
Data Source
Figure 1
Figure 2
AI summary
A double-fed wind turbine (100) with a stator path and a rotor path, the rotor path having a rotor-side (207) and a grid-side (208) converter, wherein the rotor path and the stator path terminate at a coupling point (218) and are jointly connected to an electrical supply network (210) via a medium-voltage transformer (209), wherein a stator contactor is provided in the stator path and a circuit breaker (214) is provided in the rotor path, wherein a first overvoltage protection device (215) is provided between the medium-voltage transformer and the stator contactor to protect it from overvoltages from the medium-voltage network. Fig. 2