Wind Turbine Generator Protection Circuit Filter
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Solution Overview
Problem
The increasing size and power of wind turbines lead to higher parasitic capacities between phase and earth, causing overvoltages due to interactions between power converter modulation and system components, which can shorten the life of generator insulation and bearings, and existing solutions are costly and vary by manufacturer.
Innovation Solution
A filter is introduced between the DC bus of the power converter and earth, providing an additional path for earth currents, comprising passive and active components, designed to consider the converter modulation, parasitic capacity range, and system topology, specifically a first-order series filter with a resistor and capacitor, to reduce overvoltages across a wide range of parasitic capacities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the size and power of wind turbines are increased, then the power generation capability is improved, but the parasitic capacities between phase and earth increase, causing overvoltages that reduce the life of insulation and bearings
Solution Approach 1:
A filter circuit is introduced as an intermediary component between the power converter and the generator terminals. This filter comprises a first branch with a capacitor in series with a resistor connected between phase and earth, and a second branch with an inductor connected in parallel to the series combination. The filter circuit mediates the harmful interaction between power converter modulation and parasitic capacities, providing an alternative path for earth currents that reduces overvoltages at the generator terminals while allowing the use of larger, more powerful turbines
2Reliability
If specific techniques and materials are used to reduce parasitic capacities, then the overvoltages are reduced, but the manufacturing costs increase
Solution Approach 1:
Instead of using expensive special techniques and materials during generator manufacturing to reduce parasitic capacities, the invention employs a relatively simple and inexpensive filter circuit constructed from standard electronic components (capacitors, resistors, inductors). This filter provides effective overvoltage protection without requiring costly modifications to the generator manufacturing process, making it economically viable for widespread implementation
3Reliability
If generator manufacturers use specific techniques to reduce parasitic capacities, then the overvoltages are reduced, but the solutions vary between different models and manufacturers, reducing adaptability
Solution Approach 1:
The filter circuit is designed as a universal solution that can be applied to multiple generator models and manufacturers. By placing the filter at the power converter output stage, it addresses the overvoltage problem at its source rather than requiring generator-specific modifications. The filter's standardized design with adjustable components allows it to accommodate variations in parasitic capacity across different generator models, providing a single adaptable solution rather than multiple model-specific solutions
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 filter effectively reduces overvoltages at generator terminals, extending the life of insulation and bearings, and allows a single power converter to be used with different generator models, regardless of parasitic capacity variations.
Implementation Method 1
the parasitic capacities inevitably present in a generator between phase and earth also increase in value
Implementation Method 2
power converters use modulation techniques that generate square waves, which in turn excite the parasitic capacities of the system, causing the circulation of earth currents
Data Source
Figure 1
AI summary
The present invention relates to a protection circuit for a wind-power generator that includes a filter between the DC bus of the converter and earth, providing an additional path for the earth currents of the system, thereby reducing excess voltages between phase and earth at terminals of the generator.