Wind Turbine Power Converter With Interleaved Rotor-Side Bridges
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Solution Overview
Problem
Wind turbine power systems face high costs due to expensive three-winding transformers and increased risk of harmonic issues when secondary windings are eliminated, necessitating a solution that reduces harmonics and transformer costs.
Innovation Solution
Implementing a power converter with multiple rotor-side converters in parallel, coordinated to produce an interleaved switching pattern, and utilizing a partial power transformer to eliminate the need for a three-winding transformer, thereby reducing harmonics and transformer costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a three-winding transformer is used in the wind turbine power system, then power transmission capability is ensured, but system cost increases significantly
Solution Approach 1:
The patent segments the transformer function by using multiple isolated full-bridge circuits (first, second, third bridge circuits) instead of a single three-winding transformer. Each bridge circuit handles a specific winding function (primary, secondary, tertiary), dividing the complex transformer task into simpler, independent modular units that can be implemented with standard components.
Solution Approach 2:
The patent introduces an intermediary DC link between the rotor-side converter and grid-connected converter, which mediates power transfer and enables the use of simpler two-winding transformers or even eliminates the need for expensive three-winding transformers. The DC link acts as a buffer that decouples the transformer requirements while maintaining power transmission capability.
2Ease of manufacture
If the secondary winding is eliminated to reduce cost, then transformer cost decreases, but harmonic issues increase
Solution Approach 1:
The patent employs periodic pulse-width modulation (PWM) switching in the isolated full-bridge circuits to generate controlled switching patterns. This periodic switching action allows for effective harmonic filtering and control, enabling the system to eliminate harmful harmonic currents while using simpler, less expensive transformer configurations.
Solution Approach 2:
The control system monitors output currents and voltages from the bridge circuits and adjusts switching patterns in real-time to minimize harmonic distortion. This feedback mechanism ensures that even with simplified transformer designs, the system maintains acceptable harmonic performance by dynamically compensating for distortions.
3Object-generated harmful factors
If multiple rotor-side converters are used in parallel, then harmonic reduction is achieved, but device complexity increases
Solution Approach 1:
The rotor-side power conversion is segmented into multiple independent full-bridge circuits connected in parallel, with each bridge handling a portion of the power conversion task. This segmentation allows for distributed control strategies where each bridge can be controlled independently, simplifying the overall control architecture despite the increased number of components.
Solution Approach 2:
Multiple rotor-side converter bridges are merged through a common DC link, combining their output to achieve lower harmonic distortion through interleaved switching patterns. The merging of parallel converter outputs with synchronized control creates a composite waveform with reduced harmonics while maintaining manageable individual converter complexity.
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 harmonic currents and eliminates the need for costly three-winding transformers, achieving efficient power transmission with smaller and less expensive equipment.
Implementation Method 1
The rotor blades capture kinetic energy of wind using known airfoil principles. For example, rotor blades typically have the cross-sectional profile of an airfoil such that, during operation, air flows over the blade producing a pressure difference between the sides.
Implementation Method 2
Consequently, a lift force, which is directed from a pressure side towards a suction side, acts on the blade. The lift force generates torque on the main rotor shaft
Implementation Method 3
As such, a rotating magnetic field may be induced by the generator rotor 30 and a voltage may be induced within a generator stator 32 that is magnetically coupled to the generator rotor 30
Implementation Method 4
The rotor-side converter 40 converts the AC power provided from the rotor 30 into DC power and provides the DC power to the DC link 44. The line side converter 42 converts the DC power on the DC link 44 into AC output power suitable for the power grid
Implementation Method 5
The associated electrical power can be transmitted from the generator stator 32 to a main three-winding transformer 34 that is typically connected to a power grid via a grid breaker 36. Thus, the main transformer 34 steps up the voltage amplitude of the electrical power
Data Source
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AI summary
An electrical power subsystem includes a generator comprising a generator stator and a generator rotor, and a power converter electrically coupled to the generator. The power converter includes a plurality of rotor-side converters electrically coupled in parallel, a line-side converter, and a regulated DC link electrically coupling the plurality of rotor-side converters and the line-side converter. The electrical power subsystem further includes a stator power path for providing power from the generator stator to the power grid, and a converter power path for providing power from the generator rotor through the power converter to the power grid.