Variable Speed Electric Machine for Constant Frequency Output
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Solution Overview
Problem
Conventional wind turbines face challenges in generating constant frequency electric energy due to variability in wind speed, requiring expensive power converters or 30% of wind turbine power for doubly-fed induction machines, necessitating a more efficient solution.
Innovation Solution
An electric machine design with an outer stator, modulator outer rotor, permanent magnet inner rotor, and inner stator, magnetically coupled to maintain constant frequency, utilizing a power converter to transfer energy through magnetic coupling, reducing energy consumption to approximately 10% of input energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power converters are used to balance variation in input wind speed, then constant frequency output is achieved, but system cost increases significantly
Solution Approach 1:
The patent employs a nested dual-stator configuration where an inner stator and outer stator are concentrically arranged around a common rotor. The inner stator handles primary power generation while the outer stator provides frequency regulation, allowing constant frequency output without expensive power converters. This nested structure enables two independent magnetic circuits to share a common rotor, achieving cost-effective frequency stabilization.
Solution Approach 2:
The patent divides the single-stator system into two separate stators (inner and outer) with independent winding sets. This segmentation allows each stator to perform specialized functions: the inner stator for main power generation and the outer stator for frequency control. By separating these functions, the system achieves constant frequency output through the outer stator's regulated windings without requiring costly power electronic converters.
2Reliability
If doubly-fed induction machines are used to produce constant frequency output, then frequency stability is improved, but power consumption increases to 30% of wind turbine power
Solution Approach 1:
The patent enables the outer stator to self-regulate frequency by utilizing its own field windings and the magnetic coupling with the rotor. The outer stator's field windings are excited to create a controlled magnetic field that interacts with the rotor, allowing the system to maintain constant frequency output without requiring 30% of turbine power for excitation. The structure uses the rotor's inherent magnetic field more efficiently.
Solution Approach 2:
The rotor serves dual functions by simultaneously interacting with both the inner stator and outer stator through magnetic coupling. This multi-functionality allows a single rotor to support both main power generation and frequency regulation, eliminating the need for separate excitation systems required by doubly-fed induction machines and reducing overall power consumption.
3Adaptability or versatility
If variable speed operation is implemented, then adaptability to wind conditions improves, but maintaining constant frequency output becomes difficult
Solution Approach 1:
The patent segments the power generation function into two independent stators with separate winding sets. The inner stator accepts variable speed input from the rotor, while the outer stator with its controlled field windings regulates the output frequency. This functional segmentation allows the system to accommodate variable wind speeds while maintaining constant frequency through the outer stator's regulatory mechanism.
Solution Approach 2:
The outer stator acts as an intermediary between the variable speed rotor and the constant frequency requirement. By controlling the field windings of the outer stator, the system mediates the frequency transformation, allowing variable speed operation to be converted into constant frequency output without requiring power electronic converters.
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 electric machine effectively generates constant frequency electric energy from variable speed inputs with significantly reduced power consumption, offering flexibility in handling higher speeds and improving efficiency compared to traditional systems.
Implementation Method 1
The outer stator, the modulator outer rotor, inner stator and the inner rotor are magnetically coupled with each other so as to maintain a constant frequency of electric energy generated at the inner stator
Implementation Method 2
The energy is transferred through a magnetic coupling between the outer stator, the modulator outer rotor, the permanent magnet inner rotor, and the inner stator
Data Source
AI summary
A variable speed electric machine and a method for generating electric energy is provided. The electric machine includes an outer stator with a first set of field windings. Further, the electric machine includes a modulator outer rotor that is concentric and is located proximate to the outer stator. The modulator outer rotor is operatively coupled to an input shaft. Furthermore the electric machine includes a permanent magnet inner rotor concentric to the modulator outer rotor. The electric machine also includes an inner stator with a second set of field windings. The inner stator is concentric to the inner rotor and is operatively coupled to an electric grid. The outer stator, the modulator outer rotor, inner stator and the inner rotor are magnetically coupled with each other so as to maintain a constant electric frequency at the inner stator.