Doubly-Fed Generator Variable Speed Distribution
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Solution Overview
Problem
Conventional doubly-fed induction generator (DFIG) systems in marine power generation require costly interfacing transformers and bulky MV/LV transformers, especially when dealing with high-power LV loads.
Innovation Solution
A DFIG generation and distribution system utilizing a wound-rotor induction generator with its stator connected to an MV AC bus and rotor connected to a frequency converter, which is linked to a LV AC bus through a transformer, allowing for variable speed operation and reducing the need for rotor-side interfacing transformers and main MV/LV transformer ratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional DFIG systems use interfacing transformers, then voltage transformation is achieved, but system cost increases
Solution Approach 1:
The patent extracts the transformer component from the DFIG system by directly connecting the stator to the MV AC bus, eliminating the need for rotor-side interfacing transformers while maintaining voltage transformation capability through the AC-AC converter
Solution Approach 2:
The patent introduces an AC-AC converter as an intermediary device between the DFIG stator and the MV AC bus, which performs voltage transformation and power conversion functions that traditionally required transformers, thereby reducing system cost and complexity
2Power
If conventional DFIG systems use MV/LV transformers for high-power LV loads, then power delivery is achieved, but transformer size and weight increase
Solution Approach 1:
The patent segments the power delivery function by using separate AC-AC converters for MV to LV conversion, allowing the MV/LV transformer to be smaller in size and rating while still meeting high-power load requirements through the addition of power electronic conversion capacity
Solution Approach 2:
The patent changes the operating parameters by using variable-frequency AC-AC converters that can operate at different power levels, enabling the system to deliver high power to LV loads without requiring a proportionally large MV/LV transformer
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
Enables variable speed operation for prime movers, uses fractionally-rated power electronics converters, and reduces the size and rating of main MV/LV transformers, particularly when LV loads have high power ratings, while providing dynamic reactive power compensation.
Implementation Method 1
a doubly-fed asynchronous AC generator driven by the prime mover and having a first poly-phase circuit, e.g., a stator, and a second poly-phase circuit, e.g., a rotor
Implementation Method 2
a poly-phase transformer having first windings electrically coupled to the first poly-phase circuit and the first AC distribution bus and having second windings electrically coupled to the second AC distribution bus
Data Source
AI summary
A generation and distribution system includes an adjustable-speed prime mover and a doubly-fed asynchronous alternating-current (AC) generator driven by the prime mover and having a first poly-phase circuit, e.g., a stator, and a second poly-phase circuit, e.g., a rotor. The system further includes a first AC bus electrically coupled to the first poly-phase circuit configured to deliver AC power at a first AC voltage to multiple loads, and a second AC bus connected to the second poly-phase circuit configured to deliver AC power at a second AC voltage to another group of loads, the second AC voltage being lower than the first. The system includes a poly-phase transformer having first windings electrically coupled to the first AC bus and having second windings electrically coupled to the second AC bus, and a poly-phase AC-to-AC electronic converter circuit electrically coupled between the second poly-phase circuit and the second AC bus.