Wind Turbine DC Connection System with Centralized Frequency Conversion
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Solution Overview
Problem
Conventional wind turbine generators equipped with frequency converters experience increased losses and reduced reliability due to complex electrical circuits when connected to high-voltage direct current (HVDC) systems.
Innovation Solution
A connection system that includes a main transformer to step up AC voltage levels between the generator and rectifier, utilizing a synchronous generator that is not magnetized through stator windings, and an inverter with a DC link capacitor, allowing for adjustable voltage levels and reduced reactive power needs, along with a dump load or storage device for power absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If each wind turbine generator is equipped with a frequency converter to convert variable frequency AC power to constant frequency AC power, then the generator can operate independently with variable speed, but the electrical circuit complexity increases, causing increased losses and reduced reliability
Solution Approach 1:
The patent extracts the frequency conversion function from individual turbine generators and relocates it to a centralized land-based converter station. Each generator connects directly to a DC collector grid through simplified power electronics, eliminating the need for complex back-to-back frequency converters at each turbine. This centralizes the complex conversion function while simplifying individual generator configurations.
Solution Approach 2:
The patent merges multiple individual frequency conversion functions into a single centralized conversion system at the land station. Multiple generators feed into a common DC collector grid, and their power is combined and converted to grid frequency at the centralized converter, reducing overall system complexity and improving reliability.
2Productivity
If a conventional AC generator connected to frequency converter is used, then the generator can operate at variable speed, but the complex electrical circuits cause increased losses
Solution Approach 1:
The patent replaces conventional AC/DC/AC frequency conversion systems with a direct DC connection system. Generators connect directly to the DC collector grid through simplified power electronics, eliminating the need for complex back-to-back frequency converters. This substitution reduces conversion stages and associated energy losses while maintaining variable speed operation capability.
3Loss of energy
If voltage level is stepped up from low voltage frequency converter level to collector level using transformer, then the transmission efficiency improves, but the system requires complex frequency converters at each turbine
Solution Approach 1:
The patent extracts the voltage transformation function from individual turbine transformers and implements it at the centralized land-based substation. The DC collector grid operates at standardized voltage levels, and final voltage transformation to transmission levels occurs at the land station, eliminating the need for complex transformer-frequency converter combinations at each turbine.
Solution Approach 2:
Instead of transforming AC voltage at each turbine and then converting frequency, the patent inverts the approach by directly converting to DC at standardized voltage levels at the collector grid, then transforming to transmission voltage levels at the land station. This reverses the conventional sequence and simplifies individual turbine equipment.
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 configuration reduces power losses and enhances reliability by allowing for efficient DC power transmission at higher voltage levels, minimizing the need for complex frequency converters and maintaining stable voltage levels across varying operational conditions.
Implementation Method 1
a main transformer arranged to step up an AC voltage level between said voltage source unit and said rectifier
Implementation Method 2
the rectifier, arranged to rectify the AC electrical power to a DC electrical power to be provided to the DC electrical power system
Implementation Method 3
an inverter with a DC link capacitor, allowing for adjustable voltage levels
Data Source
Figure 1
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AI summary
The present invention relates to a connection system for connecting a power generator to a DC electrical power system, with a controllable voltage source unit functionally connected in series with the power generator to receive AC electrical power from the power generator, and to generate an AC electrical power output accordingly, and a rectifier arranged to receive AC electrical power output from said voltage source unit and to rectify the AC electrical power output to a DC electrical power to be provided to the DC electrical power system. The invention also relates to method for connecting a power generator to a DC electrical power system.