Variable Frequency Wind Plant AC-DC Converter Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional AC transmission systems for bulk power from wind farms face inefficiencies due to capacitance-related charging currents, which increase with distance, leading to reduced cable capacity and higher costs in offshore wind generation and transmission systems.
Innovation Solution
Implementing a control method that uses wind speed signals from anemometers to adjust the operating frequency of a common AC-DC converter, allowing wind turbines to operate at variable frequencies, thereby enabling DC transmission and reducing the need for power conversion at each turbine, and utilizing a central control system to manage the frequency for optimized power production and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If AC transmission is used for bulk power over long distances, then power can be transmitted to remote locations, but capacitance causes charging current to flow which reduces cable carrying capability and increases costs
Solution Approach 1:
The system changes the transmission parameter from AC to DC, eliminating capacitance-related charging currents that limit AC cable carrying capability over long distances. This parameter change allows full utilization of cable capacity for power transmission without energy-wasting charging currents.
2Adaptability or versatility
If individual power electronic converters are installed at each wind turbine, then variable speed operation is enabled, but system complexity and cost increase
Solution Approach 1:
The system merges multiple individual power electronic converters into a single centralized converter at the collection point. This consolidation maintains variable speed operation capability for all turbines while dramatically reducing device complexity and quantity compared to individual converters at each turbine.
Solution Approach 2:
The system introduces an intermediary AC-DC converter at the collection point that acts as a mediator between the variable frequency AC output of wind turbines and the DC transmission line. This intermediary enables bulk power conversion for multiple turbines rather than requiring individual converters at each turbine.
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 decouples AC frequency from the grid frequency, allowing wind turbines to operate efficiently at variable speeds, reduces the burden of power conversion, and lowers operational costs by employing a single AC-DC converter for DC transmission, enhancing efficiency and reducing infrastructure needs.
Implementation Method 1
power electronic converters which are capable of converting between HVAC and HVDC
Data Source
AI summary
A method and system for reducing the cost of a combined offshore wind generation plant is provided by coupling the AC output of plural wind turbine generators to a single AC-DC converter prior to transmission of the DC power to an onshore DC-AC inverter site. The wind speed is monitored at selected locations within the wind plant, optionally, at selected turbine generators, and the operating frequency of the AC-DC converter is adjusted in accordance with a combine wind speed signal to permit operation of the plural wind turbines as a group. AC-DC followed by DC-AC conversions decouples the AC frequency produced by the wind turbines and allows the turbines to operate at variable frequency as a group.