Unidirectional Rectifier DC Link Energy Storage for Wind Turbine Startup
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Solution Overview
Problem
Existing systems for transmitting electrical power from wind farms to AC voltage networks struggle to provide energy during weak wind phases, as unidirectional rectifiers cannot generate the required frequency-stable AC voltage needed to start and operate wind turbines, leading to inefficiencies and reliance on costly or environmentally unfavorable diesel generators.
Innovation Solution
A system that includes a power generation device connected to the AC voltage network, capable of generating electrical energy even at low wind speeds, using a unidirectional rectifier and energy storage devices like rechargeable batteries or buoyancy systems to supply energy to wind turbines, allowing them to start and operate independently of wind conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a unidirectional rectifier is used for power transmission, then losses and weight are significantly reduced, but the ability to provide energy during weak wind phases or for startup is lost
Solution Approach 1:
The system performs preliminary energy storage during high wind phases when excess energy is available. Energy is stored in the DC voltage intermediate circuit and in energy storage devices (batteries, capacitors) before it is needed during weak wind phases, enabling the wind farm to maintain operations without requiring bidirectional power flow capability
Solution Approach 2:
A DC voltage intermediate circuit is introduced as an intermediary between the unidirectional rectifier and the wind turbines. This intermediate circuit decouples the rectifier from the AC voltage network, allowing energy to be stored and released without requiring the rectifier to operate bidirectionally, thus maintaining both simplicity and reliability
2Device complexity
If a unidirectional rectifier is used, then the system is simpler and more cost-effective, but it cannot generate frequency-stable AC voltage for starting wind turbines
Solution Approach 1:
The system uses self-service by having wind turbines start up from the DC voltage intermediate circuit rather than requiring external AC voltage from the rectifier. The intermediate circuit provides the necessary energy for startup, and turbines then synchronize with the existing AC voltage network, eliminating the need for the rectifier to provide startup voltage
Solution Approach 2:
The DC voltage intermediate circuit serves as a mediator between the unidirectional rectifier and the wind turbines during startup. It provides the necessary energy transfer pathway without requiring the rectifier to generate AC voltage, thus maintaining system simplicity while enabling turbine startup
3Reliability
If bidirectional power flow is implemented, then energy can be provided during weak wind phases, but weight and cost increase significantly
Solution Approach 1:
Energy is preliminarily stored during high wind phases in the DC voltage intermediate circuit and energy storage devices. This preliminary energy accumulation enables the system to provide power during weak wind phases without requiring bidirectional converters, thus avoiding the weight penalty while maintaining reliability
Solution Approach 2:
The system uses relatively simple energy storage devices (batteries, capacitors) rather than expensive bidirectional converters. These energy storage components are lighter and more cost-effective, providing the necessary energy buffer without the complexity and weight of bidirectional power conversion 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
Enables cost-effective and reliable energy supply to wind farms by generating and storing energy for wind turbines during weak wind phases, ensuring continuous operation and reducing reliance on diesel generators.
Implementation Method 1
A unidirectional rectifier (10), which can be connected on the AC voltage side to the first AC voltage network (2)
Implementation Method 2
A self-commutated converter (20), which is connected to a unidirectional rectifier (10) via a DC voltage connection (4)
Implementation Method 3
A system that includes a power generation device connected to the AC voltage network, capable of generating electrical energy even at low wind speeds, using a unidirectional rectifier and energy storage devices like rechargeable batteries
Data Source
Figure 1
Figure 2
AI summary
The invention relates to an installation (1) for transmitting electrical power between a first and a second alternating voltage network (2, 3). A self-commutated converter (20) can be connected to the second alternating voltage network (3), and is connected to a unidirectional rectifier (10) by means of a direct voltage connection (4). Said unidirectional rectifier can be connected to the first alternating voltage network (2) on the alternating voltage side, and to a wind farm (7) via said first alternating voltage network, said wind farm comprising at least one wind turbine (72) that is configured to feed electrical power into the first alternating voltage network when wind speeds are greater than a switch-on wind speed. The invention is characterised in that an energy-generating device (9A, 9B) can be connected to the first alternating voltage network (2) and/or to the at least one wind turbine (72) for the purpose of providing electrical energy, said energy-generating device being configured to convert a renewable primary energy from its surroundings when wind speeds are lower than the switch-on wind speed for said at least one wind turbine (72).