Wind Turbine DC-Link Capacitor for Grid Frequency Support
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Solution Overview
Problem
Existing methods for increasing power feed into electrical supply networks, such as using power from rotating rotors, are limited by short-term capabilities and can cause instabilities due to the physical behavior of synchronous generators, leading to issues like subsynchronous resonances, especially in changing network topologies.
Innovation Solution
A method for a wind energy installation or wind farm that monitors power balance indicators like mains frequency to adjust the feed-in of electrical power dynamically, using balancing energy calculations based on performance indicators and energy reserves to mimic the behavior of synchronous generators while avoiding overheating and thermal damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If power from rotating rotors is used to increase power feed-in, then short-term power increase is achieved, but the duration of power feed-in is limited
Solution Approach 1:
The patent applies preliminary action by storing energy in the DC-link capacitor before it is needed. The control system monitors grid conditions and charges the capacitor during periods when excess power is available, so that when a power increase is needed, the pre-stored energy can be immediately discharged to support the grid without being limited by rotor rotational energy.
2Reliability
If synchronous generators are used to support the electrical supply network, then grid support is provided, but instabilities occur due to subsynchronous resonances
Solution Approach 1:
The patent replaces the mechanical synchronous generator system with an electrical energy storage system (DC-link capacitor). Instead of relying on the mechanical inertia and electromagnetic fields of rotating synchronous generators, the invention uses electrical energy storage and controlled power electronics to provide grid support, thereby avoiding the subsynchronous resonance instabilities inherent in mechanical-synchronous systems.
3Power
If power feed-in is increased to support the electrical supply network, then network support is improved, but system protection limits may be exceeded causing thermal damage
Solution Approach 1:
The patent introduces the DC-link capacitor as an intermediary energy storage device between the wind turbine generator and the electrical supply network. This intermediary allows the system to decouple the generator output from the grid feed-in, enabling power to be stored temporarily and then released as needed without exceeding system protection limits, thus preventing thermal damage while maintaining grid support capability.
Data Source
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AI summary
The invention relates to a method for feeding electrical power into an electrical supply network by means of at least one wind turbine, or a wind farm comprising a plurality of wind turbines at a network connection point, wherein a plurality of energy generators feed power into the electrical supply network, and a plurality of consumers extract power from the electrical supply network such that there is a power balance between the input power and the extracted power in the electric supply network, which is positive if more power is fed in than is extracted. The method comprises the following steps: monitoring a power indicator representative of the power balance in the electrical supply network; determining a compensation energy quantity as a function of the power indicator; infeeding a basic electric power depending on available wind power, and changing the infeed of the basic electric power by the determined compensating energy quantity.