Grid Feed Control for Low-Frequency Oscillation Attenuation
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Solution Overview
Problem
Existing methods for attenuating subsynchronous oscillations in electrical power supply grids face challenges in detection and attenuation, particularly due to the difficulty in identifying and isolating specific frequency ranges and the potential conflict with voltage-dependent reactive power feeds.
Innovation Solution
A method involving a feed device, such as a wind power installation, that splits the grid signal into partial frequency ranges, performs frequency analysis, and generates a setpoint attenuation signal to target and attenuate low-frequency oscillations without interfering with other grid-supporting feeds, using converter-based systems to control amplitude, frequency, and phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If a fast Fourier transform is used to detect subsynchronous oscillations over a wide frequency spectrum, then detection capability is improved, but device complexity and computational requirements increase
Solution Approach 1:
The patent divides the frequency spectrum into multiple partial frequency ranges and processes each range separately using individual bandpass filters. This segmentation allows the system to detect oscillations across a wide frequency spectrum without requiring a single complex full-spectrum analysis, thereby reducing computational complexity while maintaining detection capability.
2Object-generated harmful factors
If reactive power is fed in to attenuate subsynchronous oscillations, then oscillation attenuation is improved, but conflict with voltage-dependent reactive power feed increases
Solution Approach 1:
The patent extracts the oscillation attenuation function from the general reactive power control by identifying and processing only the specific frequency components corresponding to subsynchronous oscillations. This allows the system to provide oscillation attenuation while maintaining compatibility with voltage-dependent reactive power feed by separating the control objectives into distinct frequency-based and voltage-based components.
3Measurement precision
If the total power fed in is passed through a converter arrangement for full control, then control precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies full-power converter control only where necessary for precise oscillation attenuation while allowing direct coupling for the majority of power transmission. By targeting the converter control specifically at the oscillation frequency components rather than applying it universally to all power flow, the system achieves precise control where needed while minimizing overall device complexity and cost.
Data Source
AI summary
A method for attenuating low-frequency oscillations in an electrical power supply grid by means of a feed device which feeds into the electrical power supply grid, in particular a wind power installation, wherein the electrical power supply grid has a grid voltage and a grid frequency, comprising the following steps: picking up a grid signal having the low-frequency oscillations, splitting a total frequency range of the grid signal in which oscillations to be attenuated are to be expected into a plurality of partial frequency ranges, each having a lower and an upper range frequency, performing in each case one frequency analysis of the grid signal for each partial frequency range in order to identify in each case one or more oscillations having an oscillation frequency in the partial frequency range, if present, identifying a low-frequency oscillation to be attenuated as target oscillation depending on the frequency analyses of all of the partial frequency ranges, detecting the target oscillation at least according to frequency and amplitude and optionally according to phase, determining a setpoint attenuation signal depending on the target oscillation detected according to frequency and amplitude and possibly phase for attenuating the detected target oscillation, generating a setpoint feed signal depending on the setpoint attenuation signal and a basic setpoint signal, and generating and feeding in a feed signal depending on the setpoint feed signal (QE).