Wind Power DC-Link Voltage Control for Soft Grid Stability
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Solution Overview
Problem
Wind power installations connected to soft electrical power supply grids experience severe fluctuations in DC-link voltage due to grid reactions, leading to suboptimal converter operation, especially in grids with low short-circuit power ratio.
Innovation Solution
A method for controlling wind power installations by setting the DC-link voltage based on measured grid voltage using distinct time constants, differentiating between voltage rises and drops, and considering line impedance and current phase angle, to dampen the direct coupling between grid voltage and DC-link voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the DC-link voltage is directly coupled to the grid voltage for optimal converter operation, then the converter can operate at optimal working points, but the DC-link voltage fluctuates severely in soft electrical power supply grids
Solution Approach 1:
The patent introduces an intermediary control mechanism between the grid voltage and DC-link voltage through the use of time constants T1 and T2. This mediator filters the direct coupling, allowing the converter to respond to grid voltage changes while dampening severe fluctuations in soft electrical power supply grids, thus maintaining both operational efficiency and voltage stability
Solution Approach 2:
The patent implements dynamic adjustment of the DC-link voltage based on the sign of grid voltage changes. When grid voltage increases, the DC-link voltage increases with time constant T1; when grid voltage decreases, the DC-link voltage decreases with time constant T2. This dynamic asymmetric response allows the system to adapt to varying grid conditions while maintaining stability
2Speed
If the DC-link voltage responds quickly to grid voltage changes, then the converter can maintain optimal working points, but the DC-link voltage fluctuates severely
Solution Approach 1:
The patent implements dynamic adjustment of the DC-link voltage based on the sign of grid voltage changes. When grid voltage increases, the DC-link voltage increases with time constant T1; when grid voltage decreases, the DC-link voltage decreases with time constant T2. This dynamic asymmetric response allows the system to adapt to varying grid conditions while maintaining stability
Solution Approach 2:
The patent changes the response parameters (time constants) based on the direction of grid voltage change. By using different time constants T1 and T2 for voltage increases and decreases respectively, the system optimizes the response speed while dampening severe fluctuations, achieving a balance between responsiveness and stability
Data Source
AI summary
A method for controlling a wind power installation includes measuring a grid voltage of an electrical power supply grid, setting a DC-link voltage at a converter of the wind power installation depending on the measured grid voltage and using a first time constant and a second time constant, wherein the first time constant is different than the second time constant.