Grid Feed-in Current Control for Weak Grid Stability
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Solution Overview
Problem
Existing feed-in systems face instability and limited connectivity in weak grid connection points due to low short-circuit current ratios, leading to potential instabilities and the need for costly network topology changes.
Innovation Solution
Implementing a method where multiple feed-in systems, such as wind farms, control their feed-in currents based on phase angle shifts and voltage drops across a common path section, summing their currents to stabilize the voltage reference point and maintain stability even at weak grid connection points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current-feeding regulations are operated at weak grid connection points (low short-circuit current ratio), then power feed-in capability is improved, but system stability deteriorates due to large phase angle shifts and voltage reference variations
Solution Approach 1:
The patent combines multiple feed-in systems into a coordinated group that operates collectively. By merging the control of multiple converters and considering their cumulative effect on the grid, the system achieves stable operation at weak connection points where individual systems would be unstable. The coordinated control merges information about phase angle shifts and voltage drops across all systems to determine optimal current feed-in for each system.
Solution Approach 2:
The patent implements feedback control by continuously monitoring phase angle shifts and voltage drops at the grid connection point. The control system uses this feedback information to adjust the current feed-in of each converter dynamically. The feedback loop considers the cumulative effect of all feed-in systems and adjusts individual system contributions to maintain stability while maximizing power feed-in capability.
2Ease of operation
If multiple feed-in systems operate independently at weak grid connection points, then individual system operation is simplified, but cumulative phase angle shifts cause voltage reference instability
Solution Approach 1:
The patent introduces a coordinating control mechanism that acts as an intermediary between individual feed-in systems and the grid. This intermediary collects information from each system about their current feed-in and the resulting phase angle shifts, then distributes coordinated control signals back to each system. This allows independent systems to operate while maintaining cumulative stability through the mediating coordination layer.
3Reliability
If short-circuit current ratio is increased to improve stability, then system reliability is improved, but network topology changes become necessary which increases device complexity and cost
Solution Approach 1:
The patent changes the control parameters of existing feed-in systems rather than modifying the physical network topology. By adjusting how converters regulate their current feed-in based on phase angle shifts and voltage drops, the system achieves stability without requiring additional network infrastructure. This parameter-based control approach avoids the complexity and cost of physical network modifications while maintaining reliability.
Data Source
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Figure 3A~3B
AI summary
Method for feeding electrical power into an electrical supply network by means of several feed-in systems (301, 302), wherein a feed-in system is designed as a single feed-in plant, in particular as a wind turbine (311-315), or as a feed-in park with several feed-in plants, in particular as a wind farm (301, 302) with several wind turbines, each feed-in system feeds a system feed-in current (I1, I2) into the electrical supply network via a connection node (C1, C2), each feed-in plant delivers a plant current, a system feed-in current corresponds to a plant current, or is composed of several plant currents, depending on how many feed-in plants the respective feed-in system has, a system transmission path for transmitting electrical power is provided between each of the feed-in systems and a reference point in the electrical supply network,such that the respective system feed-in current is transmitted on each system transmission path, a system transmission path for transmitting electrical power is available between each of the feed-in systems (301, 302) and the reference point (R) in the electrical supply network (304), such that the system current is transmitted on each system transmission path, the system transmission paths between a connection node (C0) and the reference point have a common path section (310) on which the system feed-in currents (I1, I2) add up to a total feed-in current (IG), at least one or each feed-in system (301, 302) controls its system feed-in current (I1, I2) depending on a phase angle shift and/or a voltage drop between the feed-in system and the reference point (R), and/or at least one or each feed-in system (311-315),its system current is controlled depending on a phase angle shift and/or a voltage drop between the feed-in system and the reference point (R), whereby the phase shift or the voltage drop is determined depending on the total feed-in current.