Grid-Forming Converter Virtual Impedance for Current Limiting Stability
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Solution Overview
Problem
Existing grid-forming converters face challenges in limiting output current while maintaining voltage source characteristics, leading to instability during disturbances and complex transient transitions.
Innovation Solution
Implement virtual impedance current limiting adjustment on the output reference voltage axes using a preset maximum output current limit value, allowing the converter to maintain voltage source characteristics and improve stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional amplitude limiting control is applied to limit converter output current, then current limiting is achieved, but the voltage source characteristics are lost and converter stability deteriorates
Solution Approach 1:
The patent introduces virtual impedance as an intermediary element in the control loop. By adding virtual impedance to the converter output, the system can limit current through the impedance drop effect without directly constraining the voltage source output, thus maintaining voltage source characteristics while achieving current limiting
Solution Approach 2:
The patent dynamically adjusts the virtual impedance parameters based on operating conditions. By changing the virtual impedance value, the system can control the degree of current limiting while preserving the voltage source behavior, resolving the contradiction between current limiting and stability
2Reliability
If current limiting control is activated during disturbance, then converter safety is improved, but complex transient transition process occurs and power angle stability deteriorates
Solution Approach 1:
The patent pre-configures the virtual impedance parameters and control strategy before disturbances occur. This preliminary setup ensures that when disturbances happen, the current limiting action is smooth and coordinated, avoiding complex transient transitions and power angle instability
Solution Approach 2:
The patent implements dynamic adjustment of virtual impedance based on real-time operating conditions and disturbance levels. This dynamic control allows the system to adaptively manage current limiting during transients, reducing transition time and maintaining power angle stability
Data Source
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AI summary
A current limiting control method and apparatus for a grid-forming converter, a converter, and a storage medium are provided. The method includes the following operations. A three-phase output reference voltage of a converter is acquired. A transformation is performed to obtain an output reference voltage on a first axis and an output reference voltage on a second axis in a preset two-phase coordinate system corresponding to the three-phase output reference voltage. Virtual impedance current limiting adjustment is performed on the output reference voltage on the first axis and/or the output reference voltage on the second axis by using a preset maximum output current limit value of the converter, to obtain an target output reference voltage on the first axis and an target output reference voltage on the second axis in the preset two-phase coordinate system, so as to acquire a three-phase target output voltage of the converter.