HVDC Converter Fault Current Limiting for AC Network Faults
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Solution Overview
Problem
High short circuit current contributions and reduced current carrying capabilities in HVDC converters pose challenges, especially with the integration of renewable energy sources, leading to potential stress on generators and switchgears, particularly with the use of green insulation gases.
Innovation Solution
A converter control system that reduces the current reference limit in response to detected faults in the AC network, using an AC voltage-dependent current limitation mechanism, allowing for adaptive adjustment of converter currents to manage short circuit stresses and maintain equipment integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the converter rating is increased to handle higher power transmission, then the transmission capacity is improved, but the short circuit current contribution increases causing stress on generators and switchgears
Solution Approach 1:
The converter control dynamically adjusts the current reference limit based on detected AC network fault conditions. During faults, the control reduces the current reference limit to prevent excessive short circuit current contribution, while maintaining high rating operation during normal conditions. This dynamic adaptation resolves the contradiction between high power transmission capability and limited short circuit stress.
2Reliability
If green insulation gases are used in switchgears for decarbonization, then environmental performance is improved, but the current carrying and making breaking capabilities are reduced
Solution Approach 1:
The converter control proactively limits the current reference before excessive currents can damage the switchgear. By preemptively reducing the current reference limit during fault conditions, the system protects the green insulation gas-filled switchgears from currents they cannot safely carry, enabling their use without compromising equipment safety.
3Reliability
If the current reference limit is reduced during faults to protect equipment, then equipment integrity is improved, but the converter current capability is restricted
Solution Approach 1:
The system dynamically adjusts the current reference limit based on real-time fault detection. During AC network faults, the limit is reduced to protect equipment integrity. During normal operation, the full current capability is available. This temporal differentiation resolves the contradiction between equipment protection and current capability.
Data Source
AI summary
A converter has an AC side to connect to an AC network. A converter control is configured to set a current reference limit to limit a converter current. The converter control is configured to reduce the limit in case a fault is detected in the AC network. There is also described a combination of the converter in a power system with a renewable power source and a corresponding method of operating a converter in a power system with a renewable power source.