HVDC Power Converter DC Fault Ride-Through via Segmented Legs
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Solution Overview
Problem
High voltage direct current (HVDC) transmission systems face inefficiencies and costly component upgrades due to DC fault conditions, which can lead to system shutdowns and cascading failures, necessitating increased complexity and lower efficiency solutions for fault ride-through capabilities.
Innovation Solution
A power converter design with multiple converter legs, each comprising a series string and a parallel string of switches and switching units, allowing for independent control of AC and DC sides to manage DC faults without shutdown, using energy storage elements and inductors to regulate line parameters to zero during faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If components with larger power ratings are employed to overcome DC faults, then the power converter can withstand DC fault conditions, but the cost of the HVDC transmission system increases
Solution Approach 1:
The converter leg is segmented into multiple strings (first string with switches, second string with switching units) connected in parallel. This segmentation allows the system to handle DC faults by selectively controlling individual strings, avoiding the need for oversized components while maintaining fault withstanding capability.
Solution Approach 2:
The invention changes the operational parameters by independently controlling the AC side and DC side of the power converter. During DC faults, the system regulates line parameters to zero and controls direct current within the converter leg, enabling fault ride-through without shutting down while using standard-rated components.
2Reliability
If the power converter shuts down during DC fault and restarts after fault clearance, then the power converter protects itself from damage, but the HVDC transmission system experiences cascading effects and may collapse
Solution Approach 1:
The power converter maintains continuous operation during DC faults by controlling direct current within the converter leg and regulating line parameters to zero. This allows the useful action of power conversion to continue without shutdown, preventing cascading effects and maintaining HVDC transmission system stability.
Solution Approach 2:
The invention introduces an intermediary control mechanism that independently manages the AC and DC sides of the converter. During DC faults, this intermediary control regulates current and voltage parameters, acting as a mediator that allows the system to withstand faults without shutdown while protecting the power converter.
3Reliability
If various approaches are used to provide DC fault ride-through capability, then the power converter can overcome DC faults without shutdown, but the number of components increases, costs increase, and efficiency decreases
Solution Approach 1:
The switching units in the second string serve multiple functions: they enable DC fault ride-through capability, allow independent AC and DC side control, and facilitate regulation of line parameters to zero during faults. This multi-functionality achieves fault ride-through without requiring additional dedicated components, maintaining system efficiency and simplicity.
Data Source
AI summary
A power converter including one or more converter legs is provided. Each converter leg includes a first string including a plurality of switches coupled to each other in series. The one or more converter legs also include a second string operatively coupled to the first string at a first node and a second node in a parallel configuration, where the second string includes a plurality of switching units, and where a second string of one converter leg of the one or more converter legs is operatively coupled to second strings corresponding to other converter legs in the one or more converter legs.