HVDC Semiconductor Switching String with Local Voltage Coordination
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Solution Overview
Problem
High voltage direct current (HVDC) power transmission requires numerous semiconductor switching elements connected in series, which complicates voltage balancing and increases switching losses due to the need for complex communication and passive circuit elements like snubbers.
Innovation Solution
A semiconductor switching string with local switching controllers that communicate directly and indirectly with neighbors to coordinate terminal voltages, reducing the need for complex communication networks and passive elements, and optimizing voltage sharing among series-connected switching elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If numerous semiconductor switching elements are connected in series to achieve high voltage rating, then the voltage rating is improved, but the device complexity increases due to the need for complex communication and voltage balancing
Solution Approach 1:
The system divides the voltage balancing control into segmented zones, where each local switching controller manages a specific semiconductor switching element and communicates only with immediate neighbors. This segmentation reduces the overall communication complexity while maintaining the high voltage rating capability of the series-connected structure.
Solution Approach 2:
Each local switching controller is equipped with intelligence to independently perform voltage balancing control based on feedback from neighboring controllers. This local quality approach eliminates the need for centralized complex communication, as each controller adapts its behavior based on local conditions and neighbor interactions.
2Stability of the object's composition
If complex communication networks are used to coordinate voltage balancing among series-connected switching elements, then the voltage balancing is improved, but the loss of energy increases due to switching losses
Solution Approach 1:
The system implements feedback control where each local switching controller receives feedback signals from neighboring controllers about terminal voltages and adjusts its switching behavior accordingly. This feedback mechanism achieves stable voltage balancing while minimizing switching losses by coordinating switching transitions based on real-time voltage conditions.
Solution Approach 2:
Each local switching controller autonomously performs voltage balancing control using information from neighbors, without requiring complex external coordination. This self-service capability reduces switching losses by enabling independent adaptation to voltage imbalances while maintaining overall system stability.
3Stability of the object's composition
If passive circuit elements like snubbers are used in series-connected switching elements, then the voltage balancing is improved, but the device complexity increases
Solution Approach 1:
The system replaces passive mechanical/circuit elements like snubbers with an active control mechanism implemented through intelligent local switching controllers. These controllers use feedback from neighboring elements to dynamically adjust switching behavior, achieving voltage balancing without requiring additional passive circuit components.
Solution Approach 2:
The local switching controllers dynamically change switching parameters such as gate voltage timing and duration based on feedback from neighboring controllers. This parameter adaptation enables voltage balancing control without the need for fixed passive circuit elements like snubbers, thereby reducing circuit complexity.
Data Source
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AI summary
A semiconductor switching string comprises a plurality of series-connected semiconductor switching elements (12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12N-1, 12N). Each semiconductor switching element (12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12N-1, 12N) includes first and second terminals (22, 24) between which current flows from the first terminal (22) to the second terminal (24) when the semiconductor switching element (12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12N-1, 12N) is switched on. Each semiconductor switching element (12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12N-1, 12N) also includes a third terminal (20) to control the said current flowing from the first terminal (22) to the second terminal (24), and a local switching controller (26A, 26B, 26N) that is operatively connected with the third terminal (20) to control a terminal voltage between the first and second terminals (22, 24). Each semiconductor switching element (12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12N-1, 12N) is arranged in direct communication with at least one other semiconductor switching element (12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12N-1, 12N), and is additionally arranged in indirect communication with a plurality of further semiconductor switching elements (12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12N-1, 12N) via the or each said semiconductor switching element (12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12N-1, 12N) with which it is arranged in direct communication. Each local switching controller (26A, 26B, 26N) is configured to vary during a switching transition the rate of change of terminal voltage of the semiconductor switching element (12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12N-1, 12N) with which it is operatively connected. The degree to which each local switching controller (26A, 26B, 26N) varies the said rate of change of terminal voltage of the semiconductor switching element (12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12N-1, 12N) with which it is operatively connected is influenced to a primary extent by the terminal voltage of the or each semiconductor switching element (12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12N-1, 12N) with which its associated semiconductor switching element (12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12N-1, 12N) is arranged in direct communication and to a secondary extent by the terminal voltage of each further semiconductor switching element (12A, 12B, 12C, 12D, 12E, 12F, 12G, 12H, 12N-1, 12N) with which its associated semiconductor switching elements is arranged in indirect communication.