HVDC Semiconductor Switching Circuit with Auxiliary Current Path
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Solution Overview
Problem
Current semiconductor switching circuits in HVDC power converters face challenges in efficiently regulating current and voltage, particularly in managing reverse recovery currents and voltage grading, often requiring bulky and complex saturable reactors, which increase size, weight, and losses.
Innovation Solution
A semiconductor switching circuit with an auxiliary current branch featuring an active switching bridge, energy storage device, and impedance device, controlled by a unit that selectively connects and disconnects the auxiliary circuit from the main current branch to create alternative current paths, allowing for regulation of current and voltage, and enabling AC and DC voltage grading without the need for high-rated components when not in use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If saturable reactors are used for current and voltage regulation in semiconductor switching circuits, then regulation functionality is achieved, but device size, weight, and complexity increase
Solution Approach 1:
The patent replaces saturable reactors (electromagnetic/mechanical components) with an auxiliary circuit comprising active semiconductor switching elements, energy storage devices, and impedance devices. This substitution eliminates bulky magnetic components while achieving the same current and voltage regulation functionality through electronic switching and energy management.
Solution Approach 2:
The patent changes the operational parameters by using controllable semiconductor switches instead of passive saturable reactors. The active switching elements can dynamically adjust their on/off states to regulate current and voltage, providing more flexible and efficient control compared to the fixed characteristics of saturable reactors.
2Reliability
If auxiliary circuit remains connected to main semiconductor switching element continuously, then regulation function is always available, but component ratings must be higher and losses increase
Solution Approach 1:
The patent implements a dynamic connection scheme where the auxiliary circuit is selectively connected to and disconnected from the main semiconductor switching element based on operational requirements. The control unit monitors switching conditions and activates the auxiliary circuit only during critical switching transitions, rather than maintaining continuous connection, thereby reducing energy losses and component stress.
Solution Approach 2:
The auxiliary circuit operates periodically during specific switching intervals rather than continuously. It is activated during turn-on and turn-off transitions of the main semiconductor element and deactivated during steady-state operation, providing regulation functionality only when needed and minimizing energy consumption and component ratings.
3Reliability
If auxiliary circuit components are rated for maximum continuous current, then circuit can handle peak loads, but component size and cost increase
Solution Approach 1:
The auxiliary circuit components are designed with dynamic current handling capability rather than continuous maximum current ratings. Since the auxiliary circuit operates only during brief switching intervals, components can be sized for peak pulse currents rather than continuous maximum currents, significantly reducing component size and weight while maintaining peak load handling capability.
Solution Approach 2:
The auxiliary circuit provides excessive current handling capability only during the brief periods when it is activated, rather than maintaining continuous high current capability. This allows components to be optimized for short-duration peak currents rather than continuous maximum currents, reducing overall component size and system weight.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances switching performance by reducing size and complexity, minimizing losses, and providing versatile functionality for current and voltage regulation, while maintaining a compact and cost-effective design.
Implementation Method 1
the auxiliary circuit including an energy storage device and/or an impedance device
Implementation Method 2
the auxiliary circuit including an energy storage device and/or an impedance device
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A semiconductor switching circuit (10), for use in a HVDC power converter, comprises: a main current branch (12) including a main semiconductor switching element (16) and through which current flows when the main semiconductor switching element (16) is switched on; an auxiliary current branch (14) connected in parallel or inverse-parallel with the main current branch (12), the auxiliary current branch (14) including an auxiliary circuit (18), the auxiliary circuit (18) including a plurality of active auxiliary semiconductor switching elements (22) connected to form an active switching bridge, the auxiliary current branch (14) further including an energy storage device (24) and/or an impedance device (20), the active switching bridge having a control unit (26) operatively connected therewith, the control unit (26) being configured to switch the active switching bridge to connect the auxiliary circuit (18) into and out of circuit with the main current branch (12) and thereby selectively create an alternative current path via the auxiliary current branch (14) whereby current flowing through the main current branch (12) is diverted to flow through the alternative current path to regulate one or more of current flowing through the main semiconductor switching element (16) and voltage appearing across the main semiconductor switching element (16), wherein the control unit (26) is configured to switch the active switching bridge to arrange the alternative current path to selectively pass through the energy storage device (24) and/or impedance device (20).