Semiconductor Switching String Voltage Control
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Solution Overview
Problem
Semiconductor switching elements in HVDC power converters exhibit varying performance characteristics, making it difficult to achieve precise voltage control and efficient operation due to differences in breakdown voltages and current handling capabilities.
Innovation Solution
A semiconductor switching string comprising series-connected semiconductor assemblies with active auxiliary circuits and control units that switch auxiliary semiconductor switching elements into conducting state to divert current through resistive elements, allowing accurate voltage control across main semiconductor switching elements, especially during reverse recovery and blocking modes, ensuring equal voltage sharing and reliable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If semiconductor switching elements are used in HVDC power converters, then high current loads can be carried and high breakdown voltages can be achieved, but different elements from the same batch exhibit different performance characteristics making precise voltage control difficult
Solution Approach 1:
An auxiliary circuit is introduced as an intermediary between the main semiconductor switching element and the voltage control system. This auxiliary circuit includes an auxiliary semiconductor switching element and a resistive element that work together to regulate the voltage across the main switching element during reverse recovery and blocking modes, thereby compensating for performance variations among different semiconductor elements
Solution Approach 2:
The invention changes the operational parameters of the semiconductor switching element by controlling the auxiliary semiconductor switching element to divert current through the resistive element. This parameter change allows the voltage across the main switching element to be determined solely by the voltage across the resistive element, enabling precise voltage control despite variations in semiconductor element characteristics
2Measurement precision
If auxiliary circuits are added to control voltage across main semiconductor switching elements, then voltage sharing can be accurately controlled, but device complexity increases
Solution Approach 1:
The voltage control function is segmented into a separate auxiliary circuit that operates independently from the main semiconductor switching element. The auxiliary circuit is further segmented into an auxiliary semiconductor switching element and a resistive element, allowing precise voltage control to be achieved through modular addition rather than complex integration
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 solution enables precise voltage control and efficient current handling, ensuring reliable and repeatable operation of HVDC power converters by accurately managing voltage sharing among semiconductor switching elements and maintaining stable voltage across each main semiconductor switching element.
Implementation Method 1
each active auxiliary circuit including an auxiliary semiconductor switching element and a resistive element connected in series with one another
Data Source
Figure 1
Figure 2
AI summary
A semiconductor switching string (10), for use in a HVDC power converter, comprises a plurality of series-connected semiconductor switching assemblies (12). Each semiconductor switching assembly (12) has a main semiconductor switching element (14). Each main semiconductor switching element (14) when switched on operates in a conducting mode in which a conducting current (ic) flows from a first terminal (20) thereof to a second terminal (24) thereof. Each main semiconductor switching element (14) while turning off transitions from a reverse recovery mode in which a reverse recovery current (irr) flows from the second terminal (24) to the first terminal (20) to a blocking mode in which no current flows between the first and second terminals (20, 24). Each main semiconductor switching element (14) has an active auxiliary circuit (30) electrically connected between the first and second terminals (20, 24) thereof, and each active auxiliary circuit (30) includes an auxiliary semiconductor switching element (32) and a resistive element (34) connected in series with one another. The semiconductor switching string (10) also includes a control unit (50) that is operatively connected with each auxiliary semiconductor switching element (32). The or each control unit (50) is configured to switch a respective auxiliary semiconductor switching element (32) into a conducting state to divert current through the corresponding resistive element (34). The or each control unit (50) is further configured to have all of the auxiliary semiconductor switching elements (32) in their conducting state simultaneously at least while each main semiconductor switching element (14) is operating in one of its reverse recovery mode or its blocking mode, whereby when a given main semiconductor switching element (14) transitions to operating in its blocking mode the voltage (v, v', v") thereacross is determined solely by the voltage across the resistive element (34) in the corresponding active auxiliary circuit (30) electrically connected between the first and second terminals (20, 24) of the said given main semiconductor switching element (14).