MMC Submodule Short Circuit Protection via Low-Inductance Diodes
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Solution Overview
Problem
Existing submodules in high-voltage energy transmission systems fail to reliably bridge connection terminals during faults, leading to potential system shutdowns due to high fault currents damaging freewheeling diodes and bonding wires.
Innovation Solution
A submodule design featuring pressure-contacted silicon semiconductor components and disc cell diodes with elastic deformation layers ensures low-inductance current paths in both directions, preventing damage and allowing safe discharge of energy stores, while thyristors are triggered to divert fault currents, ensuring continuous operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If standard industrial IGBT modules with bonding wires are used, then the submodule structure is simplified, but the bonding wires may melt or tear out due to high fault currents causing arcing
Solution Approach 1:
The invention implements beforehand cushioning by providing a semiconductor component connected in parallel with the storage capacitor that is specifically designed to accept short-circuit currents. This component acts as a cushion or buffer that absorbs the harmful fault currents before they can reach and damage the bonding wires in standard IGBT modules. The low-inductance connection ensures this protection activates immediately, preventing bonding wire damage while maintaining the use of standard industrial modules.
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
The solution reliably bypasses faulty submodules, preventing damage to freewheeling diodes and maintaining system operation by diverting high fault currents through pressure-contacted components, thus avoiding arcing and ensuring the submodule's safe discharge.
Implementation Method 1
pressure-contacted silicon semiconductor components ensures low-inductance current paths in both directions
Implementation Method 2
low-inductance current paths
Implementation Method 3
disc cell diodes with elastic deformation layers
Implementation Method 4
thyristors are triggered to divert fault currents
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a sub-module (31) for a multi-point converter, comprising a unipolar energy store (16), two connecting terminals (22, 23), and a semiconductor circuit (17, 26) that has at least two controllable power semiconductor switches (18, 19, 27, 28), a separate free running diode (20, 21, 29, 30) being connected in parallel to each switch in an opposite direction. At least one semiconductor component (32) is connected in parallel to the unipolar energy store (16) in a low-inductive manner, said component bridging the energy store (16) in the event of a fault. The aim of the invention is to provide such a sub-module that reliably bridges the two connecting terminals of the sub-module in the event of a fault. This is achieved in that each free running diode (20, 21, 29, 30) is a disk cell diode and part of a circuit unit (39) that has an emitter plate (41) and a collector plate (42), between which the disk cell diode (20, 21, 29, 30) is clamped. The collector plate (42) is connected to a collector terminal (5) of the power semiconductor switch (18, 19, 27, 28), and the emitter plate (41) is connected to an emitter terminal (4) of the power semiconductor switch (18, 19, 27, 28) that is connected in parallel to said free running diode (20, 21, 29, 30).