Double Module Submodule Cross-Firing Protection
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Solution Overview
Problem
The existing two-pole submodules in high-voltage converters face a high risk of cross-firing due to the increased voltage at the terminals, which can lead to irreparable damage from high short-circuit currents when power semiconductor switches break down.
Innovation Solution
The submodule design includes a connecting switching unit with diodes oriented in opposite directions to prevent unwanted current flow, and a mechanical bridge switch to bypass faulty units, reducing the likelihood of cross-firing and allowing for safe operation even if one of the power semiconductor switching units fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the voltage at the terminals is increased to reduce the number of submodules, then the voltage handling capability is improved, but the risk of cross-firing and short-circuit damage increases
Solution Approach 1:
The submodule is divided into two independent two-pole submodules connected in series, each with its own energy storage device and semiconductor series circuit. This segmentation isolates the high voltage stress to individual submodules, reducing the cross-firing risk in each unit while maintaining the overall high voltage capability of the series connection.
Solution Approach 2:
Diodes are connected in parallel with each energy storage device, oriented to conduct during overvoltage conditions. These diodes act as protective elements that preemptively handle voltage spikes or cross-firing events, preventing damage to the semiconductor switches before failure can occur.
2Reliability
If the number of power semiconductor switching units is increased to reduce cross-firing risk, then the reliability is improved, but the device complexity increases
Solution Approach 1:
Instead of adding multiple protective switching units in parallel, the solution segments the submodule into two independent units, each with its own protective diode. This approach achieves cross-firing protection through structural division rather than component multiplication, maintaining simplicity while improving reliability.
Solution Approach 2:
Diodes are introduced as intermediary protective elements that passively manage voltage stress and cross-firing risks. These diodes act as mediators between the high-voltage stress and the semiconductor switches, providing protection without requiring complex active switching control circuits.
3Reliability
If protective measures are added to prevent cross-firing, then the reliability is improved, but the device complexity increases
Solution Approach 1:
Passive diodes are used as protective elements instead of complex active protection circuits. These simple, inexpensive diodes provide robust protection against cross-firing and overvoltage events, offering a cost-effective and simple solution that enhances reliability without adding significant complexity.
Solution Approach 2:
Diodes serve as intermediary protective elements that passively manage voltage stress and cross-firing risks. These diodes act as mediators between the high-voltage stress and the semiconductor switches, providing protection without requiring complex active switching control circuits.
Data Source
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Figure 2
AI summary
A submodule (1) for a converter in the high-voltage range with a reduced risk of cross-ignition. The submodule has a first and a second energy storage means (3, 4) which are connected in series, a first and a second semiconductor series circuit (13, 15) which are respectively connected in parallel with the first (3) and the second (4) energy storage means and which comprise a first (6) and a second (7), and respectively a third (9) and a fourth (10), power semiconductor switching unit which can be switched on and switched off, a first connection terminal (20) which is connected to a first potential point between the first and the second power semiconductor switching unit (6, 7), a second connection terminal (21) which is connected to a second potential point between the third and the fourth power semiconductor unit (9, 10). The invention proposes arranging a connecting switching unit (8) between the first and the second semiconductor series circuit (15), arranging a first connecting branch (14) with a first connecting branch diode (17) between the first potential point and the potential point between the energy storage means (3, 4), and arranging a second connecting branch (16) with a second connecting branch diode (18) between the second potential point and the potential point between the energy storage units (3, 4), wherein the connecting branch diodes (18, 19) are oriented in opposite directions to one another.