Magnetic Coupling Devices for Semiconductor Switch Fault Protection
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Solution Overview
Problem
High-power silicon carbide semiconductor switches in power electronic converters face challenges in fault protection, particularly 'shoot through' failures due to non-optimal module integration and high di/dt, which shortens the Safe Operating Area and complicates protection circuit operation.
Innovation Solution
The use of magnetic coupling devices, such as chokes, is implemented between the current paths of semiconductor devices to suppress short-circuit currents by generating a large inductance only during faults, reducing the risk of damage to the switch leg.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetic coupling devices are added to suppress short circuit current, then fault protection is improved, but device complexity increases
Solution Approach 1:
The patent introduces magnetic coupling devices as intermediary elements between the semiconductor devices and the rest of the circuit. These devices act as mediators that suppress short circuit currents through magnetic coupling while allowing normal operation to proceed unaffected. The magnetic coupling devices are positioned in the current paths and utilize magnetic fields to achieve current suppression during faults without adding significant complexity to the overall device architecture.
2Reliability
If inductance is increased to suppress short circuit current, then fault protection is improved, but normal operation performance deteriorates due to voltage drop
Solution Approach 1:
The patent employs magnetic coupling devices that dynamically adjust their effective inductance based on operating conditions. During normal operation, the magnetic coupling is configured to present minimal impedance to the current flow, maintaining optimal power transfer. During short circuit conditions, the magnetic coupling effect intensifies, automatically increasing the effective inductance to suppress the fault current. This dynamic behavior eliminates the need for fixed high inductance values that would cause voltage drops during normal operation.
Solution Approach 2:
The patent utilizes changes in magnetic coupling parameters to achieve different operational states. By adjusting the magnetic coupling coefficient and inductance values of the magnetic coupling devices, the system can optimize performance for both normal operation and fault protection. The inductance parameters are specifically designed to provide minimal impact during normal switching operations while delivering strong suppression during short circuit events, effectively decoupling the two operational requirements.
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 effectively reduces the risk of damage to semiconductor switch legs by suppressing short-circuit currents and extending the protection circuit's response time, enhancing fault resistance in high-power applications.
Implementation Method 1
By means of the magnetic coupling device, e.g. magnetic choke or other inductor, and conductors from two different current paths of each two semiconductor devices in opposite directions passing there via/through, no (or a relatively low) inductance is generated in the magnetic coupling device at normal operation. However, in case of a short circuit, the much larger short circuit current passing via the magnetic coupling device, conducted by one of the conductors in the affected current path, results in a large inductance which suppresses the short circuit current
Data Source
Figure 1~2a
Figure 2b~3
AI summary
The present disclosure relates to a semiconductor switch leg S for a Power Electronic (PE) converter (1). The switch leg comprises a plurality of parallel connected semiconductor devices Sa-d. Each semiconductor device is connected with a positive conductor a-d+ connecting the semiconductor device to a positive terminal of an energy storing device (2) of the converter, and a negative conductor a-d-connecting the semiconductor device to a negative terminal of the energy storing device (2) of the converter, the semiconductor device together with the positive conductor and the negative conductor forming a current path across the energy storing device. The semiconductor switch leg comprises a plurality of magnetic coupling devices 3a-d, each magnetic coupling device being arranged between the two current paths of respective two neighbouring semiconductor devices of the plurality of semiconductor devices such that the current path of one of the two semiconductor devices and the current path of the other of the two semiconductor devices pass via the magnetic coupling device, and such that each current path passes via two of said plurality of magnetic coupling devices.