AbstractThe continued increase in renewable energy power production and the electrification of transportation are accelerating to achieve the goal of reducing global carbon emissions. DC transmission and distribution systems are vital for the integration of renewable energy and the electrification of transportation globally. As one of the key components for improving the flexibility and reliability of DC systems, DC circuit breakers are required and need to be further researched and developed. Amongst all types of DC circuit breakers, solid-state circuit breakers (SSCBs) have the potential to interrupt a fault current at an extremely fast speed. With the help of fault current limiting devices, DC circuit breakers can achieve easier current interruption. Superconducting fault current limiters (SFCLs) are one of the promising devices to limit fault currents in DC systems.
A superconducting SSCB for DC systems has been investigated and is presented in this thesis. The research project explores, for the first time, an SSCB integrating superconducting fault current limiting technology. In addition, this is one of the first investigations to study series and parallel connected IGBTs in a single SSCB.
The use of series and parallel configurations can increase the voltage and current levels of the DC circuit breaker. The device selection and the design of the voltage balancing circuits, IGBT gate drive circuit, and the control circuit are described in detail, which lead to the development of a 1 kV SSCB. The thermal design of the SSCB is also studied based on theoretical models, to select a suitable heatsink. Three simulation models are built using PLECS software, to simulate the steady-state and dynamic operation of the designed SSCB. An SSCB prototype has been built and is experimentally tested under both on-state and dynamic tests, which shows even current sharing and voltage balance under both tests, and demonstrates successful interruption of 1 kA DC current. The experimental results are consistent with the PLECS models simulation results.
An SFCL coil prototype with low-inductance and high-inductance connections is built, and the current limiting behaviours under different fault current levels are investigated. The SFCL with a low-inductance connection and the SSCB prototype are subsequently selected to be integrated into a superconducting solid-state DC circuit breaker. The SFCL part is capable of limiting a prospective fault current from over 3 kA to 1.2 kA. With overcurrent protection, the superconducting SSCB successfully detects and automatically interrupts the current at 1 kA.
|Date of Award||16 Jun 2021|
|Supervisor||Xiaoze Pei (Supervisor) & Vincent Zeng (Supervisor)|
- DC circuit breaker
- DC systems
- Experimental testing
- Power system protection
- Superconducting fault current limiter (SFCL)