Electrothermal Transient Behavioral Modeling of Thyristor-Based Ultrafast Mechatronic Circuit Breaker for Real-Time DC Grid Emulation

The accuracy of power electronics simulation relies on the semiconductor switch model employed. Thus, in this paper where an ultrafast mechatronic circuit breaker (UFMCB) is implemented in real-time on the field programmable gate array, a detailed nonlinear thyristor model is proposed for extra device-level information regarding design evaluation. The cascaded thyristors impose a heavy computational burden on the UFMCB simulation, and node elimination is achieved following the proposal of a scalable thyristor model. For the convenience of the circuit breaker's integration into dc grid, a pair of coupled voltage-current sources is inserted as its interface, which achieves a reduction in the dimension of system admittance matrix, and the subsequent proposal of a relaxed scalar Newton-Raphson method further expedites the simulation by decomposing the nodal matrix equation. Meanwhile, the modular multilevel converter as a dc grid terminal adopts half-bridge and clamped double submodule topologies to test system performance in conjunction with the UFMCB. Real-time execution is achieved and the results are validated by ANSYS/Simplorer and PSCAD/EMTDC in device- and system-level, respectively.