Integrated Massively Parallel Simulation of Thermo-Electromagnetic Fields and Transients of Converter Transformer Interacting With MMC in Multi-Terminal DC Grid

A computationally efficient model to study the transient interaction of the finite-element (FE) converter transformer with modular multi-level converter (MMC) can provide the advanced knowledge of the filed-circuit interactions that can be utilized for the design and test of equipment; however, the runtime of existing simulation tools developed for CPU execution usually takes days or even weeks, which is prohibitively long. In this paper, an integrated thermo-electromagnetic model is proposed for the transient simulation of FE-based transformer interacting with the MMC in a multi-terminal dc gird, with the magnetic field, thermal field, and electrical networks fully coupled. The transmission-line modeling solution is employed for the nonlinear FE problem, and each MMC is split into a number of minimum possible circuits, so that the codes can be sufficiently parallelized and implemented on the graphics processing unit with thousands of Cuda cores to be runtime friendly. The integrated model can provide the transient field distributions within the transformer and the device-level information of the MMC such as switching transients and junction temperatures. Compared with a commercial software package, the execution time of 10
⁵
time-steps decreased from several days to only hours with a speedup of more than 47 times while maintaining high accuracy.