Electromagnetic Modeling of High Voltage Multi-Level Converter Substations

In this paper, an electromagnetic simulation methodology and workflow for high voltage multi-level converter stations is presented, which is based on the transmission line matrix method as used in CST Studio Suite. The methodology makes use of the thin wire models of CST, which are well suited to represent the high voltage bus bars and cables connecting the 3-dimensional structures of the converter valves and halls. Additional key components such as grid transformers and phase reactors are included as hybrid models, consisting of 3-dimensional structures in combination with imported circuit netlists. The converter itself is modeled as impulse sources in the CST circuit schematic, where the switching pulse patterns and the cell switching characteristics are taken into account in a final post-processing step in combination with electromagnetic interference (EMI) detector models. The obtained accuracy in the target frequency range from 10 kHz to 10 MHz, is about 5 dB, when compared to actual electromagnetic (EM) field measurements.