Investigation of Reflected Wave Phenomenon in SiC-Based Two-Level Split-Phase Inverter-Fed Motor Drives

Abstract

Fast switching speed of silicon carbide (SiC) exacerbates reflected wave phenomenon (RWP) in two-level (2L) voltage source inverter (VSI)-based motor drives, causing motor side overvoltage and drive side overcurrent. The 2L split-phase (2L-SP) topology shows prospects of alleviating RWP due to its lower output $\text{d}v/\text{d}t$ facilitated by split-inductors which also serve as an output reactor. This article explores RWP in a 2L-SP-based motor drive and compares it with the 2L with an output reactor, denoted as 2L-LF. For the study, a 2L, 2L-LF, and 2L-SP configurable 18-kVA SiC-based prototype is developed and interfaced to an emulated motor load through a bundled shielded cable. At first, simplified lumped differential mode (DM) equivalent circuits are derived for modeling RWP transients in 2L-LF and 2L-SP drives. Subsequently, RWP is investigated through double pulse tests (DPT) for various cable lengths, reactor (2L-LF), and split inductor (2L-SP) values. Results show that 2L-SP exhibits lower RWP for longer cables, achieving up to 68% and 73% reduction in overvoltage and overcurrent amplitudes for an 8 m cable. An anomalous rising overvoltage pattern for short cables is observed for both drive configurations and analyzed using proposed DM equivalent circuits. Further, from a switching performance standpoint, split-inductors in 2L-SP decouple load and complementary cell's parasitics from the device during switching, achieving 17% lower switching loss than 2L-LF. Following the DPTs, continuous three-phase tests are performed for 8 m cable for both drive configurations. The 2L-SP drive achieves up to 60% and 74% reduction in overvoltage and overcurrent amplitudes than 2L-LF. Overall, 2L-SP outperforms 2L-LF in mitigating RWP in SiC-based 2L VSI motor drives.