Short Endurance Drive Cycle Analysis of MMC Based Absolute Battery Operated Harbor Vessel

Abstract

Following the successful commercialization of road-going electric vehicles, zero-emission electric marine vessels are gaining industry focus for absolute battery operation. Due to the low energy density of lithium-ion batteries, low propulsion-powered marine vessels operated frequently over short distances are found suitable for complete battery propulsion. In this paper, a modular multilevel converter (MMC) with symmetrically decentralized onboard battery banks is proposed as a marine traction inverter for a multi-purpose harbor vessel. A novel mathematical model of the marine vessel is proposed to size the propulsion motor, and generate torque-speed commands corresponding to vessel speed during the maneuver. A brief analytical discussion has presented on the selection of motor-converter configuration for marine propulsion application, considering three-phase low-voltage permanent magnet synchronous motor (PMSM) with a two-level inverter and three-phase medium-voltage PMSM with MMC. A short endurance marine drive cycle is simulated with low-speed high torque three-phase PMSM driven by MMC with integrated battery modules (BM). This study leveraged MATLAB/Simulink environment to analyze the operational performance of MMC and BMs during various phases of the short endurance marine drive cycle.