A Robust Simplified Dynamic Observer-Based Backstepping Control of Six-Phase Induction Motor for Marine Vessels Applications

This article presents a robust simplified dynamic observer-based backstepping control (RSDO-BSC) and direct torque control (DTC) synthesized with duty cycle control strategy of a six-phase induction motor (6PIM) for marine vessels applications. RSDO-BSC and DTC are employed to estimate the rotor speed, while the DTC is utilized to accomplish enhanced steady-state torque performance via accurate inputs applied to the switching table of the six-phase inverter. Furthermore, by using the duty cycle control approach, the loss components in the subspace are disregarded via the appropriate choice of virtual voltage vectors. Consequently, the 6PIM torque ripples and the current harmonics are significantly reduced. First, both the flux and the torque are decoupled using Lyapunov theory on a 6PIM two-axis mathematical model represented in the stationary reference frame. The 6PIM actual stator voltages are acquired from the dc-link voltage via the space vector pulsewidth modulated inverter. Subsequently, when the 6PIM is loaded under the rated speed, a rapid search approach is used to maximize the 6PIM efficiency. A 750-W 6PIM drive test setup employs a dSPACE 1104 for real-time implementation. The proposed RSDO-BSC performance is experimentally investigated at different speed commands, load disturbance, and low speed command with low load torque conditions.