Torque and power control of electrically driven marine propellers

In conventional electric propulsion systems with fixed pitch propellers, the low-level thruster controllers are usually aimed at controlling the shaft speed only, without fully utilizing the capabilities of the electrical motors to apply other control strategies. In the dynamic operating conditions encountered in waves, this leads to undesired oscillations in thrust, torque, and power. This paper presents a comparison study and analysis of thruster shaft speed, torque, and power controllers, and shows that significant reductions in thrust, torque, and power fluctuations can be achieved. Open-water model test experiments validate the analysis and demonstrate the performance of the proposed controllers.