Integrated control of power generation, electric motor and hybrid energy storage for all-electric ships

Abstract

Ship propulsion shafts experience large power and torque fluctuations due to hydrodynamic interactions and wave excitation. The hybrid energy storage system (HESS) is an effective solution to address the impact of these fluctuations for all-electric ships. The new HESS introduced to combat the problem, however, will interact with the power generation and motor control systems, affecting both system efficiency and reliability. In our previous work [1], we proposed an energy management system (EMS) for HESS to incorporate information from other shipboard power units to manage the energy storage components and avoid undesirable interactions, especially those interactions between the batteries and ultra-capacitors. In this work, we pursue a more proactive approach to dealing with the interactions by designing an integrated EMS that encompasses the controls of power generators, electric propulsion motor, and HESS. Through model predictive control (MPC), such an integrated approach takes advantages of the predictive nature of MPC and allows us to judiciously coordinate the different entities of the shipboard power microgrid under constraints, thereby providing benefits in system performance. Results presented in this paper compare the proposed integrated EMS with non-integrated EMS to demonstrate its benefits.