Mitigating power fluctuations in electrical ship propulsion using model predictive control with hybrid energy storage system

Shipboard electric propulsion systems experience large power and torque fluctuations on their drive shaft due to propeller rotational motions and waves. This paper explores new solutions to address the fluctuations by integrating a hybrid energy storage system (HESS) and exploring coordinated power management. A propeller and ship dynamic model, which captures the underlying physical behavior, is established to support the control development and system optimization. Given the fact that both high and low frequency contents exist in the power fluctuations, a combination of battery pack and ultracapacitor bank is proposed, coordinated control is developed, and performance is evaluated in different sea conditions. Simulation results show that the proposed HESS with model predictive control provides substantial benefits in terms of reducing fluctuation and sustaining self-operation, compared to other solutions that involve batteries or ultracapacitors alone. Moreover, our analysis shows that the benefits of HESS are achievable only through both effective power management and device coordination.