Model Predictive DC Voltage Control for all-electric ships

Abstract

With the advent of on-board Direct Current (DC) power and propulsion systems, the transmission and delivery of energy on board of ships can be carried out more efficiently as it is being done using conventional direct-diesel or Alternative Current (AC) power and propulsion systems. However, the stability of DC voltage on-board of all-electric ships with a DC power and propulsion architecture is a critical issue that has drawn attention over the last few years. In this paper, a novel Model Predictive Control (MPC) approach is proposed for the diesel-generator shaft speed control and DC voltage regulation on-board of all-electric ships, focusing on the uncontrolled rectification at the voltage conversion stage. This work considers the prime mover as a Diesel–Generator–Rectifier (DGR) set which feeds propulsive asynchronous motors through a DC-link. First, a state space model dynamic model is developed for the DGR set and the DC-link. Then, the MPC-based approach is presented. The approach is based on Input–Output Feedback Linearization (IOFL) which is used for the linearization of the highly non-linear dynamics of the system. To increase the robustness of the algorithm, a tube-based technique is adopted which is implemented through a linear auxiliary control law. Different analyses are carried out to show that the proposed control strategy is capable of handling sudden changes in load conditions as well as adverse effects of Constant Power Loads (CPL).