| The marine electric propulsion system has become popular in shipping industry recent years as it features higher energy efficiency,better environmental friendliness as well as improved maneuverability in comparison to the traditional diesel engine propulsion system.The frequent disturbance of the electric propulsion ship load results in the diesel generator operating point deviated from the optimum condition in most of its working time.This is in particularly obvious for the engineering ships with extensive load variations,since they confront more complex working circumstances during the navigation and operation period.This affects the ship power system stability and reliability,and additionally leads to the increase of the fuel consumption and consequently the emissions.In order to resolve the issues mentioned above,a hybrid energy storage device composed of the super capacitor and battery was introduced herein to stabilize the power fluctuations caused by the load disturbance and therefore.The hybrid energy storage device capacity optimization method,topological structure and control strategy were investigated thoroughly in this work.Finally,the case study was conducted based on the measured data of a Trailing Suction Hopper Dredger(TSHD),and the results reveals that the proposed hybrid energy storage device can substantially reduce the load power fluctuations,which indicates that this work provides the theoretical basis and reliable approach for the application of the energy storage devices in marine electric propulsion system.The main works are summarized as follows:(1)A brief overview of the marine electric propulsion system and its typical application was given;the energy storage technology development and the current marine energy storage technology research status were analyzed.(2)The technical indicators of the energy storage device used in marine electric propulsion system were examined;the solution of hybrid energy storage device composed of the super capacitor and battery was proposed;the working principle,charge and discharge characteristics of the super capacitor and battery were described.(3)The topological structures of bi-directional DC/DC converter in the hybrid energy storage device were compared,and the multi-port access mode was decided to use;both the advantages and disadvantages of PWM control,phase shift control and phase shifted PWM control were investigated,and the phase shifted PWM control as the method of multi-port power control was adopted.(4)The multi-objective optimization and constraint model for the capacity configuration of the hybrid energy storage device in marine electric propulsion system was developed,and the adaptive weight particle swarm optimization algorithm was used;the process of the adaptive inertia weight particle optimization algorithm given;the optimization program was implemented in MATLAB to search for the optimal capacity of the super capacitor and battery in the hybrid energy storage device based on the measured TSHD load data.(5)The power coordination allocation method for the hybrid energy storage device was studied,and the low-pass filter algorithm was proposed for the power allocation of the hybrid energy storage device;the filter coefficients of the low-pass filtering algorithm was adjusted according to the battery charge and discharge times of change and state of charge,in order to control the charge and discharge of the hybrid energy storage system and thus,reduce the loss of storage battery in the operation process;the control process of the energy storage device coordinated power allocation was presented;the power allocation program was implemented in MATLAB to simulate and analyze the power distribution of the super capacitor and battery on the measured TSHD load data. |
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