Research On Digital Design Technology Of Shipboard Integrated Electric Propulsion System

Integrated electric propulsion system(IEPS)is the direction for future ship development.Compared with traditional ship,it offers significant benefits in terms of less prime movers,reducing the life-cycle cost,increasing the survivability,etc.Meanwhile,as the propulsion system and other service loads are integrated into a single distribution network,it significantly increases the complexity of system design,which brings new challenges for ship design.Now,with the trend towards digital design for conventional ship design,computer-based design for ship development has become a trend.Considering the characteristics of IEPS design,it is imperative to study the digital design technology for IEPS.In this dissertation,the following issues in IEPS digital design technology are studied:First of all,according to the hierarchical,multi-time scale dynamic phenomenon commonly found in IEPS studies,this dissertation proposes a systematic layout for digital design to categorize the design and analysis of IEPS into three layers: Operational level(minutes/hours),System level(milliseconds)and Waveform level(microseconds),and illustrates in-depth how the proposed layout can effectively support and improve the current IEPS design practices.Based on the layout,a preliminary digital design architecture using Model-Integrated Computing(MIC)concept is proposed,and the meta-models and specifications for system design and analysis are defined at a high level of abstraction.This architecture is open and abstract,in order to implement the design and analysis functions defined by it,a digital design software platform is necessary to configure design and analysis environments in different levels and disciplines for IEPS digital design.The power flow analysis environment configuration for IEPS is provided as an intuitive example to illustrate the general procedure and usage of the digital design tool development.Secondly,mathematical modeling and numerical solution of the complex IEPS dynamics are typically time consuming and computationally expensive.This dissertation aims to address this issue by configuring modeling and simulation environments at waveform level and system level,repectively,to provide different detailed models for different design and analysis.The former is implemented based on Matlab/SimPowerSystems,while the latter provides a representative system level modeling approach,and it can automatically generate the detailed Differential-Algebraic Equations(DAEs)for IEPS and calls the corresponding solver for simulation.Based on the simulation comparisons under different scenarios of the same system between the different level modeling and simulation environments,the accuracy and computational speed are properly quantified and verified,which means the system model provided by the system level modeling and simulation environment can effectively and efficiently capture the neccssary behavior for system level analysis,and the design environment is also justified to meet the requirements of the system level designs.Thirdly,a model-based control strategy design environment is configured to address the issue of IEPS control strategy design problem.An integrated system control framework is proposed.Based on the study of system dynamic performance specifications and operation requirments,the detailed description of IEPS control problem is formulated,and the metamodel for the design environment is given.To implement the design environment,a combined sequential quadratic programming(SQP)and perturbation analysis approach is derived to solve the optimization problem after the system disturbance and under the state and control input constraints.Two case studies(propulsion load pick up,and pulse load disturbance)are presented to demonstrate the design process and control effect using the configured control strategy design environment,which proves that users can easily synthesize the system control framework under this design environment,and the control strategy designed can effectively improve the IEPS dynamic performance following a system disturbance and efficiently recover to steady state.Then,the reconfigurable problem of IEPS is studied.IEPS is a typical hybrid system contains discrete events and continous states.Discrete states are event-driven and represent the topological structure and specific configuration of IEPS,while the dynamic of continous states is described by DAEs.A reconfigurability analysis environment for IEPS is developed based on the study of hybrid system configuration,and the hybrid automaton model for IEPS is developed and extended to an automaton which consists of system normal operation configuration and fault configuration.The reconfigurability of IEPS is defined,which means after the occurance of fault,system can 1)remain the safe state under fault configuration,or 2)have the chance to return to the normal operation configuration.Method to check the system reconfigurability is proposed.Using this reconfigurability analysis environment,two hybrid automatons of a practical IEPS example under battle and cruise model after faults are developed,and the process to check the reconfigurability during system operation is also illustrated.At last,a detailed IEPS design example is presented using the digital design software platform developed in this dissertation.The waveform level and system level application model are built and automatically implemented by the software platform.The control strategy is designed,and the reconfigurablity of IEPS example is analyzed.The simulation results are presented to validate the effectiveness of the developed digital design software platform.The results of this dissertation have improtant theoretical significance and engineering application value,which can provide a digital design software platform with broad application prospect to increase the system design efficiency and improve the design quality for IEPS design and research.The results can also expand to other control system digital design and simulation.