Research On The Emulation Platform For Marine Electric Propulsion System

The ship electric propulsion technology has gained much attention all over the world because of the global energy shortage and the environmental protection requirements. However, due to the multi-variable and highly coupled and nonlinear structure, high-performance control of electric propulsion system becomes a challenging problem. Research on dynamic load emulation is a hot point of test platform study, the mathematical modeling and simulation of the marine electric propulsion system are systemically investigated in this dissertation, the main works of this dissertation are as follows:1) Based on numerous literatures, this dissertation refers and absorbs other’ merits, utilizes the model design method to put out research on semi-physical simulation system, the emulation platform dedicated to the research on propulsion control is designed and constructed, its components, and working principles are analyzed. The emulation platform was developed based on dSPACE real-time simulation system, The emulation platform that consist of an inverter-driver squirrel-cage motor emulate propeller load, a set of DC linked dual back-to-back pwm voltage-source converts. four quadrant ship-propeller model, the real-time monitoring interface, dspace controller, twin motors coupled on the same stiff shaft, The drive motor and load motor use in induction motor controlled by inverts adopted field orientation control technique, close loop speed control is adopted for drive motor, open loop torque control is used for load motor which emulates propeller load. Results show that the method combines close loop speed control and open loop torque control can emulate dynamic load. The key questions and technical essentials is studied, especially to system integration and control strategy. The emulation platform is universal,2) In order to simulate propeller load realistically, the Chebyshev polynomial fitting method is utilized to express the Nordstrom propeller, The modularization method is chosen to establish a four quadrant simulating model of propeller, The input of ship-propeller model is motor speed, which represents the propeller speed in the real condition, and its output torque reference are given to the load-motor set. The model code is downloaded to dSPACE real-time simulation platform, the operation and calculation of model is carried on by dSPACE controller. The platform provides a good development environment and research object for research on propulsion control.3) Hardware in the loop simulation enables experimental study of prototype hardware system via a real-time interaction between physical hardware and virtual model, Virtual model is used to describe the corresponding physical prototype in the system,it is often necessary to scale the signals in and out of the prototype system, a key problem with comparisons is that scaling effects when hardware of one size is simulated by hardware of another size, How to chosen scaling factors, according to dimensional analysis, applying the use of dimensionless variables, as defined by the Π Theorem, a procedure is developed via dimensionless variable method to derive input/output scaling factors. The scaling factors between scaling physical hardware and virtual model is derived from the machine motion equation, so that the experiment equipments can have the same dynamic characters as the real ship.The proposed controller incorporates droop curves on real and reactive power that enable the gensets to respond to load change, it can maintain system frequency and voltage within prescribed limit and power quality. The generation sets in paralleling connection is able to reduce the circulating reactive power in the system and share load move, the simulation results shows that using the proposed controller for diesel generation sets is able to cooperation during load change, it can improve the performance of marine power system. Development of a flexible component model used for modeling and simulation of marine power plants in Saber, such as disel generation model, speed control system of disel generation, the exciting current control system of disel generation, ship-propeller model, the flex-oriented vector strategies for variable speed drive of squirrel-cage motor, simulation of selected cases of combined power plants during extreme dynamic loads are conducted. The interaction between the motor and generator is studied. Simulation results are analyzed, simulation models are verified by the simulations and experiments based on a hardware-in-loop platform, relevant test cases are done in order to reveal the dynamic behavior of complete electric propulsion system.5) The thesis analyzed the three-phase VSR model and control strategy, the synchronous coordinate transform and the orientation method. The thesis gave out the design method of the internal current loop and external voltage loop based on the system control models. The thesis also discussed a new phase detection way of designing a PLL by using voltage vector control, the thesis analyzed the positive and negative sequence component detection under the unbalanced conditions, the paper presented a new positive and negative sequence component delayed signal cancellation method, the effectiveness of this method is demonstrated by simulation results.Modeling and simulation research of marine electrical propulsion system, which can describe static and dynamic behaviors, is helpful to discover inherent principles and to direct the design and management of the system.The research is supported by the following projects:State "211" Project-"WUT Marine Electrical Propulsion Simulation Lab"; doctor foundation projects of the State Ministry of Education of PRC (No.20040497012); the Research Fund of HSSE, WHUT, the State Ministry of Education (No. HSSE0802).