| Ship integrated electric propulsion system is a main trend in commercial and military development of the ship. But the propulsion motor power fluctuation, the output power fluctuation of the generator and ship power grid voltage fluctuations are caused by change of the propeller movements, which reduced the fuel efficiency and made the mechanical stress wear and tear of mechanical system. And the volatility of load power can be reduced by adding the energy storage equipment in the ship, which can decrease the fluctuation of the whole system power and improve the system efficiency.In this paper, the method of hybrid energy storage restraining power fluctuation of integrated electric propulsion system is researched. Firstly, the typical configuration of integrated electric propulsion system is analyzed to establish the mathematical model of key modules and the control system model of generating units and propulsion motor in combination with a typical LNG ship. The basic principles and mathematical models of lead-acid battery with super capacitor hybrid energy storage are studied, and the three order lead-acid battery dynamic model and super capacitor RC model are built respectively to simulate and analyze its charge and discharge characteristics. Combined battery and super capacitor energy complementary characteristics, and considered the system power fluctuation rate and the efficiency of the generator unit, the hybrid energy storage capacity are allocated optimally using particle swarm optimization algorithm.Then the hybrid energy storage system structure is researched and analyzed, and the coordination control strategy based on the super capacitor voltage is used. The new hybrid energy storage topological system, which is composed by battery, super capacitor device and the outer system, control the power throughput fast and precisely. Super capacitor uses the voltage and current double closed-loop bidirectional DC / DC converter controller to stabilize the DC bus voltage. Lead-acid battery uses the bi-directional DCDC converter of constant current controller to prevent lead-acid batteries over charge and discharge, which increase its serviceable life. Simulation mode of the integrated electric propulsion system and hybrid energy storage system are built in MATLAB/Simulink. It is simulated and analyzed for electric propulsion typical working conditions (starting, braking, reversing) in the case of the absence or presence of energy storage systems, which research the effect of electric propulsion system for ship power system voltage drop, motor torque and DC bus fluctuation situation. The simulation results show that the energy management strategy is proposed in this paper can better play complementary advantages for two kinds of energy storage, which has a better effect and the best economic performance to eliminate the power fluctuation of systemFinally, integrated electric propulsion system simulation interface is compiled by the MATLAB graphical user interface (GUI) to meet the different levels of simulation system The simulation results can be stored in SQL Server 2008 database, which are accessed using MATLAB to realize the simulation results comparing for different times. |
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