| With the rapid development of marine transport industry,the type number of modern ships is increasing and the environmental pollution is becoming increasingly serious.So people have more requirements of the ship's own characteristics.Under this circumstance,the ship power propulsion system have been rapidly developed because of its high mobility,low pollution and many other advantages.However,when the ship sails,it will always accelerate or decelerate based on the navigation needs.Considering that the natural environment of sea is always bad,the ship propeller will probably be out of water due to the water waves or be blocked because of seaweed and other obstacles.All these will cause a significant fluctuation of the propeller torque.As the ship power propulsion system is a stand-alone and capacity-limited power system,the fluctuations of the motor load torque will cause the fluctuations of the system power and voltage,and then have a negative impact on the transient characteristics of the system.In order to solve the problems above,this paper uses the two power energy storage system,the supercapacitor energy storage system and flywheel energy storage system.By using the power energy storage system,it's able to stabilize the short-term and high-power fluctuations of the ship electric propulsion system and improve the system transient characteristics.Firstly,according to the storage system installation location and grid type,the specific structures of the supercapacitor energy storage system and the flywheel energy storage system are determined and the mathematical models of energy storage system suitable for ship electric propulsion system are established.Then the mathematical modeling of the ship electric propulsion system is carried out.The mathematical models above are integrated into the modular simulation platform of ship electric propulsion system by using Visual Studio2010 and database software.Secondly,using the simulation platform to carry out the transient simulation analysis of the ship electric propulsion system without energy storage system.Through the analysis of the simulation results,the problem that the DC bus voltage of the system is in a critical steady state of system transient fluctuation is found.The solution of installing the power energy storage system on the propulsion side DC bus to improve the transient stability of the system DC bus voltage is proposed.Thus the transient characteristics of the whole system will be improved.Thirdly,according to the transient simulation results of the system without energy storage system,the capacity and parameters of the supercapacitor energy storage system and the flywheel energy storage system suitable for the ship electric propulsion system in this paper are designed.The voltage and current double closed-loop control strategy is used to control the super capacitor charge and discharge system.The charge and discharge process of flywheel energy storage system uses constant power control strategy.For later comparative analysis,the energy exchange control strategies between the two energy storage systems and the ship propulsion system are consistent.Finally,the transient simulation analysis of the typical working condition of the ship electric propulsion system with supercapacitor energy storage system and flywheel energy storage system are carried out.Through the simulation results,the power energy storage system can obviously improve the ship electric propulsion system transient characteristics.And the improvement of the two energy storage system is compared and analyzed. |
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