Research On The Control Strategy Of Ship DC Network Based On Supercapacitor

Integrated power system is one of development direction of ship.Compared with AC networking system,there are several outstanding advantages of DC networking system including simple generator connection,low fuel consumption,easy access to the new energy system,it will become the development direction of intelligent ships.In this paper,a DC-connected power system ship,"Zhenyang ferry 3011",was used as the research object,and a system simulation model was built based on the "Matlab/Simulink" platform to analysis the speed control of variable-speed diesel,asynchronous generator ‘ s rectification,and bus voltage stabilization control,supercapacitor control and integrated power system’s energy management strategies.The specific research contents are as follows:Firstly,make an analysis about the control of the core equipment of the DC gridconnected power system and the variable speed diesel generator.In view of the speed control problem,two methods of speed optimization of the mathematical model and speed optimization based on the universal characteristic curve were analyzed,on this basis,a stepless speed control strategy and a stepped speed control strategy were designed.For the problems of asynchronous generator rectification and constant voltage control,a non-linear compensation method was proposed,the decoupling controller was designed to realize the rotor field-oriented control,and the voltage outer loop control and magnetization were also designed.Current outer loop control was used to achieve bus voltage stabilization,and the effectiveness of the control strategy was verified by simulation experiments.Secondly,research on the control strategy of the ship’s DC power system,the principle of droop control in DC power grid was introduced,the limitations of traditional droop control were analyzed,and an improved DC bus droop control method based on voltage compensation was proposed for the problem of bus voltage drop.Aiming at the problem that the diesel engine with transient load can not respond in time,the advantages of the rapid charge and discharge of the supercapacitor energy storage device are used to compensate the DC bus energy change and reduce the DC bus voltage fluctuation.Finally,a hybrid power system based on diesel generators and supercapacitors was combined with the actual navigation conditions to propose an energy management strategy based on filter shunting.The strategy used the Belief rule base method to identify the ship’s operating conditions.In fixed-speed navigation conditions,diesel work at the optimal operating point,supercapacitors compensate for system power changes.In maneuvering conditions,low-pass filters are designed.Regarding the power decomposition,the diesel generators were controlled to bear the low-frequency part of the power,and the supercapacitors were assumed to bear the high-frequency power to avoid drastic changes in the output power of the diesel generators,thereby optimizing the operating conditions of the diesel engine,which can save fuel consumption and improve emission quality to a certain extent.