Research On Optimizing Intelligent Low-frequency Load Shedding Strategy For Marine Power Station

With the continuous development of power electronics technology,the ship’s comprehensive electric power system has received increasing attention from countries,and at the same time,higher requirements have been placed on the safe and stable operation of the ship’s power grid.The research on the problem of generator failure or load change caused by external disturbances,which causes active power shortage in the power grid system,and thus affects the frequency stability of the ship’s power grid,has not attracted great attention from scholars.This paper takes a certain kind of dual power station ship power system as the research subject,to explore a suitable low-frequency load shedding control strategy when the ship frequency changes.The main content illustrates the following three parts:In the first part,the overall structure of the ship’s power system is introduced first,and the mathematical models of the power generation subsystem,power distribution subsystem and load subsystem in the ship’s power system are established.Secondly,a simulation model of ship power system is constructed on the MATLAB / Simulink simulation software platform.Finally,under typical operating conditions,the transient stability of the ship’s power system will be verified.In the second part,the traditional adaptive low-frequency load shedding strategy is studied first.In view of the shortcomings of traditional adaptive method with poor selectivity,fuzzy control is added to the traditional adaptive algorithm.The priority of load removal is obtained by establishing membership functions of frequency and frequency change rate.After that,the traditional and improved adaptive low-frequency load shedding control algorithms are applied to the simulation model,verifying their effectiveness for grid system frequency recovery,and at the same time proving that the improved adaptive low-frequency load shedding control algorithm is far superior.In the third part,the mathematical principle of the power flow algorithm is first studied.It finds that the calculation of the control variables by the power flow algorithm is not accurate due to the error of the measurement device.In this paper,based on the principle of statistics,the weighted least squares algorithm is added to the power flow algorithm to increase the redundancy and thus the accuracy of the calculation results.Then the power flow algorithm and the improved power flow algorithm are applied to the simulation model.Finally,the simulation results of the improved power flow algorithm and the improved adaptive method are compared.It is proved that the improved power flow algorithm is more effective for frequency recovery.The simulation results show that the simulation model of the dual power station ship power system established in this paper meets the requirements of China Classification Society.The frequency of the power grid system caused by load fluctuations or generator set failure caused by external disturbances can be reduced to the rated value by applying the traditional low-frequency load reduction strategy.At the same time,it verifies that the improved adaptive method is superior to frequency recovery.Finally,applying the power flow algorithm and the improved power flow algorithm into the simulation model,and comparing the simulation results of the improved power flow algorithm with the improved adaptive method,to verify that the improved power flow algorithm is more rapid and economical.