Research On Energy Saving Based On Variable Frequency Control Of Marine Cooling Water Pump Unit

The normal navigation of the ship and the operation of the main engine are inseparable from the ship cooling water system,of which the energy consumption of the cooling water pump occupies 65%-70% of the whole central cooling water system.In the traditional ship central cooling water system,the sea water pump is designed and selected with the maximum capacity in order to ensure system safety,and the sea water pump has been working under the rated power and the cooling load of the main engine when running under variable working conditions cannot be well matched,which will lead to a large amount of energy wastage,so it is important to study the frequency control technology of the sea water pump for the energy saving and emission reduction of the ship.This thesis takes a type of 59,990 DWT bulk carrier as the research object,carries out mathematical modelling of the relevant heat load equipment,uses MATLAB/Simulink software to model and simulate the whole central cooling water system and the direct torque control system of the cooling water pump motor,and analyses and compares the simulated values of the main parameters of the main engine during rated operating conditions with the design values of the real ship,the error of seawater flow is The error of the seawater flow rate is 0.4% and the error of the seawater pump speed is 0.69%,which proves the accuracy of the simulation model.By calculating and analysing the experimental data,the main cooling water pump frequency control using direct torque control technology has a good dynamic response and the motor can save up to about 52.70% of electrical energy.The main research of this thesis is as follows.1)The forms of central cooling water systems of domestic and foreign ships are reviewed,the important working equipment and working principles in the central cooling water system are analysed,and the relevant heat load calculation of the central cooling water system is carried out based on the information of parameters such as ship type and main heat load equipment of 59990 DWT bulk carrier,which provides data support for the subsequent simulation.2)Based on the knowledge of heat transfer theory,mathematical modelling was carried out for the models of key equipment in the central cooling water system of the 59990 DWT bulk carrier such as central cooler,main engine cylinder sleeve,lubricating oil cooler and air cooler,and the mathematical model of cooling water pump speed calculation was integrated using MATLAB fitting calculation.3)The mathematical model of the cooling water pump three-phase asynchronous motor was constructed with the DTC system and the direct torque control algorithm was used to achieve good dynamic response of the ship cooling water pump motor.The modeling simulation comparison and analysis of the 6-sector and 12-sector stator magnetic chain were used to verify that the use of the 12-sector division method in this ship can achieve good dynamic response of the ship cooling water pump motor control.4)According to the mathematical model established in the previous section and the direct torque control scheme of the cooling water pump,the MATLAB/Simulink software is used to model and simulate the whole central cooling water system of the ship and analyse the working process of the system.In the Simulink model,the working conditions of the central cooling water system under different operating conditions are simulated by inputting different actual loads of the main engine and seawater temperature,and the real-time parameter information of each heat load equipment is calculated and analysed.The motor power can be reduced by 8.4k W,13.6k W and 19.5k W respectively on the original fixed speed scheme,resulting in power savings of 22.70%,36.76% and 52.70% respectively.5)Using VS Code software as the development platform,the visualisation and simulation software of the central cooling water inverter control system of the ship was developed based on C++ language.The software enables direct control of variables such as the power of the main engine and the seawater temperature,realises real-time monitoring and recording of data such as the current cooling water temperature,the flow rate of the cooling water pumps and the speed of the cooling water pumps,and feeds the data back to the user in the form of a data cloud.The study of the ship’s central cooling water system with variable frequency control of the pumping unit and the development of the visualisation simulation software provide some reference for future research on energy saving in the ship’s central cooling water system.