Water Electromechanical Coupling System Modeling And Their Interaction

In the present study of hydroelectric system, it is difficult to establish hydraulic-mechanical-electric system in respect that the related equipments and knowledge of hydraulic, mechanical, electric system are complicated and comprehensive. Consequently, experts of each field study individual system respectively. Among this research, the coupled interaction between three systems is not considered and the model accuracy always does not meet the demand of research, which lead to simplification the impacts between hydraulic, mechanical and electric system. The mismatch of model precision and lack of hydraulic-mechanical-electrical system model are the main reasons for restricting the transient study and improvement of simulation precision on hydroelectric system.Therefore, an integral coupled hydraulic-mechanical-electric system is established in Matlab/Simulink environment in this thesis. Based on this model, the interaction between systems is studied and simulation results are given and analyzed. The main contents of the thesis are listed as follows:(1) Based on the analysis of models of hydraulic, mechanical and electric components, an integral coupled system is built in Matlab environment. This model is foundation for following study of transients. Based on this model, researchers can study hydraulic system, mechanical system and electric system separately, also for the coupled system.(2) A novel equivalent circuit model of penstock is presented. The whole conduit circuit model can be built by this proposed method using one or moreπcircuit model to express penstock in the research of transients. The method can be used to form the state block of flow and head from inflow to outflow for the purpose of fast modeling of penstock, which is easy for researcher to study the impact between hydraulics, mechanism and electricity. Comparisons between various lengths of penstock and different types of waterhammer using circuit equivalent method and characteristic method are presented by digital simulation. Results of digital simulation show that the proposed method is correct and effective.(3) The influences of electrical system on coupled system are studied based on a single machine infinite bus simulation system, which include the impact of electrical disturbance, constant mechanical power model and parameters of excitation system. The simulation results are analyzed and conclusions are given.(4) The influences of hydraulic system on coupled system are studied based on a single machine infinite bus simulation system, which include the impact of hydraulic disturbance, hydraulic system models and hydraulic system parameters. The simulation results are analyzed and conclusions are given.(5) The characteristics of hydro governor and its PID control rule are studied. Two modified control modes are presented and three control modes are compared to identify the regulating quality. The influences of PID parameters on coupled system are studied and conclusions are given qualitatively.