Analysis of Synchronous Machine Dynamics using a Novel Equivalent Circuit Model
Royal Institute of Technology, Stockholm, (2009)Abstract
This thesis investigates simulation of synchronous machines using a novel MagneticEquivalent Circuit (MEC) model. The proposed model offers sufficient detail richnessfor design calculations, while still keeping the simulation time acceptably short.Different modeling methods and circuit alternatives are considered. The selectedapproach is a combination of several previous methods added with some new features.A detailed description of the new model is given. The flux derivative is chosen as themagnetic flow variable which enables a description with standard circuit elements. Themodel is implemented in dq-coordinates to reduce complexity and simulation time. Anew method to reflect winding harmonics is introduced.Extensive measurements have been made to estimate the traditional dq-modelparameters. These in combination with analytical calculations are used to determine theparameters for the new MEC model.The model is implemented using the Dymola simulation program. The results areevaluated by comparison with measurements and FEM simulations. Three differentoperation cases are investigated; synchronous operation, asynchronous start and inverterfed operation. The agreement with measurements and FEM simulations varies, but it isbelieved that it can be improved by more work on the parameter determination.The overall conclusion is that the MEC method is a useful approach for detailedsimulation of synchronous machines. It enables proper modeling of magnetic saturation,and promises sufficiently detailed results to enable accurate loss calculations. However,the experience is that the complexity of the circuits should be kept at a reasonable lowlevel. It is believed that the practical problems with model structure, parameterdetermination and the simulation itself will otherwise be difficult to master.