A method for coupled solutions of electric, magnetic and mechanical systems in dynamic simulation of PM synchronous machines

The authors describe an algorithm for the solution of the coupled electric, magnetic and mechanical problems in the dynamic simulation of elecrical machines. The method is presented in detail for the PM synchronous machines. The numerical solution of this coupled problem is carried out by simultaneously solving the electric circuit equations at different operation stages of the power electronics control circuit, the FEM equations in modelling the magnetic field and the equation of motion of the armature. Since both the electric and magnetic systems are nonlinear an iterative procedure is employed at each time step in order to achieve the convergence. The convergence is obtained when the continuity of the current in the electric circuit and the FE model is accepted. The torque of the machine is calculated using the Maxwell stress tensor and afterwards the equation of motion is integrated to obtain the mechanical response. The response of the motor drive for speed reference changes are considered