(a) Set up simulation s5 to conduct the short-circuit simulation using the machine parameters in set3a. Select a step disturbance in V_mand enter 10 for the fault duration in number of cycles. Save the two sets of plots. Save the Workspace y arrays in a data file using the MAILAB save command so that you can later plot i_f^' and δ of this run with those obtained in Parts (b) and (c).
(b) Repeat Part (a) using the parameter file, set3b. Save the two sets of plots. Reassign the Workspace y arrays in your MATLAB workspace with a unique variable name and store them in a separate data file for plotting later.
(c) Set up the simulation s1using m1 to conduct the same short-circuit run with the parameter file, set3e, and save the two sets of plots. Again, reassign the Workspace y arrays in your MATLAB workspace with a unique variable name and store them in a separate data file for plotting later.
(d) Reload the stored data files from Parts (a), (b), and (c) into the MATLAB workspace and use plot5c to plot the three δ curves on one plot and the three i_f^' curves on separate plots to avoid overcrowding. Comment on any observable differences in δ and i_f^' from these three different machine models.
Sample results from the run in Part (a) are shown in Fig. 7.29, and the combined plots of δ and i_f^' from all three runs are shown in Fig. 7.30.
7.10.6 Project 6: Six-phase Synchronous Machine
In Project 5 we saw how we could implement a simulation where there were coupling inductances between rotor circuits. Here in Project 6 we will look at how we can also handle coupling of the stator side windings in the qd rotor reference frame. We will use an example where the coupling on the stator side in the qd rotor reference frame remains in a synchronous machine with two three-phase sets of stator windings that are displaced by an angle. To obtain higher power capacity, the twin stator windings of a six-phase synchronous generator divides the generator's current into two paths to circumvent the limitations in current handling capacity of other equipment. Previously the limitation was from the interrupting capacity of breakers [70 ]; nowadays it is the current handling capacityof the power switches in the converters [71].
First, we will briefly review the equations for a six-phase synchronous machine, rearranging them into a form suitable for implementation in a simulation. Then we will proceed with the objective of this project, which is to develop and test a SIMULINK simulation of a six-phase machine. Figure 7.31 shows the windings of an idealized six-phase synchronous machine. The two sets of three-phase stator windings are labeled abc and xyz with the axes of xyz displaced by angle,ξ, ahead of abc. On the rotor are the damper kq and kd windings and the d-axis field fwinding. Since parts of the distributed windings of the two sets share common stator slots, there will be mutual slot leakages. The leakage inductances of the stator and rotor may be put in the following form [72]: