Advanced FOC with Adaptive Switching Frequency for the Integrated Multiphase ISCAD

In multiphase machines with dedicated power electronics for each phase, a major factor influencing the efficiency of the overall system is the switching frequency. In this paper a method is presented to optimize the system efficiency at every single operating point. It is calculating the optimum switching frequency online for each inverter and machine. The optimal system switching frequency is then derived for each operating point. On the basis of a conventional FOC, the switching frequency is then varied during operation, thus optimizing the overall efficiency. The analytical model to calculate the loss fraction of the system is shown in detail. The results are verified by FEM simulation and presented in efficiency maps. Measurements from the machine testbench are compared with the calculation and the quality of the analytical model is worked out. A method for changing the switching frequency during machine operation is described in detail and measurements of the changeover are presented. All measurements are performed on a multiphase PMSM machine, the ISCAD V50.