Online Control of IPMSM Drives for Traction Applications Considering Machine Parameter and Inverter Nonlinearities

In this paper, an online control method of interior permanent magnet synchronous machine (IPMSM) drives for traction applications considering machine parameter and inverter nonlinearities is presented. It is shown that the conventional technique using parameter information instantly extracted from premeasured parameter look-up tables (LUTs) only determines the local maximum torque per ampere (MTPA) operating point associated with this specific parameter information without evaluating the global MTPA achievement. Therefore, global MTPA operation may not be achieved for conventional online control IPMSM drives with extreme nonlinear machine parameters (e.g., short-period overload operations). Thus, a model-based correction method using stator flux adjustment is proposed for an online quasiglobal MTPA achievement. It is also proven that in the flux-weakening (FW) region, due to the inverter nonlinearities, a lower than expected maximum achievable torque for a demanded speed and a higher than expected current magnitude for a demanded torque may be obtained. Hence, an inverter nonlinearity compensation (INC) method exploiting the voltage feedback (FB) loop is introduced and its advantages over the conventional INC scheme are demonstrated. The proposed online control method is validated via measurements on a 10-kW IPMSM.