Accurate MTPA Control Based on Ferrari Method for IPMSM With Partial Derivative Term Calculation

The traditional Maximum Torque Per Ampere (MTPA) strategy based on the Ferrari method neglects the partial derivatives of inductance with respect to current during the modeling process. Even with precise motor parameters, this approach fails to achieve an accurate MTPA operating point at high current amplitudes, resulting in degraded control performance. To address this limitation, this paper presents an improved MTPA mathematical model that incorporates the effect of the partial derivatives of inductance with respect to current. The analysis identifies the tracking error caused by the omission of these derivatives in the Ferrari-based MTPA strategy and establishes a relationship between this error and the current amplitude. Using an inductance lookup table, a method to calculate the partial derivatives is proposed to compensate for the induced error. Furthermore, an enhanced MTPA control strategy is introduced that integrates these partial derivatives into the Ferrari method. Finally, experimental validation confirms the feasibility of the proposed approach, with results demonstrating its superiority in terms of MTPA tracking accuracy, torque output capability, and motor efficiency.