A fast and accurate numerical method for optimal torque control of interior permanent magnet synchronous motors

Abstract

In this study, a fast and accurate optimal torque control scheme for interior permanent magnet synchronous motors (IPMSMs) is presented, which enables computing the optimal current references for maximum torque per ampere (MTPA) and flux weakening (FW) operations. Instead of analytically solving the optimal torque control problem that involves computationally expensive quartic equations, a numerical optimization technique is introduced to simplify the problem and solve it in iterations with reduced computation burden. Under the reasonable assumption of a slowly varying torque reference, linearizing the IPMSM torque equation helps to derive the solutions for the MTPA and FW operations in simpler forms. Unlike conventional numerical methods, convergence to the exact solution is ensured. A simulation using a 7.5-kW IPMSM model in MATLAB verifies the effectiveness of the proposed method by comparing it with the conventional methods in terms of solution accuracy and computational efficiency.