Modified Gradient Descent Algorithm Based Maximum Torque Per Ampere Control of PMSMs

In this paper, a modified gradient descent algorithm based MTPA (Maximum Torque Per Ampere) control scheme to improve the driving efficiency of a permanent magnet synchronous motor is proposed. The modified gradient descent algorithm tracks the optimal current angle for MTPA control by using a newly defined gradient based on a change rate of copper losses. Since a magnitude of stator current is only required to track the optimal current angle for MTPA control, the proposed method is not dependent on motor parameters such as stator inductances and permanent magnet flux linkage. By using the proposed method, it is possible to track the optimal current angle that minimizes the copper losses for all load conditions in a short time, even with the motor parameters error or an offset in measured rotor position. The validity of the proposed method is verified by simulations using Matlab/Simulink for 210kW and 1.5kW IPMSMs (Interior Permanent Magnet Synchronous Motors) and experiments with a 1.5kW IPMSM.