A Study of MTPA Applied to Sensorless Control of the Synchronous Reluctance Machine (SynRM)

The present paper proposes a new Maximum Torque Per Ampere (MTPA) algorithm applied to sensorless speed control for the Synchronous Reluctance Machine (SynRM). The SynRM mathematical model is suitably modified and expressed in the γδ estimated reference frame, which could be applied in sensorless implementations. In the controller–observer scheme, an MTPA controller is coupled with a sliding mode observer (SMO) of first order. The provided equivalent control inputs are directly utilized by a modified EMF observer to estimate the rotor speed and position. Also, the MTPA control, SMO, and modified EMF observer are accordingly expressed in the γδ reference frame. In the duration of the SynRM operation, the developed MTPA algorithm succeeds in adjusting both stator current components in the γ-axis and δ-axis to the maximum torque point, while the SMO converges rapidly, achieving the coincidence between the γδ and dq reference frames. In addition, a simple torque decoupling technique is used to determine the γ-axis and δ-axis reference currents connected with the Anti-Windup Controller (AWC) for stator current control. Despite conventional MTPA methods, the proposed MTPA control strategy is designed to be robust in a wide speed range, exhibiting a high dynamic performance, regardless of the presence of external torque disturbances, reference speed variation, and even current measurement noise. The performance of the overall observer–control system is examined and evaluated using MATLAB/Simulink and considering noisy current feedback. Simulation results demonstrate the robustness and effectiveness of the proposed MTPA-based control method.