New Steady State Current Error Limiters for PMSM Drives

In permanent magnet synchronous motor drives, d-q current errors are examined using hysteresis controllers. The inverter is switched based on the hysteresis controller responses, to limit current errors, and thereby reducing current ripple. But, due to the faster current dynamic characteristics, switching the current errors within the hysteresis band becomes difficult. This results in d-q current ripples and harmonics. In this paper, two current error-limiting schemes are proposed. In the first scheme, current errors are switched within the band using additional control parameters (dynamic response of q-axis current), to select the control space vector from a switching table. Whereas in the second scheme, a duty ratio regulator is designed to achieve minimum q-axis current error. The proposed works are simulated in MATLAB/Simulink and verified through experimentation. Since the current ripple and harmonics are also reduced, the thermal impact of these performance pa-rameters on the power inverter is also studied.