High Bandwidth Current Control via Nonlinear Compensation and GaN-based VSI

Abstract

Nonlinearities in the voltage source inverter (VSI) such as dead time, switching time, delay time, voltage drops on the power switches, parasitic capacitances etc. are considered to be the main sources of the output voltage distortions. These distortions result in low order harmonics in the output current, which in turn increase core losses and create torque ripples. In particular, in the low speed and low torque applications the control performance and the stability of the system degrades substantially. Although as the switching frequency increases the effects of the dead time, the switching time and the delay time become more notable, to achieve a high current control bandwidth higher switching frequency is required. High performance VSI-fed motor drive can be realized both by reducing the effects of the VSI nonlinearities and by having a high current control bandwidth. In this work, GaN transistor based VSI-fed permanent magnet synchronous motor (PMSM) drive is used to achieve a high current control bandwidth. Since the current loop is the inner most loop of the control loop, it enables the outer speed and position loops to be faster. This high performance servo motor drive can be used in applications such as control of pedestals, robot arms, optic stabilizers, CNC machines, active vibration cancellers etc. that require high control bandwidths.