Comparison of the Effects of Nonlinearities for Si MOSFET and GaN E-HEMT Based VSIs

Abstract

Nonlinearities in voltage source inverters (VSIs) such as; dead time, switching time, delay time, voltage drops on the power switches, parasitic capacitance, 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, for low-speed applications with low-inductance motors, the control performance and the stability of the system degrades substantially, especially when the system operates in the low-torque region. In this work, the effects of these nonlinearities on the phase current and on the current control of the silicon (Si) metal oxide semiconductor field effect transistor (MOSFET) based VSI are investigated with an air cored low inductance permanent magnet synchronous motor. Furthermore, Gallium nitride (GaN) enhancement mode high electron mobility transistor (E-HEMT) based VSI is proposed to overcome this problem. Next, improvements in the current control process are demonstrated by comparing the experimental results obtained by using GaN E-HEMT and Si MOSFET based VSIs. Results show that GaN E-HEMT based VSI is a better choice for applications, which require a high bandwidth control.