Investigation on the Effect of Dead Time on the Phase of Fundamental Voltage in VSI-PMSM Drive System

Abstract

Both electric vehicle PMSM drive system and grid connected photovoltaic (PV) power generation need voltage source inverter (VSI). The dead time should be set properly when the power switches are turned on and off in the same bridge arm of VSI. During the dead time, the load is out of control, which will cause the abnormal output voltage amplitude and phase. However the influence of dead time on the output fundamental voltage phase has not been paid much attention to and studied. Firstly, in the paper, the phase shift of output fundamental voltage caused by dead time is simulated and analyzed for three-phase VSI - resistance inductance series (RL) load system under several conditions such as variable switching frequency, modulation index, output fundamental frequency and dead time. Secondly, take three-phase VSI - permanent magnet synchronous motor (PMSM) drive system for instance, the simulation analysis of output fundamental voltage phase shift and rotor positioning error caused by dead time are also performed, and an off-line method to compensate the fundamental voltage phase based on αβ coordinate is given. The above work provides a reference for further understanding the influence of dead time on fundamental voltage phase shift in VSI, so as to improve the monitoring and control precision of electric vehicle drive system. The analysis approach can be applicable to the grid connected photovoltaic (PV) power generation PMSM servo system.