Impacts of Voltage phase shift on motor loads and series custom power devices including converter thermal effects

The effects of voltage phase shift, introduced during the voltage restoration process of a series custom power device, are examined. It is shown that the internal back electromotive force of an induction motor load and the onset of the voltage phase change can lead to possible large transient currents in the motor stator and in the custom power device. The consequence is increased losses in the switching elements of the device. A numerical method is proposed for which the transient currents and the associated losses are determined. The derived thermal model then permits an assessment to be made on the resulting temperature rise within the custom power device.