Improving Dynamic Response for Variable-Speed Drive System using Four-Quadrant Chopper in Dc-Link

This research improves variable speed drive systems VSDS stability in modern industrial distribution grids by using the four-quadrant chopper in dc-link. The transfer function of the variable speed drive systems VSDS, from the output of the three-phase diode bridge rectifier to the dc-link, is found before and after using proposed chopper. Drawing Bode diagram in parallel with determining the value of both gain margin and phase margin before and after adding the four-quadrant chopper were introduced to evaluate of the proposed chopper and its effect on the stability conditions for the VSDs. System performance was tested at the input of unit-step and impulse-step inputs before and after adding the four-quadrant chopper. In addition, the frequency response characteristics in both cases were found to determine its effect on the dynamic and transient stability of the system.