Abstract: Abstract:The universal frequency convertors, in which the phaseshift sine pulsewidth modulation was used as control algorithm, have disadvantages of the slower dynamic response, the poor lowfrequency performance and the current overshoot when the frequency increasing or decreasing under heavy load. The stator resistance voltage drop compensation and the slip compensation were introduced into cascade constant voltagefrequency ratio control, and the dynamic response speed and the lowfrequency performance of the system were improved. The field operation result shows that the method has obvious effect for restraining the current overshoot.

Key words: Keywords:universal frequency convertor, current overshoot, constant voltagefrequency ratio control (V/F), dynamic response