Study Of Test Method On Sensitivity Of AC Adjustable Speed Drives To Voltage Sags

The study of tolerance of sensitive devices to voltage sags is an important basis for the analysis of the severity of voltage sag and the mitigation measures.First of all,mechanism analysis of voltage sag on adjustable speed drives is analyzed.With the energy conservation relations ?dynamic equations of DC circuit and dynamic equations of asynchronous drive,mechanism analysis of devices' interface influence factor(i.e.protection threshold,control strategy)load factor(load characteristics)and voltage sag characteristic index(i.e.voltage sag types,voltage magnitude before/after voltage sag,shape of voltage sag)on ASD are carried out.On the basis of mechanism analysis,in order to improve and standardize the voltage sag sensitivity test of ASD,a set of complete and systematic test methods are proposed according to the characteristics of ASD.Test scheme is then established.The test method mainly including test items,test platform and test procedures.Based on the test scheme and the equipment and conditions of the laboratory,the voltage sag sensitivity of ASD is experimentally studied.The main influence factors include DC under-voltage protection,overcurrent protection,torque,speed,voltage sag types,point-on-wave of sag initiation,phase-angle jump,harmonics,voltage magnitude before and after the sag,multiple voltage sags,and so on.The voltage sag sensitivity curves under different conditions are obtained by analyzing the recorded test data,which proved the correctness of the mechanism analysis and the validity of the test method.In order to accurately characterize the uncertainties of voltage sag sensitivity,the general sensitivity curves of frequency control system are obtained based on the analysis of the 10716 sets of test data.Furthermore,probability model of uncertainty area is established.