In recent years

voltage fluctuations and flicker have received much attention by both utilitiesand consumers. Correct positioning of flicker interference source is the basic premise in improving and con-trolling flicker and coordinating disputes between power supply and consumption. This paper is based onthe dynamic signal treatment of non-stationary voltage flicker based on S-transform（ST）so to achieve de-tection of voltage flicker modulation amplitude and frequency at PPC

analyze and calculate dynamic pha-sor of voltage and current and

on this basis

give the equivalent model of flicker source location and its dy-namic parameter estimation. Finally

the location result of voltage flicker source is given out quantitativelythrough the relation analysis among upstream system parameters

load current variation at downstream andvoltage variation.It is shown by the example that the method can achieve correct location of voltage flickersource in the complex distribution grid and can be used the monitoring system of power quality.