Impact of load transients on dynamic voltage restorers

The dynamic voltage restorer (DVR) is a promising and effective device for power quality enhancement due to its quick response and high reliability. Associated with the restorer is its energy-saving compensation control method which is considered to be attractive. It necessitates the injected voltage to effect a phase angle adjustment in the load-side voltage so as to maximize the use of the stored energy in the DVR. The effect of voltage phase shift on the loads is examined in this paper. The results show that both the static load and the induction motor load will exhibit drastic dynamic responses under this kind of phase shift, and analytical expressions indicate that load transient current responses are dependent of the magnitude of voltage phase shift and load parameters. The research work is an attempt to obtain qualitative measures of the interactions between the DVR and loads.