Rating and design issues of DVR injection transformer

The load side voltage disturbances can be effectively mitigated by connecting a series compensating device called dynamic voltage restorer (DVR). Generally, DVR is realized by a voltage source inverter with dc storage device and a series injection transformer. Rating and design issues of an injection transformer are of much concern for the proper operation of the DVR. Voltage underrating of the transformer may lead to its saturation whereas overrating increases the cost and size of the DVR. The voltage applied to the primary winding of the transformer is a combination of several components of different frequencies. In view of above, rating and design issues are presented in this paper. A novel method is proposed to find the voltage rating of the transformer as a function of the fundamental frequency. Furthermore, to reduce the effects of current harmonics in the transformer, A-factor is used. A PSCAD model is used to validate the efficacy of the proposed design method to find the voltage rating, and overall performance of the DVR. The experimental studies confirm the proposed method.