Switching frequency determination of a bidirectional AC–DC converter to improve both power factor and efficiency

This paper investigates the possibility to optimize both the efficiency and the power factor of energy conversion systems which include power electronic converters. The values of these important power quantities depend on different parameters, such as the switching technique and the switching frequency of the power electronic elements. Comparing the already known and used switching techniques with each other we can conclude that the sPWM method offers the highest values of the efficiency and the power factor simultaneously. However, when using this technique the basic current harmonic lags as to the voltage in case of ohmic inductive loads resulting in the decrease in the power factor. In the present work a new sPWM switching technique is suggested in order to achieve higher power factor and efficiency compared to the traditional sPWM method. The aforementioned switching technique is a modified sPWM method based on an appropriate shifting of the input current to the grid voltage. But, the following question is raised: Is there a switching frequency value in a given converter topology by which both the efficiency and the power factor gain optimal value? Thus, the main aim of the present paper is determine this specific switching frequency value. This is achieved by using a simple method based on a criterion suggested in this work. In order to demonstrate how this specific frequency value can be found, a bidirectional AC–DC converter composed of a single phase bridge and two switching elements at the DC side is used. This proposed converter topology excels in that the total number of the switching elements is minimal. The study of this subject is carried out through Matlab/Simulink simulation and experimentation.

► α-sPWM technique to improve power factor. ► Switching frequency determination method for optimizing power factor and efficiency. ► AC–DC bidirectional converter.