Research on a New Type of “APF+DVR” UPQC

Due to the coupling between serial and parallel sections of the traditional UPQC, it is relatively hard to control and also difficult to deal with the problem of large voltage sag. This paper presents a new type of “APF + DVR” UPQC, which can overcome the mentioned shortcomings of the traditional UPQC. The new UPQC topology consists of two independent parallel voltage source converters, which realize APF and DVR respectively. Switching logic for APF and DVR sections is proposed in this paper. For DVR control, a subsection control method based on DVR DC side voltage is proposed. And the calculation method of DVR DC side capacitor capacity is given. The results of simulation show that the new UPQC can realize the hardware decoupling and independent control of the series parallel side, with low static loss, fast response speed, and is not affected by voltage sag level, which can effectively solve the problem of large voltage sag.