A NOVEL DUAL-DC-PORT DYNAMIC VOLTAGE RESTORER WITH REDUCED-RATING INTEGRATED DC-DCCONVERTER FOR WIDE-RANGE VOLTAGE SAG COMPENSATION

Abstract

A novel dual-DC-port dynamic voltage restorer (DDP-DVR) is proposed. One low-voltage (LV) DC port is directly connected to the energy storage, while the other high-voltage (HV) DC port is connected to the intermediate DC bus. An integrated DC-DC converter is interfaced with these two DC ports which is aiming at providing a high DC-link voltage and maintaining the voltage injection capability even if the energy storage voltage is lower than the peak value of the injected AC line voltage. Compared with the traditional DVR that uses the DC-DC converter for all voltage sag compensation, the proposed DDP-DVR can compensate shallow voltage sags without using the DC-DC converter, and for deep voltage sags, only partial active power needs to be processed by the DC-DC converter. Therefore, the power rating of the DC-DC converter can be reduced significantly. Meanwhile, much lower power losses can be achieved by the proposed DDP-DVR due to reduced power conversion stages.

Existing System

In the existing system, DVR with energy storage and constant DC-link voltage is used.

Proposed System

The major contribution of this proposed system is to propose a novel dual-DC-port DVR (DDP-DVR). A bidirectional DC-DC converter is employed in this project because the power flow is bidirectional, and the DDP-DVR can be used for both voltage sag compensation and voltage swell compensation. The DDP converter is derived from a three-phase six-switch converter, where the direct power flow path is realized by introducing a bidirectional switch. In the case of shallow voltage sags, the integrated DC-DC converter is idle, and in the case of deep voltage sags, only partial active power is processed by the DC-DC converter. Hence, the power rating of the DC-DC converter can be reduced significantly. Meanwhile, other advantages, e.g., much lower power losses and higher efficiency, are also achieved by the proposed DDP-DVR. The modulation strategy for the DDP converter is provided considering two operation modes, and the characteristics of the DDP-DVR are analyzed in detail.

Architecture

Topology of the proposed DDP-DVR