A Multi-Functional Integrated Converter for Dynamic Voltage Restoration and Reactive Power Compensation in Active Distribution Networks

Conventionally, parallel-connected or series-connected power quality control devices cannot compensate for both the voltage fluctuation and reactive power simultaneously. To improve the equipment utilization and reliability of the existing power quality control devices, a multi-functional integrated converter (MFIC) is proposed, which can effectively integrate the functions of both dynamic voltage restoration and reactive power compensation. When the grid voltage sags or swells, the MFIC works in the series access mode to achieve voltage regulation function. When the grid voltage is normal, the MFIC works in the parallel access mode to achieve unity power factor operation at the grid side. Compared with the traditional series-connected power quality control device, the MFIC only has one more coupling capacitor, markedly improving the utilization factor of equipment. In addition, the port voltage of the converter module in MFIC is clamped to zero when a short circuit or grounding fault occurs. Meanwhile, a large equivalent impedance is formed to effectively limit the line fault current, which improves the reliability of the MFIC itself and its connected grid as well. Furthermore, the effectiveness and feasibility of the proposed topology and strategy are verified by simulation and experimental results.