Series–Shunt Multiport Soft Normally Open Points

Abstract

Soft normally open point (SNOP) is an emerging solution for distributed networks (DNs) to address voltage violation and feeder congestion caused by the increasing integration of distributed energy resources and new types of loads. Based on power electronics, SNOPs can substitute traditional tie switches for power flow regulation, voltage adjustment, and power quality improvement, enhancing the DNs’ controllability and flexibility. Existing SNOPs found in demonstration projects and the literature are generally based on the back-to-back voltage-source converter (VSC). Because it requires more full-power-rating VSCs as the number of connected feeders increases, this solution is uneconomical in multifeeder flexible interconnection scenarios due to the high device cost and volume. Alternatively, this article proposes a series–shunt multiport SNOP (S <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -MSNOP) based on a cascaded H-bridge structure and series–shunt arrangement. The proposed topology can easily extend its ports by increasing the number of submodules with small power ratings, reducing the device cost and volume. The operation principles and control strategies of the S <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -MSNOP are elaborated. Verifications on both a 1-MVA simulation model and a 3.3-kVA scaled-down experimental platform prove the feasibility and effectiveness of the S <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -MSNOP.