۱- Introduction

۲- Concept of FDN

۳- Model of dispatchable region of FDN

۴- Observation of dispatchable region of FDN

۵- Case study

۶- Conclusions

References

Abstract

Soft open points (SOPs), defined as the power electronic devices installed to replace normally open points in distribution network, can improve the flexibility of power control and thus further enhance the reliability and economy of power grids. Flexible distribution network (FDN) is a system-level concept to describe the distribution network equipped with multiple SOPs. Region method is to describe the secure range of the system operating in a geometric view. This paper adopts the region method to observe FDN for the first time. Firstly, the model of dispatchable region of FDN is proposed. The constraints of region space are formulated, considering SOPs, power flow, thermal capacity and voltage profile. Secondly, a simulation-based observation approach is also proposed to obtain the region projections on 2D and 3D sub-space. To illustrate the approach clearly, 2 small cases are given preceding a 7-feeders IEEE RBTS case. The region projections of case grids are observed and their topological characteristics are compared with those of traditional distribution network (TDN). The results indicate that FDN has advantages over traditional distribution network in operation security. For example, the region projections of FDN on 2-dimensional sub-space are about 2–۴ times larger than those of TDN with the same network topology. The dispatchable region can be further developed into a useful tool for the secure and high-efficient operation of FDN in the future.

Motivation

Advanced power electronic technology is playing an increasingly important role in distribution network [1]. Soft open points (SOPs) refer to the flexible switches in distribution networks usually using back-to-back voltage source converters. SOPs are installed at a previously normally open points (NOPs) of distribution network [2]. SOP is able to provide the dynamic and continuous active/reactive power flow controllability and limit the short current [2]. Some pilot projects have demonstrated that SOP is beneficial to distribution network in many aspects, such as optimal power flow, load balancing, voltage regulation, power supply restoration, accommodation of distributed generation (DG), and so forth, which indicates its potential in the future distribution network [3,4]. In [5], a system-level concept, flexible distribution network (FDN), was proposed. FDN is defined as the distribution network with flexible power flow controllability using multi-terminal SOPs (including two-terminal SOPs). This concept is applied in this paper. Security is the main objective of FDN operation.