Dynamic Equivalents of Active Distribution Networks Based on Active Synthesis Load Units

The traditional Active Distribution Network (ADN) equivalence method focuses on the characteristics of individual units while disregarding the distinctions from one unit to another. The low accuracy of the typical equivalent model for ADN under large disturbances affects the results of grid stability analysis. This paper proposes a novel dynamic equivalence method for ADNs based on Active Synthesis Load Units (ASLUs), providing a crucial tool for effectively analyzing the response characteristics of ADNs with a high penetration of Inverter-based Distributed Generations (IBDGs). Comprising loads and IBDGs, ASLUs serve as the fundamental units facilitating bidirectional power flow in ADNs. The transient characteristics of ASLUs and the impact of inter-unit differences on the dynamic characteristics of ADNs are analyzed. After studying the indexes that describe the dynamic characteristics of ASLUs, a Dynamic AGglomerative NESting (DAGNES) clustering algorithm is proposed based on the analysis results. Then, the algorithm is applied to group ASLUs based on their dynamic characteristics. Finally, the dynamic equivalent model of the ADN is derived by aggregating parameters from the same group of ASLUs and applying them into the proposed ADN model structure. The simulation results demonstrate that the proposed model accurately reflects the transient characteristics of the ADN under large disturbances.

I. Introduction

The advantages of photovoltaic and wind power, along with the support of government policies, have significantly contributed to the widespread installation of Inverter-based Distributed Generations (IBDGs), mainly Distributed Photovoltaics (DPVs) and Distributed Wind Turbines (DWTs), in rural and industrial areas. The transition from conventional radial distribution networks to Active Distribution Networks (ADNs) with multiple power sources has been motivated by the variability in power flow and voltage distribution [1]. IBDGs, which differ from traditional power loads in terms of dynamic characteristics, have caused notable changes on the demand side of the power system. These changes have significantly impacted the dynamic characteristics and stability of the power system [2], [3].