Unified load flow calculation for flexible interconnected AC-MTDC distribution system considering control strategy switching with high penetration of DGs. (October 2021)

• Record Type: Journal Article
• Authors: Wang, Shouxiang; Jiang, Xingyue; Zhao, Qianyu; Liu, Qi; Lin, Zhuoran; Zhao, Ge
• Is Part Of: International journal of electrical power & energy systems. Volume 131(2021)
• Publication Date: 2021-10
• Subjects: AC-MTDC distribution systems -- Load flow algorithm -- Newton-Raphson (NR) method -- Voltage-sourced converter (VSC); Electrical engineering -- Periodicals; Electric power systems -- Periodicals; Électrotechnique -- Périodiques; Réseaux électriques (Énergie) -- Périodiques; Electric power systems; Electrical engineering; Periodicals; 621.3
• DOI: 10.1016/j.ijepes.2021.107130
• Languages: English
• ISSNs: 0142-0615

Abstract

Highlights: A general load flow model is developed for AC-MTDC distribution systems. Various VSC control strategies and MTDC control strategy switching are considered. A few modifications are required for AC power flow to incorporate the MTDC model. The unified algorithm has higher computational efficiency and easy to converge. It is valid for AC-MTDC systems with arbitrary topologies and various connections. Abstract: A new unified algorithm is proposed in this paper to solve the power flow problem of AC distribution systems incorporating voltage-sourced converter (VSC) based multi-terminal direct current (MTDC) grids. In this method, the VSC modulation indices, mode changes, power losses as well as MTDC control strategy switching are all considered. Active power mismatch equations of VSC boundary buses in AC side have been modified to eliminate VSC power injection items. Various VSC control strategies are demonstrated in both active power function of DC boundary buses and reactive power function of AC boundary buses. In this way, only few modifications are required for existing AC load flow to incorporate the MTDC models. Moreover, the change of VSC operation mode and the switch of MTDC control strategies can be easily realized. The power flow calculation of AC and DC subgrids is solved simultaneously by Newton-Raphson (NR) method using a modified Jacobian matrix. Two case studies have been presented to demonstrate that the proposed algorithm is fast, flexible and effective in solving power flow of AC-MTDC distribution systems with various control strategies and can easily accommodate any changes in VSC control modes with high convergence performance.