Multi‐agent based intelligent frequency control in multi‐terminal dc grid‐based hybrid ac/dc networks

Abstract

This paper proposes a novel control scheme for frequency support in MTDC grid-based hybrid ac/dc networks. This control is based on the multi-agent system (MAS) paradigm with an adaptive frequency droop control, and is distributed in all grid-tied converters. The objective of this control is to enable the ac grids to intelligently decide on their participation on frequency support, considering their power reserves, demand, and relevant technical constraints and requirements. The main achievement of the proposed control is to minimize the rate of change of frequency (RoCoF) and frequency undershoot (f nadir), and also providing a systematic enhancement in frequency stability, particularly in the disturbed and weak ac grids. A stability analysis is performed for the proposed control, using vector Lyapunov method for interconnected systems, deriving the conditions for stable operation. Test scenarios are conducted on a modified 7-terminal C IGRE g rid, c onnecting fi ve ac gr ids. Re sults un der di fferent scenarios show the performance and robustness of the proposed control in providing significant enhancement in frequency regulation for the connected ac grids. Nomenclature Symbol Description f nom,i Nominal frequency of ac grid i ∆f i Frequency deviation from f nom,i ∆f max,i Maximum instantaneous ∆f i P gen,i Synchronous generation in ac grid i P mtdc,i Wind power delivered to ac grid i P dem,i Power demand in ac grid i P crit,i Critical power demand for ac grid i f H (P dem,i) Probability density function of power demand in ac grid i at hour of day H a i Agent representing ac grid i G Graph for multi-agent ecosystem N i Set of immediate neighbors of a i R i Set of requesting agents to a i V Set of agents in MTDC grid P req,ij Power request from a i to a j P supp,ji Power support from a j to a i (as a reply to the request P req,ij

DC Soft Open Points for Resilient and Reconfigurable DC Distribution Networks

“…Still, there have been several propositions for the use of agent-based systems. One of these concerns hybrid medium-voltage AC/DC networks, where the agents are used to support the frequency of the AC system and allow the interconnection of weak and strong grids [47]. Hybrid AC/DC systems with energy storage have also been considered, where a multi-agent system implements an event-driven microgrid control management methodology [48].…”

A distribution network traveling wave localization method based on CEEMD-DEO3S

“…Due to the common problems of poor noise robustness and difficulty in achieving precise positioning of multi-terminal lines in current fault location methods for distribution networks, with China's vigorous promotion of the construction of smart grids, it is urgent to further improve the accuracy and reliability of fault location and achieve intelligent and rapid accurate positioning [1][2].…”

Research on stability margin enhancement for low‐voltage multi‐terminal DC system based on additional damping control

“…On the other hand, the flexible access of distributed generation (DG), such as photovoltaic and wind power based on DC integration, has become a new development trend [5,6]. The application requirement of both suppliers and demanders further promotes the rapid development and demonstration of low-voltage DC power distribution and multiterminal DC (MTDC) system [7][8][9]. Generally, the formation of the multi-terminal flexible structure by using the DC network to achieve the interconnection of multiple AC systems can fundamentally change the original structure of traditional power grid, so that the MTDC system has a flexible, controllable and diversified feasible topology and good network connectivity.…”

“…So it brings the possibility of flexible power flow control, power fluctuation sharing, and enhancing the overall controllability, which can enhance the mutual support ability and power supply capacity of the multiple AC systems in a larger space and time range. Therefore, the MTDC system will become an important form of power distribution in the future [8,9]. A future renewable-electric energy-delivery and management system with a 400 V DC grid and a 120 V AC grid, is proposed by the University of North Carolina [10].…”