A review of voltage control strategies in active distribution networks Mudaser Rahman Dar Department of Electronics and Electrical Engineering Indian Institute of Technology Guwahati Assam, India m.dar@iitg.ac.in Sanjib Ganguly Department of Electronics and Electrical Engineering Indian Institute of Technology Guwahati Assam, India sganguly@iitg.ac.in Abstract—With immensely large penetration of renewable en- ergy sources (RES) and electric vehicles (EVs) in active distribu- tion networks (ADNs), the voltage control within nominal range forms one of the crucial technical challenges for distribution system operator (DSO). Considering the voltage control issues with present ADNs, this paper presents the discussion over voltage control, various control devices and their characteristics. To know the current research directions recent control strategies employed in ADNs, their classification and the comparative analysis of various control strategies are presented. Index Terms—active distribution network (ADN), renewable energy sources (RES), distributed energy resources (DERs), coordinated voltage control (CVC), electric vehicles (EVs). I. I NTRODUCTION Electric distribution systems have been continuously evolv- ing with the integration of distributed generation (DG) among which renewable energy sources form a main component. The significant DG integration mostly distributed photovoltaic (PV) systems bring about structural changes in the network. The conventional passive distribution network has turned into a dynamic ADN with controllable resources [1]. The generation uncertainties in temporal distribution further brings about operational changes resulting in sharp variation in voltage and feeder power. DERs provide a promising way to meet the soaring energy demand and secure, economical, and reliable supply considering their participation in ADN management, along-with solutions to the environmental degradation [2]. The large and persistent integration of DERs particularly rooftop PVs and residential charging electric vehicles (EVs), in recent years has inflicted numerous issues and challenges over ADN operation [3]. These mainly lead to over/under voltages, stochastically varying energy demand and reverse power flow. It further drives the distribution network (DN) to unforeseen incidents and insecure situations. This can lead to insecure operation and protection of the distribution network, violation of equipment thermal limits and change in fault current level [4]. Thus, the evolved ADN endorses the integration of control technologies and communication setup to manage the distribution system. The intermittent generation from renewable energy resources causes violation of node voltages, mainly voltage rise. Further, this adds to the deterioration of conventional discrete and slow acting device like on-load tap changer (OLTC), thus limiting the use of traditional methods for voltage control [4]. The network nodes can have under voltage if the load or electric vehicle charging station (EVCS) is connected. This kind of situation leads to improper operation of OLTC and excessive wear and tear. The voltage profile is badly aggravated in situations where the over-voltages and under-voltages occur simultaneously in the network. The large-scale integration of EVCSs impose additional stochastic demand on the grid bringing about frequent under- voltages and further leads to the augmentation of stochastic nature of ADN. The existing DN lacks the infrastructure for such wide integration and topological changes [2]. Considering all the said issues, the active network management (ANM) employing control and communication becomes necessary to coordinate other resources, which are potentially effective in ADN optimal operation and voltage regulation. By ANM fast volt/var control (VVC) is achieved, and wear and tear of OLTC is reduced. Thus, the utility needs to take the responsibility to regulate the voltage deviations especially the over voltages and minimize losses. With the significant advancements in information and communication technology and extensive research in power electronics, the various issues of DER integration and EV penetration can be mitigated to a promising level. Apart from compensating in increasing power demand they can be operated as fast acting control devices to mitigate voltage issues to a promising level [5]. This paper reviews the VVC in recent studies and their comparative aspects. A brief description of Voltage control problem and its mitigation is discussed in Section II. The various control devices used for voltage control are discussed in section III along with their characteristics. Section IV discusses various control strategies used in ADNs and their comparative analysis is provided. Considering the need for online voltage control section V discusses real-time control approach in ADNs followed by conclusion in section VI. II. DISTRIBUTION SYSTEM VOLTAGE CONTROL: PROBLEM AND ITS MITIGATION Distribution system voltage control mainly deals with dimensions like power quality, stability, and the efficiency of the power distribution system. Integration of DG units and EVs affect the voltage profile of the distribution network (DN) ISBN: 978-1-6654-6242-6 Part number: CFP22O01-ART 145 2022 IEEE Calcutta Conference (CALCON) | 978-1-6654-6242-6/22/$31.00 ©2022 IEEE | DOI: 10.1109/CALCON56258.2022.10060319 Authorized licensed use limited to: INDIAN INSTITUTE OF TECHNOLOGY GUWAHATI. Downloaded on April 25,2023 at 21:29:08 UTC from IEEE Xplore. Restrictions apply.