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2013-06-13 - Colloque/Article dans les actes avec comité de lecture - Anglais - 4 page(s)

Bakhshideh Zad Bashir , Lobry Jacques , Vallée François , Durieux Olgan, "Improvement of On-Load Tap Changer Performance in Voltage Regulation of MV Distribution System with DG Units Using STATCOM" in 22nd International Conference & Exhibition on Electricity Distribution (CIRED 2013), Stockholm, Sweden, 2013

  • Codes CREF : Electricité courants forts (DI2400)
  • Unités de recherche UMONS : Génie électrique (F101), Physique générale (F901)
  • Instituts UMONS : Institut de Recherche en Energétique (Energie)

Abstract(s) :

(Anglais) The introduction of DG units into the distribution systems creates some new technical challenges for distribution system operators. Indeed, it increases system fault level, uncertainty of the system and also alters voltage regulation issue and power flow pattern of the system. In the conventional distribution feeder (without DG unit), voltage decreases towards the end of the feeder, as the impedance of line causes a voltage drop. With the presence of DG production, power flow direction can be inversed and we can deal with voltage rise problem. Therefore, if the integration of DG units has to be increased, designing a new voltage control method is necessary in order to guarantee safe system operation. In this paper, a new technique is proposed for the voltage regulation of a medium voltage (MV) distribution grid in presence of DG units. The proposed technique consists of two different control methods which are based on the joint action of on-load tap changer (OLTC) of transformer and reactive power compensation by STATCOM. Practically, controlling system voltage by use of OLTC is one of the most common ways for voltage regulation in MV systems. This method is easy to implement and design. OLTC which is generally installed on transformer of HV/MV substation changes the turn ratio of the transformer to maintain the voltage along the feeder within a defined range. However, OLTC can be limited for voltage regulation of long radial distribution feeders as it changes the sending point voltage of the feeder. Indeed, in a radial distribution system with DG units that are connected at the end of the line, the biggest voltage rise will occur at the DG connected point (at the end of the line) and in order to keep the voltage of DG connected bus within the defined range, OLTC must decrease noticeably the sending point voltage of feeder and this action can cause a serious voltage drop at the sending point. In this study, the drawback of using OLTC in a radial distribution feeder with DG generation at the end of the line will be solved using reactive power compensation at the DG connected bus. Reactive power compensation is one of the important methods for voltage regulation of the new distribution grids but it increases energy losses and decreases the network capacity. In this paper, the OLTC action is proposed as the main voltage control method and when it cannot manage the voltage of all buses effectively, reactive power compensation is used to return the voltage of DG connected bus inside the range that is acceptable for OLTC action. To make it more vivid, the reactive power compensation offered by STACOM only helps OLTC action to manage the extreme voltage violations whereas the normal voltage violations are solved by simple OLTC action. Therefore, the combination of these two control methods enables us to efficiently manage voltage problems of a radial MV distribution system (with DG generation at the end of the line) and as STATCOM is only used in extreme conditions, it does not considerably increase network losses. Evaluation of system losses in different test cases will be presented. Also, it must be noted that in Belgium, HV/MV transformers are operated by the TSO whereas MV grids are operated by the DSO. Therefore, involvement of both TSO and DSO is necessary in the implementation of the proposed voltage regulation technique.