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									                                                                                              2012 Paris Session

http : //www.cigre.org
                       SC C6 Distribution Systems and Dispersed Generation
         Preferential PS1: Planning and operation of active distribution of active distribution
 networks including Dispersed generation (DG), storage and Demand Side Integration (DSI )


                 Implementation of a centralised voltage control experiment in presence of
                              Distributed Generation in ERDF’s MV network

                Sébastien Grenard               Cécile Brolly            Olivier Devaux           Olivier Carré
                  EDF R&D                         EDF R&D                 EDF R&D                    ERDF
                   France                          France                  France                    France

                                                 sebastien.grenard@edf.fr


            The penetration of distributed generation (DG) in the French electric system has widely increased in
            the last years, with PV panels and wind farms connections to the Medium and Low voltage networks,
            either on dedicated MV feeders or to the existing network (MV and LV feeders with a mix of both load
            and generation). In the latter case, the voltage profiles along feeders are impacted leading to voltage
            rise issues, mainly in rural networks dominated by long overhead lines with a low consumption level.
            To be able to face these impacts, ERDF (French Distribution Network Operator) envisages to
            implement a centralized voltage control function which adjusts the voltage profiles in real-time. As
            described in the paper, the experimentation of such control function in a zone of ERDF’s network is a
            first step before its deployment.

            The centralized control function requires a cost efficient instrumentation of the MV network which
            enables an assessment in near to real time of the voltage profiles along MV feeders. The accuracy of
            instrumentation is critical for the efficiency of the voltage control algorithms, while synchronization of
            the measurements retrieval is compulsory for the “near to real time” state estimation on which the
            voltage algorithms rely. The distribution network state estimation function and the voltage control
            functions will be implemented in the control center tools of ERDF.

            The voltage management approach determines a voltage control set point at the MV busbar of HV/MV
            substations in order to keep all voltages in the MV and LV networks within statutory limits: such
            control signal is sent from the SCADA system to HV/MV substation RTUs. This control can be
            considered as a secondary voltage control. On-load tap changers of HV/MV transformers will then
            keep the MV busbar voltage near this voltage reference: this local control can be considered as a
            primary voltage control.

            The central voltage management design is then discussed: its ability to deal with local voltage and
            flow control existing both at the HV/MV substation and at DGs, its coordination with the reactive
            power flow control at the interface between the DSO and the TSO, and its consistency with network
            planning and DG connection policies.

            This paper further describes the different control actions and their influence: control of the voltage set
            point at the HV/MV substation, the control of active and reactive power of DGs. Then, the different
            equipments’ requirements for the implementation of a centralized control function are discussed:
                 Sensor’s number and position in the network, sensors’ accuracy
                 RTUs’ functionalities
                 Communication requirements

            The interaction between the centralized control function and the different existing and foreseen local
            control functions are presented. Such possible interactions should be carefully studied during the
            design phase of the functions. Therefore, this paper will depict how the algorithms and the time



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constant of the functions should be tuned in order to avoid or minimize the impact of these possible
interactions.

Finally the paper illustrates how the function is planned to be integrated with the existing SCADA
system of ERDF distribution control centers. Such architecture must be flexible enough to enable other
functionalities to be integrated in the future.




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