CEZ Distribuce is the biggest Distribution System Operator (DSO) in the Czech Republic and the leader of one of the 5 demonstrators of the InterFlex project. In cooperation with the DER owner (CEZ Obnovitelne zdroje s.r.o.), CEZ Distribuce has launched the demonstration of voltage regulation systems at the small hydro plant Hracholusky with 3,1 MW of installed capacity.

Small hydro ”Hracholusky” is connected to the medium voltage distribution network. The solution aims to reduce voltage fluctuations caused by the small hydro plant in medium voltage distribution networks in the selected area by targeted regulation of its reactive power (“volt-var control”) thus allowing a significant increase of the DER hosting capacity.

Required voltage set points are sent by the Distribution Management System (DMS) through a GPRS/LTE communication path to the DER control system. The targeted regulation of reactive power on the DER side is based on the difference between the required voltage set point and the instantaneously measured voltage at the point of grid connection. The voltage regulation system is in regular operation today and its performance will be evaluated in detail in the upcoming months.

Based on the results, CEZ Distribuce already proposed and standardized an update of the actual DER hosting capacity evaluation process to allow connection of more DERs to the medium voltage distribution networks (if DERs are equipped with volt-var control system).