LAUSR

Abstract As a result of the global decarbonisation policy, the increased penetration of RES (Renewable Energy Sources) into the electrical power system is introducing some serious technical challenges, one of the most serious being to maintain voltage profiles within acceptable/allowable limits. The unpredictable generation of a considerable share of the renewable energy can result in voltage deviations that system-network operators are not able to control effectively. At the present stage of the technology, the power electronic converters that are applied for most of the RES are used as a kind of adapter that ensures optimal RES operation and transmits the active power to the grid. But each of these converters, together with an energy source (or sink), inherently also exhibits the characteristics of a FACTS device. As a result, there should be no hindrance to applying the theories for enhanced EPS (Electric Power System) stability limits, developed for FACTS devices, also for RES converters. Many of the problems that are caused in an EPS by the large share of RES could be solved by the RES itself, also at the system level, if properly controlled and IT connected to each other and to the system operator. In this context, the present paper reviews the impact of FACTS devices on the voltage stability with methods based on the calculation of PV curves. An analytical, in-depth approach can clearly demonstrate the theoretical feasibility of FACTS devices for voltage-stability enhancement. The paper presents such an approach for CSC, SSSC, SVC and STATCOM, based on an analytical calculation of the area between the PV curves and the voltage margins in a PV diagram. The basic contribution of the paper is a theoretical explanation of the suitability of various FACTS devices for maintaining an optimal voltage profile, taking into account any variation of a device parameter.