Increase of Transient Stability Level of Gas Turbine Power Plant Using FACTS

The article is devoted to the development of the mathematical models of modern devices of flexible alternating current transmission systems (FACTS) when calculating the modes and stability of power systems and to the analysis of influence of the specified devices on transient stability of the generators. The considered scheme contains the generators with the gas turbine drive that have electromechanical parameters providing lower level of transient stability compared to units of higher power rating, which in some cases requires implementation of measures for transient stability enhancement. As examples of FACTS the following devices have been considered: compensating device based on voltage- sourced converter (STATCOM), static synchronous series compensator (SSSC) and the unified power flow controller (UPFC). The known examples of mathematical models of FACTS devices vary in complexity. For a preliminary assessment of the effectiveness of the FACTS devices, it is proposed to use simplified models that adequately reflect their impact on transients. The use of models made it possible to establish a positive impact of the devices on transient stability of generating equipment in case of short circuits in the electric network. The important conclusion here is that the use of the UPFC device based on two converters (with a corresponding increase in cost) compared to one converter device (STATCOM or SSSC) slightly increases the level of transient stability and the limit time of short circuit disconnection. The proposed method of simulating the FACTS devices is suitable for numerical calculations of transient processes in electric power systems, in particular, to estimate the impact on the transient stability level of the parallel operation of power plants in case of disturbances. © The Authors, published by EDP Sciences, 2019