Strong Excitation Control and Stabilization of Operating Modes in a Multi-Machine Power System

In the previously published articles “Features of strong excitation control of synchronous generators in a complex power system” (Élektricheskie Stantsii, 2019, No. 7) and “Improving power system stabilization in response to grid disturbances” (Électrichestvo, 2020, No. 5), the author experimentally showed that the method conventionally used in the Unified Energy System (UES) of Russia for stabilizing the operating modes of complex power systems under external disturbances is not always efficient. This stabilization method uses signals from automatic excitation regulators (AER) based on the deviation and voltage frequency derivative on the generator terminals. In oscillating transient modes, however, these signals differ significantly in phase from the deviation and rotation frequency derivative of the generators. Instead of damping the occurring oscillations, this process can amplify their amplitude and duration. The author proposed a method for stabilizing the operating modes of power systems by the signals of deviation difference between the rotation frequency of each generator and the voltage frequency on the busbars, as well as the derivative of mismatch between them. The conducted full-scale tests confirmed the efficiency of the proposed method. Following the publication of the above articles, the efficiency of the method was confirmed in a critical discussion presented in the Élektricheskie Stantsii journal. This article discusses the physical difference between the proposed and conventional methods for stabilizing the operating modes of power systems, and explains the efficiency of the proposed method under the operating conditions of complex power systems. Experimental oscillograms of transient processes that have not been published before are presented.