Comparative Eigenvalue Analysis of Synchronous Machine Emulations and Synchronous Machines

Abstract

This paper presents a comparative eigenvalue analysis of the stability characteristics and small signal dynamics of four different control strategies for Synchronous Machine Emulation (SME) by power electronic converters, considering a Synchronous Machine (SM) as the benchmark system. The four SME techniques are selected to represent the most established general approaches for emulating the inertial characteristics of SMs in the control of power electronic converters. The small-signal stability assessment is based on the analysis of system eigenvalues, including evaluation of participation factors and parametric sensitivities. All the investigated techniques can be tuned to obtain similar inertial dynamics under grid frequency variations, but exhibit differences in other small-signal characteristics due to the distinct control system implementations. Among the analyzed cases, the current-controlled virtual synchronous machine has the highest damping of the most oscillatory mode. However, the study shows that the most oscillatory modes of the other techniques are associated with the LCL impedance, and could be further attenuated by active damping techniques.