Impact of Variation of Virtual Inertia and Virtual Damping on Frequency and Power Angle Responses of Virtual Inertia Emulation Controlled Converter

Conventional power electronic converters that interface converter interfaced renewable generation to power grids are static with no rotating energy, leading to almost zero inertia. This means that high penetration of converter interfaced generation in a system grid reduces its equivalent system inertia. Since power system frequency stability is inversely proportional to the equivalent system inertia, low moment of inertia in a grid results in frequency stability degradation, causing large frequency oscillations and high rates of frequency change during severe disturbances. Virtual Inertia Emulation Controlled (VIEC) converter is an interfacing voltage source converter innovatively controlled in order to emulate the damping and inertial properties of a conventional synchronous generator. In a grid connected VIEC converter, virtual inertia and virtual damping parameters define the initial transient frequency and power angle behaviour of the system during power disturbances. Thus the study of the impact of variation of these parameters is useful when designing VIEC converters as well as investigating their stability especially in their applications involving interfacing renewable energy generation into power grids. This paper investigates the impact of variation of virtual inertia and virtual damping on the frequency and power angle response of virtual inertia emulation controlled converters. The transfer function of a grid connected VIEC converter was derived. Modelling and simulation of its transient response was carried out in MATLAB/Simulink. The conclusions derived will guide in selection of virtual inertia and virtual damping parameters during design of VIEC converters.