Fixed-parameter damping methods of virtual synchronous generator control using state feedback

Abstract

Virtual synchronous generator (VSG) control is a promising control method for grid-tied inverters, as it can provide inertia support for the grid. However, VSG-controlled grid-tied inverters are subjected to intrinsic low-frequency oscillation, because the emulation of swing equation of a conventional synchronous generator (SG) also introduces an oscillatory mode. In this paper, a damping term produced from state feedback control is added to VSG control to solve this issue. This method is then further developed by applying a low pass filter to the measured active power, to improve its ripple attenuation ability, at the cost of increased design complexity. Both the proposed state feedback damping method without and with low pass filter have one more design degree of freedom than previous methods, which is used to improve dynamic response to active power reference change. The small-signal analyses and experimental results show that both methods can well damp the intrinsic low-frequency oscillation with better dynamic responses than previous fixed-parameter damping methods, whereas the method with a low pass filter has the best overall performance thanks to its improved ripple attenuation ability.