Extra transient block for virtual synchronous machine with better performance

Abstract

An extra transient block (ETB) for virtual synchronous machine (VSM) that is able to provide extra transient damping and adjust transient inertial to better stabilise the frequency of the VSM in a shorter time during transient period without altering the steady-state performance is proposed in this study. The ETB uses extra parallel series lead-lag blocks to get the transient frequency output to make the stability of the VSM less intensive to the parameter design of the virtual inertial and damping coefficient so that an easier parameter design method can be used. In other words, this method helps to solve the contradiction between dynamic response and stable performance, especially when the damping coefficient cannot be freely modified to increase damping for a large inertial value because of the mutual dependence between damping coefficient and droop coefficient caused by the use of inner reference frequency. Moreover, a simplified method for the parameter design of the ETB is proposed and the small-signal model of the ETB-based VSM is also derived. After that, the power coupling situation is analysed and comparisons with other control strategies are presented. Furthermore, time-domain simulation results are demonstrated to verify the effectiveness of the proposed method.