Comparison of Virtual and Conventional Synchronous Generators Based on a Modularized Analysis Tool

Abstract

It is questionable that if virtual and conventional synchronous generators could provide identical dynamic support to the power system. In order to summarize the difference, this paper introduces a MIMO-based analysis tool for modelling power systems integrated by conventional or power-electronic interfaced generators. The scalable tool is used to test modelling accuracy of individual generators using dynamic simulation. For small-signal stability analysis, the tool does linearization based on MIMO models, and then couple all generators/loads though the passive network, with the network transient included. During transient stability analysis, VSG's ability to emulate SG's dynamic responses depends on whether the converter has a strong overloading limit, and the current control loop is tuned fast. In practice this could be hard to realize, considering that the converter's current limit is slightly higher than 1.0, and thus the current controller tends to be easily saturated during voltage sags, and the VSG could enter constant-power mode. During small disturbances, VSG could have a low-frequency inertia response similar to SG, yet it can introduce new oscillation modes, depending on the control parameter configuration. Due to lack of stator-flux transient modelling, the high-frequency oscillation of VSG is evidently deviated from that of SG.