HUA Yunyue, YANG Chaoran, HE Guoqing, XIN Huanhai
With the increase in the proportion of new energy generation, the inertia of power system decreases. A virtual synchronous machine can provide inertia for the power system. At present, most of the parameter configuration of the virtual inertia is analyzed from the perspective of small-signal or frequency stability. These two factors have been simultaneously considered by a few studies to conduct virtual inertia configuration. Moreover, research on the configuration of virtual inertia mainly focuses on the voltage-source virtual synchronous machine, while a current-source virtual synchronous machine is rarely studied. To solve this problem, the influence of virtual inertia parameters on the small-signal stability and frequency stability is analyzed by establishing synchronous dominant loop models for voltage-source and current-source virtual synchronous machines. Results show that the small-signal stability of the system can be improved by decreasing the virtual inertia. However, under power perturbation, the output frequency of the current-source virtual synchronous machine will superimpose the transient component of Vq dominated by the virtual inertia, resulting in overshoot. If the virtual inertia parameter is too small, the frequency will not meet the grid-connected operation standard. Based on this, for the system to simultaneously exhibit good small-signal stability and frequency stability, the configuration of virtual inertia needs to be restricted by the two kinds of stability. Finally, the conclusion of this study is verified through the simulation of the inertia configuration of a single infinite machine system and an island two-machine system.
