Comparison on Frequency Stability of High Inverter Penetration Power System with Different Grid-forming Controls

With the penetration rate of renewable energy has been rapidly increasing in power system, synchronous generators (SGs) are gradually replaced by power electronics. However, wind turbines and photovoltaics nearly have none moment of inertia, they exhibit grid-following characteristics and can’t provide effective support. As a result, grid-forming inverters (GFMs) are proposed for improving the grid stability. In this article, the transient response of GFMs with droop and virtual synchronous generator (VSG) methods are studied, and motor-generator pair (MGP) with improved power control is proposed as a novel grid-forming method. Frequency stability of grid-forming inverters, SGs and MGPs considering control delay and current limitations are studied through IEEE standard 3-generator 9-bus system to demonstrate the differences between grid-forming methods and required characteristics for frequency stability, this article provides a broader view for grid-forming.