Impact of Installation Location and Active Power Limitation of Grid-Forming Inverters on Frequency Stability

The frequency stability has deteriorated due to the penetration of the inverter-based resources and the reduction of synchronous generators. A virtual synchronous generator, which is a major control type of grid-forming inverters (GFMIs), can contribute to the power system stability. However, the output of GFMIs after a disturbance may be suppressed due to their capacity constraints or their reserved power. The time for starting output suppression of GFMIs varies depending on their installation locations because of oscillations between generators that occur in a large-scale bulk power system. The impact of the time taken to reach the active power limitation (APL) of GFMIs on frequency stability should be evaluated to construct a stable power system operation. This study evaluated the impact of differences in the time taken to reach the APL of GFMIs on the center of inertia frequency using a Japanese standard bulk power system model, which is called IEEJ WEST10 grid model. The relationship between the APL of GFMIs and the frequency variation was analyzed based on the swing equation. In addition, the relationship was evaluated quantitatively in terms of the rate of change of frequency and nadir from the numerical simulation results.