A Coordinated Q-V And P-F Droop Control of Grid-Forming Inverters for Enhanced Voltage and Frequency Stability

Abstract

This script presents an adaptive coordinated Q-V and P-f droop control strategy for the grid-forming inverters operating in low inertia power systems. The proposed controller simultaneously regulates active power frequency and reactive power voltage dynamics through adaptive droop coefficients driven by real time disturbance indices. A complete nonlinear MATLAB model incorporating inverter dynamics, virtual inertia, LCL filtering, measurement delays and weak grid characteristics was developed and evaluated under three severe operating disturbances, a 30% load increase, 25% load reduction and 250% reactive power step, together with photovoltaic irradiance variations. Simulation results demonstrate that the coordinated controller maintains system frequency within approximately ± 0.3 Hz and voltage within ±0.05pu despite rapid power fluctuations. Compared with conventional fixed droop control, the adaptive strategy exhibits reduced frequency nadir deviation, smaller voltage dip, faster settling characteristics and lower integral error indices. Furthermore, weak grid analysis confirms that the controller preserves stable operation across a wide range of Short Circuit Ratios indicating improved robustness for renewable dominated distribution networks. The proposed coordinated droop framework therefore provides an effective solution for enhancing transient stability, grid resilience and autonomous voltage frequency support in future inverter-based power systems.