Active Support Performance Analysis of Photovoltaic Inverter Based on DC Voltage Inertia Control

As the grid-integration proportion of photovoltaic power generation and the penetration rate of power electronic devices in power system gradually increase, the strength of the power grid is weakened and the system inertia is reduced. The conventional grid-following control (GFL) based photovoltaic inverter, lacking inherent active support capability, increases the risk of grid instability. In contrast, the grid-forming (GFM) control strategies enhance system stability by actively establishing grid voltage and frequency, thereby reducing reliance on phase-locked loops (PLLs) and enabling direct reliable support for weak grids. To investigate the active support capability of DC voltage inertia (DCVI) control strategies in photovoltaic inverters, a simulation model of a grid-integrated photovoltaic system is established in this study, through which the active support performance of GFL/DCVI control strategies is analyzed and evaluated under various operating conditions: (1) Small disturbance test: load shedding disturbances at the point of common coupling (PCC) are implemented, with evaluation indicators focusing on the PCC frequency/voltage responses; (2) Large disturbance test: single-phase/two-phase-to-ground faults conditions at the PCC are simulated, with comprehensive assessment of frequency dynamics and voltage behaviors under fault conditions. The simulation results demonstrate that the DCVI control strategy exhibits favorable voltage and frequency support performance, which is better than the conventional GFL strategy.