High-Dynamics P-E and Q-f Control of PV Inverters for Strong and Weak Grids

The increase of power electronic-based generators is causing the replacement of synchronous generators, which poses new challenges to electrical grid stability. In particular, when grid-following inverters are connected to weak grids, stability problems related to the PLL used for synchronization arise. To address this issue, grid-forming controls are widely proposed. However, the conventional implementations, such as droop control or virtual synchronous generator, lead to slow power controls, which are not suitable for photovoltaic systems with no storage. Thus, to improve the control dynamics, this paper proposes a new P-E and Q-f control. This control uses the reactive power for grid synchronization, avoiding the use of a PLL, and is valid for both inductive and resistive lines. Furthermore, thanks to the controller design developed in the paper, the control remains rapid and stable for very weak grids. Simulation results validates the control design and shows that the proposed control is much faster than the droop control for all types of grids.