A PLL Strategy With Fractional‐Order Lead Correction Enhances the Weak Grid Adaptability of LCL Grid‐Connected Inverter

As the impedance of the power grid increases, the power grid state will exhibit weak grid characteristics. The grid‐connected inverter is indispensable as the connection unit between the large power grid and the distributed generation system. However, there is an interaction between the grid‐connected inverter and the grid impedance, which can easily induce the broadband oscillation of the grid‐connected system. To solve this problem, a phase‐locked loop (PLL) control strategy based on fractional‐order lead correction is proposed, which further improves the phase margin and dynamic response performance of the system by flexibly adjusting the differential and integral orders. The simulation and a 1.5 kW experimental prototype show that the system can still operate stably under weak grid conditions with a short‐circuit ratio (SCR) of 1.7, proving the feasibility of the proposed control strategy.