In recent years

the utilization of renewable energy and the proportion of distributed generation in power grid systems have been increased significantly

and the trend of power electronics in power systems is becoming more and more evident. The problem that arises is that when the grid voltage is unbalanced

the performance of grid-connected inverters decreases which shall be eliminated in the power grid

otherwise it can seriously affect the stability of the power system. Therefore

the control of grid-connected inverters under unbalanced grid conditions is particularly critical. The output power and current quality of the system under unbalanced grid voltage conditions are the main concerned data of grid-connected inverters. In this paper

a three-phase three-wire LCL-type grid-connected inverter is taken as an example

the issues of phase detection inaccuracies and power fluctuations are analyzed

and an improved phase-locked loop (PLL) and power-current cooperative control strategy is proposed. This method can refer to the reference current formula and coordination coefficients to achieve smooth switching among grid-connected current

active power

and reactive power. The feasibility and effectiveness of the proposed strategy are verified through Matlab/Simulink simulations and experiments on the RT-LAB platform.