Adjustable PID control based on adaptive internal model and application in current shared control of multi inverters

For the current shared problem of multi inverters connected the grid in the micro-grid, the virtual reactance is introduced to solve the strong coupled problem between active power and reactive power when the line shows resistive characteristic, so the distribution of power among inverters can be achieved by conventional power droop control. Then the reference voltage obtained by power droop control has been transformed into reference current for controlled objective. Considering that the parameters of multi inverters connected the grid are unknown precisely or time-varying slowly, a kind of adjustable PID controller based on adaptive internal model is designed, and high precise current control is achieved. The simulation results show that good steady and dynamic performance can be obtained by the proposed control scheme.