Power Sharing and Parallel Inverters Control in Islanded Microgrids

This paper deals with the control of parallel voltage source inverters (VSI) in microgrid islanded mode while sharing the active and reactive power required by the load. Firstly, an islanded microgrid composed of n distributed energy resources (DER) connected to each other through VSI and nonlinear load is modelled. Thereafter, a master slave based control strategy is proposed. One of the VSI is designated as a master and it is responsible for controlling the microgrid AC bus voltage and responsible, also, for setting the reference current to be supplied by the slave VSI. In the other hand, the slaves are responsible for controlling their output currents following the references received from the master VSI; in that way, the active and reactive power are shared among all the DER proportionally to their rated generated power. The control of the VSI voltage and current is ensured applying the backstepping technique. Using Lyapunov theory, the closed loop system is globally asymptotically stable. From the simulation case study, the proposed control strategy ensures the voltage control of the n parallel VSI as well as the power sharing between the n DER without being overloaded.