Decentralized control of parallel connection of two distributed generation units

This paper presents a decentralized control strategy for the autonomous (islanded) operation of parallel connection of two distributed generation (DG) units. The DG units are electronically interfaced to the host grid at the same point of common coupling (PCC), where the local load is also supplied. In the grid-connected mode, the voltage-sourced converter (VSC) of each DG unit controls the exchange of real and reactive power components with the host grid, based on the conventional dq-current control strategy. In the islanded mode, one of the DG units provides voltage and frequency control for the island, and the other DG unit continues to operate with the pre-islanding dq-current control strategy. The performance of the proposed decentralized controller is validated based on a laboratory scale experimental setup. The experimental results show that the proposed decentralized controller provides robust voltage control for the islanded two-parallel DG system and can sustain the stability of the system against the load perturbations and the external disturbances.