Power Sharing Enhancement Strategies for Parallel-Connected Voltage Source Inverters With Common dc and ac Buses in Islanded Microgrids: Two New Control Schemes

Smaller rated modular converters are often connected in parallel, as opposed to the installation of a single converter with a high power rating. This is typically done to achieve a more reliable power supply with reduced cost. The work presented in this article is directed toward achieving proportional load power sharing between modular connected distributed generators (DGs) comprising inverters with common ac and dc buses in ac microgrids that are islanded. Two new schemes have been proposed to achieve this, and their performances have been compared with that of a recently proposed decentralized linear adaptive virtual impedance (AVI) variation strategy. The control schemes have been tested for a wide variety of loads and integrated seamlessly with the conventional and inverse droop control approaches for enhanced performance under varying network $\text{X}/\text{R}$ parameters. The novel strategies are also validated on a modified 13-bus system with three DGs using offline simulations on MATLAB/Simulink. Validations using controller-hardware-in-the-loop (CHIL) setups are also carried out for meshed network conditions, different loads, and different DG power ratings and droop controller configurations.