Cross-current power control for coordination of multiple grid forming inverters

The number of distributed energy resources (DERs) and battery energy storage systems (BESS) is increasing recently. Most of the DERs are renewable energy sources such as photovoltaic power (PV) and wind power plants. Since the DER and BESS generate dc power or ac power with a frequency different from the grid frequency, those are connected to the power grid by power electronic inverters. However, the inverters do not have inertia and synchronizing power, necessary for stabilizing the power grid in case of grid disturbances. For providing virtual inertia to the inverter, grid following control (GFL) and grid forming control (GFM) methods are being researched in the world. However, parallel operation of voltage source converters often causes undesirable current, which is called cross-current flows between each GFM. This paper proposes a cross-current power control method for the GFM inverters in parallel operation and shows a simulation model of the proposed method. MATLAB/Simulink is used in the simulation. The paper also reports the results of simulations forvalidating the proposed control method.