Virtual impedance shaping

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for shaping grid currents output from parallel inverters in a power distribution system with virtual impedances. In one aspect, a method includes receiving a measurement of the current output from the inverter, processing the measurement of the current to extract a first current component having a particular frequency, obtaining a second current component based on the measurement of the current and the extracted first current component, weighing the first and second current components with respective first and second impedances to obtain respective first and second component voltages, the first impedance having a lower impedance amplitude than the second impedance, obtaining a shaped voltage based on the first and second component voltages, and outputting a control signal to the inverter, the control signal causing the inverter to output the shaped voltage to the power distribution bus.