Sigmoid Functions Applied in Proportional + Resonant Reference for Current Harmonic Sharing

The concept of distributed generation and microgrids allowed different alternative of power sources to be integrated to the main grid, made possible due to the evolution and improvement of power converters, like DC-AC inverters. This paper proposes an alternative harmonic current sharing methodology without communication between the inverters in the microgrid. Sigmoid functions designed for each frequency in each inverter manage the amplitudes of currents references of PR controller, assigning the appropriate amount to each element taking into account the capacity and availability of each inverter. The grid connected system is composed by two VSIs operanting in parallel at the point of common coupling, as well as the non-linear load. The results presented a harmonic compensation evaluating VSIs with different power capacities. In a first scenario, the VSIs were designed for only supply active power, and in a second scenario, the converters provided almost all the harmonic needed for a non-linear load.