Harmonic Power Allocation Strategy in Islanded Microgrid Based on Remaining Capacity and Adaptive Virtual Harmonic Impedance Control of Inverter

1ABSTRACT: In an islanded microgrid, the harmonic current generated by the nonlinear loads causes the inverters of the generation units to assume a part of the harmonic apparent power. Researchers are mainly committed to realizing the harmonic power sharing between the multiple inverters to avoid the overload of the inverters. However, this sharing strategy ignores the difference of the inverters in the voltage quality improvement abilities so that the voltage quality of the microgrid cannot be effectively improved. To this point, a harmonic power allocation strategy which gives priority to improving the voltage quality of the microgrid is proposed. The virtual harmonic impedance of the inverter is adaptively adjusted in the fourth quadrant according to its remaining capacity and harmonic power. In this way, the harmonic impedance from the inverter to the microgrid bus reaches the minimum on the premise that no inverters is overloaded, thus providing a low impedance path for the harmonic current and improving the voltage quality as much as possible. To achieve this, the stability region of the inverter’s virtual harmonic impedance is determined by the root locus analysis, and a variable parameter integral controller is further proposed to make the adaptive virtual harmonic impedance control coordinate both the regulation speed and the convergence performance. The effectiveness of the proposed method is verified by the simulation and the hardware-in-the-loop experiment. © 2023 Power System Technology Press. All rights reserved.