Voltage harmonic reduction using virtual oscillator based inverters in islanded microgrids

In islanded mode, the voltage and frequency of microgrids are determined by the interface voltage source inverters. Hence, the power quality can be deteriorated under unbalanced and nonlinear load conditions. This paper proposes a new method that combines Virtual Oscillator Control with Proportional-Resonant control to mitigate voltage harmonic distortion. This work proposes a modified nested loop proportional-resonant controller, in which the fundamental frequency unit is located in the outer loop, whereas the harmonic frequency units are used in the inner loop. The harmonic control units are introduced to reduce harmonics at the point-of- common-coupling and to guarantee non-fundamental power sharing among inverters. The proposed control structure eliminates the harmonics at selected frequencies, while retaining the main advantages of the virtual oscillator control method. Simulations in Matlab/Simulink verify the effectiveness of the proposed method.