Stability analysis and improvement of LCL-converters based microgrid

Multiple resonances can occur in LCL-converters based microgrid due to the interactions of the converters with the considerable grid impedance in a low voltage distribution system. In addition, some special loads may also aggravate the resonances. This paper proposes a model of the microgrid for stability analysis. It is revealed that the impedance mismatch between the LCL-converters and the external network including the grid impedance and the loads could excite resonance in some specific frequency bands. An impedance matching controller is then proposed to solve the problem. The controller combines the proportional resonant (PR) regulator with the full state feedback loop. Superior to the traditional methods, the scheme is proposed from the perspective of the stability of the whole microgrid instead of just the single LCL-converter. Simulation and experimental results validate the effectiveness of the proposed method.