Análise da estabilidade de inversores conectados em paralelo em rede isolada, sem interconexão no controle e com aumento do amortecimento via malha de deslocamento de fase

Abstract

This work presents the small signal stability of sinusoidal PWM inverters connected in parallel in a standalone system, that is, without the presence of an infinite bus. The inverters have no interconnection control, so that only local variables are referred. The control strategy of each inverter unit is based on the Pxω and QxV droops and it has an additional loop δxP designed to increase the damping. This loop feeds the deviation of the active power of inverter from its nominal value back into the reference voltage phase, resulting in a control action that produces small shifts in the inverter voltage phase. A small signal model in state space form is proposed, which corresponds to the system linearization around an arbitrary equilibrium point. The proposed model is validated by simulation and experimental results. Root locus analyses are also presented to show the effect of the additional loop in the system damping. The proposed small signal model, main contribution of the presente work, allows the knowledge in advance of the stability and power sharing of an islanded microgrid composed by PWM sinusoidal inverters connected in parallel.