Improvement of stability on dc microgrid using dual series virtual impedance based fuzzy controller under variation of constant power load

This paper investigates the stability issue in direct current microgrid (DC MGs) due to linear and nonlinear constant power load (CPL). The deterioration can be damped out by inserting virtual resistances to minimize the impact of negative resistance of the CPL. However, large virtual resistances caused low stability region. This paper proposed a dual series virtual impedance with fuzzy logic-based voltage and current feed-forward controller. The dual series virtual impedance and fuzzy logic (FL) are used for improvement of transient behavior and steady-state error. However, the crossover frequency increased by inserting CPL is minimized but not much improved by virtual impedance controller. A fuzzy logic-based voltage and current feedforward controller moves from instable to stable region. With FL based current feedforward controller, the crossover frequency has been minimized from 454 rad/sec to 23.8 rad/sec for 5 kW load. The feedforward current can not only improve the transient response but also mitigate the crossover frequency for small-signal modelling stability of microgrids. The comparative stability and transient performance have been demonstrated for variation of CPL (5–9 kW) and source. The hardware prototypes and simulation analysis are used to validate the proposed stable operation criteria of the DC microgrid.