Current-limiting strategy based on PR controller and active power filter for droop controlled microgrid

In order to protect the power electronic equipment and make the output current amplitude of distributed generation (DG) maintain a stable value for different short-circuit faults, this paper proposed a current-limiting strategy based on proportional-resonant controller (PR), filtering inductance reference current (FIRC), and shunt active power filter (APF) for droop controlled microgrid. First, the relationship is discussed in detail among the output current of DG, the output voltage of DG and FIRC, theoretical derivation demonstrates that the error between output current of DG and FIRC can be decreased through adjusting the value of PR parameters, filtering capacitance and the compensation current obtained by APF. Moreover, some advantages of proposed strategy for microgrid protection are discussed. Then, when the fault is detected, the current-limiting strategy is implemented by setting the FIRC value. Finally, the experiments prove that the proposed strategy can precisely limit the maximum phase current to the given value which cannot be influenced by the short-circuit fault type, grounding resistance, fault initial phase, non-linear load, and so on.