Reactive power sharing using modified virtual impedance and local load measurement for islanded microgrid

The reactive power sharing is a big issue in the microgrid especially in islanded mode which has local load connected and there is no power refere nce available from grid. The reactive power sharin g error is usually caused by the mismatch of impe dances in connecting circuit. Different connecting circuits may have different impedance which resul ts in different voltage drop across these impedanc es in connecting circuit and hence mismatch of ac tive and reactive power. The P-ω droop normally r esults in good active power sharing. However, rea ctive power sharing by Q-V droop is not so accura te and results in unequal reactive power sharing. This mismatch problem becomes worse when mic rogrid has local load connected. To solve the problem of reactive power sharing in microgrid, this paper presents a modified virtual i mpedance based reactive power sharing techniqu e which takes into account the mismatch of imped ance in connecting circuits for parallel DG's. This paper also considers of mismatch caused by local load connected with microgrid before point of com mon coupling PCC. By adjusting virtual impedanc e in a particular way presented in this paper, the mismatch of impedances can be compensated. T his way virtual impedance can be regulated so tha t all DG's have similar overall connecting circuit im pedance which will result in equal reactive power sharing. The calculation method of virtual impeda nce method is given and validated by both MATLA B SIMULINK simulation and experimental platfor m. The result are shown in results section below.