Abstract: There are different voltage quality requirements at different zones and busesof multi-bus microgrids on isolated island. In order to meet the needs of variety of power quality presented by each bus, a zonal control of voltage quality of multi-bus islanded microgrid should be carried out. Aimed at this problem, a hierarchical and zonal optimizing control strategy is proposed based on the analysis of compensation mechanism of voltage unbalance in multi-bus islanded microgrid. This hierarchical and zonal control configuration includes three levels and among them in the secondary control level, an unbalance compensation reference (UCR) is generated as the compensation basis of distributed generator(DG) to achieve voltage unbalance compensation at the public coupling point. In the tertiary control level, the artificial bee colony(ABC) algorithm is used to obtain the optimal tertiary compensation gain (TCG_i), so that the DG output power reference value is adjusted to make each DG compensation amount distributed according to the proportion of its capacity and realize hierarchical and zonal optimizing control of voltage quality. It is verified by simulation result that the compensation policy proposed will be effective and feasible.

Key words: microgrid of power, zonal control, voltage unbalance compensation, optimizing control, triple compensation gain