Allocation of Dump Load in Islanded Microgrid Using the Mixed-Integer Distributed Ant Colony Optimization

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In highly penetrated microgrids (MGs), the problem of voltage and frequency deviations exceeding their permissible limits, becomes significant with higher share of renewable based distributed generation (DG). The existing real-time control systems of highly penetrated MGs cannot cope on its own with such deviations, owing to the large generation and demand mismatch mainly during off-peak hours. A dump load (DL) can help with voltage and frequency regulation by consuming excess generation. However, further investigation is required to highlight the importance of optimal DL allocation on the operation of MGs. The mixed-integer distributed ant colony optimization is introduced as a novel application in droop controlled islanded MGs to minimize voltage and frequency deviations and system losses. The optimization problem was formulated as a single- and multiobjective problem to allocate a DL and the optimal droop settings for DG in islanded microgrid (MG) during off-peak hours. The proposed optimization method was teamed up with a special backward/forward sweep load flow method to account for DG droop characteristics and enhance the solution convergence. The method was applied to the IEEE 69- and 118-test systems and validated against competitive swarm and evolutionary metaheuristics. Results have shown that an optimally sized and allocated DL with optimized droop setting could minimize voltage and frequency deviations to an acceptable level, while reducing power losses incurred by the installation of such load into the MG.