Multi-Objective Siting and Sizing of Energy Storage Systems in Active Distribution Networks Considering Reactive Power Support from Energy Storage Converters
High photovoltaic penetration makes active distribution networks sensitive to voltage deviations, reverse power flow, and feeder operating stress. Energy storage converters can provide two complementary services: active power energy shifting and local, within-step reactive power support for voltage regulation. This paper develops a converter-aware multi-objective siting and sizing model in which installation buses, energy capacities, and PCS ratings are optimized jointly. The model explicitly represents the P-Q capability circle, voltage-droop reactive power command, reactive headroom, SOC limits, radial power flow, voltage deviation, and network loss; annualized cost and throughput-based degradation are retained as bounded planning terms rather than the sole design target. An adaptive multi-objective differential evolution (AMODE) algorithm solves the mixed discrete–continuous nonlinear problem using Latin hypercube initialization, adaptive mutation and crossover, hybrid mutation, an external archive, feasibility repair, and TOPSIS selection. IEEE33 and IEEE69 case studies are evaluated over thirty independent runs. In IEEE33, the selected plan raises the minimum voltage from 0.8866 to 0.9579 p.u. and reduces daily losses by 11.70%. The ablation study shows that removing PCS reactive support reduces the minimum voltage to 0.9190 p.u., demonstrating the technical role of converter-based Q support. The larger IEEE69 experiments further assess Pareto-front quality, feasibility, and statistical robustness. The hourly quasi-static formulation represents local converter action within each planning interval; it does not evaluate sub-second control or electromagnetic transients.