Bi-level programming based optimal reactive power allocation for hierarchical voltage/var control in partitioned distribution network

This paper proposes a novel reactive power allocation optimization method based on the bi-level programming (BP) model. Considering hierarchical voltage/ var control in partitioned distribution network and dynamic coupling relationships between periods, the BP model is applied to make a research on the optimized expansion of existing allocation. In the proposal, lower model aims to maximize the balance of reactive power locally while upper model targets at minimizing the voltage deviation from expected value. Besides the upper and lower model are interlinked and coordinated through the nodal voltage. Simultaneously, two contribution factor indexes are employed to quantify the ability of improving the voltage quality and optimizing the branch flow. And these indexes can be derived from the voltage-var sensitivity and branch flow-var sensitivity. Then according to the indexes, the best ones are chosen as compensation nodes and employed in the bi-level programming model. Finally the results of the American PG&E 69-buses distribution network validate the rationality and effectiveness of the proposed method.