Sensitivity Analysis and Approximate Dynamic Programming based Voltage Control Strategy for Three-Level Coordination of "Substation"-"Feeder"-"Distribution Unit-Area"

Distributed energy resources are integrating into distribution networks rapidly in recent decades, bringing new voltage coordinated control issue for distribution networks. A voltage coordinated control LQR optimization model is proposed based on voltage - control inputs sensitivity for three-level coordination of "Substation"-"Feeder"-"Distribution Unit-Area" considering the active and reactive power control capabilities of distributed energy resources, including photovoltaic generation, energy storage, reactive power compensator at user side, and transformer tap changer in substation. An approximate dynamic programming based optimization algorithm is proposed to obtain the optimal control strategy. The proposed optimization model and algorithm are verified by case studies on a substation system. Case study results demonstrate that the proposed optimization model and algorithm can enhance the voltage profile of the substation system, and the line losses can be reduced as well.