Optimal Reactive Power Control in Hybrid Power Systems

Abstract

Optimal reactive power flow accounts for the major reduction in active power loss as well as more stable system operation. This article presents a novel model for optimal reactive power flow in hybrid power systems. Hybrid systems consist of an AC-DC system and flexible AC transmission system devices. Contrary to conventional methods that approximate the reactive power optimization in hybrid AC/DC systems to a simple AC reactive power optimization joint with a DC-part re-initialization stage, this study yields the optimum reactive power flow by simultaneously adjusting the control factors of both AC and DC parts. Conventional control factors associated with the AC part consist of control bus voltage, transformer tab, and static VAR compensators. This work introduces a number of DC part-related control factors, including Vdc , Idc , and DC transformer tabs to be used beside the conventional control factors inferred from a unified power flow controller aided AC system. Also, the contribution of control parameters of the unified power flow controller is considered in the reactive power optimization modeling. The proposed method is performed on modified IEEE 14- and 30-bus systems, and it is shown to have less calculation burden and more minimized cost function than the conventional method.