Mixed power flow analysis using AC and DC models

Steady-state power flow analysis for large-scale networks requires substantial computation because of the extensive interconnections among power systems. Traditionally, network equivalent techniques have been used to reduce computational demand by eliminating the external system. These techniques, then, cannot reflect changes in the external system. This study presents a mixed approach with ac and dc power flow models for power flow analysis to decrease computational complexity and capture variations in the external system. A high level of accuracy in the targeted central part of the system is achieved using the detailed ac model. The less detailed dc model is used to reduce computational requirements and still reflect changes in the external system. Case studies with the IEEE 118-bus system are provided to compare performance among the proposed, the ac and the dc models.