Enhancing Power Flow Control with UPFC-DG Coordination

Abstract

In order to effectively co-ordination the dynamic Flexible Alternating Current Transmission Systems called FACTS together with Distributed Generation (DG) is vital for improving grid stability, efficiency, and reliability. However, these resources are often planned in isolation, overlooking their interactions. In particular, existing works rarely address the Unified Power Flow Controller (UPFC), which is a multiple converter FACTS device under conflicting objectives such as enhancing the Available Transfer Capability (ATC), reducing power losses, and mitigating voltage deviations. This paper presents a bi-level multi-objective optimisation framework for coordinated UPFC–DG planning across transmission and distribution networks. Multi-Objective Particle Swarm Optimisation (MOPSO) is employed, with the outer level determining DG placement and sizing, and the inner level optimising UPFC allocation. Both real power (PV) and real–reactive power (PQ) DG models are considered. Validation was carried out on a synthetic WSCC 9 buses and IEEE 16 nodes as the transmission and distribution network respectively shows that coordinated UPFC–DG planning outperforms UPFConly cases, with PQ-type DG offering the most significant improvements. Results are expressed as Pareto-optimal tradeoffs, providing system planners with insights for enhancing power flow control, security, and efficiency