Minimal Reduction of Unscheduled Flows for Security Restoration: Application to Phase Shifter Control

Abstract

Abstract-More and more transmission system operators, noticeably in Europe, equip their systems with phase shifting transformers to counteract transit flows that take place in a large meshed interconnection. This paper proposes algorithms for the coordinated control of several phase shifters by one operator with the objective of reducing the unscheduled flow through its system. Minimum reduction of unscheduled flow and minimum deviation with respect to present operating point are sought in order to minimize the trouble caused, while ensuring secure operation. Attention is paid to combining pre-and post-contingency controls. The resulting algorithms, simple and compatible with real-time applications, are illustrated on a realistic test system. Index Terms-Corrective control, correctively secure operation, optimal power flow, phase shifting transformer, preventive control, transit flow, unscheduled flow.

Coordination of phase-shifting transformers to improve transmission network utilisation

“…Marinakis et al in [14] propose algorithms to form a tool for the coordinated control of several phase shifters by one transmission system operator. First, the authors explain that within an interconnected AC power system in which a number of TSOs are responsible for operation of different areas, power flows can alter from what is planned due to fault outages, changes in demand, changed availability of renewable generation or new energy trades.…”

“…In [15], the authors of [14] propose a framework for the coordination of control actions of several TSOs that operate PSTs within the same interconnected network. The settings imposed on a single PST may have profound effect on distant parts of the network and since the different TSOs operating them may be operating with different objectives, conflicts can occur that endanger the security of the whole system.…”

“…It is not clear from [14][15][16][17] whether the proposed algorithms have been discussed with system operators to establish the degree to which they would be prepared to trust the outputs from 'black boxes', or whether a method such as particle swarm optimisation can be relied on during rapidly changing emergency conditions.…”

Maximum undergrounding degree of HV subtransmission networks as dictated by unscheduled power flows

“…At transmission level, control of parallel flows by means of phase-shifting transformers or flexible AC transmission systems (FACTS) control has been extensively studied [12][13][14][15]. Exact evaluation of parallel flow is straightforward using load-flow techniques, which in turn, need to be performed for each development (undergrounding) scenario.…”

Integrated coordination of AC power flow controllers and HVDC transmission by a multi-agent system

“…coordination for determining PFC settings based on (mostly centralized) OPF methods ( [4], [5], [6], [7]); and ii. distributed coordination based on simple decentralized algorithms and being independent of central entities (first approach in [8]).…”