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This paper presents supervisory control of a dynamic flow controller (DFC) based on the discrete-event systems (DES) theory. A DFC can be considered as a flexible ac transmission system controller and includes a mechanically-switched phase-shifting transformer, a multimodule thyristor-switched capacitor, a multimodule thyristor-switched reactor, and a mechanically switched capacitor. Owing to the inherent discrete switching nature of a DFC, its components are modeled as finite automata; then, a DES supervisory control is designed to implement the control logic of the DFC system in different modes of operation (i.e., 'automatic' and 'auto/manual'). It is shown that the specifications are controllable and the synthesized supervisors are nonblocking in both modes and the modular supervisors nonconflict in auto/manual mode. Index Terms--Discrete-event systems (DES), dynamic flow controller (DFC), power flow, supervisory control.

This paper introduces a hybrid flow controller (HFC) as a new member of flexible ac transmission system (FACTS) controllers for steady-state and power-flow control of power transmission lines. HFC is a hybrid compensator (i.e., provides series and/or shunt compensation). Structurally, an HFC unit is composed of a mechanically switched phase-shifting transformer, a mechanically switched shunt capacitor, and multimodule, series-connected, thyristor-switched capacitors and inductors. This paper describes the steady-state operation, single-phase equivalent circuit, power-flow model, and V-I and P-Q characteristics of the HFC. This paper highlights the steady-state technical features of the HFC for power-flow control of a study system and also provides a quantitative comparison of the HFC, UPFC, and PST. Index Terms--Flexible ac transmission system (FACTS), power flow, thyristor-switched series capacitor (TSSC), thyristor-switched series reactor (TSSR), unified power-flow controller (UPFC).