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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).

With respect to rapid growth of offshore wind power, multi-terminal HVDC system is going to be an attractive way of the power transmission for remote and large offshore wind farms. Since the HVDC cables are the vital component of the multiterminal HVDC transmission system, an accurate and fast fault detection method is necessary for protection and maintaining uninterrupted power delivery to the main grid. This study presents a novel method to diagnose HVDC cable faults and unbalancing of DC capacitor bank in multi-terminal voltage source converter HVDC systems for offshore wind farms. Transient voltage of cable sheath is investigated as a main parameter for detecting types of cable faults. Extensive simulations are performed on EMTDC-PSCAD platform and the results show the effectiveness of the proposed technique. [ABSTRACT FROM AUTHOR]