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Flexible AC transmission systems (FACTS) devices can control power flow in the transmission system to improve asset utilization, relieve congestion, and limit loop flows. High costs and reliability concerns have restricted their use in these applications. The concept of distributed FACTS (D-FACTS) is introduced as a way to remove these barriers. A new device, the distributed static series compensator (DSSC), attaches directly to existing HV or EHV conductors and so does not require HV insulation. It can be manufactured at low cost from conventional industrial-grade components. The DSSC modules are distributed, a few per conductor mile, to achieve the desired power flow control functionality by effectively changing the line reactance. Experimental results from a prototype module are presented, along with examples of the benefits deriving from a system of DSSC devices. Index Terms--Distributed FACTS, flexible AC transmission systems (FACTS), interconnected power systems, power system economics, power system planning, power transmission congestion, power transmission control, power transmission lines.

A significant barrier to improving the power quality at industrial facilities is the lack of contemporaneous and historical power quality and reliability data. A new Web-enabled near-real-time power quality and reliability monitoring system, termed I-Grid, has been developed to provide such information on a nationwide basis. The ultralow-cost sensors record power events and send event data via the Internet to the system database servers using an internal modem. Data display, e-mail event notification, site administration, and summary reporting of the data are achieved via a Web browser. In cooperation with the U.S. Department of Energy, the Electric Power Research Institute, and leading utilities and manufacturers, the deployment of these sensors has begun, with a target deployment of 50 000 monitors across the U.S. and Canada over the next 2-4 years. This paper discusses the implementation of this grid information resource, and discusses data captured by the network since early monitors were deployed in 2001. Index Terms--Power distribution reliability, power measurement, power quality, power system measurements, power system monitoring, power system reliability, power system transients, power transmission reliability, voltage sags.

A new LCL resonant dc-dc converter topology is presented in which the resonant CL components are located after the output rectifier diodes. The push-pull converter topology is suitable for unregulated low-voltage to high-voltage power conversion, as in battery-powered systems, where input currents can exceed input voltages by an order of magnitude. The resonant circuit operates at twice the switching frequency, allowing for small resonant components. The MOSFET primary switches operate under zero-voltage switching (ZVS) conditions due to commutation of the transformer magnetizing current and the snubbing effect of the inherent drain-source capacitance. Output rectifier turn-off is effectively snubbed by the resonant capacitor. Laboratory tests show 93% efficiency at 12-V 160-A input, 235-V 1.8-kW output. Surge capability of up to 5 kW for 1 s has been tested. Circuit simulations and experimental results are presented and are shown to have excellent agreement with fundamental mode analysis. Index Terms - DC-DC converter, push-pull topology, resonant converter, zero-voltage soft switching.

Four control topologies for single-phase uninterruptible power system (UPS) inverters are presented and compared, with the common objective of providing a dynamically stiff, low total harmonic distortion (THD), sinusoidal output voltage. Full-state feedback, full-state command controllers are shown, utilizing both filter inductor current and filter capacitor current feedback to augment output voltage control. All controllers presented include output voltage decoupling in a manner analogous to 'back-electromotive force (EMF)' decoupling in dc motor drives. Disturbance input decoupling of the load current and its derivative is presented. An observer-based controller is additionally considered and is shown to be a technically viable, economically attractive option. The accuracy transfer function of the observer estimate is used to evaluate its measurement performance. Comparative disturbance rejection is evaluated by overlaying the dynamic stiffness (inverse of output impedance) frequency response of each controller on a single plot. Experimental results for one controller are presented. Index Terms - Control systems, dc-ac power conversion, impedance, inverters, observers, state space methods, state estimation, transient analysis, voltage control.

Voltage sags, transients, and momentary interruption of power together constitute 92% of the power quality problems encountered by typical industrial customers. The series-parallel-connected Dynamic Sag Corrector (DySC) provides statistically significant protection at greatly reduced cost. The DySC is rated from 1.5-kVA one phase to 2000-kVA three phase and features a patented single-stage power conversion circuit with minimal stored energy. A unique circuit allows operation with opened upstream circuit breaker. This paper presents a detailed discussion of DySC operating principles and validation of performance. It also provides conditions under which this new category of product can be applied. Index Terms--DVR, dynamic sag corrector, DySC, power quality, voltage interruptions, voltage sags.