Gregory F. Reed

Improved power quality solutions using advanced solid-state switching and static compensation technologies

Utility distribution networks, sensitive industrial loads and critical commercial operations all suffer from various types of outages and service interruptions which can cost significant financial loss per incident based on process down-time, lost production, idle work forces and other factors. The types of interruptions which are experienced can generally be classified as power quality related problems caused by voltage sags and swells, lightning strikes and other distribution system related disturbances. In many instances, the use of a solid-state transfer switch (SSTS) and/or a distribution level static compensator (D-STATCOM) can be some of the most cost-effective solutions for these types of power quality problems. The SSTS, which essentially consists of a pair of thyristor switch devices, enables seamless transfer of energy from a primary source to an alternate source in order to avoid service interruption upon a deficiency in power quality. The D-STATCOM, which consists of a thyristor-based voltage source inverter, uses advanced power electronics to provide voltage stabilization, flicker suppression, power factor correction, harmonic control and a host of other power quality solutions for both utility and industrial applications.

Engineering the Future

A collaborative effort to strengthen the U.S. power and energy workforce. Some of us are old, some of us are young, and some of us refuse to acknowledge the difference. At any age, electric power and energy engineers contribute to the sustainability of life on this planet and the future growth of technology and society on all fronts. At a time when the U.S. economy is still struggling to employ more people, the power and energy sector worries about new talent to replace retiring experience. This article introduces readers to the Power and Energy Engineering Workforce Collaborative (PWC), an initiative on the part of IEEE Power & Energy Society (PES). The PWC was created to strengthen the U.S. power and energy workforce needed for the smart grid of the future and related technologies. Much of the material included here comes from the document shown in Figure 1. As these workforce issues greatly affect the United States, this work is being closely coordinated with IEEE-USA.

Ship to Grid: Medium-Voltage DC Concepts in Theory and Practice

Corporate research centers, universities, power equipment vendors, end users, and other market participants around the world are beginning to explore and consider the use of dc in future transmission and distribution system applications. Recent developments and trends in electric power consumption indicate an increasing use of dc-based power and constant power loads. In addition, growth in renewable energy resources requires dc interfaces for optimal integration. A strong case is being made for intermeshed ac and dc networks, with new concepts emerging at the medium-voltage (MV) level for MV dc infrastructure developments.

Maximum Power Point Tracking Using Model Reference Adaptive Control

This paper proposes an adaptive control architecture for maximum power point tracking (MPPT) in photovoltaic systems. MPPT technologies have been used in photovoltaic systems to deliver the maximum available power to the load under changes of the solar insolation and ambient temperature. To improve the performance of MPPT, this paper develops a two-level adaptive control architecture that can reduce complexity in system control and effectively handle the uncertainties and perturbations in the photovoltaic systems and the environment. The first level of control is ripple correlation control (RCC), and the second level is model reference adaptive control (MRAC). By decoupling these two control algorithms, the system achieves MPPT with overall system stability. This paper focuses mostly on the design of the MRAC algorithm, which compensates the underdamped characteristics of the power conversion system. The original transfer function of the power conversion system has time-varying parameters, and its step response contains oscillatory transients that vanish slowly. Using the Lyapunov approach, an adaption law of the controller is derived for the MRAC system to eliminate the underdamped modes in power conversion. It is shown that the proposed control algorithm enables the system to converge to the maximum power point in milliseconds.

Survey of battery energy storage systems and modeling techniques

Grid level energy storage systems are a cornerstone of future power networks and smart grid development. Better energy storage systems are one of the last hurdles hindering the integration of renewable generation. There are currently many methods of implementing energy storage, ranging from pumped hydro storage to sodium-sulfur battery storage. All energy storage technologies share a common disadvantage which is high initial installation costs. This survey was undertaken with the intent of identifying the technological state of battery energy storage for power systems, as well as providing a background on the modeling and simulation of those battery technologies.

Advantages of voltage sourced converter (VSC) based design concepts for FACTS and HVDC-link applications

The application of FACTS and HVDC technologies, in the form of voltage sourced converter (VSC) based designs; continue to be implemented throughout North America and other parts of the world for improved transmission system control and operation. FACTS and HVDC-link technologies allow more efficient utilization of existing transmission networks and help to better facilitate needed transmission system expansion. The wide-scale application of these technologies leads to numerous benefits for electrical transmission system infrastructure, including increased capacity at minimum cost; enhanced reliability increased capacity at minimum cost; enhanced reliability through proven performance; higher levels of security by means of sophisticated control & protection; and improved system controllability with state-of-the-art technology concepts. Both conventional and advanced forms of FACTS and HVDC transmission technologies exist and are in operation today. Advanced solutions are in the form of VSC based designs, including configurations for static synchronous compensators (STATCOM), unified power flow controllers (SSSC), and VSC-based back-to-back DC links (VSC-BTB), to name a few. This paper highlights the advantages provided by the VSC design concept for FACTS ad HVDC-link system applications.

A comparative study of MPPT methods for distributed photovoltaic generation

Photovoltaic (PV) energy generation is becoming an increasingly prevalent means of producing clean, renewable power. PV is renewable, reliable, and domestically secure. One of the most important components of PV systems is the inverter technology that converts the direct current (DC) power output from the PV panel or array to alternating current (AC) used on both the individual end-user and centralized grid levels. The large variety of inverters share the same general goal: to allow for the most efficient and stable transfer of as much power as possible. One specific means of accomplishing this goal is the inclusion of a Maximum Power Point Tracking (MPPT) DC-DC converter. The purpose of MPPT is to ensure that the PV panel or array is always producing power as near to the knee of its I-V curve as possible. This extracts the maximum amount of power at any given time. In constantly sunny situations, there is little impact on overall performance of a particular MPPT design on the PV system, as only small voltage differences due to the particular construction of each panel effects the overall voltage outputs. However, cloud cover changes the output from a PV panel drastically with reduced solar irradiation causing the current of the solar panel to drop. It is postulated herein that the stability and quality problems created by central MPPT during periods of differing solar irradiation on various panels could be solved with a system of MPPT distributed on each panel. These would then feed collectively to a central inverter. To test these systems, a PSCAD model was developed for both centralized and distributed MPPT systems, and the solar irradiation was randomly varied. This allowed for observation of the stability and quality of the output voltage for each system.

The VELCO STATCOM based transmission system project

The Vermont Electric Power Company, Inc., (VELCO) initiated a major transmission system project involving a reconfiguration of a key 115 kV substation and the installation of a STATCOM-based dynamic reactive compensation system. This project has an in-operation date of May 2001. The paper gives an overview of the VELCO transmission system project with emphasis on the STATCOM-based dynamic reactive compensation system. The major items with respect to the STATCOM system addressed in this paper include: power system requirements; STATCOM system description; STATCOM system layout; and STATCOM construction and installation.

SDG&E Talega STATCOM project-system analysis, design, and configuration

San Diego Gas & Electric (SDG&E) initiated a major transmission system enhancement project involving a key 230/138 kV substation and the installation of a STATCOM-based dynamic reactive compensation system. This project is currently scheduled by SDG&E for an in-service date in October 2002. This paper gives an overview of the SDG&E transmission system project with emphasis on the STATCOM-based dynamic reactive compensation system. The major items with respect to the STATCOM system addressed in this paper include: power system requirements; STATCOM system description; STATCOM system layout; STATCOM construction and installation.

Development of a novel hybrid switch device and application to a solid-state transfer switch

Numerous industrial and commercial operations suffer from various types of outages and service interruptions which can cost significant financial loss per incident based on process down-time, lost production, idle work forces, and other factors. The types of interruptions which are experienced can generally be classified as power quality related problems caused by voltage sags and swells, lightning strikes, and other system related disturbances. In many instances, the use of a solid-state transfer switch can be one of the most cost-effective solutions for these power quality problems. The SSTS, which essentially consists of a pair of thyristor switch devices, enables seamless transfer of energy from a primary source to an alternate source in order to avoid service interruption upon a deficiency in power quality. As a result, power quality problems become transparent to the critical or sensitive customer loads that the SSTS protects. However, a thyristor is not a pure conductor and raises some issues in terms of loss consumption and cooling. In a conventional SSTS, line current flows in the thyristors continuously, causing a great deal of loss consumption and element heating during normal operation. As a result, relatively large cooling equipment is required which imposes additional operating costs on the user in order to maintain thyristor cooling. It also results in reduced efficiency and lower reliability in the device.