It is expected that in the near future the use of high-voltage dc (HVDC) transmission and medium-voltage dc (MVDC) distribution technology will expand. This development is driven by the growing share of electrical power generation by renewable energy sources that are located far from load centers and the increased use of distributed power generators in the distribution grid. Power converters that transfer the electric energy between voltage levels and control the power flow in dc grids will be key components in these systems. The recently presented modular multilevel dc converter (M2DC) and the three-phase dual-active bridge converter (DAB) are benchmarked for this task. Three scenarios are examined: a 15 MW converter for power conversion from an HVDC grid to an MVDC grid of a university campus, a gigawatt converter for feeding the energy from an MVDC collector grid of a wind farm into the HVDC grid, and a converter that acts as a power controller between two HVDC grids with the same nominal voltage level. The operation and degrees of freedom of the M2DC are investigated in detail aiming for an optimal design of this converter. The M2DC and the DAB converter are thoroughly compared for the given scenarios in terms of efficiency, amount of semiconductor devices, and expense on capacitive storage and magnetic components.

Comparison of the Modular Multilevel DC Converter and the Dual-Active Bridge Converter for Power Conversion in HVDC and MVDC Grids

Flexible AC transmission systems (FACTS) devices are used to control power flow in the transmission grid to relieve congestion and limit loop flows. High cost and reliability concerns have limited the widespread deployment of FACTS solutions. This paper introduces the concept of distributed FACTS (D-FACTS) as an alternative approach to realizing cost-effective power flow control. By way of example, a distributed series impedance (DSI) and a distributed static series compensator (DSSC) are shown that can be clipped on to an existing power line and can, dynamically and statically, change the impedance of the line so as to control power flow. Details of implementation and system impact are presented in the paper, along with experimental results.

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Distributed FACTS - A New Concept for Realizing Grid Power Flow Control

Significant work has been done on the sensing of utility assets. Most proposed approaches have been based on the principle of using few relatively expensive sensors and wireless communication links to provide a sample of data on the status of the power line. This paper introduces the concept of a distributed power line sensornet (PLS) as an alternative approach to realizing cost-effective power grid monitoring. By way of an example a distributed sensor module is proposed that can be clipped on to an existing power line and have the following four core functions: continuously monitoring critical line parameters in the immediate vicinity of the sensor; estimating the line status and identifying incipient faults in a changing environment; operating as a node of the sensornet communication system; power and fault management while allowing sensing and communication functions. Details of implementation and system impact are presented in the paper, along with simulation results.

Power line sensornet - a new concept for power grid monitoring

Review Article: A comprehensive review of the application characteristics and traffic requirements of a smart grid communications network

In the last two decades, emerging use of renewable and distributed energy sources in electricity grid has created new challenges for the utility regarding the power quality, voltage stabilization and efficient energy utilization. Power electronic converters are extensively utilized to interface the emerging energy systems (without and with energy storage) and smart buildings with the transmission and distribution systems. Flexible ac transmission systems (FACTSs) and voltage-source converters, with smart dynamic controllers, are emerging as a stabilization and power filtering equipment to improve the power quality. Also, distributed FACTSs play an important role in improving the power factor, energy utilization, enhancing the power quality, and ensuring efficient energy utilization and energy management in smart grids with renewable energy sources. This paper presents a literature survey of FACTS technology tools and applications for power quality and efficient renewable energy system utilization.

Review of FACTS technologies and applications for power quality in smart grids with renewable energy systems

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 an 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.

http://pq-ride.co.kr/dataroom/files/(%BF%B5%B9%AE)IEEE%20Cost%20Effective%20Industrial%20Power%20Line%20Conditioning.pdf

Dynamic sag correctors: cost effective industrial power line conditioning

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

A Distributed Static Series Compensator System for Realizing Active Power Flow Control on Existing Power Lines

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.

A distributed static series compensator system for realizing active power flow control on existing power 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.

A grid information resource for nationwide real-time power monitoring

This paper provides insight into a failure mechanism that impacts a broad range of industrial equipment. Voltage surges have often been blamed for unexplained equipment failure in the field. Extensive voltage monitoring data suggests that voltage sags occur much more frequently than voltage surges, and that current surges that accompany voltage sag recovery may be the actual culprit causing equipment damage. A serious limitation in equipment specification is highlighted, pointing to what is possibly the root-cause for a large percentage of unexplained equipment field failures. This paper also outlines the need for a standard governing the behavior of equipment under voltage sags, and suggests solutions to protect existing equipment in the field.

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W.E. Brumsickle

Papers

Dynamic sag correctors: cost effective industrial power line conditioning

A Distributed Static Series Compensator System for Realizing Active Power Flow Control on Existing Power Lines

A distributed static series compensator system for realizing active power flow control on existing power lines

A grid information resource for nationwide real-time power monitoring

Equipment failures caused by power quality disturbances