The ever increasing progress of high-voltage high-power fully controlled semiconductor technology continues to have a significant impact on the development of advanced power electronic apparatus used to support optimized operations and efficient management of electrical grids, which, in many cases, are fully or partially deregulated networks. Developments advance both the HVDC power transmission and the flexible ac transmission system technologies. In this paper, an overview of the recent advances in the area of voltage-source converter (VSC) HVdc technology is provided. Selected key multilevel converter topologies are presented. Control and modeling methods are discussed. A list of VSC-based HVdc installations worldwide is included. It is confirmed that the continuous development of power electronics presents cost-effective opportunities for the utilities to exploit, and HVdc remains a key technology. In particular, VSC-HVdc can address not only conventional network issues such as bulk power transmission, asynchronous network interconnections, back-to-back ac system linking, and voltage/stability support to mention a few, but also niche markets such as the integration of large-scale renewable energy sources with the grid and most recently large onshore/offshore wind farms.

VSC-Based HVDC Power Transmission Systems: An Overview

Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

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A review of single-phase improved power quality AC-DC converters

The authors discuss high-voltage power conversion. Conventional series connection and three-level voltage source inverter techniques are reviewed and compared. A novel versatile multilevel commutation cell is introduced: it is shown that this topology is safer and more simple to control, and delivers purer output waveforms. The authors show how this technique can be applied to either choppers or voltage-source inverters and generalized to any number of switches.<<ETX>>

Multi-level conversion : high voltage choppers and voltage-source inverters

In this paper, the principle of modularity is used to derive the different multilevel voltage and current source converter topologies. The paper is primarily focused on high-power applications and specifically on high-voltage dc systems. The derived converter cells are treated as building blocks and are contributing to the modularity of the system. By combining the different building blocks, i.e., the converter cells, a variety of voltage and current source modular multilevel converter topologies are derived and thoroughly discussed. Furthermore, by applying the modularity principle at the system level, various types of high-power converters are introduced. The modularity of the multilevel converters is studied in depth, and the challenges as well as the opportunities for high-power applications are illustrated.

Modular Multilevel Converters for HVDC Applications: Review on Converter Cells and Functionalities

New regulations impose more stringent limits on current harmonics injected by power converters that are achieved with pulsewidth-modulated (PWM) rectifiers. In addition, several applications demand the capability of power regeneration to the power supply. This work presents the state of the art in the field of regenerative rectifiers with reduced input harmonics and improved power factor. Regenerative rectifiers are able to deliver energy back from the dc side to the ac power supply. Topologies for single- and three-phase power supplies are considered with their corresponding control strategies. Special attention is given to the application of voltage- and current-source PWM rectifiers in different processes with a power range from a few kilowatts up to several megawatts. This paper shows that PWM regenerative rectifiers are a highly developed and mature technology with a wide industrial acceptance.

http://www.lcda.cl/descargas/rodriguez_dixon_pont_espinoza_lezana05.pdf

PWM regenerative rectifiers: state of the art

This paper presents a preliminary economic study on the feasibility of using electric vehicles (EVs) to provide demand response, carried out as part of the GREEN Grid project. A mathematical model is developed to track the charge cycle of an EV battery, and this in turn provides estimates of the cost associated with battery life degradation under different scenarios. Three case studies are presented in this paper: the first investigates the potential cost saving for the EV owner by confining the charging of an EV battery to the night tariff period; the second investigates the financial gain associated with regulating the charging of an EV battery based on spot prices; and the third investigates the possible economic benefit for the EV owner of participating in the electricity market by buying energy at low prices and selling at high prices. The first case also includes the situation of just a battery being used to store energy during the night to run a household during the day. Results show that it is most economical to charge an EV during the night (Case 1), but that it varies considerably depending on the region in New Zealand. Regulating the charging rate depending on the spot price (Case 2) provides a small benefit. Using the EV to trade energy (Case 3) is, in most cases, uneconomic given the degradation of battery life. The variation of Case 1 also shows that at current battery costs, it is not economic to store energy during the night for use during the day. Given that there will be other costs associated with these activities, such as the charger equipment capable of both importing and exporting energy from the grid, the economics do not appear to favour use of EVs for demand response provision, except for the case of simply adjusting the time of charging to suit the tariff.

Electric vehicles and demand response: an economic perspective

A benchmark test system for testing frequency dependent network equivalents for electromagnetic simulations

Voltage sags are common events on the electric power network caused by network faults and the large load connections. This power quality issue can affect a wide range of electrical equipment malfunctions, interruptions or losses and are of particular concern to industry. A complete knowledge of the source is a prerequisite before any remedial action is taken. On the other hand, it is not feasible to fully monitor voltage sags occurred throughout the network. For this reason state estimation techniques have been extended into power quality issues and called Power Quality State Estimation (PQSE). This paper, introduces the use of Transient State Estimation (TSE) as one type of PQSE for voltage dip/sag assessment. The presented approach makes use of mismatch nodal voltage to identify the type and location of voltage dip/sag origin via limited number of measurement points within the network. Then, this algorithm is applied to a distribution test system to verify its performance in presence of measurement noise.

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The use of Transient State Estimation for voltage dip/sag assessment

Successfully applied all over the world NEPLAN one of the most complete planning, optimization and simulation tool for transmission, distribution, generation and industrial networks.

Power System Analysis Software

The multi-level current reinjection (MLCR) concept produces high quality line current waveforms in current source converters (CSC) by injecting an reinjection current. Two rein-jected waveforms: Symmetrical waveform and Linear waveform are known. In this paper the influence of varying the zero width period (ZWP) of symmetrical waveform on line current harmonics of self-commutated MLCR CSC is studied. Different ZWPs are used and optimum ZWP is identified. The effect of different ZWP of the linear waveform on the thyristor based MLCR CSC is presented. This paper also investigates the effects of negative firing angle on the THD levels of the line currents drawn by both CSCs using PSCAD/EMTDC.

http://ieeexplore.ieee.org/iel5/6389590/6401249/06401306.pdf

Neville R. Watson

Papers

Electric vehicles and demand response: an economic perspective

A benchmark test system for testing frequency dependent network equivalents for electromagnetic simulations

The use of Transient State Estimation for voltage dip/sag assessment

Power System Analysis Software

Influence of zero width period on the AC-side line current harmonics of 5-level MLCR CSC