Voltage-Source Converters have brought numerous advantages to HVDC transmission. However, they suffer from high losses and are usually weak against faults on the DC-side. In this paper, a new topology which brings together some concepts from traditional Current Source Converters and multi-level converters, is presented. Two stacks of Hbridge cells alternate to construct the converter voltage using director switches made of IGBTs in series. The resulting converter generates AC current with low harmonic content and with low loss. Furthermore, the converter is still very responsive in case of a fault. This paper first explains the composition and the working of this converter, then detailed simulations at 20 MW illustrate the performances and low losses of this converter under normal conditions. The ability of this topology to deal with abnormal conditions is also demonstrated, especially its ability to keep control of the current despite the collapse of the DC bus voltage, e.g. a DCside fault.

Front underride involving tractor-trailers and small passenger vehicles remains a concern to those wishing to improve highway safety. Although a number of Front Underride Protection Device (FUPD) designs have been studied for effectiveness with respect to performance under crash scenarios, the development process of such devices has been seemingly restricted to a disconnected method. This is to say; in order to truly optimize an FUPD, all influencing factors should be studied together as a unit, while conducting intelligent parameter variation to improve performance. NCAC’s 2010 Toyota Yaris Finite Element model is subjected to multiple rigid bar crash testing in order to investigate compatibility with changing ground clearance and contact bar cross sectional height. Three FUPDs are then modeled using topology and multi-objective parametric optimization including shape variation in conformity with ECE R93 static load standards. These guards are then subjected to dynamic testing versus the Yaris model.

The paper describes the project to refurbish the Konti-Skan HVDC Link between Sweden and Denmark, which included the replacement of the existing Pole 1, and the addition of top level bipole controls for both the refurbished Pole 1 and the existing Pole 2. The complex project included working in 2 different countries with 2 different client utilities, each requiring different scopes and with 2 contracts each with their own currencies. The project scope included up-rating the converters to match the already upgraded DC line and cable conductor circuit. The paper covers the drivers which prompted the need for refurbishment and how it was justified, and then present the details of the project implementation and the in-service performance.The paper also briefly covers previously completed refurbishment and upgrade work on other HVDC projects around the world and known plans to refurbish, replace or even relocate presently operating HVDC projects.

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