Abstract

Abstract

Abstract
A fully operational Multi-Terminal DC (MTDC) grid will play a key role for the creation of AC systems interconnection and to integrate offshore wind farms. Disturbances (at both AC and DC side) may culminate in the sudden disconnection of onshore HVDC-VSC (High Voltage Direct Current - Voltage Source Converter). To continue operating the DC grid under these conditions, the development of control functionalities is required. A communication-free advanced control scheme is proposed to be used as a supplementary local control acting at VSC level and aiming on providing fast active power accommodation in the DC grid, culminating on the mitigation of the resulting DC overvoltage. The implementation of the proposed control mechanisms exploits a set of coordinated local control rules at the converter stations and at wind turbines (WT) level. The performance of the proposed strategies is discussed and assessed through numerical simulation in the paper.

Abstract
Power systems with high wind penetration experience increased variability and uncertainty, such that determination of the required additional operating reserve is attracting a significant amount of attention and research. This paper presents methods used in recent wind integration analyses and operating practice, with key results that compare different methods or data. Wind integration analysis over the past several years has shown that wind variability need not be seen as a contingency event. The impact of wind will be seen in the reserves for non-event operation (normal operation dealing with deviations from schedules). Wind power will also result in some events of larger variability and large forecast errors that could be categorized as slow events. The level of operating reserve that is induced by wind is not constant during all hours of the year, so that dynamic allocation of reserves will reduce the amount of reserves needed in the system for most hours. The paper concludes with recent emerging trends.

Abstract
In this paper is presented a methodology to identify and evaluate the influence of the external elements on the Transmission System Operator's (TSO) responsibility area. The algorithm is based on the influence factor approach and is described for this purpose. This algorithm offer a concrete support in the determination of the observability area, which at the end remains in the responsibility of a single TSO. The influence factor is a numerical value used to quantify the greatest effect of the outage of an external network component on any internal network branch. The proposed methodology was applied to identify and to assess the influence of the external elements on the Portuguese transmission network. All simulations of the Portuguese and Spanish systems were performed using the computational software package PSS/E of Siemens/PTI. The results obtained with the proposed methodology are compared with the solutions produced by the horizontal network methodology.

Abstract
A new strategy was purposed and is being tested during this year, to increase students' participation and promote continuous learning and students' engagement in master's courses classes. With the implementation of the Bologna Process, the spectra of students has increased, which increases the difficulties faced by the lecturers since these students present different backgrounds and knowledge, thereby increasing the number of hours necessary to assure the completion of the programs. A description of a new approach design to increase students' participation, which is being tested in three different Universities and Polytechnic Institutes in Portugal is presented in this paper and some preliminary results are discussed.