• Energy Research

Presently, there is a rising interest towards multiterminal high voltage direct current networks which use multilevel converters. Furthermore, even though full-bridge submodule topologies have some advantages over half-bridge, there is less research regarding simulation and control of multiterminal networks with such topology. The goal of this paper is to bring forward a detailed modelling method for modular multilevel converters, which use full-bridge submodules, in the context of multiterminal networks. Moreover, great attention is given to the process of converter controller tuning. The simulation and control method are demonstrated using Matlab/Simulink.

This paper deals with voltage regulation issues based on compensation reactors in the 400 kV network of the Romanian Transmission Power System. For secure operation reasons, voltage regulation plays an important role in a power system. As over- or under-voltages occurs due to the reactive power surplus or deficit, shunt reactors are employed to maintain the voltage within admissible limits. Currently, 100 MVAr reactors are switched on/off to regulate the voltage in the 400 kV nodes. However, large voltage spikes are experienced, causing dangerous stress on the switching equipment. The aim is to adapt the actual fixed reactors in some power system nodes with thyristor controlled reactors (TCR) or a combination of a smaller fixed reactor and a TCR. Dynamic simulations and load flow calculations have been carried out to show these differences using Eurostag and Neplan simulation software on the Romanian Power System database.

In this paper an optimal strategy for electric vehicle (EV) charging is proposed to achieve the best network operating conditions, with the help of battery energy storage systems (BESS), while integrating photovoltaic power plants (PV). The electric vehicles can both participate in demand response (DR) and serve as energy storage facilities. They can respond to DR signals, such as price variations or direct control messages by modulating their power consumption, thus providing necessary flexibility to the grid operator. The simulations are performed on a test network, and the mathematical model has been implemented in Microsoft's CPLEX tool. The results have shown that in order to cope with the challenges generated by a large number of EVs, coordination of the EV charging not only reduces the difference between the peak and valley of the load demand, but also generates a number of favorable factors and improving the network operation.

Abstract The quality of life was significantly improved in the last century mainly as regards the access to services. However, the heavy industrialization and the increasing population in the urban areas has been a big challenge for administrators, architects and urban planners. This paper provides a brief presentation of the evolution of the “smart city” term and the most representative characteristics of it. Furthermore, various alternative terms that were proposed to describe the multiple characteristics of the future cities are analyzed. A connection between smart city and smart grid is also presented.

This paper presents a solution for integrating Electrical Vehicles in the Smart Grid through unbundled Smart Metering and Virtual Power Plant technology dealing with multiple objectives. Within this frame, EV can benefit of cost-effective energy during the charging period but can also provide multiple ancillary services to the network, by wisely using their storage capability and their flexibility in coupling to the grid. Simulation of an EV providing services under a multi-objective VPP is also presented, with analysis and conclusions about the technical feasibility of such applications.

Capturing the dynamic behavior of the power distribution grids, especially under high penetration of renewables, is of high interest for grid operators. The distribution power grids are not fully observable due to lack of sufficient metering infrastructure, especially downstream of medium voltage substations. Therefore, fusion of data recorded at significantly different reporting rates was proposed to increase the situational awareness of the system with non-negligible effect on the accuracy of the monitoring tool. Higher reporting rates are possible for next generation smart meters, but they raise higher concerns about data privacy, already an issue for smart meters rollout. This work proposes a framework for knowledge extraction from high reporting-rate smart metering data. The process takes place at smart meter level and with low computation and communication costs and preserving user privacy, with the scope to increase the accuracy of the monitoring tools for distribution power grids. The methodology makes use of statistical metrics able to capture system dynamics relevant for network diagnosis. The proposed approach is validated on a three-phase low voltage power flow model applied to a realistic testbed microgrid and real field measurements synchronized at one second.

This paper focuses on the active power loss minimization by optimal voltage control in a power system using a new optimization algorithm. The cost function is assumed to be convex. The algorithm we propose to address the numerical solution of this problem is based on the exploitation of the convex problem structure using a sequential convex programming framework that linearizes the nonlinear power balance constraints at each iteration. The convex subproblem is then solved using a dual fast gradient method. We provide mathematical guarantees for the linear convergence of the algorithm towards a local solution. This approach allows an optimal voltage for each bus, while achieving the (local) economical optimum of the whole power grid. The newly developed algorithm can be run over large electricity networks, as we show on several numerical simulations using the classical IEEE bus test cases.

Technological developments are pushing for new solutions based upon massive integration of renewable electricity generation in networks already facing many challenges. This paper presents a novel approach to managing the energy transfer towards prosumers making use of smart management of local energy storage. The proposed design (including storage dimensioning) is based on several operating scenarios in which the prosumer might operate as: (i) a “load only” entity (from a grid perspective), thus exhibiting investment resiliency against regulatory changes and high energy efficiency; or (ii) a prosumer, in case regulatory opportunistic profit might be available. This can be realized within a newly proposed Uni-directional Resilient Consumer (UniRCon) architecture. The major aim of the proposed architecture is to achieve optimal self-consumption while avoiding curtailment even in a changing regulatory environment like, for example, the total lack of incentives for generation based on renewable energy sources (RES). One of the major advantages of the proposed architecture consists in the adaptability to changes in the regulatory and market environment. The term resilience is used with multiple meanings: (a) the prosumer’s financial resilience against regulatory changes when investment calculations assume no-grid injections; (b) the prosumer’s technical resilience, with electrical design based on standalone operation; (c) the resilience of clusters of interconnected end-user installations with enabled community-level electricity exchange, independent of the existing main grid supply; (d) the contribution to grid resilience, by enabling AC microgrid (MG) operation in island mode when large portions of the grid are formed by clusters of UniRCon prosumers (the ease of islanding segmentation of the local grid in case of emergencies). For proof of concept, three use-cases are detailed: (i) photovoltaic (PV) installations connected behind the meter; (ii) PV and storage available and controllable behind the meter; and (iii) the UniRCon architecture. The three use-cases are then compared and assessed for four near-future timelines as starting points for the investment. Numerical simulations show the attractiveness of the UniRCon solution in what concerns both system operation costs and supply resilience. Savings are expressed as opportunity savings arising from difference in tariffs while charging and discharging the storage unit and due to the avoidance of curtailment, as well as special taxes for the connection of PV (depending on regulatory environment). An extension of the UniRCon concept is presented also at community scale, with neighbourhood energy exchange inside a resilient cluster.

This paper presents the results of a feasibility study for installing FACTS devices in the South-Eastern part of Romanian power grid (Dobrogea - a peninsular area), to increase the transfer capacity to the rest of the grid. This study assumed, on one hand, the scheduled increase in generated power in the area, mainly due to two new units in the Cernavod a nuclear power plant (1400 MW installed power) and wind generation with an estimated installed power of over 1600 MW. On the other hand, the scenarios considered the present topology and future developments of the transmission network. The increase in generated power in the S-E part of the power grid may lead to changes in the power market schedules, causing generation decrease or even shut down of other generators, leading to power flow changes and power system stability problems.