• Energy Research

Capítulos en libros This paper presents a review of the reactive power support and voltage control management in the Spanish transmission network. This is regulated by two market mechanisms: (i) the network constraint management, and (ii) the voltage control ancillary service. Constraint management is conducted by the SO, who asks generators to modify their outputs to solve power system voltage problems. On the other hand, the ancillary service consists of: (i) an annual auction where reactive regulation capacity VAR resources are agreed, and (ii) the scheduling and real-time operation of these VAR resources. Nowadays, only the first mechanism is fully implemented, while the ancillary service is partially established. Some improvements are proposed for future developments. info:eu-repo/semantics/publishedVersion

AbstractNowadays, the amount of distributed generation (DG) connected to distribution networks is increasing significantly. In a European context, one of the main drivers for this growth is the support of electricity generation from renewable energy sources (RES) and combined heat and power (CHP) plants. Hence, these DG units mostly consist of non‐controllable generation. Distribution is a regulated activity which is, at least, legally and functionally unbundled from the generation activity. These issues, together with the fact that distribution networks were not originally designed to accommodate generation, pose significant challenges on distribution network planning and operation. One of the major concerns of distribution system operators (DSOs) is the impact that large penetration levels of DG may have on distribution network costs. This paper presents a quantification of the impact of DG on distribution network costs in three real distribution areas. Different scenarios of demand and generation have been analysed for each region. Two possible situations are taken into account in each scenario: maximum net demand and maximum net generation. The computation of the distribution network costs was carried out by means of two large‐scale distribution planning models called reference network models (RNMs). Copyright © 2010 John Wiley & Sons, Ltd.

Capítulos en libros The development of smart grid solution concepts, such as islanding, make it possible to improve the security of supply in networks. The results experimented in real-life test systems must be extrapolated to wider areas and in other locations, which is not straightforward. The scalability and replicability analysis (SRA) aims to identify the relevant factors that affect smart grid implementations and understand the effects of their variation on the results achieved by smart grid solutions. This paper presents the SRA of an islanding use case in a medium voltage network using cogeneration. Furthermore, the results obtained have been used to obtain a set of scalability and replicability rules for islanding use cases that can be applied in other cases. info:eu-repo/semantics/publishedVersion

Artículos en revistas The promotion of electricity generation from renewable energy sources (RES) and combined heat and power (CHP) has resulted in increasing penetration levels of distributed generation (DG). However, large-scale connection of DG involves profound changes in the operation and planning of electricity distribution networks. Distribution System Operators (DSOs) play a key role since these agents have to provide flexibility to their networks in order to integrate DG. Article 14.7 of EU Electricity Directive states that DSOs should consider DG as an alternative to new network investments. This is a challenging task, particularly under the current regulatory framework where DSOs must be legally and functionally unbundled from other activities in the electricity sector. This paper proposes a market mechanism, referred to as reliability options for distributed generation (RODG), which provides DSOs with an alternative to the investment in new distribution facilities. The mechanism proposed allocates the firm capacity required to DG embedded in the distribution network through a competitive auction. Additionally, RODG make DG partly responsible for reliability and provide DG with incentives for a more efficient operation taking into account the network conditions. info:eu-repo/semantics/publishedVersion

The penetration level of plug-in electric vehicles (PEVs) has the potential to be notably increased in the near future, and as a consequence, power systems face new challenges and opportunities. In particular, PEVs are able to provide different types of power system ancillary services. The capability of storing energy and the instantaneous active power control of the fast-switching converters of PEVs are two attractive features that enable PEVs to provide various ancillary services, e.g., primary frequency control (PFC). However, concurrently, PEVs are obliged to be operated and controlled within limits, which curbs the grid support from PEVs. This paper proposes a new model for PEV using a participation factor, which facilitates the incorporation of several PEV fleets characteristics such as minimum desired state of charge (SOC) of the PEV owners, drive train power limitations, constant current and constant voltage charging modes of PEVs. In order to reduce computational complexity, an aggregate model of PEVs is provided using statistical data. In the end, the performance of PEVs for the provision of PFC is evaluated in a power system. Results show that PEV fleets can successfully improve frequency response, once all the operating constraints are respected. info:eu-repo/semantics/draft

Artículos en revistas The level of secondary reserve needed in a power system is traditionally settled by system operators according to engineering criteria. This paper proposes a novel methodology to determine the optimum level of secondary reserve based on both engineering and economic criteria. Within the proposed approach a price elastic-quantity demand curve for the secondary reserve is built. This approach assumes that the provision of secondary reserve is made under a competitive market. In this market, the supply curve that collects the bids from generators providing secondary reserve is matched with the calculated elastic demand cost curve. The cross of the supply and demand curves determines the optimal level of secondary reserve and the price for provision of the service. The developed approach is illustrated with a case study based on the current day-ahead secondary reserve market in Spain. info:eu-repo/semantics/publishedVersion

Artículos en revistas The current increase of solar generation in the power system, especially at low-voltage (LV) and medium-voltage (MV) levels, poses a great challenge from the distribution system operation point of view. Centralized voltage control schemes have been presented in the literature as a promising solution to deal with the voltage violations that may be caused by these high solar PV penetration levels. However, this approach relies on the accuracy of forecasted data to optimize the set-points and on the effectiveness of communication infrastructures to send them from the central unit to the inverters at the PV panels. This article presents a novel methodology developed in the European project SUSTAINABLE to assess the impact of forecasting and communication on centralized voltage control. This methodology has been applied trough simulation in two Portuguese networks used for the demonstration activities of the project, one in LV and another in MV. The results show that the accuracy of the data used to calculate the set-points as well as the time interval used for their transmission have a significant impact in these applications and highlight the importance of dedicating resources to improve both forecasting tools and communication systems. info:eu-repo/semantics/publishedVersion

Artículos en revistas The recent advances in smart metering and communication technologies in electricity distribution networks could bring new opportunities to distribution system operators (DSOs). In particular, new forms of Active Demand (AD) could be developed to help DSOs to alleviate network congestions and decrease peak capacity requirements, which could in turn reduce or postpone the need for network reinforcements. This paper explores the mechanisms that would allow DSOs to incorporate AD procedures into their network planning strategies. A Reference Network Model (RNM) is used to quantify the potential economic benefits that AD could bring to distribution grids. The analysis is supported by a case study of two rural and urban areas of Spain, based on realistic large-scale exemplary networks and real consumption data. info:eu-repo/semantics/publishedVersion