Flexible Operation of Industrial Processes Acting as Power Reserves

Harvesting energy from renewable resources, such as wind and sun, is our priority. Wind power installed capacity in the UK and Nordic systems is increasing dramatically in recent years. However, one cannot precisely predict renewable energy output: if wind stops blowing, turbines don’t produce electricity. Moreover, we expect to receive power whenever we switch on or plug in electrical appliances. Since electricity cannot be stored efficiently, reserves must be available to continuously match the difference between generation and consumption. The number of occasions in which not enough reserves are available is growing because of renewable generation, increasing the risk of blackout. Conventional generators (e.g. gas-fired power stations) can control their power output to keep the frequency as close as possible to 50 Hz. This poster concentrates on flexible use of industrial plants, which can vary their electricity consumption and act as reserves whenever an imbalance arises. However, since flexibility is only a by-product of the plant, special care is devoted to assure stable and safe operation of the main industrial production: for instance, a plant that uses electricity to liquefy metal at high temperatures may reduce its power consumption for some time, provided that the metal doesn’t solidify. Industrial load flexibility is the largest unexploited resource in power system reliability: frequency control schemes must be revisited in light of load participation. The aim of this research is to prove that flexibility of industrial plants allows for more renewable energy integration while preserving supply stability

Frequency Restoration Reserve Control Scheme with Participation of Industrial Loads

In order to accommodate larger amounts of renewable energy resources, whose power output is inherently unpredictable, there is an increasing need for frequency control power reserves. Loads are already used to provide replacement reserves, i.e. the slowest kind of reserves, in several power systems. This paper proposes a control scheme for frequency restoration reserves with participation of industrial loads. Frequency restoration reserves are required to change their active power within a time frame of tens of seconds to tens of minutes in response to a regulation signal. Industrial loads in many cases already have the capacity and capability to participate in this service. A mapping of their process constraints to power and energy demand is proposed in order to integrate industrial loads in existing control schemes. The proposed control scheme has been implemented in a 74-bus test system. Dynamic simulations show that industrial loads can be successfully integrated into the power system as frequency restoration reserves. © 2013 IEEE

Monitoring and management of power transmission dynamics in an industrial smart grid

This article is a position paper whose purpose is to give the context for presentations in a special session at PowerTech 2013. The special session is being proposed by the EU FP7 Real-Smart Consortium, a Marie Curie Industry-Academic Pathways and Partnerships project. The paper gives an overview of topics on modeling, monitoring and management of power transmission dynamics with participation from large industrial loads. © 2013 IEEE

Model predictive control for power system frequency control taking into account imbalance uncertainty

© IFAC.Model predictive control (MPC) is investigated as a control method for frequency control of power systems which are exposed to increasing wind power penetration. For such power systems, the unpredicted power imbalance can be assumed to be dominated by the fluctuations in produced wind power. An MPC is designed for controlling the frequency of wind-penetrated power systems, which uses the knowledge of the estimated worst-case power imbalance to make the MPC more robust. This is done by considering three different disturbances in the MPC: one towards the positive worst-case, one towards the negative worst-case, and one neutral in the middle. The robustified MPC is designed so that it finds an input which makes sure that the constraints of the system are fulfilled in case of all three disturbances. Through simulations on a network with concentrated wind power, it is shown that in certain cases where the state-of-the-art frequency control (PI control) and nominal MPC violate the system constraints, the robustified MPC fulfills them due to the inclusion of the worst-case estimates of the power imbalance

Applying model predictive control to power system frequency control

Model predictive control (MPC) is investigated as a control method which may offer advantages in frequency control of power systems than the control methods applied today, especially in presence of increased renewable energy penetration. The MPC includes constraints on both generation amount and generation rate of change, and it is tested on a one-area system. The proposed MPC is tested against a conventional proportional-integral (PI) controller, and simulations show that the MPC improves frequency deviation and control performance. © 2013 IEEE

Dynamic simulation of large-scale power systems using a parallel schur-complement-based decomposition method

Power system dynamic simulations are crucial for the operation of electric power systems as they provide important information on the dynamic evolution of the system after an occurring disturbance. This paper proposes a robust, accurate and efficient parallel algorithm based on the Schur complement domain decomposition method. The algorithm provides numerical and computational acceleration of the procedure. Based on the shared-memory parallel programming model, a parallel implementation of the proposed algorithm is presented. The implementation is general, portable and scalable on inexpensive, shared-memory, multi-core machines. Two realistic test systems, a medium-scale and a large-scale, are used for performance evaluation of the proposed method

The hidden world of artificial cavities in the northern Campania Plain: architectural variability and cataloging challenge

In Campania (southern Italy), sinkholes phenomena induced by the widespread presence of anthropogenic cavities in the Neapolitan and Caserta provinces are frequent and well-known. Nevertheless in many urban centers of this area, cavities have been reported in specific geological investigations although their real extent is almost unknown. In these towns the underground mining activities were performed to extract volcanic tuffs for buildings. The urban development have sealed every signal of the presence of cavities, which thus represent a geological hazard and contribute to subsoil instability of many places. The need to carry out a survey of underground quarrings in urban centers has two reasons: a) The anthropic hypogea represent an absolute documentary value, still unduly neglected and little used for the purposes of a correct and sustainable management of the territory, natural resources and historical and artistic heritage. The enhancement and sustainable reuse of hypogea contributes to enhancing the cultural and tourist promotion of a territory. b) In a correct urban management, the knowledge of the city subsoil is a priority, as the presence of cavities may easily trigger the collapse of the shallow or deeper soils. The difficulty of drawing up a univocal cataloging system lies in the definition of database framework that includes all the possible architectural, geological and geotechnical elements of the cavities. In fact, the type of extraction is not the same throughout the territory even over short distances as it was strongly conditioned by the lithological characteristics of the volcanoclastic material in the subsoil, as well as by the purpose of extraction. The construction of a cavity system initially involved an excavation carried out as a “bottle” or a “bell” from the ground level up to the tuff unit, developing at depth according to its thickness. During excavation, access points were realized through the poorly lithified or loose deposits, with a square or pseudo-circular cross-section; sometimes they were supported by containment walls made of tuff bricks resting on the lower tuff bank. A single vertical excavation is sometimes added at certain distance, so as to determine in depth the coalescence of several chambers, also through the construction of narrow tunnels or wide passages, long connecting tunnels, multiple level chambers. Access shafts were often realized with a system of stairs with one or more ramps, with steps directly carved into the tuff. This contribution will show the main cavity typologies recognized across an area north of Naples, although the study is still far from exhaustive. Data were managed into a GIS environment such as to provide a first proposal of a geological underground database framework

Model predictive load–frequency control taking into account imbalance uncertainty

© 2015 Elsevier Ltd.Nonlinear model predictive control (NMPC) is investigated for load frequency control (LFC) of an interconnected power system which is exposed to increasing wind power penetration. The robustified NMPC (RNMPC) proposed here uses knowledge of the estimated worst-case deviation in wind-power production to make the NMPC more robust. The NMPC is based on a simplified system model that is updated using state- and parameter estimation by Kalman filters, and it takes into account limitations on among others tie-line power flow. Tests on a proxy of the Nordic power system show that the RNMPC is able to fulfill system constraints under worst-case deviations in wind-power production, where the nominal NMPC is not

Correlation between ion composition of oligomineral water and calcium oxalate crystal formation

The ion content of drinking water might be associated with urinary stone formation, representing a keystone of conservative nephrolithiasis management. However, the effects of specific ions on calcium oxalate crystal formation and their mechanism of action are still highly controversial. We report an investigation of the effects of oligomineral waters with similar total salt amount but different ion composition on calcium oxalate (CaOx) precipitation in vitro, combining gravimetric and microscopic assays. The results suggest that the “collective” physicochemical properties of the aqueous medium, deriving from the ion combination rather than from a single ionic species, are of importance. Particularly, the ability of ions to strengthen/weaken the aqueous medium structure determines an increase/decrease in the interfacial energy, modulating the formation and growth of CaOx crystals