Showing papers by "Pierluigi Mancarella published in 2018"

A General Model for Thermal Energy Storage in Combined Heat and Power Dispatch Considering Heat Transfer Constraints

Abstract: Heat transfer (HT) is a major constraint in thermal system analysis. However, when discussing utilizing the flexibility provided by the heating sector, for example, using thermal energy storage (TES) to increase operational flexibility of combined heat and power (CHP), the HT process is often ignored. This may mean infeasibility of the resulting schedules. In response to this, this paper proposes a general TES model which takes detailed HT analysis into account. By setting the relevant parameters, this model can be used to describe the HT process for both sensible heat (SH) and latent heat (LH) TES devices. An iteration method is proposed to deal with the nonlinearity introduced by the HT constraints, and to solve the joint nonlinear dispatch problem for CHP with TES. The simulation results show that explicitly considering the HT process is essential to realistically assess and therefore make full use of the flexibility provided by TES. Moreover, the comparison between LH and SH TES shows that LH can provide more flexibility for the system, especially when the starting energy level in the TES device is low.

Integrated Dispatch Model for Combined Heat and Power Plant With Phase-Change Thermal Energy Storage Considering Heat Transfer Process

Abstract: Combined heat and power (CHP), with its limited flexibility, is one of the leading causes for the curtailment problem of variable renewable energy source (VRES) in Northern China. To increase the flexibility for CHP, thermal energy storage (TES) is considered to be an effective solution, and a phase-change TES demonstration pilot project is now being constructed in Northern China. Almost all the previous studies have modeled the TES device without considering the heat transfer process, which is a main constraint in thermal system analysis. Thus, in this contribution, we consider the heat transfer process for the phase-change TES device installed in a CHP plant based on the steam's three-stage heat transfer model and the entransy dissipation-based thermal resistance theory. An integrated electrical–thermal dispatch model concerning conventional thermal units, VRESs, and CHP units with phase-change TES device is given, and an iteration method for solving this nonlinear programming problem is proposed. Case studies show that it is vital to consider the heat transfer process in the modeling of CHP plant with phase-change TES device, and it has significant influence on the flexibility that the TES device can provide when the working conditions vary.

Integrated Approach to Assess the Resilience of Future Electricity Infrastructure Networks to Climate Hazards

Abstract: Electricity systems are undergoing unprecedented change, with growing capacity for low-carbon generation, and an increasingly distributed approach to network control Furthermore, the severity of climate related threats is projected to increase To improve our understanding of the risks from these changes, this paper presents a novel modeling approach to assess the resilience of future electricity networks to climate hazards The approach involves consideration of the: 1) evolution of electricity networks in response to changes in demand, supply, and infrastructure development policies; 2) implication that these policies have on network configuration and resilience; and 3) impacts of potential changes in climate hazard on network resilience We demonstrate the research on the National Electricity Transmission System of Great Britain and assess the resilience of this system to changes in the intensity of wind storms under alternative energy futures The analysis shows that infrastructure policies strongly shape the long-term spatial configuration of electricity networks and consequently this has profound impacts on their resilience Though the system is resilient to wind storms under the current climate, our analysis shows that the system fails to meet electricity demand after an increase of only 5–10% in the intensity and frequency of wind storms, and a 50% increase could lead to the loss of 85% of peak winter demand The approach is useful for identifying and communicating potential network risks to wider stakeholders and policy makers seeking to design a transition toward a low-carbon, yet resilient, future electricity systems

System Strength and Weak Grids: Fundamentals, Challenges, and Mitigation Strategies

Abstract: Converter-based renewable energy sources (RES) and battery energy storage (BES) devices that are asynchronously connected to the system are becoming more and more widespread. A number of relevant stability issues, usually in areas with little synchronous generation, are being experienced, particularly in terms of voltage stability. In this context, the scope of this work is to review the key aspects of the so-called “system strength” that is associated with “weak grids” where such instabilities arise, its definitions, assessment metrics, and adverse operational impacts that may emerge. The paper is then discussing two main mitigation strategies to improve short-term voltage stability in weak power systems. The first is to provide voltage stability services by converter-based technologies to support the system voltage in weak areas. The second proposition is to employ FACTS devices to increase system strength. Finally, limitations and challenges regarding the operation of converter-based technologies and FACTS devices in weak grids are presented and followed by key recommendations.

Heat Electrification: The Latest Research in Europe

Abstract: Heat represents roughly 50% of the European Union's (EU ) final energy demand (Figure 1). But in the past, heat was largely absent in the energy debate, given the traditional focus on energy supply data, which only shows heat fuels, mainly fossil fuels and a small fraction of electricity. The potential synergies between heat and electricity in the transition to a clean energy system have been recognized in the EU's 2016 heat strategy. The increasingly decarbonized electricity system powered by renewable electricity can provide clean heat supply, while the flexibility of heat demand can support electricity peak management and the integration of variable renewable energies.

Frequency Response Constrained Economic Dispatch with Consideration of Generation Contingency Size

Abstract: Primary frequency response (PFR) requirements to stop frequency excursion after contingency are usually calculated on the basis of the potentially largest contingency, which is therefore a direct driver for frequency response adequacy. Future lower-inertia systems with larger volumes of non-synchronous renewables might require much higher levels of PFR to guarantee frequency adequacy; this might in turn significantly constrain system operation. Contingency size reduction could then potentially lead to a more efficient operation, and in extreme cases, it might be necessary to find feasible operation points. Hence, focusing on generation contingency, this paper presents a novel mixed integer linear dispatch model that includes a set of hyperplanes that describe PFR requirements as a function of both system inertia and maximum contingency size (as a variable of the problem) to comply with predefined frequency response constraints such as rate of change of frequency (ROCOF) and frequency nadir. This allows efficient control of the contingency size in order to reduce operational costs and renewable curtailment associated to the need for additional inertia and/or spinning headroom to guarantee adequate frequency response. The proposed approach is demonstrated through Australian case studies, also including specifically developed frequency response security maps.

Co-optimization of a Multi-Energy Microgrid Considering Multiple Services

Abstract: The energy system is changing to accommodate emerging distributed energy resources. Grid-connected microgrids can be a means to coordinate distributed energy resources to aid integration, whilst also improving power system reliability. Microgrids can provide various grid services, i.e., energy arbitrage, frequency control ancillary services, and network reliability services. These services may improve business cases for microgrids when considering the relevant price signals in a transactive energy context. However, assessing the potential of microgrids to provide multiple grid services is challenging, particularly when inherent technologies draw flexibility from coupling different energy vectors in a multienergy context. This requires detailed modelling of energy resources and buildings within microgrids, as well as the markets and business cases. In the light of the above, this work proposes a microgrid multi-service co-optimization model, running with a five-minute resolution. This model identifies the response of microgrids to price signals related to different grid services. Particular contributions are found in novel transactive based formulations of different types of frequency control ancillary services modelling and reliability services modelling, taking into account of various distributed generation and heating technologies. Economic values of reliability services are estimated using sequential Monte Carlo simulations of network contingencies. The methodology is demonstrated through business case assessment, placing focus on conflicts and synergies between different services, with pragmatic case studies based on the Australian context.

The Influence of Location of Distributed Energy Storage Systems on Primary Frequency Response of Low Inertia Power Systems

Abstract: The paper investigates the impact of primary frequency response (PFR) support, provided by distributed energy storage systems (ESS), depending on their location in low inertia power systems. The analysis is performed for three operating conditions of the network. For each operating condition, the decrease in the network load is balanced by disconnecting a part of synchronous generation (SG) that reduces the system inertia and increases the proportion of RES. The uncertainties in power generation of renewable energy sources (RES) and loading forecast are also incorporated into simulations.The results clearly show that the effect of location of ESS on PFR is negligible if the inertia of the system is not substantially reduced. However, when the proportion of RES becomes greater than SG, the ESS installed in the lowest inertia provide significantly better PFR support to the system. The studies are performed in a modified 16 machine and 68 bus network.

Smart distribution networks, demand side response, and community energy systems: Field trial experiences and smart grid modeling advances in the United Kingdom

Abstract: Emerging smart grid solutions are perhaps the most attractive options to meet the ever-increasing needs for economic, reliable, sustainable, and socially acceptable energy production and consumption in the United Kingdom. In particular, smart solutions are vital to cater to the integration of economic and low carbon distributed energy resources (DERs) at the community level. However, there is still little understanding of how to effectively use DERs in bringing about benefits for the energy system or enhance distribution networks to enable the smart operation of DERs. This chapter presents the latest UK research in smart grid applications and distribution networks and how intelligent community energy systems are enabled by DERs. Results from several British and European projects involving trials in UK networks and communities are presented. It is demonstrated that new and more intelligent tools are needed to deploy and use smart solutions properly.

Analysis of Optimal Power Flow Formulations for HVAC and VSC-HVDC Transmission Networks

Abstract: The Optimal Power Flow (OPF) problem has been widely studied by researchers and electric industry practitioners for many years. Most of these studies use DC power flow equations to represent the transmission system. However, future power systems will have to deal with new challenges, including integration of renewable energy resources, HVDC links, FACTS devices, etc. The DC formulation may not be appropriate to comprehensively model the behaviour of the new system, for which AC formulations might be required. In this paper, the integration of point-to-point and multi-terminal VSC-HVDC in three nonlinear and DC OPF formulations is analysed using three different test systems. The Knitro and CPLEX solvers are used as optimisation tools. The results show that the generation dispatch resulting from the DC formulation could overload the VSC-HVDC and HVAC transmission branches in the real operation. Moreover, it is demonstrated that the nonlinear formulations can produce good quality solutions that preserve the secure operation of the transmission system.

Specialized Heuristic Algorithms for AC Transmission Expansion Planning Problem

Abstract: In recent years, AC power flow equations have been gaining relevance to represent the transmission planning problem This trend will continue growing because of fast improvements of both computational resources and robust optimization techniques Relevant problems associated with the voltage magnitude and reactive power may be difficult to represent in the transmission planning problem if the DC mathematical formulation is used instead of the AC formulation However, the AC formulation remains difficult to solve even with the nowadays solution methodologies Therefore, the development of new methods that allows to solve effectively the AC formulation are highly relevant In this paper, novel heuristic methods to solve the transmission planning problem are proposed The results show that the proposed heuristics for the AC transmission planning problem are both effective and efficient to solve the problem Moreover, it has been determined the most suitable heuristic criteria for the proposed heuristics The simulations are performed in the North Northeast Brazilian test system