Dimitrios Papadaskalopoulos

Decentralized Participation of Flexible Demand in Electricity Markets—Part II: Application With Electric Vehicles and Heat Pump Systems

Realizing the significant demand flexibility potential in deregulated power systems requires its suitable integration in electricity markets. Part I of this work has presented the theoretical, algorithmic and implementation aspects of a novel pool market mechanism achieving this goal by combining the advantages of centralized mechanisms and dynamic pricing schemes, based on Lagrangian relaxation (LR) principles. Part II demonstrates the applicability of the mechanism, considering two reschedulable demand technologies with significant potential, namely electric vehicles with flexible charging capability and electric heat pump systems accompanied by heat storage for space heating. The price response sub-problems of these technologies are formulated, including detailed models of their operational properties. Suitable case studies on a model of the U.K. system are examined in order to validate the properties of the proposed mechanism and illustrate and analyze the benefits associated with the market participation of the considered technologies.

Microgrids: Enhancing the Resilience of the European Megagrid

The European electricity system of the future faces challenges of unprecedented proportions. By 2020, 20% of the European electricity demand will be met by renewable generation while, by 2030, a substantial proportion of the electricity generation would become largely decarbonized. Furthermore, beyond 2030, it is expected that significant segments of the heat and transport sectors will be electrified to meet the targets proposed by the EU governments for greenhouse gas emission reductions of at least 80% in 2050.

Decentralized Coordination of Microgrids With Flexible Demand and Energy Storage

Scalability and privacy concerns have created significant interest in decentralized coordination of distributed energy resources (DERs) within microgrids. Previously proposed approaches, however, fail to achieve feasible solutions under flexible demand (FD) and energy storage (ES) participation. After justifying and demonstrating this challenge, this paper develops a novel Lagrangian relaxation-based mechanism achieving feasible, near-optimal solutions in a decentralized fashion, considering both active and reactive power. A two-level iterative algorithm eliminates the infeasibility effect of FD and ES nonstrict convexities, and prevents the creation of new demand peaks and troughs by the concentration of their response at the same low- and high-priced periods. Tradeoffs associated with the design and operation of the mechanism are analyzed, and the value of additional information submission by the DER, in enabling the quantification of an optimality bound of the determined solutions and significant improvements in communication requirements, is assessed. These contributions are supported by case studies on an LV microgrid test system.

Decentralized participation of electric vehicles in network-constrained market operation

This paper builds on previous work by the authors in developing a novel market mechanism enabling decentralized market participation of flexibly-charging electric vehicles (EV) and addresses the challenge of incorporating the effect of the transmission network on market operation. The formulation of the proposed Lagrangian Relaxation (LR)-based mechanism is extended to account for network capacity constraints. A LR heuristic method introducing location-specific restrictions on flexible EV demand response is developed for producing high quality market clearing solutions without extensive computational requirements. Case studies on a representative model of the UK transmission network demonstrate and quantify the conditions and the extent to which the location-specific LR heuristic improves the solution with respect to previous approaches and the economic value of flexible EV market participation in relieving network congestion.

Dynamic pricing in highly distributed power systems of the future

Existing energy systems and markets are characterized by a relatively small number of participants interacting in high-volume wholesale markets with end-users mainly participating in separate retail markets. This paper presents a work which aims to develop a Distributed Energy Market that brings together all participants in an integrated real-time marketplace. Operation in such markets will be based on dynamic pricing of various services, starting from energy generation, ancillary services and active demand participations. For this operation, new market and businesses models and rules need to be developed and tested.

Factoring Flexible Demand Non-Convexities in Electricity Markets

Summary form only given. Uniform marginal pricing cannot generally support competitive equilibrium solutions in markets with non-convexities, yielding surplus sub-optimality effects. Previous work has identified non-convexities associated with the generation side of electricity markets and proposed different approaches to address surplus sub-optimality. This paper extends this concept to incorporate the demand side. Non-convexities of flexible demand (FD) are identified, including options to forgo demand activities as well as discrete and minimum power levels, and resulting surplus sub-optimality effects are demonstrated through simple examples and a larger case study. Generalized uplift and convex hull pricing approaches addressing these effects are extended to account for FD non-convexities. Concerning the former, generalized uplift functions for FD participants are proposed, and a new rule is introduced for equitable distribution of the total surplus loss compensation among market participants. Regarding the latter, it is demonstrated that convex hull prices are flattened at periods when FD is scheduled to eliminate surplus sub-optimality associated with the FD ability to redistribute energy requirements across time.

It's All About Grids: The Importance of Transmission Pricing and Investment Coordination in Integrating Renewables

In Great Britain, it is projected that an unprecedented amount of transmission investment will take place in the next decade and that these investments will be the largest transmission network reinforcements since the post-World War II expansion. In Figure 1, the projected range, to 2030, of onshore, offshore, and crossborder investments is presented against the estimated asset values. The value of the transmission assets is expected to more than double to 2030 with investments projected between 20 billion and 50 billion pounds across onshore (main transmission system), offshore (connecting mainly offshore wind farms) and cross-border interconnection transmission projects. The exact level and cost of these transmission investments will depend on a number of factors, including the location of new conventional and renewable energy sources (RES) plants (considering on- and offshore developments); decommissioning of existing ones; demand growth; cross-border trading of energy and ancillary services; and uptake of distributed generation, energy storage, demandside response, and other smart grid technologies.

Optimization of operating and investment costs of active management deployment in distribution networks

This paper introduces an original methodology for the co-optimization of operating and investments costs associated with the deployment of active management strategies in power distribution networks. The resulting large-scale optimization problem is solved using Benders decomposition. The concept is demonstrated using a module-based generic distribution system model. Case studies for different active management strategies (involving generation curtailment, reactive power compensation and transformer tap changers) and various DG penetration and density levels are presented and analyzed.

Participation of electric vehicles in electricity markets through a decentralized mechanism

In the emerging power systems setting, the realization of the demand flexibility potential needs to be coupled with its integration in electricity markets. Decentralization of market mechanisms constitutes a major challenge towards the achievement of such integration. In this paper, a decentralized day-ahead pool market mechanism is proposed, based on Lagrangian Relaxation (LR) principles. Issues related to demand participation through the proposed mechanism are addressed from the perspective of electric vehicles (EV) due to their significant flexibility potential. Their local, surplus maximization bidding problems are formulated taking into account their detailed, inter-temporal characteristics. Discontinuities in their market behaviour and their impacts on equilibrium existence are identified and a suitable LR-heuristic method is proposed to reach a satisfactory feasible market clearing solution when such discontinuities make an equilibrium solution unattainable. Benefits realized through the proposed approaches are quantified and analyzed through suitable case studies.

Integrating customers' differentiated supply valuation in distribution network planning and charging

Due to the lack of observability and controllability in current distribution networks, the traditional planning and charging framework makes the oversimplifying assumption of uniform supply valuation for every customer of the same sector and every unit of supplied energy. Building on the advanced metering and control capabilities of the emerging smart grid, this paper explores the impact of integrating the differentiated valuation of electricity supply for different customers and different levels of supplied energy in distribution network planning. Customer interruption costs are reduced, since supply interruption of customers with low supply valuation and the non-critical part of their demand is prioritized during network failures. As a result, the need for capital intensive network reinforcements is limited and the total network expenditure is reduced. Furthermore, a cost-reflective network charging scheme based on the principles of locational marginal pricing is proposed, enabling an equitable treatment of customers with differentiated supply valuation.