The growing uptake of wind and photovoltaic technologies requires further sources of system-level flexibility to avoid or defer significant investments. The ability to control, to some extent, customer demand (load management, LM) is one of these sources of flexibility. However, the direct involvement of a large number of customers makes the scalability of such approach a major challenge. A mostly unexplored solution to overcome the challenges of managing thousands or millions of customers is to leverage the positive correlation between voltage and demand. More precisely, Distribution Network Operators (DNOs) can control existing regulation devices to reduce customer voltages and so triggering a reduction in demand. This scheme, hereafter called voltage-led LM, avoids the direct involvement of customers overcoming one of the major barriers of traditional LM solutions. To understand whether this approach can be of any significance, a methodology able to quantify such reduction in demand need to be developed. However, the few methodologies available in the literature neglect the interactions across voltage levels and their influence on the benefits of the scheme. Moreover, time-varying demand profiles and load models are not always considered. Finally, the impact that the widespread adoption of distributed energy resources might have, is also neglected. This thesis addressed these gaps by developing a four-stage approach in which the time-varying volume of demand reduction that the scheme can unlock is quantified considering for the first time the influences among all voltage levels in distribution network. To reduce the complexity each voltage level is analysed separately whilst maintaining the corresponding dependencies. The methodology, also able to extrapolate the results at national scale, can quantify the impact that the uptake of residential scale PV units might have on the scheme. The methodology is demonstrated with a real UK case study where 10-min resolution time-series daily and seasonal analysis are performed. For the first time real network models across the whole distribution network, from 132 kV to 400 V, have been adopted. The interactions across voltage levels, the adoption of realistic load models, the variety of network models and the use of a time-varying approach, all aspects simultaneously considered for the first time in a case study, have shown to play a key role in the quantification. In Great Britain the scheme is expected to provide a significant volume of flexibility of around 1.8GW (60 GW of peak demand). The presence of PV, at least in the short term, has shown to have only a marginally effect on the benefits unlocked by the voltage-led LM scheme, making such scheme promising even in a low carbon future.

The co-optimization of energy and reserves has become a standard requirement in integrated markets. This is due to the inverse relationship that exists between energy and reserves. The provision of reserves generally reduces the amount of primary energy a generating unit can produce and vice versa. This suggests that these products should be procured through a simultaneous auction to ensure optimal procurement and pricing. Furthermore, forward markets dictate that this co-optimization of energy and reserves be done over a multi-period planning horizon. This dissertation addresses the problem of optimal scheduling and pricing of energy and reserves over a multi-period planning horizon using an optimal power flow formulation. The extension of the problem from a static optimization problem to a dynamic optimization problem is presented. Price definitions for energy and reserves in terms of shadow prices emanating from the optimization algorithm are provided. It is shown that the proposed formulation of prices leads to the cascading of reserve prices and eliminates the problem of “price reversal” where lower quality reserves are priced higher than higher ii quality reserves. Pricing conditions are also established for the downward substitution of higher quality reserves for lower quality reserves. The proposed pricing formulations are tested on the IEEE 24 Bus Reliability Test System and on the South African power network. The simulated results show that cascading of reserve prices does occur and that prices of different types of reserves are equal when downward substitution of reserves occurs. Zonal reserve requirements result in higher energy and reserve prices, which in term result in higher procurement costs to the system operator and higher profits to market participants. Congestion on the network also results in higher procurement costs to the system operator and higher profits to market participants in the case of zonal pricing of reserves. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / unrestricted

No description available.

Local electricity markets can be defined broadly as 'future electricity market designs involving domestic customers, demand-side response and energy storage'. Like current deregulated electricity markets, these localised derivations present specific stochastic optimisation problems in which the dynamic and random nature of the market is intertwined with the physical needs of its participants. Moreover, the types of contracts and constraints in this setting are such that 'games' naturally emerge between the agents. Advanced modelling techniques beyond classical mathematical finance are therefore key to their analysis. This thesis aims to study contracts in these local electricity markets using the mathematical theories of stochastic optimal control and games. Chapter 1 motivates the research, provides an overview of the electricity market in Great Britain, and summarises the content of this thesis. It introduces three problems which are studied later in the thesis: a simple control problem involving demand-side management for domestic customers, and two examples of games within local electricity markets, one of them involving energy storage. Chapter 2 then reviews the literature most relevant to the topics discussed in this work. Chapter 3 investigates how electric space heating loads can be made responsive to time varying prices in an electricity spot market. The problem is formulated mathematically within the framework of deterministic optimal control, and is analysed using methods such as Pontryagin's Maximum Principle and Dynamic Programming. Numerical simulations are provided to illustrate how the control strategies perform on real market data. The problem of Chapter 3 is reformulated in Chapter 4 as one of optimal switching in discrete-time. A martingale approach is used to establish the existence of an optimal strategy in a very general setup, and also provides an algorithm for computing the value function and the optimal strategy. The theory is exemplified by a numerical example for the motivating problem. Chapter 5 then continues the study of finite horizon optimal switching problems, but in continuous time. It also uses martingale methods to prove the existence of an optimal strategy in a fairly general model. Chapter 6 introduces a mathematical model for a game contingent claim between an electricity supplier and generator described in the introduction. A theory for using optimal switching to solve such games is developed and subsequently evidenced by a numerical example. An optimal switching formulation of the aforementioned game contingent claim is provided for an abstract Markovian model of the electricity market. The final chapter studies a balancing services contract between an electricity transmission system operator (SO) and the owner of an electric energy storage device (battery operator or BO). The objectives of the SO and BO are combined in a non-zero sum stochastic differential game where one player (BO) uses a classic control with continuous effects, whereas the other player (SO) uses an impulse control (discontinuous effects). A verification theorem proving the existence of Nash equilibria in this game is obtained by recursion on the solutions to Hamilton-Jacobi-Bellman variational PDEs associated with non-zero sum controller-stopper games.

The high penetration of renewable energies (RE) in power systems is increasing the volatile production on the generation side and the presence of distributed energy resources (DER) over the territory. On the other hand, Virtual Power Plants (VPPs) are an aggregation of DER managed as a single entity to promote flexibility services to power systems. Therefore, VPPs are a valid approach to cope with the arising challenges in the power system related to RE penetration. This report defines the concept of a utility-scale VPP, as a tool to stabilize the grid and increase the flexibility capacity in power systems. For this purpose, the report places special emphasis in the use cases that can be developed with a utility-scale VPP. Nevertheless, implementing a utility-scale VPP is a complex procedure, as VPP solutions are highly customizable depending on the scope and the conditions of each project. For this reason, this report analyses the main factors that must be taken into account when implementing a VPP solution. The report concludes that the two most critical factors that define the viability of a VPP project are, first, the energy market design and regulatory framework and second, the technical requirements. These two must always align with the scope of the project and the use cases intended to be developed. Further, other minor factors, including a cost estimate for a VPP solution, are also considered in the report. / Den höga penetrationen av förnybara energier i kraftsystem ökar den flyktiga produktionen på produktionssidan och närvaron av distribuerade energiresurser över territoriet. Å andra sidan är virtuella kraftverk en sammanställning av distribuerade energiresurser som hanteras som en enda enhet för att främja flexibilitetstjänster till kraftsystem. Därför är virtuella kraftverk: er en giltig strategi för att hantera de uppkomna utmaningarna i kraftsystemet relaterat till förnybara energier genomslag. I denna rapport definieras konceptet med en virtuella kraftverk verktygsskala som ett verktyg för att stabilisera nätet och öka flexibilitetskapaciteten i kraftsystem. För detta ändamål lägger rapporten särskild tonvikt på användningsfall som kan utvecklas med en virtuella kraftverk-nytta. Trots det är implementering av en virtuella kraftverknyckelskala en komplex procedur, eftersom virtuella kraftverk-lösningar är mycket anpassningsbara beroende på omfattning och villkor för varje projekt. Av denna anledning analyserar denna rapport de viktigaste faktorerna som måste beaktas vid implementering av en VPP-lösning. Rapporten drar slutsatsen att de två mest kritiska faktorerna som definierar ett virtuella kraftverk projekts livskraft är, dels energimarknadens utformning och regelverk och för det andra de tekniska kraven. Dessa två måste alltid anpassa sig till projektets omfattning och användningsfall som är avsedda att utvecklas. Vidare beaktas även andra mindre faktorer, inklusive en kostnadsuppskattning för en virtuella kraftverk lösning, i rapporten.