Recent blackouts in US and continental Europe: is liberalisation to blame?

The paper starts with a detailed technical overview of recent blackouts in the US, Sweden/Denmark and Italy in order to analyse common threads and lessons to be learnt. The blackouts have exposed a number of challenges facing utilities worldwide. Increased liberalisation of electricity supply industry has resulted in a significant increase in inter-area (or cross-border) trades which often are not properly accounted for when assessing system security. The traditional decentralised way of operating systems by TSOs, with each TSO looking after its own control area and little information exchange, resulted in inadequate and slow response to contingencies. A new mode of coordinated operation for real-time security assessment and control is needed in order to maintain system security. This new mode of operation requires overcoming a number of organisational, psychological, legal and technical challenges but the alternative is either to risk another blackout or run the interconnected system very conservatively, maintaining large security margin at a high cost to everyone. The paper also includes technical appendices explaining engineering power system concepts to non-engineering audience

Electricity Network Investment and Regulation for a Low Carbon Future

The requirement for significantly higher electricity network investment in the UK seems certain as the capacity of distributed generation and large scale renewables increases on the system. In this paper, which forms a chapter in the forthcoming Book “Delivering a Low Carbon Electricity System: Technologies, Economics and Policy”, the authors make a number of significant suggestions for improvement to the current system of network regulation. First, they suggest that the RPI-X system needs to be overhauled in favour of a simpler yardstick based system and which allows for more merchant transmission investments. Second, future regulation should involve more negotiated regulation involving agreements between network owners and purchasers of network services. This would be particularly advantageous for decisions on new network investments. Third, more extensive use needs to be made of locational pricing within the transmission and distribution system in order to facilitate the least cost expansion of low carbon generation, including micropower. Fourth, consideration needs to be given to ownership unbundling of distribution networks from retail supply. This would better facilitate the entry of distributed generation and the development of appropriate competition between grid and off-grid generation supply and demand side management. Finally, there needs to be a significant increase in R&D expenditure in electricity networks supported by customer levies

A Tracing Method for Pricing Inter-Area Electricity Trades

In the context of liberalisation of electricity markets world wide, the need for agreed protocols for electricity trades between systems with different charges poses a special challenge. System operators need to know how much a given trade uses the network, in order to allocate an appropriate portion of their costs to that trade. This paper discusses a technique, tracing, for determining how much each of a number of trades uses different parts of the electricity network. The scheme is based on the assumption that at any network node, inflows are shared proportionally between outflows (and vice versa). The paper outlines the technique and shows how it could be applied to the problem of charging cross-border trades. The paper goes on to demonstrate that the technique has a game theoretic rationale, in that it produces the Shapley value solution to a game equivalent to this allocation problem

Corrective control: stability analysis of Unified Controller combining frequency control and congestion management

This paper analyses stability of the Unified Controller (UC) that combines frequency control and congestion management and therefore makes it possible to move from preventive to corrective power system control. Earlier work by the authors of UC proved asymptotic stability of the methodology but the proof was based on a simplified first-order model of the turbine and turbine governor. We show that a higher order model of the turbine governor leads to eigenvalues with small but positive real parts. Consequently, we develop a modification of the methodology that decouples the physical and control systems and therefore results in all the eigenvalues having negative real parts. We illustrate the effectiveness of the modification on a realistic model of 39-bus model of New England power system implemented in Power System Toolbox (PST)

Comparative analysis of services from soft open points using cost–benefit analysis

Soft Open Points (SOPs) are power electronic-based devices which can replace Normally Open Points (NOPs) in distribution networks. They can improve network performance by enabling controllable power transfer between adjacent feeders. This flexible meshing can provide a wide range of services, including loss reduction, reduced renewables curtailment, improved reliability, reinforcement deferral, or enabling flexibility services. This paper proposes a novel framework, based on the Cost–Benefit Analysis methodology, to quantify and compare the cost-effectiveness of SOPs for providing each of these five value streams. The framework includes the development of mathematical models that encapsulate the key variables that drive competitive SOP use cases, as well as providing detailed analysis to determine quantitative estimates for each of the parameters. Results suggest that, whilst all services could be cost-effective, that reinforcement deferral and reduced DG curtailment are most likely to find wide usage. It is also suggested that the fast response time of SOPs as compared to conventional NOPs is unlikely to be a viable value proposition for improving reliability via conventional loss of load metrics such as energy not supplied. A detailed case study demonstrates that in marginal cases, where a SOP has a similar system net benefit compared to Business-as-Usual, that all services need to be considered rather than just single value streams in isolation. It is concluded from the research that there are multiple potential competitive applications for SOPs in future distribution networks.</p

Optimal Power Flow as a Tool for Fault Level Constrained Network Capacity Analysis

The aim of this paper is to present a new method for the allocation of new generation capacity, which takes into account fault level constraints imposed by protection equipment such as switcvhgear. It simulates new generation capacities and connections to other networks using generators with quadratic cost functions. The coefficients of the cost functions express allocation preferences over connection points. The relation between capacity and subtransient reactance of generators is used during the estimation of fault currents. An iterative process allocates new capacity using Optimal Power Flow mechanisms and readjusts capacity to bring fault currents within the specifications of switchgear. The method was tested on a 12-bus LV meshed network with 3 connection points for new capacity and 1 connection to a HV network. It resulted in significantly higher new generation capacity than existing first-come-first-served policies

Renewable Electric Energy Integration: Quantifying the Value of Design of Markets for International Transmission Capacity

Integrating large quantities of supply-driven renewable electricity generation remains a political and operational challenge. One of the main obstacles in Europe to installing at least 200 GWs of power from variable renewable sources is how to deal with the insufficient network capacity and the congestion that will result from new flow patterns. We model the current methodology for controlling congestion at international borders and compare its results, under varying penetrations of wind power, with a model that simulates an integrated European network that utilises nodal/localised marginal pricing. The nodal pricing simulations illustrate that congestion - and price - patterns vary considerably between wind scenarios and within countries, and that a nodal price regime could make fuller use of existing EU network capacity, introducing substantial operational cost savings and reducing marginal power prices in the majority of European countries.Power market design, renewable power integration, congestion management, transmission economics

Hybrid open points: an efficient tool for increasing network capacity in distribution systems

This letter introduces the Hybrid Open Point (HOP), a device consisting of an electromechanical switch connected in parallel with a power converter, for the purpose of providing additional network capacity in interconnected distribution systems. The HOP switch is used for bulk power transfer at low-cost, whilst the HOP converter provides targeted power transfer when the HOP switch is open. The device can replace either a Normally Open Point (Type 1 HOP) or a Normally Closed Point (Type 2 HOP). Simple interconnection and teed interconnection configurations are studied considering fault level and radiality constraints, with realistic use-cases identified for both HOP types. The HOP is shown to provide secure network capacity more cost-effectively than the classical Soft Open Point