Adam J. Collin

Development of Low-Voltage Load Models for the Residential Load Sector

A bottom-up modeling approach is presented that uses a Markov chain Monte Carlo (MCMC) method to develop demand profiles. The demand profiles are combined with the electrical characteristics of the appliance to create detailed time-varying models of residential loads suitable for the analysis of smart grid applications and low-voltage (LV) demand-side management. The results obtained demonstrate significant temporal variations in the electrical characteristics of LV customers that are not captured by existing load profile or load model development approaches. The software developed within this work is made freely available for use by the community.

Optimal Power Flow for Maximizing Network Benefits From Demand-Side Management

This paper applies optimal power flow (OPF) to evaluate and maximize network benefits of demand-side management (DSM). The benefits are quantified in terms of the ability of demand-responsive loads to relieve upstream network constraints and provide ancillary services, such as operating reserve. The study incorporates detailed information on the load structure and composition, and allows the potential network benefits, which could be obtained through management of different load types, to be quantified and compared. It is demonstrated that the actual network location of demand-manageable load has an important influence on the effectiveness of the applied DSM scheme, since the characteristics of the loads and their interconnecting networks vary from one location to another. Consequently, some network locations are more favorable for implementation of DSM, and OPF can be applied to determine the optimal allocation of demand-side resources. The effectiveness of the presented approach is assessed using a time-sequential OPF applied to typical radial and meshed U.K. distribution networks. The results of the analysis suggest that network operators could not just participate in, but also encourage and add value to the implementation of specific DSM schemes at the optimum network locations in order to maximize the total benefit from DSM.

An 11 kV steady state residential aggregate load model. Part 1: Aggregation methodology

This paper, which is part one of a two-part series, presents a general methodology for the development of improved aggregate load models for steady state power system analysis. Using the UK residential load sector as an example, the paper shows how component-based low voltage (LV) aggregate load models can be obtained using measurements, statistical and other available data and information on load structure and active/reactive power demands. The presented aggregate LV load models are connected to typical LV and medium voltage (MV) network configurations, in order to obtain correct aggregate load models at higher voltage levels. Part two paper discusses how the presented aggregate load models can be modified to include the analysis the effects of demand side management and microgeneration technologies have on the overall performance of LV/MV networks.

Reliability performance assessment in smart grids with demand-side management

The paper discusses possible impact of demand-side management (DSM) functionalities on the improvement of reliability performance and formulation of novel reliability assessment procedures of future electricity networks (so called “smart grids”). Firstly, traditionally used continuity of supply metrics and indices are assessed for a given reliability test system without considering any DSM scheme. Differences in the results for reliability indices for test system modelled with bulk loads and system modelled with detailed network configurations supplying connected loads are quantified, emphasising the errors that occur when parts of the system are neglected during the estimations of reliability performance. Afterwards, the effect of DSM on the reliability performance of the same test network are analysed, in order to assess potential benefits of DSM to the network operators, particularly with respect to their annual performance reports. Finally, possible changes in used reliability metrics are discussed, as smart grids will allow to substitute standard lumped representation of system loads at higher voltage levels with a more accurate and detailed information on load demands and load structures, including estimated contribution of demand-manageable portion of system load to the total demand.

Harmonic cancellation of modern switch-mode power supply load

Switch-mode power supplies (SMPS) are one of the most common category of loads, typically found in large numbers in modern power supply systems. These devices usually draw non-linear current and are, therefore, significant sources of harmonics. Although it is well known that the presence of harmonics will result in negative effects (e.g. higher thermal stresses and overloading, or increased neutral conductor currents), the assessment of the actual harmonic levels is not a simple task.

Modelling of electric vehicle chargers for power system analysis

This paper presents simple equivalent models of electric vehicle (EV) chargers, based on the measurements of a range of actual EVs. The developed models of the EV chargers are capable of correctly reproducing instantaneous input current waveforms, retaining all relevant electrical characteristics, including harmonic content. To analyse the effects of increased penetrations EV chargers on low-voltage network, the developed EV charger models are combined with the models of existing loads, as a part of the aggregate residential load mix.

An 11 kV steady state residential aggregate load model. Part 2: Microgeneration and demand-side management

This paper is part two of a two-part series on the development of improved aggregate load models for steady state power system analysis. Part one paper presented a general methodology for building component-based low voltage (LV) aggregate load models from statistical information on load structure and measurements of active/reactive power demands. The developed LV aggregate load models are then connected to typical LV and medium voltage (MV) network configurations, in order to obtain correct aggregate load models at higher voltage levels. This paper discusses how the presented LV and MV aggregate load models can be modified in order to include microgeneration technologies and demand-side management (DSM) functionalities in the analysis. Using the UK residential load sector as an example, it is shown that the assessment of microgeneration should be correlated both spatially and temporally with the aggregated load. The effects of DSM generally depend on the applied scenario, but may have a more pronounced effect on the aggregate demands.

Realising the potential of smart grids in LV networks. Part 2: Microgeneration

This paper, which is the second part of a two-part series, considers the influence of microgeneration technologies on the overall network performance and quality of supply of low-voltage residential customers in future “smart grids”. The paper uses the network models and demand-side management (DSM) scenarios developed in the Part 1 paper to further assess changes in active/reactive power flows, system losses, voltage profiles and harmonic emissions due to the combined effects of implementing microgeneration, energy storage and DSM.

Modelling the electrical loads of UK residential energy users

To fully assess the impact of possible demand-side management (DSM) actions on a system-wide scale, detailed low-voltage (LV) load models are required. This paper describes the development of a flexible, bottom-up approached profiling tool that transforms user activity profiles into load models. That will allow studying the grid and the influence of the implementation of DSM. The proposed profiling tool allows for variations in the three main areas that will determine the energy demand: the user behaviour, user electrical loads and ambient conditions.

Cancellation and attenuation of harmonics in low voltage networks

Increasing numbers of various power electronic equipment, used both as passive devices (e.g. front-end rectifier loads) and as active devices (e.g. inverter-interfaced generation), is one of the main contributing factors to the higher harmonic distortion levels in low voltage distribution networks. The analysis and results presented in this paper discuss and demonstrate how modern power electronic devices interact with each other and with the low voltage network. To represent the effects of harmonic cancellation and harmonic attenuation, different types of power electronic equipment are analysed for several characteristic system impedance values and typically distorted voltage waveforms.