Future Electricity Networks Research Articles

Optimal Recourse Strategy for Battery Swapping Stations Considering Electric Vehicle Uncertainty

Battery swapping stations (BSSs) present an alternative way of charging electric vehicles (EVs) that can lead toward a sustainable EV ecosystem. Although research focusing on the BSS strategies has been ongoing, the results are fragmented. Currently, an integrated way of considering stochastic EV station visits through planning and operations has not been fully investigated. To create comprehensive and resilient battery swapping stations, a two-stage optimization with recourse is proposed. In the planning stage, the investment for battery purchases is recommended even before the EV station visit uncertainties are made known. In the operation stage, the battery allocation decisions, such as charging, discharging, and swapping are then coordinated. To apply the recourse strategy in creating representative scenarios, the EV station visit distribution techniques are also proposed using a modified K-means clustering method. Aside from the sensitivity analysis made with swapping prices and charging intervals, the strategy comparisons with conventional strategies have also demonstrated the practicality of the BSS coordination to future electricity and transportation networks.

Theoretical analysis of the efficiency of a V2G wireless charger for Electric Vehicles

V2G (Vehicle-to-grid) technology will report important benefits for the operation and safety of the grid. In order to facilitate the expansion of the V2G technology in a future, it is recommended to offer the drivers with easy to use methods to charge and discharge their EV batteries. In this sense, wireless chargers are expected to play a relevant role in the future electrical networks as it reduces the users intervention. The development of this kind of system is still open to improve them in terms of their operation, their compliance and their control. An important issue for the evaluation of these systems is the efficiency, which measures the power losses occurring in the system. This paper addresses a deep study about the losses in a bidirectional wireless charger. Then, it provides with a mathematical model to characterize them. This model is validated by means of experimental results conducted in a 3.7-kW prototype.

Flexible Grid Connection and Islanding of SPC-Based PV Power Converters

At the present time, distributed generation systems are required to disconnect from the main grid when there is an outage. In order to fulfill this requirement, photovoltaic (PV) power plants are equipped with anti-islanding algorithms, embedded in the converters controller, to avoid the island operation. However, the current trends in the development of the future electrical networks evidence that it is technically feasible and economically advantageous to keep feeding islanded systems under these situations, without cutting the power supply to the loads connected to the network. Nevertheless, commercial PV power converters are programmed as grid-feeding converters and they are unable to work in island mode if there is not an agent forming the grid. In order to overcome this problem, the synchronous power controller (SPC) is presented in this paper as a suitable alternative for controlling PV inverters. As will be further discussed, this controller permits PV plants to operate seamlessly in grid-connected and island mode, with no need of changing the control structure in either case. Moreover, the participation of SPC-based power converters integrating energy storage enables other grid-feeding systems to contribute to the grid operation in island conditions. The good results achieved with the SPC in different conditions will be shown in simulations, and also with experiments considering a real PV power plant combining SPC and commercial PV inverters.

A High Step-Up Ratio Soft-Switching DC–DC Converter for Interconnection of MVDC and HVDC Grids

DC grid technology is regarded as a promising solution for future electric networks integrating a great amount of renewable energies. It calls for high-efficiency dc–dc converters with high voltage step-up ratio to interconnect medium-voltage (MV) dc distribution grids and high-voltage (HV) dc transmission grids. This paper presents an isolated bidirectional soft-switching dc–dc converter combining two-level converters in parallel on the MV side and a modular multilevel converter (MMC) on the HV side. A dedicated control method of the proposed converter is presented. By the proposed method, a certain reactive current is injected into the MV side by the MMC to ensure soft-switching on the MV side. The proposed converter presents low power-semiconductor total device rating and low semiconductor losses over a wide power range at variable input and output voltages. Simulation of a 50 kV/400 kV, 400 MW converter is conducted to evaluate semiconductor losses and verify the validity of this work.

Generic model of a VSC-based HVDC link for RMS simulations in PSS/E

Abstract HVDC transmission technology is a key factor for the development of future electric power networks. A generic modelling representation of such systems is important for their performance evaluation. This paper addresses the difficulties of creating a generic model in PSS/E for dynamic studies and offers a set of simulation results compared with another RMS simulation tool (PowerFactory). It is shown through the comparison process the generic model produces similar results with the PowerFactory model even though differences in the modelling approach are present.

Large Prefabricated Concrete Panels Collective Dwellings from the 1970s: Context and Improvements

The period between 1960s and 1970s had a significant impact in Romania on the urban development of major cities. Because the vast expansion of the industry, the urban population has massively increased, due the large number of workers coming from the rural areas. This intense process has led to a shortage of homes on the housing market. In order to rapidly build new homes, standard residential project types were erected using large prefabricated concrete panels. By using repetitive patterns, such buildings were built in a short amount of time through the entire country. Nowadays, these buildings represent 1.8% of the built environment and accommodate more than half of a city’s population. Even though these units have reached only half their intended life span, they fail to satisfy present living standards and consume huge amounts of energy for heating, cooling, ventilation and lighting. Due to the fact that these building are based on standardised projects and were built in such a large scale, the creation of a system that brings them to current standards will not only benefit the building but also it will significantly improve the quality of life within. With the transition of the existing power grids to a “smart grid” such units can become micro power plants in future electricity networks thus contributing to micro-generation and energy storage. If one is to consider the EU 20-20-20 commitments, to find ideas for alternative and innovative strategies for further improving these building through locally adapted measures can be seen as one of the most addressed issues of today. This research offers a possible retrofitting scenario of these buildings towards a sustainable future. The building envelope is upgraded using a modular insulation system with integrated solar cells. Renewable energy systems for cooling and ventilation are integrated in order to provide flexibility of the indoor climate. Due to their small floor area, the space within the apartments is redesigned for a more efficient use of space and an improved natural lighting. Active core modules are placed on top of the unused attics and a solar panel array is introduced. Furthermore accessibility issues are addressed by facilitating access for disabled people and implementing an elevator system that currently these building do not have.

Power Quality Measurements of a Horizontal Axial Small Wind Turbine

As small wind turbines are increasingly used, the assessments of power quality may thus become paramount. Unlike the large-scale wind turbines which are optional required to perform power quality measurements during production certification stage; however the power quality measurements are often neglected in small wind turbines since they are not requested on the certain of national grid codes at low-voltage distribution system level. Considering the high penetrations of small wind turbines may be connected to the future urban electric network, the paper performs the power quality on-site measurements of a horizontal axle small wind turbines. The issues may include the discussion of measurement system structure, the description of measurement method, and the analysis of wind turbine power characteristic, voltage/current trends, harmonics and flicker phenomena. The measured data collected in the study will valuable for the further analysis of power systems connected with the small wind turbines.

Control of Energy Storage

In the attempt to tackle the issue of climate change, governments across the world have agreed to set global carbon reduction targets. [...]

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

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.

A systems approach to quantifying the value of power generation and energy storage technologies in future electricity networks

A new approach is required to determine a technology's value to the power systems of the 21st century. Conventional cost-based metrics are incapable of accounting for the indirect system costs associated with intermittent electricity generation, in addition to environmental and security constraints. In this work, we formalise a new concept for power generation and storage technology valuation which explicitly accounts for system conditions, integration challenges, and the level of technology penetration. The centrepiece of the system value (SV) concept is a whole electricity systems model on a national scale, which simultaneously determines the ideal power system design and unit-wise operational strategy. It brings typical Process Systems Engineering thinking into the analysis of power systems. The model formulation is a mixed-integer linear optimisation and can be understood as hybrid between a generation expansion and a unit commitment model. We present an analysis of the future UK electricity system and investigate the SV of carbon capture and storage equipped power plants (CCS), onshore wind power plants, and grid-level energy storage capacity. We show how the availability of different low-carbon technologies impact the optimal capacity mix and generation patterns. We find that the SV in the year 2035 of grid-level energy storage is an order of magnitude greater than that of CCS and wind power plants. However, CCS and wind capacity provide a more consistent value to the system as their level of deployment increases. Ultimately, the incremental system value of a power technology is a function of the prevalent system design and constraints.

Guest Editorial Special Section on Contemporary Issues in Power Quality

The aim of this special issue is to present original research which is aimed at addressing some of these new challenges and opportunities. The expectation of this special issue is that it will provide pathways for further research that is aimed at managing power quality in future electricity networks.

Towards accurate estimation of fast varying frequency in future electricity networks: The transition from model-free methods to model-based approach

Accurate estimation of fast varying fundamental frequency in the presence of harmonics and noise will be required for effective frequency regulation in future electricity networks with high penetration level of renewable energy sources. Two new algorithms for network frequency tracking are proposed. The first algorithm represents a robust modification of classical zero crossing method, which is widely used in industry. The second algorithm is a multiple model algorithm based on the systems with harmonic regressor. Algorithm allows complete reconstruction of the frequency content of the signal, using information about the upper bound of the number of harmonics only. Moreover, new family of high-order algorithms together with new stepwise splitting method are proposed for parameter calculation in systems with harmonic regressor for the accuracy improvement. Statistical methods are introduced for comparison of two new algorithms to classical zero crossing algorithm. The modified algorithm provides significant improvement compared to the classical algorithm, and the algorithm with harmonic regressor provides further improvement of the statistical performance indexes with respect to the modified algorithm.

Power-Quality Management in New Zealand

Power quality (PQ) is a major concern in the relatively small island electrical network of New Zealand. The potential influx of new technologies, such as electric vehicles, heat-pumps, light-emitting diode lighting, etc., could potentially cause electromagnetic-compatibility problems in the future. To manage the PQ into the future, a government-funded project entitled Power Quality (PQ) in Future Electricity Networks (NZ) was instigated. This project was co-funded by the Electricity Engineers' Association of NZ (EEA) and the main deliverable was PQ guidelines that EEA members could adopt in their grid connection codes. Other objectives were to influence device standards and identify mitigation techniques. This paper gives an overview of this project and presents some key findings.

Energy Optimization for Distributed Energy Resources Scheduling with Enhancements in Voltage Stability Margin

The need for developing new methodologies in order to improve power system stability has increased due to the recent growth of distributed energy resources. In this paper, the inclusion of a voltage stability index in distributed energy resources scheduling is proposed. Two techniques were used to evaluate the resulting multiobjective optimization problem: the sum-weighted Pareto front and an adapted goal programming methodology. With this new methodology, the system operators can consider both the costs and voltage stability. Priority can be assigned to one objective function according to the operating scenario. Additionally, it is possible to evaluate the impact of the distributed generation and the electric vehicles in the management of voltage stability in the future electric networks. One detailed case study considering a distribution network with high penetration of distributed energy resources is presented to analyse the proposed methodology. Additionally, the methodology is tested in a real distribution network.

Profit maximization algorithms for utility companies in an oligopolistic energy market with dynamic prices and intelligent users

Dynamic energy pricing provides a promising solution for the utility companies to incentivize energy users to perform demand side management in order to minimize their electric bills. Moreover, the emerging decentralized smart grid, which is a likely infrastructure scenario for future electrical power networks, allows energy consumers to select their energy provider from among multiple utility companies in any billing period. This paper thus starts by considering an oligopolistic energy market with multiple non-cooperative (competitive) utility companies, and addresses the problem of determining dynamic energy prices for every utility company in this market based on a modified Bertrand Competition Model of user behaviors. Two methods of dynamic energy pricing are proposed for a utility company to maximize its total profit. The first method finds the greatest lower bound on the total profit that can be achieved by the utility company, whereas the second method finds the best response of a utility company to dynamic pricing policies that the other companies have adopted in previous billing periods. To exploit the advantages of each method while compensating their shortcomings, an adaptive dynamic pricing policy is proposed based on a machine learning technique, which finds a good balance between invocations of the two aforesaid methods. Experimental results show that the adaptive policy results in consistently high profit for the utility company no matter what policies are employed by the other companies.

Modelling of energy storage dispatch for generation system adequacy studies

Energy storage systems (ESS) are expected to play an important role in future electricity networks and more modelling efforts are required to include them in generation system adequacy (GSA) studies based on sequential Monte Carlo simulations. This paper proposes a new, generic approach to ESS dispatch modelling that takes into account both technological and control aspects required for the simulation-based GSA evaluations. The model features the application of detrended residual load that includes renewable production and distinguishes between different operating timescales. Moreover, by using the correction of ESS dispatch based on the classical proportional integral controller technique the model achieves a realistic representation of storage level variations. In this paper all the necessary model equations and parameter identification procedures are provided along with their underlying assumptions. The effectiveness of the new dispatch model is demonstrated by using a GSA study for a generation system comprising thermal power plants and hydroelectric ESS with annual and daily operating cycles.

ELECTRICITY THEFT DETECTION AND LOCALISATION IN UNKNOWN RADIAL LOW VOLTAGE NETWORK

The distribution of electricity involves both technical and non-technical losses. One major cause of non-technical loss is the illegal abstraction of electricity which is also known as ‘Electricity Theft’. The illegal usage of electricity has many associated problems, both for utilities and consumers of electricity, implying that there is a pressing need for theft detection and localisation. Traditional methods of identifying illegal electricity consumers are time consuming and ineffective as measurements have to be performed at a large number of suspected locations. Smart metering in future electricity networks will lead to a more efficient automated system for the detection and localisation of electricity theft. This will enable immediate action to be taken by distribution network operators against the offenders and will help to improve the quality, reliability and security of electricity supply systems. The aim of this study was to analyse the performance of an electricity theft detection and localisation technique in an unknown grid. The method assumed the availability of measured voltages, currents, and powers from installed smart meters. The detection step was a power comparison process and the localisation step was a voltage comparison process. The investigation involved analysis in the presence of single and simultaneous multiple thefts. To better represent future networks with increasing penetration of renewable energy generators, distributed generation was added to the system and the capability of the detection and localisation technique was further explored. All the simulations were performed in Matlab/Simulink. It was found that the method performed satisfactorily, with a minimum stolen power of 450 W successfully detected and localised.

DEVELOPMENT OF ELECTRIC NETWORK IN EUROPE: THE CURRENT SITUATION AND PERSPECTIVES

Maintaining and improving reliable, efficient grids is vital for a modern society. The European transmission and distribution networks are ageing and they are faced with different challenges that may push them to evolve following different trends and conflicting drivers. The present paper aims therefore at assessing the current situation and at evaluating the possible future evolution of the electricity grids in Europe. It analyses technological state of the art and the expected deployment of advanced technology in transmission and distribution. The study highlights the main barriers hindering the development of the present grids and the design of future electricity networks and tries to identify a possible way forward. The paper also focuses on possible synergies with other sectors. Many actions still need to be taken, both at European and national level, to develop the future electricity networks.

Nuclear power can reduce emissions and maintain a strong economy: Rating Australia’s optimal future electricity-generation mix by technologies and policies

Legal barriers currently prohibit nuclear power for electricity generation in Australia. For this reason, published future electricity scenarios aimed at policy makers for this country have not seriously considered a full mix of energy options. Here we addressed this deficiency by comparing the life-cycle sustainability of published scenarios using multi-criteria decision-making analysis, and modeling the optimized future electricity mix using a genetic algorithm. The published ‘CSIRO e-future’ scenario under its default condition (excluding nuclear) has the largest aggregate negative environmental and economic outcomes (score=4.51 out of 8), followed by the Australian Energy Market Operator’s 100% renewable energy scenario (4.16) and the Greenpeace scenario (3.97). The e-future projection with maximum nuclear-power penetration allowed yields the lowest negative impacts (1.46). After modeling possible future electricity mixes including or excluding nuclear power, the weighted criteria recommended an optimized scenario mix where nuclear power generated >40% of total electricity. The life-cycle greenhouse-gas emissions of the optimization scenarios including nuclear power were <27kg CO2-e MWh−1 in 2050, which achieves the IPCC’s target of 50–150kg CO2-e MWh−1. Our analyses demonstrate clearly that nuclear power is an effective and logical option for the environmental and economic sustainability of a future electricity network in Australia.

Measurement of 40 power system harmonics in real‐time on an economical ARM ® Cortex™‐M3 platform

Within future homes and electrical power networks, emphasis is being placed on intelligent, distributed measurement devices. In particular, the recognition of individual or aggregated loads through harmonic signature has been proposed as a useful way to enhance the value of home energy monitoring/control. Clearly, the cost of implementing such measurement devices is a major barrier to acceptance. In a recent project, a challenge was set to implement real-time software on an ARM® Cortex™ LPC1768 microcontroller platform (chip cost c. £4). The software must be capable of measuring a single-phase AC frequency, real and reactive power flows and provide a full breakdown of the voltage and current (and power) behaviour via harmonic analysis from DC to the 40th, in real-time with a new output every 20 ms. In addition, the algorithm must be capable of adapting the measurement when the frequency is not nominal (50 Hz) so that spectral leakage is minimised. It is found that the LPC1768 processor is capable of supporting such an algorithm when it is coded appropriately. This knowledge de-risks the proposed use of such cheap microcontrollers for these relatively complex tasks.