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This paper provides an experimentally validated optimal control approach based on a Hamilton–Jacobi–Bellman (HJB) model for optimising aggregated distributed energy resources across multiple energy carriers. The research incorporates nonlinear effects arising from storage degradation, conversion efficiency and self-discharge as well as multiple energy carrier storage. A semi-Lagrangian HJB solver was implemented on low-cost digital controllers, and integrated into a real fully functional cloud-based aggregation platform. The computational cost is kept at a minimum, enabling on-line computations on the low-cost controller, while maintaining a rigorous proof of convergence to the theoretical value function of the nonlinear, non-convex optimal control problem. The controller links into a distributed optimal control platform that is using local as well as cloud-based information and performs all the computation and decision-making locally. The distributed controllers were tested and validated on site with an electrical and a thermal storage device. Experimental results confirm that the framework is practical, accommodates nonlinear effects and inaccurate external forecasts, has a small computational cost, is robust and can deliver significant cost benefits to the stakeholders.

This paper investigates the integration of a wind farm with electric vehicles capable of Vehicle-to-Grid operation, and the impact of this integration on the reliability of the energy supply to the load. The operational reliability of wind farms was considered, in order to predict the outage probability. The operational reliability model was implemented on a small power system, and a case study analysis was undertaken of the influence of Vehicle-to-Grid in the event of an outage at the wind farm. Several reliability indices were calculated for the case study. Results show a significant improvement of the system’s reliability by the presence of Vehicle-to-Grid functionality, since it is able to compensate for the power lost during a wind farm outage.

Resilience is a vital concept in engineering, business, and natural sciences, and is a measure of the ability of an entity to withstand High Impact Low Probability (HILP) events. During the COVID-19 pandemic, which started in late 2019/early 2020, power system utilities around the globe have responded in effective and efficient ways to enhance the resilience of their organisations, both in terms of real time operations and prudent management of its infrastructure, in order to continue their mandate in providing reliable supply to meet customer demands. This paper presents the CIGRE definition for power system resilience, established by the C4.47 Working Group in 2018, and demonstrates the application of resilience-oriented thinking within the electrical sector. The response and recovery efforts are described, with respect to the key actionable measures that are an integral part of the power system resilience definition, taken before, during and after the COVID-19 pandemic. A practical conceptual framework is also presented, for thinking about resilience in terms of three key components of resilience strategies: organisational, infrastructure and operational resilience. The paper also discusses the different strategies adopted in response to COVID-19, based on the C4.47 members’ experiences during the pandemic. Finally, a case study is presented, which proves the effectiveness of a set of response measures, using graph theory and the characteristics of the staff-asset interactions.

This paper centres on the performance of PI and hysteresis controllers for AC fault ride through for an MMC VSC - HVDC transmission system. In the simulated MMC converter test system, a 600 MW VSC-HVDC transmission line connects two farms, formed from combined offshore wind turbines and wave converters, to the two onshore AC grids. The model in this study included two 300kV DC submarine cables with a cable length of 100km. In the reported simulation a three-phase to ground fault, a single line to ground fault, a double line to ground fault and a line-to-line fault were applied to the onshore AC network. The simulation results reveal reductions in DC voltage overshoot and transient energy with the PI-based controller (compared to the hysteresis controller) for 3- phase to ground, line to ground and line - to - line to ground faults respectively, with no difference for line-to-line faults.

Multiple energy carrier systems stem from the need to evolve traditional electricity, gas and other energy systems to more efficient, integrated energy systems. An approach is presented, for controlling multiple energy carriers, including electricity (AC or DC), heat, natural gas and hydrogen, with the objective to minimise the overall cost and/or emissions, while adhering to technical and commercial constraints, such as network limits and market contracts. The technique of multi-agent systems (MAS) was used. The benefits of this approach are discussed and include a reduction of more than 50% in the balancing costs of a potential deviation. An implementation of this methodology is also presented. In order to validate the operation of the developed system, a number of experiments were performed using both software and hardware. The results validated the efficient operation of the developed system, proving its ability to optimise the operation of multiple energy carrier inputs within the context of an energy hub, using a hierarchical multi-agent system control structure.

This paper presents a Virtual Power Plant (VPP) decision making approach which uses fuzzy logic and a novel "insecurity" metric, based on human psychology. The VPP approach is modelled as a multi-agent system, which aims to minimize carbon emissions and/or energy cost, using an aggregation structure similar to energy or carbon markets. The "insecurity factor" reflects the operational flexibility of micro-generators, translated to a numerical value through fuzzy logic. The system was able to create a functional internal VPP market, where the micro-generators were trading autonomously according to external price signals and taking into account their own needs and limitations, as well as short-term forecasts.

Research stations in the Antarctic have their own electrical generation facilities and are not interconnected to any grid. Scarcity of fuel and unavailability of interconnection characterize these Antarctic energy systems as mission-critical isolated microgrids. In this work, an energy management strategy has been proposed for South African Antarctic research station SANAE IV for improving fuel efficiency. The proposed strategy consists of optimal dispatch of generation and installation of a thermal load controller for the supply side, and a novel demand response scheme for the demand side. The system was simulated using HOMER Microgrid Analysis Tool. Results showed an 8.30% decrease in fuel consumption, which corresponds to 21,876 litres of diesel annually. These savings can be achieved without major capital expenditure or difficult engineering work.

An agent-based control system that manages the battery charging of electric vehicles in power distribution networks is presented. The electric vehicle battery charging schedules are calculated according to electricity prices and distribution network technical constraints. The design of the multi-agent system is described. The real-time operation of the multi-agent system was demonstrated in a test-bed of a laboratory micro-grid.

A methodology was developed and tested for controlling the emissions from a group of micro-generators aggregated in a Virtual Power Plant. The methodology is based on the EU Emissions Trading Scheme. A multi-agent system was designed and simulations were performed. The operation of the system was demonstrated experimentally using micro-generation sources installed in two laboratories. Two days of experiments were performed. Results show that system emissions have been controlled with a good accuracy, since only small deviations between desired and actual emissions output were observed. It was found that Virtual Power Plant controllability increases significantly by increasing the number of participating micro-generators.

Micro-generation has the potential of reducing CO 2 emissions from the power sector. This study investigates the emissions performances of some cases of domestic microgeneration during operation. By comparison to the conventional generation options, savings of 10–45% were found, depending on the energy mix. Waste heat recovery by the micro-CHP was found to be the largest carbon saver in this study, along with the zero-carbon wind and photovoltaic micro-generation. Some carbon savings were also attained by avoiding energy losses throughout the transmission and distribution system.

Planned Communities (PCs) present a unique opportunity for deployment of intelligent control of demand-side distributed energy resources (DER) and storage, which may be organized in Microgrids (MGs). MGs require balancing for maintaining safe and resilient operation. This paper discusses the implications of using MG concepts for planning and control of energy systems within PCs. A novel tool is presented, based on decision trees (DTs), with two potential applications: (i) planning of energy storage systems within such MGs and (ii) controlling energy resources for energy balancing within a PC MG. The energy storage planning and energy balancing methodology is validated through sensitivity case studies, demonstrating its effectiveness. A test implementation is presented, utilizing distributed controller hardware to execute the energy balancing algorithm in real-time.

This paper discusses the AC fault ride through of two terminal modular multilevel converter (MMC) VSC based HVDC integration of combined offshore wind and wave farms. The combined offshore wind and wave farms are modelled as a controllable three phase voltage source connected to a 600MVA, 460kV/370kV transformer. A 31- level MMC has been selected because of acceptable harmonic attributes. Two 300kV DC submarine cables with length of 100km have been employed in this study. A voltage source has been connected in series with an inductive resistive circuit to give a short circuit ratio of 3.5. This paper finally presents a comparative simulation analysis of hysteresis based and PI based DC voltage controller for fault ride through (FRT) capability. The analysis showed that the PI method resulted in smaller overshoots and dips. A high switching frequency PWM based electromagnetic transient (EMT) model in MATLAB/Simulink was developed for the analysis.

This paper presents a method of utilising the Energy Hubs concept, a whole systems approach, to optimise and control the input fuels to a given load or demand. A Raspberry Pi was used as a controller for a co-firing Combined Heat and Power (CHP) generator. The control of the two fuel inputs was validated. It was found that the methodology can minimise the desired objective effectively. In addition, the control arrangement was found to be suitable for controlling an industrial valve which regulates the fuel input to the CHP generator.

The inclusion of Distributed Energy Resources (DER) into the grid is a great way to maximize and increase power generation at large. However it could also result in power quality issues due to their generation being dependent on external factors such as the weather. This paper aims to investigate power quality problems and potential solutions in low-voltage networks with high penetration of DER sources. The PV-Grid system is modelled and simulated using real PV irradiance and temperature data collected from PV panels during the day time on 22 of May 2015. The I–V and P-V characteristics of the PV-array were extracted to create a realistic model of the solar panels used in this paper. A Distribution STATic COMpensator (D-STATCOM) is utilized as the grid-connected inverter to perform conversion of power, power management, and compensation of reactive power. The simulation results presented demonstrate the use of the D-STATCOM to both convert the real power to AC and contribute towards the management of system reactive power at up to 100% of its rating.

An approach is presented for controlling multiple energy carriers, such as AC and DC electricity, heat, Natural Gas, hydrogen, using the control technique of multi-agent systems. The main elements of a hierarchical control system are given and their integration with the concept of energy hubs is explained. The interactions between the different agents are described. Electric vehicles are considered as mobile resources within the overall system. Finally, the benefits of this approach are laid out.

The microgrid (MG), as an operational paradigm for the exploitation of distributed energy resources (DER), has been thoroughly studied the past few years. However, applications are largely limited to test sites and demo installations, lacking the business argument in favor of the wider deployment of the MG concept. Planned communities (PC), a residential development concept aiming to channel the population growth away from the overcrowded and polluted city centers, can serve as a business model for the application of the MG control architectures and philosophies. This paper intends to link the core characteristics of the PC to existing MG sites and installations, providing evidence of their suitability for MG development.

VSC based Multi-terminal HVDC transmission is employed for the integration of offshore wind and wave farms. Flexibility, reliability and reduced transmission losses are the main/primary reasons for preference of MTDC networks. The transmission layout still suffers from some drawbacks, of which the most prominent is fault ride through capability in terms of its response to either a temporal or permanent loss of converter station(s). This paper presents the simulation analysis of hysteresis based and PI- based DC grid voltage control techniques for fault ride through capability of a 4 terminal HVDC network (MTDC), which consisted of a wind farm, wave farm and two onshore converters. The analysis showed that the PI method resulted in a faster response time as well as smaller overshoots and dips when a three phase to ground fault occurs. A detailed electromagnetic transient (EMT) study was performed using MATLAB/Simulink.

The potential of redox flow batteries to provide power balancing services within a microgrid was studied. Modelling of a benchmark microgrid was performed, to determine the technical and commercial suitability of redox flow batteries to be used for balancing energy generation and demand throughout a single day. It was found that the battery would fit in a service room of a residential block and would be suitable for balancing the whole microgrid. Based on the calculated usage patterns and the technology's characteristics, it was determined that redox flow batteries are suitable for energy storage in urban microgrids.

This paper describes the development of a simple experimental rig for a three-terminal HVDC transmission system that was designed with voltage source converters (VSC) for onshore wind farms. Two wind power plants (WPPs) were interconnected and directly connected to the inland grid through a 12V 1.44W DC link. A Master-Slave control arrangement was considered and partially implemented to maintain voltage of the DC link and inland grid. A double inputs-single output configuration was considered due to its small scale design. The design of the rig was also modelled for real life situations using MATLAB/Simulink. The results obtained showed that DC link voltage steady state was reached with a slight delay and with minimum overshoot, under purely resistive load, while, on the other hand, an appreciable overshoot would be experienced under inductive loads, though steady state was quickly reached.

Future Electric Vehicle (EV) penetration scenarios predict that in the next decades, thousands of electric vehicles will appear on the UK roads. Electric vehicle batteries are no longer considered fit for purpose after certain amount of degradation, e.g. below 80% of their initial capacity. However, they can be re-purposed for other uses, including stationary electricity storage. This paper examines the future availability of end-of-life electric vehicle batteries, and their potential use as distributed energy storage. The cost of infrastructure upgrades due to the additional peak load of electric vehicles is compared with the estimated distributed energy storage installation cost.

This paper examines theoretical models of smart distributed storage devices located at customer premises for powering local DC lighting and electronic loads, and explores enabled business models and field data from deployments of example Smart DC/Storage systems by Moixa Technology.

According to a study carried out for the formerly Department of Trade and Industry (DTI) and the British regulatory authority (OFGEM), installed micro-generation capacity in the UK could grow to as much as 8GW by 2015 (Energy Saving Trust, 2005; Ingram & Probert, 2003). This will require a new and highly decentralised approach to energy planning and policy. In addition to resolving the everyday causes of power disturbances and outages at local and regional levels, the electricity industry has to be able to restore service after major events (e.g. floods and storms). Ensuring reliability has and will continue to be a priority. The recent blackouts in UK (Blades, 2008; British Broadcasting Corporation [BBC], 2010) highlight the significant public and private interest in electricity reliability. During times of crisis caused by the rolling blackouts in California in 2001, it was found that customers are willing to pay very high prices for reliable power (Lawton et al., 2003). Backup generation ownership reveals that the owners place a high value on reliability, and therefore are willing to pay for the cost of operating backup generation to reduce the impact of an actual outage. Micro-generation can be used to sustain the distribution system during unavailability of the transmission in-feeds and brings opportunities for the improvement of security of supply to customers in major events, such as floods or storms (Kato et al., 2007; Kondo et al., 2008). Energy storage systems have been identified as a potential source to support microgeneration, to improve their carbon performance (Skarvelis-Kazakos et al., 2010) and to offset the intermittency of renewable energy micro-sources (Grau et al., 2010). Integration of individual small scale distributed generators in the low voltage (LV) side of the grid could provide benefits for the customers, not only from an economic point of view but also as an electric supply guarantee. Supply continuity could be reached by associating a number of loads (customers) and micro-sources into different subsystems (micro-grids). Thus, a micro-grid will be able to work in parallel with the grid, with the capability to switch to offgrid mode (intentional islanded) in case of a grid emergency (Grau et al., 2009a). Technical recommendations, such as G59/1 (Energy Network Association, 1991), G83/1 (Energy Network Association, 2008) and the standard 1547 from Institute of Electrical and Electronics Engineers (IEEE, 2003), specify that micro-generation sources must be disconnected in the case of loss of the grid. The fact that the micro-generation sources would not be controlled by the utility grid in an islanded mode, could lead to operation beyond the grid requirements. This could prove hazardous, not only for the utility equipment, but also

Three approaches for grid integration of Electric Vehicles (EVs) through a Virtual Power Plant (VPP) concept are introduced. A classification of these different ways for realizing a VPP based on the control structure, resource type, and the aggregation approach is discussed. This is followed by a description of the three VPP approaches, which are referred to as direct, hierarchical, and distributed control approaches. For each of the three approaches, the necessary operational steps are discussed and the differences are highlighted. Finally, a case study is presented to demonstrate EV integration through a VPP concept.

Electric Vehicles are anticipated to have a considerable percentage of the vehicle market sales in the forthcoming years. The additional energy requirements for charging their batteries may affect the network operation, in terms of stability and reliability, especially when these are synchronized with the system peak demand. This issue will present power system operators with the challenge to efficiently integrate Electric Vehicles into power systems by exploiting their ability to behave as manageable loads. The Multi-Agent System technology has been proven a promising way to manage distributed energy resources in electrical networks. A multi-agent system approach to manage the charging of the Electric Vehicle batteries is described. The types of agents required to satisfy the technical operation and the market participation of Microgrids with Electric Vehicles are provided.

Battery charging of Electric Vehicles (EVs) will increase the power demand in distribution networks. It is anticipated that this will cause voltage drops, thermal overloads and an increase in losses. These impacts will be affected by the behaviour of the owners of EVs. A typical 3-phase LV residential distribution network model is used to evaluate the effects of EV battery charging on distribution networks with Distributed Generation (DG). The uncertainties associated with the ownership of EVs, the rating of charging equipment, the occurrence and the duration of charging, together with the spatial distribution uncertainties of DG installation, were addressed with a probabilistic approach. A case study was performed for the year 2030, considering three EV and two DG penetration levels. A control function which reschedules EV battery charging was defined based on customer preferences and distribution network constraints. Thermal overloads, voltage drops, and losses associated with each case were reported. The effects of the coordinated EV battery charging on these impacts were analysed.

A future perspective micro-grid with a medium-term prediction for 2030 is described. The present state of intentional islanding is briefly reviewed. Distributed Generators (DGs) and Electric Vehicles (EVs) to sustain the local distribution system in the event of interruption of supply are considered. Projections regarding their availability are presented and different penetration scenarios are addressed. Environmental benefits of a future micro-grid are described through a comparison of the maximum and minimum EV and micro-generation penetration predictions.

Battery charging of electric vehicles (EVs) will increase the power demand in distribution networks. It is anticipated that this will cause voltage drops, thermal overloads and an increase in losses. The severity of the impact will depend on the EV owners' behaviour. A generic three-phase low voltage (LV) residential distribution network model was used to evaluate the effects of EV battery charging on distribution networks, the effect of a smart charging regime for EVs as well as the contribution of dispersed micro-generation (mGen) sources. The uncertainties associated with the residential loads, m-Gen and EV owners' behaviour, were addressed with a probabilistic approach. A case study was performed for the year 2030 using both deterministic and probabilistic approaches. The probabilistic assessment showed the importance of the above uncertainties.