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The control of multiple battery energy storage systems (BESSs) to provide frequency response will be a challenge in future smart grids. This paper proposes a hierarchical control of BESSs with two decision layers: the aggregator layer and the BESS control layer. The aggregator layer receives the states of charge (SoC) of BESSs and sends a command signal to enable/disable the BESS control layer. The BESS controller was developed to enable the BESSs to respond from the highest to lowest SoC when the frequency drops, and from lowest to highest when it rises. Hence, the BESS’s response is prioritised to reduce the impact on the power system and end-users during the service. The BESS controller works independently when a failure occurs in the communication with the aggregator. The dynamic behaviour of the population of the controllable BESSs was modelled based on a Markov chain. The model demonstrates the value of aggregation of BESSs for providing frequency response and evaluates the effective capacity of the service. The model was demonstrated on the 14-machine South-East Australian power system with a 14.5 GW load. 254 MW of responsive capacity of aggregated batteries was effective in reducing the system frequency deviation below 0.2 Hz following a sequence of disturbances.

COVID-19 pandemic, despite its devastating impact, accelerated the shift to e-learning in higher education. Particularly in the electrical machines courses, that often include laboratory experiments. However, no detailed models of transformers, developed in Simulink/MATLAB®, were reported in the literature. Hence, in this paper, a virtual laboratory consists of models of single-phase transformers was built for the first time. The proposed models are easy to use and modify, and allow all machines’ parameters to be altered for students to replicate easily to support and enhance the learning process of electrical machines courses. Consequently, the developed models are effective tools for educational and research purposes. Dynamic models of single-phase, two-winding, transformers and step-up and step-down auto-transformers were developed using Simulink/MATLAB®. Two different approaches for modelling were proposed, the block diagram representation and Simscape based models. The two modelling methods were validated against the built-in transformer model. The developed models have been successfully integrated into electrical engineering courses at Middle Technical University, Baghdad, Iraq. Therefore, all developed models are freely available online at a dedicated repository.

The devastating impact of Covid-19 pandemic accelerated the shift to e-learning in the higher education. Particularly in the electrical machines’ courses, that often include laboratory experiments. However, no detailed models of DC motors, developed in MATLAB/simulink, were reported in literature. Hence, in this paper, a virtual laboratory consist of models of DC motors was built for the first time. The proposed models are easy to use and modify, and allow all machines’ parameters to be altered for students to replicate easily to support and enhance the learning process of electrical machines courses. Consequently, the developed models are effective tools for educational and research purposes. Dynamic models of DC motors were developed using MATLAB/Simulink, namely separately excited, permanent magnet, shunt-connected and series-connected DC motors. Two different approaches for modelling were proposed, the block diagram representation and Simscape based models. The two modelling methods were validated against the built-in DC machine model. The proposed models are easy to use and modify, and allow all machines’ parameters to be altered for monitoring and comparison purposes. Consequently, the developed models are effective tools for research and educational purposes.

—Increasing amount of Distributed Generation (DG)\ud connected to distribution networks may lead to the voltage and\ud thermal limits violation. This paper proposes a Virtual Energy\ud Storage System (VESS) to provide voltage control in distribution\ud networks in order to accommodate more DG. A VESS control\ud scheme coordinating the demand response and the energy storage\ud system was developed. The demand response control measures the\ud voltage of the connected bus and changes the power consumption\ud of the demand to eliminate voltage violations. The response of\ud energy storage systems was used to compensate for the\ud uncertainty of demand response. The voltage control of energy\ud storage system is a droop control with droop gain values\ud determined by voltage sensitivity factors. The control strategy of\ud the VESS was applied to a medium-voltage network and results\ud show that the control of VESS not only facilitates the\ud accommodation of higher DG capacity in the distribution network\ud without voltage violations or network reinforcements but also\ud prolongs the lifetime of transformer on-load tap changer.

The role of ancillary services related to the frequency control have become increasingly important in the smart grids. Demand Side Response is a competitive resource that can be used to regulate the grid frequency. This paper describes the use of heat pumps and fridges to provide ancillary services of frequency response so that to continuously balance the supply with demand. The power consumption of domestic units is usually small and, therefore, the aggregation of large numbers of small units should be able to provide sufficient capacity for frequency response. In this research, dynamic frequency control was developed to evaluate the capacity that can be gathered from the aggregation of domestic heat pumps and fridges for frequency response. The potential of frequency response was estimated at a particular time during winter and summer days. We also investigated the relationship between both loads (domestic heat pumps and fridges) to provide Firm Frequency Response service. A case study on the simplified Great Britain power system model was developed. Based on this case study, three scenarios of load combination were simulated according to the availability of the load and considering cost savings. It was demonstrated that the aggregation of heat pumps and fridges offered large power capacity and, therefore, an instantaneous frequency response service was achievable. Finally, the economic benefit of using an aggregated load for Firm Frequency Response service was estimated.

As a result of the increasing integration of renewable energy sources, power system is changing to a low inertia system with intermittent power supply. Frequency stability is therefore difficult to be maintained. Rather than increasing the spinning reserve capacity from conventional fossil-fuel generators, the use of Energy Storage System (ESS) for frequency response is considered as a technically viable low-carbon solution. To facilitate the grid-level study which aggregates a number of wide-spread small-size ESS, simplified models of multi-type ESSs including batteries and flywheels were developed. A generalized frequency controller was developed and applied to the aforementioned types of ESS. The controller coordinates the response amongst a population of ESS based on the units' State of Charge indicator. An adaptive droop control is combined with the coordinated control to guarantee a linear frequency response provided by a smaller number of ESS units. The number of charging and discharging of each unit is therefore reduced which prolongs the lifetime of the ESS units. Case studies were carried out by connecting a number of multi-type ESSs to a simplified GB power system model. Results show that the grid-scale ESSs are able to provide frequency response similar to but faster than frequency-sensitive generators. Implementation of ESS is therefore technically feasible to support the grid frequency stability with the reduction in the spinning reserve capacity.

This paper forms a Virtual Energy Storage System (VESS) and validates that VESS is a cost-effective way to provide the function of energy storage through the utilization of the present network assets represented by flexible demand. As a solution to convert to low carbon cities, a VESS is firstly modelled to store and release energy in response to regulation signals by coordinating the demand response (DR) from domestic refrigerators in London and the conventional flywheel energy storage systems (FESS). The coordination of DR and FESS mitigates the uncertainties of DR and reduces the capacity of costly FESS. The VESS is applied to provide ancillary services to the power system and contributes to the reduction of carbon emission through the replacement of spinning reserve capacity of fossil fuel generators. Case studies were carried out to validate and quantify the capability of the VESS to vary the stored energy in response to grid frequency. Economic benefits of using VESS for frequency response services were firstly estimated and a potential saving of £91m-£103m is expected.