Grid connection delays pose a significant challenge for the National Energy System Operator (NESO) in Great Britain (GB). As of 2024, the average time between a connection request and the issuance of an offer has reached five years, with some applications facing projected connection dates over a decade away. While NESO is undertaking a reform process to address these issues, this too introduces uncertainty, as some sites may lose their existing positions in the connection queue.This study presents a qualitative, sector-based analysis of current and emerging grid connection challenges faced by stakeholders across various energy production and consumption sectors. These sectors include transportation (with a focus on rail electrification and the growing deployment of electric vehicles), renewable technologies and energy storage, as well as the expanding presence of data centres and logistics hubs.Qualitative analysis is conducted to assess grid connection issues across different regions of GB, highlighting variations in future electricity demand and comparing these to national trends. The study also maps the geographic distribution of sector-specific energy demands, offering insight into regional disparities and the spatial concentration of anticipated load growth.

Onboard Energy Storage Systems (OESS) have multiple applications in electrified railways. One such application is in discontinuous electrification where an electric train travels across a route that has some electrified and some non electrified sections. Where this is intentional, the OESS can be optimised for the specific design requirement. However, when a normally electrified route experiences a power failure in the Traction Power Supply System (TPSS) this would stop all electric only trains running. A method of using OESS to reduce delays and cancellations associated with TPSS failures is presented and a case study performed using a model developed for discontinuous electrification. A moderately sized 50kWh OESS can be used to allow resilient operation over failed sections approximately 6km in length, when simulated to have 55% of the route in a failed state. A small delay is incurred compared to the normal timetable when using the OESS however this can be compensated through changes to driver behaviour. The results presented here show utilisation of a small energy store greatly enhances resilience of electric railways when failures occur.

With sodium-ion batteries now becoming widely available from commercial manufacturers, and their deployment in a growing number of energy storage applications, it is becoming increasingly important that their performance be well understood. A key benefit of sodium-ion cells over their lithium-based counterparts it the ability to be discharged to zero volts without damage.This work presents the results of an experimental study to assess the performance impact of zero-volt operation on a commercial sodium-ion cell. The cell is subjected to a series of test procedures in which it is discharged to 0 V, and the resulting performance impact of these operations is measured in terms of capacity delivery and DC internal resistance. Post-testing analysis of the cell shows limited appreciable degradation in either of the examined metrics as a result of zero-volt operation.

Energy storage systems are becoming increasing reliant upon for the balancing of the electrical grid with new frequency response services being introduced by system operators to exploit their potential. However, these storage systems have a finite energy storage capacity and therefore energy management strategies are required. In this paper a newly introduced frequency response service for the Great Britain electrical grid, Dynamic Regulation, is investigated to establish the control parameters and how these can be used for energy management. Two control methods are presented, the first being a base case for a standard response and the second, a dynamic control, exploiting the extremities of the allowable service envelope. Simulated results using real-world frequency data show that the latter control method can improve the availability of a battery energy storage system, potentially resulting in higher revenues and a reduction in the number equivalent full cycles.

This paper presents a sensitivity analysis on the power to energy ratio for Energy Storage Systems (ESS) providing frequency response services on the Great Britain electricity network. Two services are considered; dynamic frequency response and dynamic containment, with the latter being a new service introduced in Oct 2020 by the Electricity System Operator. Each service proportionally responds in power to changes in grid frequency with each service differing in the response envelope. Whilst these services are based on power, for energy-limited assets such as ESS, the ratio of power to energy has an effect on its ability to deliver the service 100% of the time. In this paper, the availability, compliance against service terms and conditions, and equivalent cycles are considered showing that there is a significant difference between the two services. Currently, these services are delivered by battery ESS, however, it is demonstrated that the newer dynamic containment service can be effectively delivered by a higher power to energy ratio ESS and therefore offers opportunities for other technologies such as supercapacitors and flywheels.

Grid-connected batteries typically consist of 10’s of thousands of cells, where the Battery Management System (BMS) reports cell level voltage data which is normally used to protect the system against voltage limit violations. The work presented in this paper proposes a methodology to use this data to identify key model parameters (capacity and impedance) of the cells within the system. It is discussed how the method is reached, before experimentally demonstrating it using two battery systems to test the procedure at different scales, with comparison to individual cell tests. Results validate the theory, with data from a large number of cells measured in-situ (1584) being presented.

Large-scale battery energy storage systems (BESS) are drawing the attention of researchers as numbers installed globally is rising rapidly. Like single cells, the battery states, most importantly state of charge (SOC) and state of health (SOH) of BESSs are essential for their operation. However, for large-scale battery systems, the data granularity, accuracy and quality are limited compared with the cell-level. To achieve accurate state estimation of battery systems the selection of data used for processing is essential. In this paper, it is shown that how to evaluate and select system-level data for SOC and SOH estimation. These methods are expected to be used for other BESSs.

The collinear Mecanum drive (CMD) is a novel robot locomotion system, capable of generating omnidirectional motion while simultaneously dynamically balancing, achieved using a collinear arrangement of three or more Mecanum wheels. The CMD has a significantly thinner ground footprint than existing omnidirectional locomotion methods, which does not need to be enlarged with increasing robot height as to avoid toppling during acceleration or external disturbance. This combination of omnidirectional manoeuvrability and a thin ground footprint allows for the creation of tall robots that are able to navigate through much narrower gaps between obstacles than existing omnidirectional locomotion methods. This allows for greater manoeuvrability in confined and cluttered environments, such as that encountered in the personal service and automated warehousing robotics sectors. This article derives the kinematics and dynamics models of the CMD, analyzes controllability and accessibility, and determines the degree to which a CMD can be linearized by feedback. A partial feedback linearization is then performed, and three practically useful nonlinear controllers are derived using a backstepping design approach, all with convergence and stability guarantees for the fully coupled nonlinear model. These are demonstrated both in simulation and on a real-world CMD experimental prototype.

While much research has been conducted into the generation of smooth trajectories for underactuated unstable aerial vehicles such as quadrotors, less attention has been paid to the application of the same techniques to ground based omnidirectional dynamically balancing robots. These systems have more control authority over their linear accelerations than aerial vehicles, meaning trajectory smoothness is less of a critical design parameter. However, when operating in indoor environments these systems must often adhere to relatively low velocity constraints, resulting in very conservative trajectories when enforced using existing trajectory optimisation methods. This paper makes two contributions; this gap is bridged by the extension of these existing methods to create a fast velocity constrained trajectory planner, with trajectory timing characteristics derived from the optimal minimum-time solution of a simplified acceleration and velocity constrained model. Next, a differentially flat model of an omnidirectional balancing robot utilizing a collinear Mecanum drive is derived, which is used to allow an experimental prototype of this configuration to smoothly follow these velocity constrained trajectories.

Incorporating energy storage systems (ESSs) into electric railways has been shown to be advantageous for energy saving and power quality enhancement. For DC railways, the connection method of the ESS to the track may impose restrictions on charging and discharging the ESS to control the state of charge (SOC). Without management of the SOC, the ESS is shown in this study to reach minimum or maximum limits, reducing its effectiveness due to unavailability. Whilst it is possible to oversize the capacity of ESS, this incurs increased costs and requires more physical space. The main objective of this study is to propose and validate a control algorithm that prevents the ESS from reaching the maximum or minimum SOC limits whilst maintaining the benefits of the system. The main concept of the proposed control method is to dynamically update the voltage and current setpoints of the ESS to manage its SOC. The control algorithm is implemented in the MATLAB software and the simulation results are validated against experimental results, using a track emulator and supercapacitor. The findings demonstrate that, with appropriate dynamic charge/discharge control, the SOC levels can be adequately managed and no external load or source is required.

Vehicle to vehicle (V2V) charging system had been present which can work together with plug-in EVs charging or operate independently. V2V charging technology can effectively solve the problem of a limited number of plug-in stations and the exhaustion of EVs during the journey. Wireless power transfer (WPT) technology has become a priority technology for V2V charging due to its convenience. This paper proposes an angular offset analysis in wireless V2V system and compares the effects of three transmitter coil structures on system efficiency. The CST simulation results show that the H-field of the two-coil (angle) transmitter structure is higher than the other two benchmark structures. Meanwhile, the hardware implementation results show that when the resonant coils have an angular offset, two-coil (angle) transmitter structure can effectively improve the system efficiency compared to the other two benchmark structures.

The UK government has pledged to remove all UK diesel locomotives from the rail network by 2040 however, 60% of the rail network is still unelectrified, this study analyses the introduction of battery electric multiple unit trains (BEMU) as a solution. This paper details the analysis of an unelectrified route and the development of a battery model using a train electrical power demand profile derived using an industry validated traction power model. The effect of sizing the battery to limit c-rate is investigated along with a discussion of different battery chemistries. It is revealed in the analysis that the dwell time at the charging station is an important consideration. Finally, an existing grid connected 2MW energy storage system is used to validate the model. The results of the study demonstrate that a BEMU can replace diesels on the line studied with a weight decrease of up to 46%.

The increased uptake of renewable energy generation has lead to a growing interest in grid-connected energy storage systems, such as batteries and flywheels, for maintaining grid stability. A number of countries have developed schemes for the provision of frequency response services, with some grid operators, such as National Grid in Great Britain and Eiregrid in Ireland, having a range of static and dynamic services. For the provision of dynamic services, the use of tighter frequency margins, which results in the unit providing frequency response more regularly and in higher volumes, may be incentivised through higher payments. One example of such a scheme is in Ireland under the Eiregrid DS3 programme, where a tariff system that incorporates both the performance and frequency margins of units providing dynamic response has been introduced. This paper examines how the choice of frequency margins affects overall payments for Battery Energy Storage Systems (BESS) operating in the Irish grid. Analysis is performed by simulating the BESS system using Irish grid frequency data. The results provide insights into how the frequency margins affect payments for different frequency response services, and show how payments to a BESS providing dynamic frequency response are maximised.

Clean energy has become increasingly important in different countries and Electric vehicle (EV) are commonly viewed as part of the solution. EV sales are steadily increasing and there is now much focus on the infrastructure to charge them. This paper is focused on public and private EV car parks where installing an increasing number of charging stations, with growing power requirements due to faster-charging technology, is a burden to the electrical grid. It is often the case, that for either technical or commercial reasons, that the power feed for the car park is restricted or it is advantageous to dynamically manage the peak power to reduce electrical costs. In this paper, an EV car park is modeled that contains a defined number of rapid chargers with a limited incoming power supply. Using real traffic data simulations, the power feed demand profile can be obtained. This study proposes four methods to manage the charge of EVs when the power feed is limited in capacity resulting in a necessary sharing of power. Simulation results show that by controlling the charge rate of each EV the overall power limits can be met. Furthermore, it is shown that the method chosen can be used to influence the variance in SOC across all EVs.

The slow development of energy storage technology combined with a limited number of plug-in charging stations negatively affects people's desire to purchase pure battery electric vehicles. A new wireless vehicle-to-vehicle charging technology structure is proposed, which can function with plug-in electric vehicles or operate independently. With a limited number of charging stations this technology can be used to increase charging opportunities through vehicle-to-vehicle (V2V) charging. V2V charging requires a number of technical challenges to be overcome, including the angular offset of the wireless power transfer resonant coils. The mutual inductance between two resonant coils is a key parameter for high power and efficient transfer of power. This paper presents the theory of angular offset multi-turn coil design.

This paper investigates the benefits of distributing thermal load across multiple devices on a single heatsink, with a focus on how this might be a benefit in the use of multilevel converters. The analysis uses finite element modelling to derive trends in performance, which combined with real world data permits for a bulk analysis in to whether multilevel converters have thermal benefits, and if so, to how great an extent. The paper concludes that there are significant and quantifiable benefits to distributing the thermal load, but high order multilevel converters may yield little benefit over lower order systems.

The use of output bounds and trajectory extension enables Model Predictive Direct Current Control (MPDCC) to achieve low current distortion for a given switching frequency, making it very well-suited to high-power applications where switching frequencies in the range of a few hundred Hz are typical. One of the main drawbacks of MPDCC, however, is the large computational requirement associated with model-based extension of the output current trajectories. In order to overcome this, approximate extension techniques must be used for practical implementation, making the analysis of such techniques very important. This paper addresses the existing gap in the literature by providing a comprehensive review of Linear (LE) and Quadratic (QE) extrapolation techniques for MPDCC. Using a MATLAB-based simulation of a grid-connected Neutral-Point-Clamped (NPC) converter as a case study, the relative performance of the different extrapolation techniques is evaluated using the trade-off between switching frequency and current distortion. The execution times of the various strategies are also provided using a TI TMS320F280049 microcontroller as an example control platform.

With the development of power electronic converters, size reducing and reliability extending are desired. For modern converter that utilises inductors or transformers, the dimensions of magnetic components are commonly inversely proportional to its switching frequency. With the increase of switching frequency, higher dv/dt may cause miss-triggering faults and unstable turn-off. Those issues can be relieved by applying a negative bias to conduct the turn-off. However, a separate DC-DC converter is normally required to generate this negative voltage. In this paper, a novel self-driven negative bias generator for high-side switch is introduced. The novel gate driver can provide bipolar gate driving capability without the need for a separate negative voltage supply. A prototype converter has been built and verified that the proposed bipolar gate driver could effectively generates the required negative voltage for power semiconductor driving without using a charge pump or switching converter.

The electricity system has to balance demand and supply every second, a task that is becoming evermore challenging due to the increased penetration of renewable energy sources and subsequent inertial levels. In the UK, a number of grid frequency support services are available, which are developed to provide a real-time response to changes in the grid frequency. The National Grid Electricity Transmission (NGET) - the primary electricity transmission network operator in the UK - has introduced a new faster frequency response service, called the Enhanced Frequency Response (EFR), which requires a response time of under one second. Battery energy storage systems (BESSs) are ideal choice for delivering such a service. In this paper a control algorithm is presented which supplies a charge/discharge power output with respect to deviations in the grid frequency and the ramp-rate limits imposed by NGET, whilst managing the state-of-charge (SOC) of the BESS to maximise the utilisation of the available energy capacity. Using the real UK market clearing prices, a forecasted battery state of charge (SOC) management strategy has been also developed to deliver EFR service whilst scheduling throughout the day for energy arbitrage. Simulation results demonstrate that the proposed algorithm delivers an EFR service within the specification whilst generating arbitrage revenue. A comparative study is also presented to compare the yearly arbitrage revenue obtained from the model of the Willenhall and an experimental Leighton Buzzard battery storage system. Simulation results on a 2MW/1MWh lithium-titanate BESS are provided to verify the proposed algorithm based on the control of an experimentally validated battery model.

In 2013, the University of Sheffield commissioned a 1 MWh lithium-titanate (LTO) battery energy storage system (BESS), directly connected to the grid through an 11 kV feed. With a view to later on develop a comprehensive model structure for the whole battery pack - key to many online battery management system (BMS) operations - in this paper, an in-depth frequency-domain analysis is performed on one of the constituent 2.3 V 20 Ah LTO cells, using a potentiostatic sine-swept method. A first-order resistor-capacitor (RC) equivalent-circuit model is put forward, capable of representing the LTO cell's impedance magnitude with an error of less than 0.1 mΩ. Thereafter, the performance of the proposed one-RC model structure for online SOC estimation is experimentally verified using the Extended Kalman Filter (EKF). The verification test is performed on a dynamic pulsed-power profile, derived from a real grid frequency-support service that is offered by several BESSs in the UK.

Multilevel converters are an emerging industrial technology and are the subject of a substantial amount of research. However, they are yet to find their way into many mainstream engineering applications. This paper presents a method of quantifying the benefits and disadvantages of multilevel converters of increasing order. The analysis focuses on the cascaded H-bride topology for grid-tie battery inverter applications. The analysis includes both semiconductors losses and semiconductor driver losses. It is shown that multilevel converters can have significant benefits over their conventional counterparts, but that more levels is not necessarily better. This paper's important result is to create a quantitative measure of the pros and cons of multilevel architecture.

This paper presents the results of a series of tests to determine the influence of high-frequency injected ripple currents on the Dynamic Charge Acceptance (DCA) performance of lead-acid batteries. A wide-bandwidth battery model is described, this being a hybrid of the standard Randles model and a high-frequency model previously described in literature. A bespoke test procedure is described, based on the existing DCA Short Test profile. The results demonstrate that the injection of ripple currents can significantly improve charge acceptance.

The application of Wireless Power Transfer (WPT) systems is primarily limited by its energy transfer efficiency. For modern WPT that utilises Strongly Coupled Magnetic Resonances (SCMR), which transfers energy by using the mutual inductance between coils, a higher efficiency can be achieved compared with a conventional air-core transformer module. An SCMR normally works at a desired frequency which is typically the self-resonant frequency of the receiver. However, this frequency varies during system operation where a changing environment, moving coil positions and variable loads may occur. In this paper, a hybrid wireless Phase Lock Loop (PLL) is proposed to lock the phase difference between the WPT's transmitting current and receiving voltage, at which point the system achieves maximum efficiency. A prototype WPT system is built verifying that the proposed wireless PLL effectively controls the wireless power system and operates at optimal frequencies under varying conditions.

Persistent of excitation of the input/output signals is a necessity for any online parameter identification technique. In most real battery systems, the drive signals may not fully satisfy this condition at all times, which can lead to divergence and failure of the incorporated battery management system. Therefore, in this paper, a hybrid battery parameter identification concept is proposed whereby the parameters are initially identified using a special random signal called the pseudo random binary sequences. Thereafter, the Kalman filter algorithm is implemented online to estimate and track any `disturbances' caused by varying operating conditions. A dynamic European drive cycle is used to experimentally verify the excellent performance of the proposed technique against a more precise electrochemical impedance spectroscopy method.

This paper reports the development and implementation of an adaptive lithium-ion battery monitoring system. The monitoring algorithm is based on the nonlinear Dual Extended Kalman Filter (DEKF), which allows for simultaneous states and parameters estimation. The hardware platform consists of an ARM cortex-M0 processor with six embedded analogue-to-digital converters (ADCs) for data acquisition. Two definitions for online state-of-health (SOH) characterisation are presented; one energy-based and one power-based. Moreover, a method for online estimation of battery's capacity, which is used in SOH characterisation is proposed. Two definitions for state-of-power (SOP) are adopted. Despite the presence of large sensor noise and incorrect filter initialisation, the DEKF algorithm poses excellent SOC and SOP tracking capabilities during a dynamic discharge test. The SOH prediction results are also in good agreement with actual measurements.

This paper presents the results of a series of tests to determine the Dynamic Charge Acceptance (DCA) performance of small form-factor 2 V, 6 Ah, carbon-enhanced VRLA cells designed for Hybrid Electric Vehicle (HEV) applications. A test procedure has been written for a battery test system, based on a modified DCA Short Test profile. Results have been obtained for a batch of cells, tested at various temperatures, rest periods and states of charge. These conditions have been chosen to mimic a range of real-life scenarios which could potentially be encountered during HEV operation. The resulting analysis demonstrates clear variations and trends in DCA performance which may be used to inform conditions for future testing regimes. The same test procedure is then applied to standard lead-acid cells and the results compared.

A modern Wireless Power Transfer (WPT) system is commonly realized by Strongly Coupled Magnetic Resonances (SCMR), which transfer energy by using the mutual inductance between coils. The application of wireless power transfer is critically limited by its energy transfer efficiency. SCMR systems are designed to transmit at a frequency that is equal to the self-resonant frequency of its power receiver, in applications where the self-resonant frequency varies during operation the measurement of the frequency is typically not possible. In this paper, a phase shift control based Maximum Efficiency Point Tracking (MEPT) approach is proposed along with implementation methodologies to enable real-world application. A prototype wireless power system with MEPT featured is built which verifies that the new MEPT method could effectively track the optimized frequencies continuously on the fly and maximise the efficiency of the WPT.

The open-circuit voltage (OCV) forms the basis for many real-time state-of-charge (SOC) estimation algorithms. The OCV-SOC relationship for most battery chemistries often provides a good estimate for SOC. However, for the lithium-ion iron phosphate (LiFePO4) variation of the lithium-ion cell chemistry, the OCV curve is fairly flat over the operational SOC range. Thus, even the smallest error in the OCV obtained from a battery model can lead to divergence in SOC from the actual value. Therefore, as a remedy this paper presents a separated framework for the Extended Kalman Filter (EKF) estimation of SOC, with real-time process noise assessment. In this paper, the states and parameters of a non-linear cell model, namely the two time-constant Randle's model, are also identified using the dual implementation of the EKF algorithm in real time.

Wireless Power Transfer (WPT) is critically dependent on its power converter, typically implemented as a two-stage AC-DC-AC converter. Matrix converters, which feature as bi-directional conversion between input AC power and desired AC or DC power output, may be considered as the ideal converter topology for WPT, however, are constrained by their complexity and cost. In this paper, a low cost microcontroller based matrix converter WPT system design is proposed and examined. Finally, a prototype WPT system is built successfully demonstrating that the design provides a cost efficient approach to exploit the advantages that matrix converters can provide.

A sensitivity analysis for a two time-constant Randies' circuit model to its forming resistor-capacitor elements is presented. The model parameters are identified for a cylindrical lithium-ion iron phosphate cell using the electrochemical impedance spectroscopy technique and a nonlinear least squares approach. Initially, it is shown that the model parameters vary as a function of the battery's state-of-charge. Then, each model parameter is allowed to vary up to ±50% of its best-fit value. Finally, the significance of each parameter for the calculation of the battery's average available power (state-of-power) over a specific band of frequency is analysed.

In order for successful second-life implementation of Electric Vehicle (EV) battery packs, the viability of the intended second-life use must be ascertained based on a cost-benefit analysis and technical appraisal of the estimated condition of the available battery packs. This paper discusses the issues in measuring State-of-Health (SoH) and other battery condition metrics of a battery pack. Measurements on real-life battery packs sent for recycling are taken that demonstrate a typical 85% SoH; slightly higher than predicted by Original Equipment Manufacturers (OEM). A model is introduced that can simulate the energy demand in a home/dwelling being met by a number of sources including mains (utility) power, photovoltaic generation (PV), and second-life battery storage. The model is applied to three scenarios using second-life battery storage, to create energy costs savings through time-shifting of energy using on-peak/off-peak electricity tariffs. For each scenario a cost-benefit analysis is produced, indicating that whilst energy costs savings can be achieved, excessive usage of the battery pack can cause the payback period of the capital investment to be longer than the predicted second-lifetime of the battery pack. However, the final scenario demonstrates that combining the battery pack with local generation, such as PV, yields cost savings that are significant at 75%, and the payback period is within the estimated lifetime of the battery pack.

An investigation is made in this paper of the possibility of enhancing the performance of controllers of unstable systems while retaining safety critical function. In this case, a general dynamics F16 fighter is considered in simulation. A fuzzy logic controller is designed and its membership functions tuned by multiobjective genetic algorithms in order to design an augmented flight controller with enhanced manouverability which still retains safety critical operation. The controller is assessed in terms of pilot effort and thus reduction of pilot fatigue. The controller is incorporated into a six degree of freedom real-time flight simulator, and flight tested by a qualified pilot instructor.