Impact assessment of frequency support by electric vehicles: Great Britain scenario 2025

A desire to reduce environmental pollution coupled with advances in battery technology are some of the drivers for the massive growth in the use of Electric Vehicles (EVs) worldwide. The objective of this paper is to assess the impact that large groups of EVs, connected to frequency-responsive charging stations, have on the frequency response of the Great Britain (GB) power system during a sudden generation loss event. The assessment considers the minimum expected system’s rotational inertia and the predicted EV charging demand in GB for the year 2025. The developed model employs a representative block for the EV clusters which are formed based on the type of frequency support service they can provide. The effects of the expected EV penetration, type of EV charging, charger delay and sensitivity of the control are evaluated. OPAL-RT has been used to run the simulation and perform the assessment. The simulation results highlighted the positive effects of employing EVs as a distributed energy storage system (DESS) in regards to the system frequency response (SFR)

Probabilistic assessment of enhanced frequency response services using real frequency time series

This paper presents a probabilistic assessment of the novel enhanced frequency response (EFR) service in the Great Britain (GB) transmission system. Real frequency measurements with one-second resolution, released by National Grid (NG) corresponding to the years 2014 and 2015, are used for the performance assessment. Initially, the frequency quality is evaluated against Security and Quality of Supply Standards (SQSS) of NG. Afterwards, battery energy storage systems (BESSs) with different power to energy ratios have been modelled and fed with the GB frequency time-series while providing two variants of EFR service. Then, a state of charge (SOC) management algorithm is implemented for comparison purposes. Finally, cumulative probability distribution functions (CDF) are created to analyse the performance of the BESS. The high utilization rates obtained for one the EFR services suggests that for the provision of EFR to be profitable for the providers, the service should refocus towards the post-fault or frequency containment region

Controller to enable the enhanced frequency response services from a multi-electrical energy storage system

The increased adoption of renewable energy generation is reducing the inertial response of the Great Britain (GB) power system, which translates into larger frequency variations in both transient and pseudo-steady-state operation. To help mitigate this, National Grid (NG), the transmission system operator in GB, has designed a control scheme called Enhanced Frequency Response (EFR) specifically aimed at energy storage systems (ESSs). This paper proposes a control system that enables the provision of EFR services from a multi-electrical energy storage system (M-EESS) and at the same time allows the management of the state of charge (SOC) of each ESS. The proposed control system uses a Fuzzy Logic Controller (FLC) to maintain the SOC as near as possible to the desired SOC of each ESS while providing EFR. The performance of the proposed controller is validated in transient and steady-state domains. Simulation results highlight the benefits of managing the SOC of the energy storage assets with the proposed controller. These benefits include a reduced rate of change of frequency (ROCOF) and frequency nadir following a loss of generation as well as an increase in the service performance measure (SPM) which renders into increased economic benefits for the service provider

Electrical energy storage systems and electric vehicles for provision of fast frequency response

The last years have seen a swift increase in the proportion of connected renewable energy sources (RESs) in modern power systems to lessen unsafe levels of CO2 in the atmosphere and cut fossil fuels dependence. Despite the environmental gains of a decarbonised power system, a higher proportion of RESs could affect the grid's safe operation in at least two ways, i.e.reduce the amount of rotational inertia and increase the uncertainty of the energy balance. As RESs typically lack storage capabilities and are connected to the grid through power electronic converters (PECs), they are decoupled from the mass of synchronously rotating generators that provide inertia and counteract frequency changes, leading to quicker frequency dynamics. Furthermore, the intermittent nature of wind and solar PV makes energy balance requirements less predictable. [Continues.

System identification applied to a single area electric power system under frequency response

This research paper proposes a methodology to apply identification methods to find a simplified model of three different governors in a single area electric power system (SAEPS). A SAEPS with different governors-turbine is presented: a hydraulic turbine, a steam turbine and a steam reheat turbine. In this same investigation, an analytic reduction has been performed, a fifth order system was found analytically, thus a transfer function equivalent to the three different governor-turbine elements was obtained, this equivalent transfer function models the complete behavior of the three devices. Two systems identification (SI) algorithms have been proposed to apply them to this generic subspace state-space (N4SID) and generalized poisson moment functionals (GPMF) electrical system, these presented similar results. The results of the performance and simulation analysis exhibit that using the SI technique, fifth, fourth and third-order systems were obtained that graphically show a very small estimation error compared to the original signal, this fact could be check simulating the simplified models using the same input-output data. The results are presented in a table that shows a comparison of the model respond the fifth, fourth, third and second-order systems

Framework for real-time simulation of hardware in the loop applied to primary frequency control

This research paper proposes a framework to perform (hardware in the loop) HIL simulation in real-time (RT), the framework includes steps for the formulation of the Target RT Computer and Open Source System, which are important elements in RT modelling. In order to carry out tests, the implementation of the frequency response of a single area electric power system, including primary frequency control, is proposed. The electric power system was prepared to be implemented in the RT-Lab software that is compatible with MATLAB Simulink, in order to simulate in real-time with the Opal OP4510 device. Besides, the controller was designed in Simulink to be able to implement through the Arduino programming platform; they were also connected to work in HIL in RT. The results of the simulation and performance analysis show that for the case proposed with HIL, the primary control happens within a few seconds of the frequency variation. The control helps to reestablish the balance between the generated power and power demanded, thus stabilizing the system frequency. Elements formulated using this framework were successfully used in the primary frequency control

Data-driven fuzzy C-means equivalent turbine-governor for power system frequency response

This research paper proposes a turbine-governor modelling technique based on equivalent FCM (Fuzzy C-Means) for a control area of an equivalent power system used for frequency response analysis. The FCM algorithm implementation is proposed to find an equivalent Fuzzy model of n turbine-governors that are in an area of the electric power system (EPS). The FCM algorithm is mainly used to generate the rules for the fuzzy model; this algorithm uses input-output data, deviation of frequency, velocity and its derivatives, these are numerical data of a control area of the electrical system that contains n turbine-governors. Two cases are used to test the equivalent FCM model: (i) model of three areas simulink model, where area two has been modified by adding four turbine-governors to verify that it is possible to define an equivalent FIS model based on data, and (ii) the multi-area system, that is extracted from a reduced system frequency response model of an electric area of Great Britain Power System (GBPS), which contains three different types of turbine-governors, the data for this model was obtained from DIgSILENT-PowerFactory. The equivalent fuzzy model is tested under the same conditions as the original system with n turbine-governors, and they are compared against each other. The simulation results and performance analysis show it is possible to find an equivalent model with excellent performance with FCM and that the parameters of the FIS model can be adjusted if necessary, with ANFIS

RoCoF calculation using low-cost hardware in the loop: multi-area Nordic power system

This research paper presents a rate of change of frequency (RoCoF) implementation using low-cost hardware in the loop (HIL) with application to Nordic Power System (NPS). Two methods to calculate the RoCoF are presented: Incremental difference one step and moving window (MW) or rolling window. HIL) approach is used to reach natural noise levels found in the frequency signal obtained from real power devices. The low-cost HIL implementation is based on two Arduinos ® in the loop. An Arduino ® working as standalone is used to generate an analogue signal representative of one area of the NPS, a second Arduino ® in the loop contains the RoCoF calculation methods and filters. This paper analyses the effect of including lowpass filters (LPFs) because the noise of the frequency affects the RoCoF calculation. Three cases are implemented in the Arduino ® and compared with Simulink ® /MTALAB™ simulations: Base Case: no filter and noise signal, Case I: LPF applied to the input frequency signal, Case II: LPF at the frequency signal and LFP at the output of the RoCoF (smoothing). Results demonstrate that RoCoF calculation methods worked correctly in the HIL and using two LPFs clean the signal from the noise produced by the Arduino ®