The journey towards sustainable transportation has significantly increased the grid penetration of electric vehicles (EV) around the world. The connection of EVs to the power grid poses a series of new challenges for network operators, such as network loading, voltage profile perturbation, voltage unbalance, and other power quality issues. This paper presents a coalescence of knowledge on the impact that electro-mobility can impose on the grid, and identifies gaps for further research. Further, the study investigates the impact of electric vehicle charging on the medium-voltage network and low-voltage distribution network, keeping in mind the role of network operators, utilities, and customers. From this, the impacts, challenges, and recommendations are summarized. This paper will be a valuable resource to research entities, industry professionals, and network operators, as a ready reference of all possible power quality challenges posed by electro-mobility on the distribution network.

Harmonic modeling of low-voltage networks with many devices requires simple but accurate models. This paper investigates the advantages and drawbacks of such models to predict the current harmonics created by single-phase full-bridge rectifiers. An overview is given of the methods, limiting the focus to harmonic analysis. The error of each method, compared to an accurate numerical simulation model, is quantified in frequency and time domain considering realistic input scenarios, including background voltage distortion and different system impedances. The results of the comparison are used to discuss the applicability of the models depending on the harmonic studies scale and the required level of detail. It is concluded that all models have their applicability, but also limitations. From the simplest and fastest model, which does not require a numerical solution, to the more accurate one that allows discontinuous conduction mode to be included, the trade-off involves accuracy and computational complexity.

In the presence of multiple power converters in a power system the total current may exhibit zero-crossing distortion in the form of recurrent damped oscillations with high magnitude. These oscillations are synchronized with the power system frequency. This paper presents a comprehensive analysis of the input current of single-phase ac-dc converters fitted with power factor correction (PFC) controllers. Emphasis is given on the impacts of the source impedance, and on how the number of converters connected to a common coupling point (PCC) impacts the PFC controller’s performance. A system model is developed followed by simulation and measurements in a real installation with electronic ballasts used to drive fluorescent lighting tubes. Results show that the recurrent damped oscillations originating from PFC controllers are close to the harmonic range and with a very low level of cancellation between devices. The magnitude therefore increases proportionally with the number of devices. As the source impedance increases, instability may occur. Possible explanations for these observations are discussed.

This paper presents the role of the medium-voltage network and low-voltage loads in harmonic voltages with low-voltage customers and harmonic propagation. A general model, as well as a detailed transfer function-based model, are used. By applying them to an existing network, it is shown that remote low-voltage loads have a significant impact on the source and transfer impedance. The main impact occurs for a specific range of frequencies below the resonant frequency of the low-voltage network. The general model is able to estimate this frequency range with an acceptable level of accuracy. Furthermore, by utilizing the concept of overall transfer impedance, it is shown that voltage harmonic levels for harmonic orders around this frequency range are determined mainly by aggregated remote emission rather than local emission.

This report summarizes the situation with knowledge and challenges regarding the large-scale introduction of electromobility in the Swedish power grid. 

The content convers a range of systemic perspectives in terms of challenges and impacts that the fast-growing amount of charging associated with electromobility poses to the actual power system. From this, several important questions are addressed in order to predict the future positive and negative impacts of this.

A description of electromobility in technological terms is given by presenting various configurations of electric vehicles, charging infrastructure and energy supply. 

The focus is placed on the possible impacts on the low-voltage networks, mainly exploring the power quality issues and grid hosting capacity. The following power quality issues are addressed: rms voltage (slow voltage variation, overvoltage, undervoltage, fast voltage variations), unbalance, waveform distortion (harmonics, interharmonics, and supraharmonics), and power system stability. The hosting capacity is examined to predict whether the charging demand from electromobility can be accommodated in the existing power system considering the involved challenges.

Furthermore, the aspect related to the charging process and people’s travelling patterns under a stochastic point of view is analyzed. With the advantages that electromobility brings, it is noticeable that people will change the way they move around. Insights from this perspective make it possible to predict how the grid needs to change to accommodate the future needs.

From the found evidences in this report, it is noticed that the harmonic content of the current injected from electric vehicles charging is not negligible, but it is low in relation to the harmonics produced by other connected loads in the low voltage network. The biggest impact is on the rms voltage, which might drop and exceed the limits set by standards if a charging management is not available. Additionally, interharmonics results have shown to be a potential issue due the charging process. Other evidences from this report provides additional support for future discussions and debates regarding the impacts of electromobility on the electrical system.

Advances in power electronics, increasing share of renewables in the energy system and e-mobility cause an increase of disturbances in the frequency range 2-150 kHz, also known as supraharmonics. A rigorous, credible and agreed measurement framework is essential to evaluate electromagnetic compatibility (EMC) in this frequency range. While a normative method exists for measuring equipment emission in the laboratory, no normative method exists yet for the measurement of supraharmonic disturbance levels in the grid. The aim of this research is a detailed comparison of potential measurement methods derived from existing standards IEC 61000-4-7, IEC 61000-4-30, CISPR 16-1-1 and a critical assessment of their suitability for disturbance measurements in grid applications. Based on a comprehensive set of synthetic signals and real measurements from laboratory and field, this article studies the ability of the methods to assess the typical characteristics of supraharmonic emission with relevance to EMC coordination. It presents the benefits and drawbacks of the existing measurement methods and discusses the suitability of possible modifications for grid compliance assessment. The results and recommendations intend to be an input for the present activities of IEC SC 77A WG 9 to define a normative method for the measurement of supraharmonic disturbance levels to be included in the next edition of IEC 61000-4-30.

Harmonic analysis studies of modern power systems commonly employ Norton and Thévenin equivalents at harmonic frequencies for the nonlinear devices. This approach neglects the so-called nonlinear interaction phenomenon. This paper addresses the difference between the results from the commonly-used model and the actual harmonic distortion measured in a low-voltage installation. A number of indices are introduced to quantify the nonlinear interaction. These indices allow a quantification of the extent to which the commonly-used model is also to predict harmonic voltages and currents in a modern low-voltage installation. The proposed model and the subsequent mathematical analysis are illustrated through measurements from different combinations of PV inverters and LED lamps using different technologies. The results show that deviation is dependent on the used technology, network impedance, and source voltage waveform. Other findings are that nonlinear interaction happens mainly in the low harmonic orders and impacts are more perceived on the harmonics phase angle. Possible explanations for these observations are discussed.

This paper investigates the characteristics of emission in the frequency range 2-150 kHz (supraharmonics) in time and frequency domain and how it propagates under different scenarios posed by the customer connections and changes in the grid. The analysis is based on measurements performed in a low-voltage installation, considering the simultaneous operation of a set of PV inverters and LED lamps in order to create changes in both impedance and emissions. The results confirm that supraharmonics tend to interact with nearby devices in the customer installation. As the number and constellation of emitting devices change so does the propagation of the supraharmonics. The propagation towards the grid can either increase or decrease with the increasing number of connected devices depending on the ratio between the impedances of the device and the grid impedance. Devices’ technology plays an important role in defining supraharmonic characteristics, emission levels and propagation. Finally, a qualitative analysis of the individual devices’ impedance and discussion of some of the practical aspects is provided.

Electric vehicle chargers and solar photovoltaic inverters are two types of household loads that can potentially impact the power quality of the grid. This paper presents a view of the consequences that the connection of these two nonlinear loads into a low-voltage installation can create on voltage harmonic distortion. The analysis considers the combined impact on network impedance and current harmonic distortion. First, the network impedance for phase-to-neutral connections is obtained considering the uncertainty in customer impedance. For this, a Monte Carlo simulation and the concept of transfer impedance are used. Second, based on real measurements, the current harmonic distortion of these two nonlinear loads are used to calculate the resulting voltage distortion at any bus of interest in the network. The analysis is applied to an existing low-voltage network in Sweden. Based on the study case, results show that some harmonics may increase by about 83 % as a function of the penetration of electric vehicles and photovoltaic installations.

This paper presents harmonic voltage measurements for a part of a distribution network including low-voltage (400 V) and medium-voltage (10 kV). Measurements were performed during 2017 and 2018 in the north of Sweden. This paper shows correlations between different harmonic orders in low voltage and the correlation between low and medium-voltage harmonics. This information can be used for harmonic propagation studies in distribution networks. The results showed significant correlation between the 5 ^th and 7 ^th harmonics for low-voltage side and very high correlation between 5 ^th harmonic order in low-voltage and medium-voltage. It is also observed that 5 ^th harmonic has almost the same values for all transformers connected to the same 40 kV network.