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The increasing application of non-linear power-electronic based devices in low voltage networks might have a negative impact on power quality, particularly on harmonics. To estimate the harmonic levels or to identify possible resonances, respective network simulations involving a large number of power electronic devices are necessary. These require realistic device models, which need to represent both the harmonic emission and the input admittance characteristic, as otherwise simulations might not converge or result in unrealistic results. While many proposals exist for harmonic emission models, not much approaches can be found regarding the input admittance. This study intends to fill this gap and presents a modelling approach combining the harmonic emission and the input admittance characteristic in a single model. Therefore, the classic Norton model is extended by a generic circuit-based part, which consists of linear, passive components and is parameterised based on measurements. The extended Norton model is applied to six photovoltaic inverters and 18 electric vehicle chargers and its application are demonstrated in a harmonic simulation.

With an increasing number of power converters using fast switching technologies, more cases of interference between devices in the frequency range from 2 to 150 kHz occur. The most widely used technique in such devices is pulse-width modulation (PWM) [e.g. in photovoltaic inverters (PVIs), active harmonic filters, battery storage systems and some types of electric vehicle chargers]. Only little is known about the behaviour of those sources, the factors influencing their emission and the interaction with other devices and the propagation in the network. To extend such knowledge, reliable and accurate models are required. In this study, a quantitative model for the prediction of voltages and currents in this frequency range is developed and verified. Since in most cases no information about internal circuits and controls of the devices is available, a measurement-based black-box approach is used. The emission around the switching frequency of single-phase voltage-source power converters is combined into a single emission source represented by a Thevenin equivalent. The general method to parameterise the model is presented and exemplarily applied for two PVIs and one battery-electric vehicle charger. Moreover, the interaction of two devices at a joint point of connection is simulated and compared with real measurements.

Modelling of harmonics in large medium voltage (MV) distribution networks has so far been a challenge due to the presence of a large number of harmonic sources contributing to total harmonic voltages. This study proposes a deterministic methodology of modelling harmonics in large real MV distribution networks using aggregate harmonic source models parameterised based on measurements and results from the literature. In this research, background harmonic voltages from the sub-transmission system are parameterised based on measurements in the analysed network. Aggregate harmonic current emission of different customer categories in low-voltage (LV) networks (households and small commercial customers) parameterised based on several measurements in LV networks was dominated by residential or office customer type configurations. The harmonic current emission of industrial customers is parameterised based on the results from published literature. Two methods for modelling harmonic sources are used and compared: (i) modelling according to the IEC 61000-3-6 summation law and recommended summation exponents and (ii) modelling using complex phasors. The results of the models show a good match with the measurements from power quality monitors installed in the analysed MV network. Based on these results, the method according to the IEC 61000-3-6 is recommended for large MV distribution networks.

Smart grids encourage the use of new technologies such as electric vehicles, smart metering, as well as the use of renewable energy sources. One of the crucial challenges in designing smart grids is to improve the quality of the power delivered. Besides harmonic current generation in the frequency range below 2 kHz, these new technologies are also responsible for current emission in the range of 2–150 kHz, commonly known as supraharmonic emission. The supraharmonic analysis has not been explored for years, due to the lack of standards and equipment that are capable of reaching this frequency range. In recent years, the frequency range above 2 kHz has become the object of study by power quality researchers. This work proposes a technique to access the supraharmonics with reduced sampling rate and resolution enhancement. The technique is based on analog filter bank and compressive sensing. The use of the filter bank allows the reduction of the number of samples processed by the Fast Fourier Transform (FFT). In addition, it is proposed a method to improve frequency resolution of supraharmonic estimation, based on the technique of compressive sensing (CS). The use of the CS algorithm allows to achieve enhanced frequency accuracy without significantly extending the total observation time.

A framework for the comparison of measurement methods of conducted emissions in the frequency range 2-150 kHz is presented. In addition to present non-normative methods published by the IEC, alternative approaches in the literature are considered. Furthermore, test signals and key metrics are described. The comparison results will provide a baseline for specification of a new normative method for power grid measurements.

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.

In the last decade, mainly due to political incentives towards energy efficiency, the share of lamps with power electronic interfaces, like Compact Fluorescent Lamps (CFL) and Light Emitting Diode (LED) lamps, has significantly increased in the residential sector. Their massive use might have a substantial impact on harmonic currents and, consequently, on the current flowing in the neutral conductor. This paper analyzes the impact of modern energy-efficient lighting technologies on the neutral conductor current by using a synthetic Low Voltage residential grid. Different load scenarios reflecting the transition from incandescent lamps, via CFL, to LED lamps are compared concerning the neutral conductor current at different points in the network. The inherent randomness related to the use of lighting devices by each residential customer is considered employing a Monte Carlo simulation. Obtained results show that the use of CFL has a greater impact on the neutral conductor current of Low Voltage (LV) residential grids and that, with increasing use of LED lamps, a decreasing impact can be expected in the future. Fil: Hernández, Jairo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentina Fil: Romero Quete, Andrés Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentina Fil: Meyer, Jan. Technische Universität; Alemania Fil: Blanco, Ana María. Technische Universität; Alemania

Harmonic resonance in Low-Voltage networks is increasingly observed majorly caused due to increase in capacitive based modern power electronic equipment. This paper presents a systematic mathematical outlook on harmonic resonances and the effects of various parameters on its sensitivity. Frequency-domain based models for a single and multi-feeder network with distributed loads are considered for analysis. Various factors such as a change in load demand, change in distance between busbar and loads, and change in distribution transformer’s power capacity are considered and their effect on harmonic resonance sensitivity is analyzed.

The leakage currents produced by typical household devices are investigated. Accurate measurements of 18 single devices and 16 mixes of devices were made using a high accurate laboratory setup. The influences of the voltage distortion, voltage magnitude and frequency dependent network impedances are also addressed. The results showed that the leakage current produced by new devices, like electric vehicles and photovoltaic inverters, is higher than the leakage current produced by traditional household appliances. The network impedance and the voltage distortion have a considerable effect on the resulting leakage currents, especially voltage distortions with supraharmonic components seem to produce an additional increase of the leakage currents.

This paper reports the issues and challenges behind the proposal to include interharmonic limits in the next revision of the IEEE Standard 519 as discussed within the interharmonic distortion sub-group formed in the framework of the Harmonics WG (519) of the IEEE PES Transmission & Distribution Committee.

This paper presents an experimental study on the transient response of three commercially available photovoltaic (PV) inverters on step changes in the supply voltage distortion. Step changes of individual harmonics are applied to three different PV inverters varying in order, amplitude and phase angle. Moreover, different times of switching in terms of the fundamental frequency, i.e. points on wave, are considered. From the laboratory results presented, it can be seen that the inverters behave very different. To quantify the dynamic response characteristics, three parameters of interest are defined and evaluated: the overshoot of the grid-side current, the settling time and the eigenfrequencies of the transient response. The dependencies of these parameters on the above mentioned impact factors are analyzed, which can be used e.g. to develop dynamic models of PV inverters. The paper demonstrates the importance for assessing the transient response (dynamic behavior) of PV inverters and the individuality of their behavior, which requires inverter-make dependent models for grid-studies. A single model covering different makes of inverters is insufficient.

In addition to the low order harmonics, power electronic systems tend to emit high frequency emissions (HF) in the range of 2 - 150 kHz where photovoltaic (PV) inverters play an important role. The recent high penetration of PV inverters in electricity distribution networks has necessitated the development of PV inverter models suitable for HF studies. Some of the major concerns associated with this work include selecting a suitable modelling approach, building experimental setups and achieving a compromise between the simplicity and the accuracy of the model. Based on research undertaken using commercially available single-phase PV inverters, this paper presents in detail how the aforementioned concerns can be handled to develop inverter models that are suitable for HF emission studies.

This paper studies the behavior of grid-connected single-phase photovoltaic inverters in low voltage grids. The interaction of the inverter control, the grid-side filter and the power grid can lead to harmonic instabilities. The term is used, since its origin is not depending on the active or reactive power at fundamental frequency but an interaction of the inverter control with the impedance of the power grid at frequencies in the harmonic range. In power electronics, the power grid impedance is typically assumed as an RL- equivalent so that a critical RL- combination above which the inverter becomes instable can be calculated by using the Nyquist criterion. Neglecting resonances in a power grid can result in an erroneous assessment of stability based on the Nyquist criterion. This is of importance since recent field measurements indicate that the origin of harmonic instabilities of PV-inverters is primarily related to resonances in the grid impedance. This paper studies the behavior of a single-phase PV-inverter based on a simulation model for different impedance conditions of the power grid to illustrate the impact of the grid impedance and its resonances. The results are compared with laboratory measurements of commercially available PV-inverters.

—This paper introduces a new measurement method for supraharmonic distortion with improved robustness against power frequency deviations. The proposed method is based on wavelet analysis and it is designed to analyze a 10 cycles measurement interval. Fourier-based methods, instead, must analyze a fixed 200 ms window in order to avoid apparent shifts of the supraharmonic frequency components. The results of the experimental measurements presented in the paper show that the Fourier-based method suggested in IEC 61000-4-7 standard produces results affected by the value of the power frequency. The proposed method, instead, provides results completely inde- pendent of the power frequency. This feature also removes the need of a previous high pass filtering stage, required for the IEC method. Moreover, the proposed method has the additional advantage of working on the same measurement interval as traditional harmonics (below 2 kHz), feature that can reduce the complexity of measurement instruments.

This paper presents an identification methodology for filter circuits of commercially available power electronic devices based on laboratory measurements. The filter circuit is one of the main components with significant impact on the harmonic behaviour, in particular for modern power electronic devices. The generic approach does not require detailed knowledge about the circuit layout and is applicable for all single-phase power electronic devices where a voltage measurement on both sides of the filter circuit is possible. Current measurements on the circuit board, which are usually not practicable, are not required. The model parameters of the filter circuit are represented by two admittances for each considered frequency. The parameter identification is based on the analysis of the frequency couplings of power electronic devices. The proposed method is validated by simulations and exemplarily applied for a commercially available photovoltaic (PV) inverter in the laboratory. The measurement-based parameter identification can also provide more reliable results compared to the white-box simulation of a particular device, as the partly large manufacturing tolerances of the elements are inherently considered in the measurements.

Owing to the energy policies and the consequent transition to renewable energy sources, the amount of photovoltaic (PV) installations is continuously increasing in many countries. As PV inverters u ...

The increasing use of solar power connected to the public grid and the associated concern for deteriorating power quality triggered the formation of a joint working group with the aim to describe a ...

Harmonic resonances in electricity networks can cause significant amplification of harmonic voltages/currents. They can also affect the stable operation of power electronics with internal software controls, like photovoltaic inverters (harmonic instabilities). Up to now capacitor banks are treated as main reason for resonances in residential low-voltage (LV) networks and as long as they are detuned, no resonances at frequencies

The number of devices with high-frequency switching circuits is growing continuously. These techniques are used for increasing the energy efficiency or for reducing the classical harmonics by using e.g. active power factor correction circuits. These devices can have a significant emission in the frequency range 2–150 kHz, which is also referred to as supraharmonics. This study introduces a set of indicates and criteria for classification of supraharmonics emission to support the standardisation work and to understand the characteristic of the emission in this frequency domain as well as time domain analysis and is applied to a set of almost 120 household appliances and the results of the analysis are summarised.

The frequency range between 2 and 150 kHz has recently gained significant attention, triggered by standardization needs and increased emission in this wide frequency range. This paper gives an overview of the state-of-the-art concerning these so-called supraharmonics, and noticeably indicates the research challenges associated with waveform distortion in this frequency range, with emphasis on the following aspects: emission; propagation; interference; measurements; standardization; modelling and simulation.

The total harmonic current emission in a public low-voltage (LV) network is mainly determined by the large number of electronic devices, which use different circuit topologies with different harmonic emission characteristics. Consequently, the total harmonic current measured at the LV busbar can provide valuable qualitative information, for example, about dominating circuit topologies. This paper describes and applies a methodology to characterize the harmonic current emission of an LV network by a prevailing phasor. Using measurements from 130 German public LV networks, the “prevailing” location of 3rd and 5th harmonic current is analyzed with respect to different types of consumers. The results are compared with initial measurements received from other countries. Based on the prevailing phasor, a simplified method for an approximate estimation of the impact (cancellation potential) of a particular LV network or a new equipment technology (e.g., electric-vehicle charging) on the harmonic levels in a public distribution network is proposed.

This paper presents results of experimental and analytical evaluation of power-dependent harmonic emission of three common types of modern low-voltage (LV) power-electronic (PE) devices. After a detailed analysis of comprehensive test results, based on both existing and new waveform distortion indices, the development of component-based models of PE devices is discussed. This paper demonstrates the importance of including PE devices' controls for accurate modelling of their characteristics over the entire range of operating powers. Most of the analyzed PE devices exhibit strong power-dependent changes of characteristics, additionally influenced by supply-voltage conditions, which are important for the analysis of both existing networks and future 'smart grids'.

The paper presents and evaluates three advanced methods for the characterization of the low-voltage (LV) grid access impedance for the frequency range assigned to Narrow Band-Power Line Communications (NB-PLC): 9 kHz to 500 kHz. This study responds to the recent demand from both regulatory bodies and Distribution System Operators about the need for accurate and validated methods for this frequency band, due to the limited knowledge of the impedance values in the electrical grid and their influence on NB-PLC transmission channels. In this paper, the results of a collaborative work to develop different proposals to overcome the challenges for the proper characterization of the frequency and time-varying grid impedance, from different theoretical approaches, are presented. The methods are compared in a controlled and isolated scenario: the impedance characterization of passive filters. Then, the results are validated two-fold: first, against theoretical simulations, based on the schematics provided by the manufacturer, and second, against the measurement results of a precision impedance meter, used as a reference of accuracy. The results demonstrate a high degree of precision of the three proposals to characterize the access impedance of the LV grid.

We present the manufacturing and utilization of an all-polymer arrayed waveguide grating (AWG) interacting with a fiber Bragg grating (FBG) for battery status monitoring on the example of a 40 Ah lithium-ion battery. The AWG is the main component of a novel low-cost approach for an optical interrogation unit to track the FBG peak wavelength by means of intensity changes monitored by a CMOS linear image sensor, read out by a Teensy 3.2 microcontroller. The AWG was manufactured using laser direct lithography as an all-polymer-system, whereas the FBG was produced by point-by-point femtosecond laser writing. Using this system, we continuously monitored the strain variation of a battery cell during low rate charge and discharge cycles over one month under constant climate conditions and compared the results to parallel readings of an optical spectrum analyzer with special attention to the influence of the relative air humidity. We found our low-cost interrogation unit is capable of precisely and reliably capturing the typical strain variation of a high energy pouch cell during cycling with a resolution of 1 pm and shows a humidity sensitivity of &minus, 12.8 pm per %RH.

This paper is the first part of a two-part series on aggregate load models of residential customers for application in harmonic studies. Part 1 paper builds on the previous work on component-based time-domain models (TDMs) of main types and categories of loads found in residential load sector and presents two aggregate TDMs. The first is based on a detailed modelling of individual loads in the aggregate load mix, where types, numbers and power demands of considered loads are obtained from the available energy consumption statistics, while mean values, ranges and distributions of circuit parameters are determined from the generic TDMs. The second model is based on a much simpler representation of the aggregate load mix, where main load categories and sub-categories are modelled with the corresponding 'single-equivalent TDMs', for which circuit parameters are determined by scaling-up generic TDMs to represent power demand of all loads in the same category/sub-category. Particular attention is paid to the harmonic cancellation effects (diversity factors) between loads in the same (sub)category and loads from different (sub)categories, which are evaluated by probabilistic Monte Carlo approach and validated with available network measurements. In Part 2 paper, the presented TDMs are converted in corresponding frequency-domain models, which are expressed in the form of coupled harmonic admittance matrices.

This paper investigates the impact of high frequency (HF) voltages in the range of 2 – 150 kHz present in the electricity distribution networks on the lifetime of electrolytic capacitors used as the DC link in switch mode power supplies (SMPS) of grid connected equipment. In this study, both time domain simulations and controlled laboratory experiments have been employed.

The energy supply system in many countries is currently undergoing a period of transition. New technologies like energy efficient lighting, small photovoltaic units or electric vehicles have the potential to affect significantly the power quality, e.g. harmonics, in future low voltage networks. Therefore, harmonic simulations are becoming increasingly important. However, depending on the level of detail, they require a large number of input data regarding the network components and the connected customer installations. This data can be difficult to obtain and usually, certain assumptions have to be made. This paper demonstrates exemplarily how different simplifications influence the results of harmonic studies in networks with a large number of distributed photovoltaic installations. It starts with a very simplified simulation, which is then more and more extended by including e.g. the existing equipment or the background distortion. Finally, a probabilistic network simulation is performed and the results are compared with each other.

The increasing use of renewables, e-mobility and great demand for energy-efficient devices in the mass-market segment have an impact on Power Quality in the electrical network. In addition to classical harmonic interferences, both the end users and the network operators face the challenge of higher frequency disturbances, which refers to distortion in the frequency range 2–150 kHz, also known as supraharmonics. While malfunctions caused by supraharmonic emission are well documented in the literature, its long-term impact is not well investigated. This paper discusses the long-term effect of supraharmonics on modern lighting equipment and deals with the thermal stress of the aluminum electrolytic capacitor. The aim of research is to clarify the process of additional temperature increase caused by supraharmonic emission. Based on a comprehensive laboratory study the paper gives an overview of different heating mechanisms and identifies relevant impact factors.

This paper presents a modular model for single-phase photovoltaic (PV) systems for low-voltage studies. The main aim of the model is to assess the harmonic behavior of these systems. Besides steady state analysis, the model allows also dynamic studies, e.g. of harmonic instabilities. In order to identify and assess possible reasons for such instabilities on the inverter side, an easy interchangeability of the model components is provided based on a modular concept. The modular model can be applied to simulate various PV-system implementations in time-domain simulations. An impedance-based assessment based on the fingerprint method is used to assess the different behavior of the PV-systems regarding their topology and the choice of parameters. A comparison between different Phase Locked Loops (PLLs) and different designs of the grid-side filter is drawn to illustrate the different behavior of the PV-system in a steady state operating point. The model is implemented in MATLAB/Simulink and the Simscape Power Systems library.

This paper provides an in-depth analysis of the methodologies proposed by the IEC 61000-4-7 and IEC 61000-4-30 standards for the supraharmonic frequency range. The paper presents the stat-of-the-art concerning supraharmonics and describes the existing standardized measurements for supraharmonics. The different ways of performing the measurements proposed by such standards are compared. The main contribution and novelty of the paper are the comparative analysis of the standardized measurement methods which considers both efficiency and computational complexity of them. Analyzes considering real signals, a real time signal, a time-varying synthetic signal and the influence of the noise level for the methodologies proposed by the IEC 61000-4-7 and IEC 61000-4-30 standards were performed. Finally, alternative ways of measuring supraharmonics are suggested. One may conclude that the method described in IEC 61000-4-30 showed to be less immune to noise and less complex (in terms of mathematical operations required during processing) than that described in the IEC 61000-4-7, but loses accuracy in estimating high-amplitude supraharmonic components.

Harmonic analysis studies of modern power systems commonly employ Norton and Thevenin 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.

With the high penetration of power electronic interfaces and the increased use of power line carrier communication, high frequency (HF) emissions (supraharmonics) in the range of 2–150 kHz are emerging as a new power quality issue in distribution networks. Both IEC 61000-4-7 and IEC 61000-4-30 recommend the use of a high pass (HP) filter during measurement/analysis of these emissions. However, the filters used so far in HF measurements have non-linear phase characteristics making phase details unsuitable for further analysis. As a solution, this paper proposes a digital, offline, zero-phase HP filter having near ideal magnitude characteristics and a zero phase response.

In recent years there has been an increasing interest in identification and quantification of the prevailing harmonic source at the point of common coupling (PCC). For this purpose, some indices have been proposed and reported in relevant standards and literatures such as IEC61000-3-6. However, the issue of isolating the customer contribution from variations in the utility-side is still under discussion. The aim of this research paper is to demonstrate the impact of variations in the utility-side (i.e. harmonic impedance and background distortion) on the indices for customer emission assessment. This paper addresses two common indices known as IEC approach and harmonic vector method as well as three further indices. Investigations are simulation-based for line-commutating equipment and measurement-based for self-commutating equipment. Results show inconsistency of customer contribution indices in the case of variations in the utility side.

Electromagnetic Compatibility (EMC) issues in the frequency range between 2 kHz and 150 kHz, also known as supraharmonics, were limited for a long time to industrial applications. Due to the increasing amount of mass-market equipment operating with switching frequencies above 2 kHz, the importance of (non-intentional) supraharmonics emission in public low voltage networks increased considerable during the last decade. Parts of the frequency range are also used in many countries by narrowband Power Line Communication (PLC) for meter reading (intentional emission). Consequently interferences can occur not only between devices with non-intentional emission, but also between those devices and the narrowband PLC applications. An increasing number of reported disturbances related to the supraharmonic frequency range emphasize its growing importance. This paper provides a systematic classification of possible types of interference in the frequency range 2 kHz – 150 kHz and illustrates them be several example measurements performed in public low voltage networks. It provides some design recommendations for electronic equipment and indicates future research needs.

The paper presents detailed time-domain models of three commercially available single-phase photo voltaic (PV) inverters for harmonic studies. The inverters are used for rooftop applications and are expected to be distributed in low voltage (LV) networks in large numbers. The models are used to compare the sensitivity of the three PV inverters regarding different supply voltage distortions and grid impedance conditions. The effect of resonant harmonic amplification of inverter current is studied based on the harmonic impedance concept. Characteristical features of the PV inverter structure defining its harmonic emission in case of weak grids with voltage distortion are analyzed.

The number of devices capable to measure Power Quality (PQ) parameters has continuously been increasing in all voltage levels. Consequently, the amount of available PQ data is also growing very fast. This data contain a lot of valuable information about the behaviour of PQ, but up to now, it is mostly used only to assess compliance with limits (e.g. EN 50160 in Europe). Beside long-term characteristics (trends) and medium-term characteristics (seasonal effects), in particular the analysis of short-term characteristics can provide useful information about deviations from a “typical” behaviour, which are usually caused by significant changes in customer or network behaviour (e.g. connection of new disturbing equipment). As manual screening of the data is not feasible, automated methods to identify such “anomalies” are required. A classification scheme of anomalies in PQ measurements is introduced and applied for selected examples. In order to identify anomaly consisting of multiple values new method is presented. Finally, performance of the method is assessed and anomalous days are classified accordlnz to introduced scheme.

Measurements have shown that the harmonic currents emitted by lamps with electronic ballast depend on the circuit topology and the existing supply voltage distortion. This paper quantifies the impact of supply voltage distortion on the harmonic and supraharmonic current emission of individual Light Emitting Diode (LED) lamps and compact fluorescent lamps (CFL). It also characterizes several Power Quality (PQ) parameters when those lamps are connected to pure sinusoidal waveform.

The voltage and current unbalance in low voltage (LV) grids depends on the background distortion of the upstream grid and the emission characteristic of the devices connected to the grid. Based on an extensive measurement database of single households, individual feeders and whole LV grids, the paper discusses the emission characteristic of the negative sequence voltage of the upstream grid and the emission levels of symmetrical components of the currents in LV grids. The results of the survey are useful to develop simplified models to estimate the unbalance in LV grids.

Researchers and standard-setting organizations recently have paid much attention to power quality disturbances in the frequency range between 2–150 kHz, which is also referred to as supraharmonics. The majority of the commercial PQ monitors cannot access this high frequency without hardware and firmware update for more complex processor and Analog to Digital Converter. The central focus of this work is to present a technique to access the supraharmonics without significantly modification of the hardware and software of the PQ analyzers. The technique is based on analog filter banks and subsampling approach. The use of subsampling technique allows the reduction of the number of samples processed by the Fast Fourier Transform FFT. Through a systematic analysis, it was verified that the proposed methodology reduces computational complexity.

Due to the increasing number and capacity of grid connected power electronic interfaces associated with distributed generating systems, there is increasing concern on the associated power quality problems. Amongst these, high frequency (HF) emissions (referred to as Supraharmonics) in the range 2–150 kHz has become a topic of growing interest within power quality research communities. An increasingly prominent grid connected devices which can contribute to these HF emissions are the photovoltaic (PV) systems. In this paper, HF emissions from seven small (output power ≤ 10kW), grid-tied, photovoltaic inverters (both single phase inverters and three phase inverter composed of three single phase inverters) are analysed using measurements carried out under controlled conditions in laboratory environments. It is shown that under fixed network conditions, these HF emissions are affected by the MPPT (Maximum Power Point Tracking) voltage and the output power level of the PV inverter. Moreover, a strong correlation between the behaviour of HF emissions and the topologies of inverters was observed; an important factor in developing high frequency models of PV inverters.

Plug-in Electric Vehicles (PEVs) are progressively penetrating world markets. A significant impact on harmonic distortion in distribution networks is expected due to large-scale charging of PEVs at homes. Therefore, models that accurately predict the individual current injections are needed to perform harmonic studies, in particular frequency domain models such as those based on Frequency Coupling Matrices (FCM). In this paper, Fourier descriptors are used to estimate and compare the FCMs of a commercially available on-board PEV charger. Two models were calculated for two different supply reference conditions, namely, a sinusoidal voltage with no distortion, and a flat-top voltage. To that end, extensive laboratory measurements were carried out. Results show similar values in the parameterized admittances for both reference conditions. These results indicate a wide linear range in the coupled Norton model for this load, and should be probably attributable to the active power factor correction topology of the charger.

The use of Fourier descriptors (FD) for the assessment of frequency coupling matrices (FCM) of power electronic devices is considered. After some recalls on FDs, FCM approach is discussed showing how the matrices elements can be built basing on the use of maximum two FDs under linearity hypothesis. Then, a non-linearity index that allows to check the validity of the assumed “linearity hypothesis” and to quantify the obtainable accuracy is introduced. Numerical simulations on two very simple non linear circuits are performed to show the sensitivity of the FCM elements to magnitude and phase angle variation of the background harmonic distortion using FDs and the usefulness and the behavior of the non linearity index.

This paper is the first part of a two-part series on the development of aggregate frequency domain models of PV inverters (PVIs). The developed PVI models are expressed in the form of harmonic admittance matrix (HAM) of a coupled Norton model, also known as the harmonic fingerprint model (HFM). The development of accurate measurement-based HFMs requires considerable amount of measurements, which further increase in case of PVIs, as they typically exhibit strong power- dependent changes in harmonic emission. The authors propose a novel approach, which significantly reduces the number of measurements, as it requires only two sets of measurements at a single operating power: one with the fundamental voltage component, and another with individual voltage harmonics added one by one to the fundamental component. These two sets of measurements are used to calculate a “reference HAM”, which is then multiplied by two coefficients calculated from the power-dependent changes of the PVIs total subgroup current harmonic distortion, THDSj. The presented methodology is illustrated and validated using a comprehensive laboratory tests with three different PVIs and it can be easily applied to other types of power electronic devices with similar characteristics.

This paper deals with emission in the frequency range 2 kHz to 150 kHz, also known as supraharmonic or high frequency (HF) emission. The emission characteristic of different devices like electronic mass-market equipment or electric vehicle (EV) chargers and the interaction of these devices between themselves and with the low voltage grid are presented. The source of the supraharmonic emission and its characteristic are explained based on two different topologies and three different control strategies of an active power factor correction (PFC) circuit. Active PFC circuits are often used in EV chargers in order to meet the requirements with respect to harmonics given by standards. In addition to the characteristic of the supraharmonic emission, the interaction of multiple devices is explained based on a simple simulative model as well as by measurements of an installation with multiple EVs. Furthermore, some challenges in measuring the supraharmonic emission are described.

Harmonic emission assessment in a distribution network with existing background voltage harmonics is a challenge for Renewable Power Producers (RPP) aiming to achieve grid code compliance. Dynamic interaction of harmonic sources at a Point of Common Coupling (PCC) renders the general summation law in IEC 61000-3-6 impractical, as harmonic phasors do not conform to the addition of rms values using alpha factors. The dynamic interaction of different PV plants and non-linear traction loads connected to the same 132 kV PCC is analyzed to validate the practical constraints in assessing grid code compliance requirements It is demonstrated that an innovative application of phasor aggregation, albeit scientifically challenged, could present a pragmatic approach for engineers tasked with network Power Quality performance.

A stochastic method is presented in this paper to estimate the future voltage unbalance in a low-voltage distribution network with high-penetration of single-phase photovoltaic inverters (PVIs). The location and phase allocation of the PVIs are considered as input parameters for the stochastic simulation. The method has been applied to three different low-voltage networks: two in Sweden and one in Germany. In the Swedish networks, for 6-kW single-phase PVIs, it is likely that the contribution from single-phase photovoltaic inverters to the voltage unbalance exceeds 1%. The 2% value is unlikely to be exceeded. In the German network, for 4.6-kW single-phase PVIs, the voltage unbalance is between 1.35% and 2.62%. The risk of high-voltage unbalance can be reduced by a combination of controlled distribution over the phases and a reduction of the maximum size for a single-phase PVI.

The limitation of harmonic currents emitted by individual equipment and customer installations is essential in order to maintain harmonic voltages below compatibility or planning levels and consequently to ensure Electromagnetic Compatibility (EMC). At present, a large variety of methods exists worldwide for calculating harmonic emission limits, majorly expressed as harmonic currents. A systematic search on available methods has been performed for more than 70 countries from all over the world. Finally 16 individual methods for low voltage (LV), medium voltage (MV) and high voltage (HV) networks have been selected for a detailed quantitative comparison based on a probabilistic approach. This paper compares harmonic emission limits of the different methods for individual customer installation and is focused on generating installations. The first part provides details about the framework of comparison; the second part summarizes the results for the different voltage levels.