On Harmonic Emission Assessment: A Discriminative Approach (original) (raw)

Power quality and electromagnetic compatibility Harmonic emission assessment on a distribution network : the opportunity for

2017

Harmonic emission assessment in high-voltage networks with a number of renewable power plants (RPP) interconnected is challenging. A sound scientific methodology readily accessible to engineers is needed to validate the compliance to grid code requirement set by the distribution system operator. Harmonic phasors recorded coherently all over the network can cause an impractical volume of data. This study investigates the opportunity to improve existing methodologies by application of the prevailing angle in a harmonic phasor as an approach to significant reduction of data and then demonstrate the evaluation of grid compliance in a network with a number of RPP interconnected. It is shown that the unrelated dynamic nature of the different non-linear energy sources does compromise the practical application of the prevailing harmonic phase angle. It is then concluded that the dynamic nature of RPP necessitates continuous monitoring of grid code requirements on harmonic emission.

A SOUTH AFRICAN REVIEW OF HARMONIC EMISSION LEVEL ASSESSMENT AS PER IEC61000-3-6

Large-scale renewable power producing plants are being integrated into South African networks. Network operators need to ensure that Renewable Power Plants (RPP) do not negatively affect the power quality levels of their networks, as harmonics amongst others could become a concern. IEC 61000-3-6 details a method for allocating voltage harmonic emission limits for distorting loads. This method works well for the allocation of emission limits however; it does not address the management of harmonic emissions once a plant is connected to the network. The management of harmonic emissions requires that network operators measure or quantify the emissions from loads and generators to determine compliance. Post-connection quantification of harmonic levels and compliance is a challenge for network operators. The question asked is: “How should a network operator measure/quantify the harmonic emissions of a load/generator to establish compliance with the calculated limits as per IEC 61000-3-6?” This paper reviews, within a South African context, methods of assessing harmonic emission levels and then evaluates these methods by means of field data. Opportunities for improvement are identified and operational requirements discussed.

Harmonic emission assessment on a distribution network: the opportunity for the prevailing angle in harmonic phasors

CIRED - Open Access Proceedings Journal, 2017

Harmonic emission assessment in high voltage networks with a number of Renewable Power Plants interconnected is challenging. A sound scientific methodology readily accessible to engineers is needed to validate the compliance to grid code requirement set by the Distribution System Operator. Harmonic phasors recorded coherently all over the network can cause an impractical volume of data. This paper investigate the opportunity to improve existing methodologies by application of the prevailing angle in a harmonic phasor as an approach to significant reduction of data and then demonstrate the evaluation of grid compliance in a network with a number of Renewable Power Plants interconnected. It is shown that the unrelated dynamic nature of the different non-linear energy sources does compromise the practical application of the prevailing harmonic phase angle. It is then concluded that the dynamic nature of Renewable Energy Plants necessitates continuous monitoring of grid code requirements on harmonic emission.

Impact of Grid Connected Photovoltaic System on Total Harmonics Distortion (THD) of Low Voltage Distribution Network: A Case Study

2018

Environmental considerations have led to rapid uptake of photovoltaic (PV) systems in many parts of the world. PV intermittency and unpredictability have presented new challenges to the electricity distribution network service providers. In recent years, the demand for a solution to the electricity shortage has increased. So, in Egypt the number of photovoltaic rooftop systems (PVRS) increased. A large number of grid-connected PV generators connected to distribution networks through PV inverters are potentially causing harmonic problems. The Middle Egypt Electricity Distribution Company (MEEDC) installed its first monocrystal PVRS 22.9 and 17.1 kWp on its buildings; many measurements have been carried out for electric energy parameters before and after PVRS installation to assure matching with the IEC standard. Moreover, the influence of temperature variations on the output power of PVRS was monitored under the climatic condition of Upper Egypt. This study presents several measurements (voltage variations, current, power factor, THDi and THDv) obtained from the PV site and compares these with the power quality indices and standard. Besides, this study shows the effect of temperature on the monthly and yearly yield in kWh generated by PVRS.

Methods for Harmonic Analysis and Reporting in Future Grid Applications

IEEE Transactions on Power Delivery, 2016

The rollout of advanced metering infrastructure, advanced distribution automation schemes, and integration of generation into distribution networks, along with a raising of awareness of power quality (PQ), means that there is an increase in the availability of power system monitoring data. In particular, the data for harmonics, whether it is voltage or current harmonics, is now available from a large number of sites and from a diverse range of PQ instruments. The traditional analysis and reporting of power quality examines harmonic orders to the 50th. This means that the harmonic data available for analysis are significantly larger than, for example, steady-state voltage variations where only a few parameters are examined (e.g., the voltage on each phase). Higher frequency components, sometimes called highfrequency harmonics, in the 10-250 kHz range arising primarily due to power-electronic interfaced generation are also becoming significant. Given the vast amount of harmonic data that will be captured through grid instrumentation, a significant challenge lies in developing methods of analysis and reporting that reduces the data to a form that is easily understood and clearly identifies issues but does not omit important details. This paper introduces a number of novel methods of analysis and reporting which can be used to reduce vast amounts of harmonic data for individual harmonic orders down to a small number of indices or graphical representations which can be used to describe harmonic behavior at an individual site as well as at many sites across an electricity network. The methods presented can be used to rank site performance in order for mitigation strategies. The application of each method described is investigated using real-world data.

Statistical characterisation of harmonic current emission for large photovoltaic plants

International Transactions on Electrical Energy Systems, 2013

Harmonic current emission of photovoltaic (PV) systems is a well-known problem. However, its quantitative characterisation, which requires the compilation and use of abundant statistical data, had never been satisfactorily dealt with. This paper discusses the multifaceted statistical characterisation of these emissions in a large PV plant. The topics addressed are harmonic current magnitude and its phase angle in relation to PV power output level and background harmonic voltages. Harmonic current emission in PV systems should be recorded during any single 1-week period throughout a full year. Because power quality metres are expensive, it is more economical to measure this type of emission with simple, cost-effective equipment. This paper thus presents a new assessment method for harmonic emission based on PV power output level, which is the main parameter affecting the emission, and which is easily monitored by most PV inverters. This new method uses statistical data to define a dependence model for the PV power output of PV harmonic current emissions. Such a model is rarely provided by PV inverter manufacturers. However, the simpler dependence model required for this method can be obtained by inexpensive power quality metres. This new method also produces accurate results at low process costs.

Modelling Renewable Energy Sources for Harmonic Assessments in DIgSILENT PowerFactory: Comparison of Different Approaches

2021

With the increasing number of Renewable Energy Sources connected to the power grid, the impact on system operation is becoming more evident. To assess this impact, accurate computer models are required for both the power system and the devices connected to it. Various types of system integration studies need to be performed in order to study both steady-state and abnormal operation. Among the steady-state analyses, power quality studies assess the impact of Renewable Energy Sources on parameters such as voltage levels and harmonic content. Harmonic studies are gaining more attention because of the nature of renewable energy sources which are mainly connected to the power grid through electronic power converters, thus producing undesirable harmonics. This paper analyses various settings, solvers and harmonic source models in a commercial software – DIgSILENT PowerFactory – to ensure accurate calculation and correct interpretation of harmonic assessment. A simple model comprising seve...

Measurement of Simplified Single- and Three-Phase Parameters for Harmonic Emission Assessment Based on IEEE 1459-2010

IEEE Transactions on Instrumentation and Measurement

This article investigates the feasibility of using a simplified approach, based on the measurement of power ratio parameters, for harmonic emissions assessment at the point of common coupling (PCC). The proposed approach comes from the common concept of power factor correction and the definitions of the IEEE Std. 1459-2010, where line utilization and harmonic pollution levels are evaluated by means of ratios between the power quantities of the apparent power decomposition. In addition to the IEEE Std. 1459-2010 indicators, in this article, the behavior is studied of additional parameters that are conceptually similar to those defined by the IEEE Std. 1459-2010. The suitability of such parameters is discussed, for both singleand three-phase balanced/unbalanced cases, taking into account both their behavior in different scenarios and their effectiveness when the measurement uncertainty is taken into account. The study is supported by some simulation results that have been obtained on an IEEE benchmark power system, which allows reproducing linear and nonlinear load conditions, balanced and unbalanced operating conditions, and the presence of capacitors for power factor correction.

A Review of Total Harmonic Distortion Factors for the Measurement of Harmonic and Interharmonic Pollution in Modern Power Systems

Energies

Harmonic distortion is one of the disturbances that most affects the quality of the electrical system. The widespread use of power electronic systems, especially power converters, has increased harmonic and interharmonic emission in a wide range of frequencies. Therefore, there are new needs in the measurement of harmonic distortion in modern electrical systems, such as measurement in the supra-harmonic range (>2 kHz) and the measurement of interharmonics. The International Electrotechnical Commission (IEC) standards define new total harmonic distortion (THD) rates based on the concept of frequency groupings. However, the rates defined in the IEC standards have shortcomings when measuring signals such as those present in the outputs of power systems with abundant interharmonic content and presence of components in the supra-harmonic range. Therefore, in this work, a comparison is made between the different THD factors currently defined, both in the literature and in the standards...