Harmonic Distortion Measurements Research Articles

Mapping and assessment of harmonic voltage levels for railway traction supply stations in Sweden

Assessing harmonic distortion measurements in the electric railway power systems (ERPS) requires evaluating the time-varying behavior, interactions, and performance in different time scales. This paper aims to map and assess harmonic voltage levels in 13 traction converter stations for the Swedish railway power supply system, with findings that have direct practical implications. For that, measurements from the public and railway grid sides for 69 weeks are analyzed. Statistical values are explored for the harmonic voltage spectra and total harmonic distortion (THD) variation. The public grid side measurements are investigated using 95th percentile weekly values, and performance is evaluated by comparing the recommended planning levels of IEC 61,000–3–6. The intraweek variation complements the information about the time-varying behavior of the THD. The 95th percentile, minimum daily values, and intraday variation are explored to understand the time-based behavior since there are no reference limits from standards for comparison, looking to the railway grid side. Extended analysis is placed on the railway grid side to highlight some aspects of measurement time-aggregation based on 10-min values, and time-series trend analysis is used to confirm traffic planning impact. Discussion and findings regarding railway operation, the technology deployed at the traction converter station, time-varying behavior, traffic planning impact, measurement time-aggregation, and spectra patterns were presented.

Comparison of Approaches for Assessing Linearity of Impedance Measurements

Electrochemical impedance spectroscopy experiments are inherently nonlinear for systems affected by faradaic reactions. The methods used to determine whether an experiment is sufficiently linear include observation of current as a function of potential, known as Lissajous plots, measurement of total harmonic distortion, and post-experiment assessment of consistency with the Kramers–Kronig relations. An experimental approach is employed to compare sensitivity of these methods to determination of nonlinear response in electrochemical impedance measurements. The Lissajous figures showed linear behavior for a total harmonic distortion equivalent to 1 percent of the fundamental; whereas, the measurement model analysis revealed nonlinear behavior only for larger perturbation amplitudes.

Background harmonic distortion measurement at power networks with wind farms

Standard IEC 61400-21 specifies that background voltage distortion must be lower than the threshold limits specified in standards. However, this background distortion information is not used for calculating the real harmonic emission from the wind turbine leading to misleading voltage harmonics assessment from the wind turbine. In this paper a methodology for assessing the real harmonic emission from wind turbines is proposed based on current and voltage measurements where the background harmonic distortion at the Point of Common Coupling is considered.

Survey of harmonic distortion measurements from customer grid supply in trains

Survey of harmonic distortion measurements from customer grid supply in trains

Harmonic Distortion Characteristics Generated by Heating Ventilation Air Conditioning System Case Study in PCR Laboratory

Good power quality is required in health facilities since the increasing use of microprocessor-based equipment. Poor power quality in the electric power system can cause medical equipment in health care centers to malfunction and give incorrect medical diagnoses. Since 2020 we are facing a new type of Virus (Covid-19), this virus requires special laboratory construction with specific air conditioning systems (temperature, humidity, and pressure) to process specimens. This paper presents measurement results of harmonic distortion characteristic by Variable Frequency Drive (VFD) of Heating Ventilation Air Conditioning (HVAC) system in PCR Laboratory at Clinic A. The VFD in this system is used to adjust the rotation of the exhaust fan and outdoor unit. The measured voltage, current and power are used to assess power quality. The main power quality problems found in medical facilities are voltage flicker, neutral currents, and total harmonic distortion (THD) values. The measurement of total harmonic distortion (THD) is used to find the source of the harmonics. Potential problems can be identified within the facility. The results of this study can be used to develop, test, and validate the system that has been used.

Analysis of harmonic voltage distortion simulation study results compared to actual levels measured at the 383 MW nearshore wind park Fryslân

In 2021 the 89 WTG, 383 MW nearshore Wind Park Fryslân (WPF) in the IJsselmeer, the Netherlands became operational. The electrical infrastructure of the wind park can be regarded as a worst-case for harmonic voltage distortion. Extensive simulation studies have therefore been done by WPF using impedance loci to represent the transmission network. The studies confirmed that the capacitive behavior of the wind park electrical infrastructure, in combination with a weak inductive high-voltage grid, result in amplification of background harmonics and harmonics emitted by the WTG. However, comparing harmonic distortion measurements with the simulation results for Windpark Fryslân, the paper identifies specific limitations of the existing approach for proving grid code compliance regarding harmonic voltage distortion. Since background harmonic distortion is currently not considered in load flow studies, small changes in assumptions (for example WTG impedance) can cause an amplification or damping of the background distortion of a certain harmonic order. This means that overall harmonic voltage distortion may be both under- and overestimated. To mitigate this risk, more precise impedance data could be made available by the grid operator. Also, background harmonic distortion at the PCC should be considered in harmonic studies to improve both the correctness and the accuracy of simulation results.

Characterization and Clinical Use of Bone Conduction Transducers at Extended High Frequencies

Measurement of bone conduction (BC) hearing thresholds at extended high frequencies (EHF; above 8 kHz) is of clinical interest but is technically complicated by limitations in standard BC transducer output, a lack of calibration standards and sparse clinical data from human subjects. A recently described calibration scheme using an artificial mastoid and interposed accelerometer is applied in this study to characterize and compare acceleration and computed force outputs over the 4–20 kHz range of two standard BC transducers: the RadioEar® B71 and B81, as well as two non-standard, commercially available BC transducers: the Tascam® HP-F200 and the Aftershokz® AS400. Measures of linear output growth, harmonic distortion and acoustic radiation are assessed and compared across devices. A maximum linear input voltage is established for each BC transducer using measurements of linear output growth and total harmonic distortion. At maximum linear input level, the Tascam shows superior force output by 25 to 40 dB above 8 kHz and the widest dynamic EHF range. Acoustic radiation per output force was lowest for the Tascam, whereas the AS400 behaved more like an air conduction earphone than a force generator. In a cohort of 15 normal hearing volunteers, BC thresholds, measured with the Tascam and reported in dB re 1 rms μN, were consistent with historical measures of EHF BC thresholds in similar subjects using an alternative BC transducer.

Methodology for Improving High-Power Harmonic Measurement Accuracy and Stability

With continued dimension scaling of the semiconductor devices, the parasitic parameters become increasingly obvious and it affects the device performance directly. The harmonic distortion is one of the key factors to limit the RF system bandwidth resource and channel capability. Therefore, it is crucial to precisely extract the nonlinear index of the device and system. High-precision harmonic distortion extraction on a device’s intrinsic characteristics could be beneficial not only to device modeling but also to circuit design. However, the harmonic distortion measurement is highly sensitive to the peripheral circuit and instrumentations, especially in high power stimulus; its repeatability and stability are also hard to control. This paper aims to contribute to the subject by extending the measurement methodology, combining isolation compensation with a dual trace phase tuning (DTPT) technique to obtain the optimal harmonic value. As shown by the experiment results, the optimized approach could achieve high measurements of both accuracy and stability. The proposed methodology is validated with measurement data and compared with conventional measurement architecture. The assessment results prove that the proposed methodology could improve 30.66% and 28.84% measurement accuracy both on second and third harmonics. Simultaneously, the proposed methodology decreases gauge repeatability and reproducibility (GRR) from 56.49% to 7.13%.

Carrier Transition Techniques for Parallel Connected VSCs Using Cross-Coupled Inductors

Parallel inverters can be connected using cross-coupled inductors (CIs) to produce high-quality line voltages in three-phase ac systems. Since no fundamental flux is present in the inductor cores, their size can be made considerably smaller than alternative inductor configurations. Interleaved switching and phase-shifted carriers (PS-PWM) can be used to produce multilevel three-phase line voltages. A modified approach (MPS-PWM) improves the quality of the line voltages by changing the phase of the carriers, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">carrier swapping</i> , based upon the magnitude of the modulating signals. Since carrier swapping in MPS-PWM can cause the inductor circulating currents and flux patterns to jump and have dc offsets, two carrier transition techniques are presented to eliminate these jumps: <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">carrier manipulation</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pulse injection</i> . These techniques represent open-loop PWM control, dependent only on the carrier phase change being used, and can easily be applied to an arbitrary number of parallel-connected inverters. The circulating currents and inductor flux patterns follow predictable patterns, allowing the CIs to be designed more precisely. The relative merits of using MPS-PWM over PS-PWM are assessed using measurements of the load current total harmonic distortion and the line voltage harmonic volt–seconds. The feasibility of the parallel inverter system described is verified using simulations and results from an experimental laboratory prototype.

A high-precision harmonic distortion measurement algorithm and its system design based on time-domain matrix operations

In this paper, a harmonic distortion measurement algorithm and its system design based on time-domain matrix operations are proposed, which can quickly calculate the harmonic amplitudes, phases and total harmonic distortion of a signal. To realize the calculation of harmonic signal parameters in the time domain, we proposed a method to convert the nonlinear function representing the signal into a linear function, constructed a matrix equation, and solved the equation by the row transformation method, which significantly reduced the complexity of the algorithm. Finally, based on the proposed algorithm, a system design was implemented by the digital signal processing theory, and the measurements showed that the system achieves an amplitude error of nearly 1% and a THD error of less than 0.3% when measuring the generated 10 kHz fundamental with 5-order harmonics. The system can be used to measure and calculate the amplitudes and THD of harmonic distortion signals with high precision.

Problem of Total Harmonic Distortion Measurement Performed by Smart Energy Meters

Abstract Currently, electricity is treated as commodity that should be delivered from a distributor to a consumer with a certain quality. The power quality is defined by the set of measures with specific limit values. One of the basic measures is the Total Harmonic Distortion (THD), which allows to assess the level of the voltage distortion. The measurement of THD ratio should be carried out in accordance with the normative specification. It is assumed that this requirement is met by class A power quality analyzers. Currently, measures are taken to monitor power quality in a large number of measurement points with the use of smart energy meters that are part of the Advanced Metering Infrastructure (AMI). The paper presents the problem of THD ratio measurement by AMI meters if voltage fluctuations occur. In such situation, inconsistency in measurement results of AMI meters and class A power quality analyzers occurs. The problem is presented on the basis of laboratory study results in which disturbances in power grid are recreated.

Robust optimization based harmonic mitigation method in islanded microgrids

Power quality issues in islanded microgrids comprising of various renewable energy sources have recently gained more attention. As the harmonic mitigation capability from distributed energy resources will vary for different network topologies, this paper introduces a unified single-end harmonic mitigation approach using a robust optimization model. In the proposed method, a central controller receives voltage harmonic distortion measurements of all buses in the microgrid, optimizes the global information, and then sends back the optimal voltage harmonic components to the local controller of each distributed generation units, which is added to the voltage reference generated by the respective droop controllers locally. The robustness lies in the design of the objective function in the central controller to solve a multi-attribute optimization problem in minimizing both the average total harmonic distortion (THD) and THD of the critical bus in the microgrid considering different coefficients for each term. It has been proved with a set of numerical simulations with different parameters that the search space is reduced around the global minima, which considerably reduces the search time and the number of iterations. The results show that the suggested controller is robust and effective with respect to the different coefficients of the modified objective function to mitigate voltage harmonic distortion in islanded microgrids.

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

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 (&gt;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, to show which of them are the most suitable for assessing harmonic and interharmonic contamination in power system signals such as those present at the output of inverters.

An Experimental Analysis of Harmonic Distortion Indices In Home Based Electrical Appliances and Improvement Using Passive Filter

Nowadays, the growing use of non-linear loads in home appliances gives rise to harmonic pollution in the electrical power distribution system, which degrades the power quality. Many domestic appliances have power electronic converters that characteristically draw a non-sinusoidal current waveform. Short-term effects of non-linear appliances are causing malfunction and damage of electronic devices and long-term effects are thermal losses in equipment and cable, hasty aging, and reduced life period of devices. The whole impact depends on the power ratings and quantity of electrical appliances and their harmonic diversity. Usually, the existence of harmonics and their effects in a domestic zone are not monitored as compared to the industrial and commercial sectors. To ensure the quality of power, it is necessary that a harmonic study is carried out to identify the details of harmonic pollution that is polluting sources, the parameters or quantities they pollute in each instance, and effective improvement methods. In this paper, experimental analysis was performed which focuses on traditional single-phase home-based electrical appliances causing the quality of power down, and implementation of the passive filter is suggested for improvement in the quality of power. All experimental harmonic distortion measurements of home-based electrical appliances were performed in the power electronic laboratory of QUEST Nawabshah. Harmonic distortion indices measurements of home-based electrical appliances have been taken using the fluke power quality Analyzer (PQA) instrument. The analysis shows that from many types of loads, switch mode power supply (SMPS) based load is rich in harmonic distortion. Therefore, an equivalent model of SMPS load in MATLAB/Simulink is developed to analyze improvement in power quality by designing and implementation of the passive filter. The outcome of this research work will be helpful to make the source current sinusoidal by reducing harmonic distortion and thus improve the power quality.

Characterization of dynamic distortion in LED light output for optical wireless communications

Light-emitting diodes (LEDs) are widely used for data transmission in emerging optical wireless communications (OWC) systems. This paper analyzes the physical processes that limit the bandwidth and cause nonlinearities in the light output of modern, high-efficiency LEDs. The processes of carrier transport, as well as carrier storage, recombination, and leakage in the active region appear to affect the communications performance, but such purely physics-based models are not yet commonly considered in the algorithms to optimize OWC systems. Using a dynamic modeling of these phenomena, we compile a (invertable) signal processing model that describes the signal distortion and a parameter estimation procedure that is feasible in an operational communications link. We combine multiple approaches for steady-state and dynamic characterization to estimate such LED parameters. We verify that, for a high-efficiency blue GaN LED, the models become sufficiently accurate to allow digital compensation. We compare the simulation results using the model against optical measurements of harmonic distortion and against measurements of the LED response to a deep rectangular current modulation. We show how the topology of the model can be simplified, address the self-calibration techniques, and discuss the limits of the presented approach. The model is suitable for the creation of improved nonlinear equalizers to enhance the achievable bit rate in LED-based OWC systems and we believe it is significantly more realistic than LED models commonly used in communications systems.

VSI LC filter optimized by a genetic algorithm from connected to island microgrid operation

In microgrids (MG) with a high penetration of renewable energy sources (RES) power converters are used to regulate the produced energy to a single voltage and frequency reference value across the MG. Adequate incorporation of an LC filter at the output of power electronic devices allows the attenuation of harmful harmonics that can be introduced to the MGs energy bus. By traditional methods, LC filter values can be calculated by means of the power rating, switching frequency, cutoff frequency, and using the bode frequency domain. Nonetheless, in the transition from a connected to an autonomous MG operation, the calculated LC filter can lead to high harmonic injection. As a result, a tuning methodology capable of obtaining the right set of parameters for the LC filter for a transition event can improve the performance of the MG. This work optimizes the LC output parameters with respect to the size of the filter components, the IEEE Std 519-2014, and bandwidth of the filter, within a bounded region of values subjected to performance conditions such as voltage output, and the produced total harmonic distortion (THD) measurements during the transition from a connected to an autonomous operation. In a case study, genetic algorithm optimization is used to obtain the LC filter parameters and compared to a conventional arithmetic methodology to obtain the values of the filter. The optimization results in a set of values that lead to a higher harmonic attenuation after the transition rather than a conventional method using the switching frequency as the main design factor.

Nonlinear distortion signal generation and THD measuring device

In order to generate nonlinear distortion when the amplifiers work in the nonlinear region, the system uses the transistor amplifiers to combine the analog switch and MCU to realize nonlinear distortion signal generation and THD(Total Harmonic Distortion) measurement device. The system is mainly composed of fixed gain amplifier circuit, multi-type signal selection circuit, class A and B complementary symmetric circuit, analog switch and microcontroller. The input signal is fixed as a 1KHz, 20mVp-p sinusoidal signal. Based on the influence of quiescent operation point on the common emitter amplifier circuit and the characteristics of Type B push-pull circuit, the analog switch is turned on or off by pressing the button of MCU to adjust the static working point and circuit structure to realize output of different types of signals. THD was calculated by sampling ADC inside MCU and FFT processing. The experimental results show that the system can successfully output sinusoidal signals and four kinds of nonlinear distortion signals (top distortion, bottom distortion, bidirectional distortion and cross-over distortion), and the peak-to-peak values are all greater than 2Vp-p. THD measurement error is less than 0.6%, which can achieve a more accurate measurement of total harmonic distortion.

A Proposed Harmonic Monitoring System for Large Power Users Considering Harmonic Limits

Most power utilities within Southern Africa are faced with the challenges of harmonic distortion due to the high penetration of renewable energy sources (RES) and the use of electronic devices. There is an excessive total harmonic distortion (THD) measured at the point of common coupling (PCC). In this paper, a proposed harmonic monitoring system for large power users (LPUs) is developed. This proposed system considers harmonic limits of the individual and THD of the customers allowed injecting into the network, which should be part of the contractual electricity supply agreement (ESA). Hence, it will enable the monitoring of harmonic distortion to be smooth by determining whether the customer has passed or failed compliance for individual harmonic order and the THD of the voltage. The measurements of harmonic distortion are done using the Unipower power quality (PQ) analyzers that are connected at different points within the industrial network. Measurements of harmonic distortion of an industrial site are compared to the simulation results performed by DIgSILENT software to validate the proposed harmonic monitoring system. Based on the validation results, it is recommended that the ESA between the power utilities and the customers should consist of the harmonic limits.

Studi Harmonisa Akibat Komponen Penyearah Pada Gardu Traksi Kereta Rel Listrik (KRL)

The electrification system on the Jabodetabek Electric Train uses a direct current system of 1500 VDC. The 1,500 VDC overhead system is supplied from the traction substation which is equipped with a silicon rectifier component. This rectifier component can produce harmonics that can distort the medium voltage source of 20 kV PLN and in the long run, can cause damage to electrical equipment. This study aims to determine the value of the harmonic voltage and current and to design a harmonic filter on the KRL traction substation. The results of harmonic distortion measurements on 20kV / 1.2kV cubicle at traction substations with PQA show a maximum THD-v of 3.43% (according to IEEE standards) and a maximum THD-i of 94.86%. The maximum TDD value is 0.73% (according to the IEEE standard), but the 5th, 7th and 11th IHD-i exceed the IEEE standard, with values of 70.04%, 43.38%, and 21.5%. The design of harmonic filters using ETAP 12.6.0 shows the value of THD-i dropped to 0.00%.

Analysis of direct power control AC-DC converter under unbalance voltage supply for steady-state and dynamic response

This paper presents an analysis of Direct Power Control (DPC) technique for the Three-Phase Pulse Width Modulation (PWM) AC-DC converter under unbalanced supply condition. Unbalance condition will cause the presence of unbalanced current and voltages thus produce the negative components on the grid voltage as well as severe performance degradation of a grid connected Voltage Source Inverter (VSI). The input structures for conventional DPC has been modified with a three simpler sequence networks instead of coupled by a detailed Three-Phase system method. The imbalance voltage can be resolved by separating from the individual elements of voltage and current into symmetrical components called Sequence Network. Consequently, the input power relatively improved during unbalanced condition almost 70% through the measurement of Total Harmonic Distortion (THD) from the conventional Direct Power Control (DPC) in individual elements which is higher compared to separate components. Hence, several analyses are performed in order to analyze the steady state and dynamic performance of the converter, particularly during the load and DC voltage output reference variations.