Total Harmonic Distortion Measurements Research Articles

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.

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.

Fast online diagnosis for solid oxide fuel cells: Optimisation of total harmonic distortion tool for real-system application and reactants starvation identification

This study investigates the potential application of total harmonic distortion (THD), as a fast online monitoring tool, to identify the early signs of failure modes in solid oxide fuel cells (SOFC). Indeed, the timely detection and identification of faults is crucial for applying mitigation strategies to avoid irreversible damage and increase the system lifetime. Two of the most common faulty conditions are considered in this work, namely fuel and air starvation. This experimental work aims at progressively triggering these errors in a controlled manner, by following different realistic scenarios, and recording THD values on a frequent basis. Several well-established laboratory monitoring tools, like electrochemical impedance spectroscopy (EIS), complemented by the distribution of relaxation times (DRT) are used to analyse and support the interpretation of the THD measurements. A sensitivity analysis on the THD parameters, namely the signal amplitude and the number of harmonics, is carried out to identify the optimal combination of parameters and achieve the best faults detectability. Finally, the impact of the fuel flow direction and the operating temperature are examined. The results of this work are summarised as practical guidelines to better employ the THD technique to identify the early warning signs of reactants’ starvation.

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.

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.

Nonlinear distortion of angle modulation signal in output power amplifiers

The output power amplifier is operated in nonlinear mode to increase its efficiency, at which the signal is distorted more. The goal is to analyze effects of nonlinearity on the modulating signal of angle-modulated signal distortions for single-ended and push-pull output power amplifiers with memory and without it. The amplifier characteristic ic(vBE) is preset by the cubic polynomial. The output voltage of memoryless amplifier uout(t) is found by Ohm's law. And in case with amplifier with memory, the output voltage uout(t) is found by Complex amplitude method with a Fourier series of function ic(t). The output voltage uout(t) is represented as the narrowband process with envelope of the waveform U1(t) and initial phase Ф1(t) to determine the angular modulation law Ф1(t) at the amplifier output. The function U1(t) is defined as combination of in-phase А(t) and quadrature В(t) components. The distortion estimate based on Total Harmonic Distortion (THD). The measurement of THD is defined as the ratio of the RMS amplitude of a set of higher harmonic frequencies to the RMS amplitude of the first harmonic. The spectrum of function Ф1(t) is represented a Fourier series. In single-ended memoryless amplifier and non-cutoff mode, the THD decreases as m increases and THD of modulating signal is {37.6; 18.8; 6.3%} at m {0.5; 1; 3}. In cutoff mode, the smallest THD is {15.18; 5.13%} at m {1; 3} as θ = 140o. In push-pull memoryless amplifier and θ = 90o, the THD is {22.2; 11.1; 3.7%} at m {0.5; 1; 3} which is 1.7 times less than in a single-ended amplifier without cutoff. This is due to compensation even-order harmonic of amplified signal at the output of a pushpull amplifier. In this case of memoryless amplifier, the transistor load is a parallel RLC circuit. The distortion decreases under m increases at first (up m is 1.5), but then rapidly increases (from m is 1.7). This is due to increase of the parasitic harmonics level caused by the nonlinearity of the phase-frequency characteristic of RLC circuit. The calculations show that THD of modulating signal is 3.35, 9.02 and 22.88 % at Q = 10 and m {0.5; 1; 3}, respectively. In cutoff mode, the smallest THD is at θ = 90o and it does not depend on θ at large values of m. In push-pull amplifier with memory, the THD is 2.8, 2.5 and 3.0 times less than for a singleended amplifier without cutoff at Q {2.5; 5; 10}, respectively. The results of this paper can be used for the design of signal processing systems.

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.

REALIZATION OF TOTAL HARMONIC DISTORTION MEASUREMENT OF ACOUSTIC SOURCE SIGNAL SYSTEM FOR FREQUENCY OF 125 HZ AND 1000 HZ

<p>The measurement of total harmonic distortion (THD) of an acoustic source signal system has carried out in Laboratory Acoustics and Vibration, Sub-directorate of National Measurement Standards for Acoustics and Vibration - BSN. The aim of this research is, therefore, to measure and analize the THD values that produced by the system that consists of a signal generator, a power amplifier, and a passive loudspeaker with fundamental frequencies of 125 Hz and 1000 Hz. This measurement should be implemented because it has never been performed in this laboratory. Moreover, this system always be used for either calibration or measurement of acoustical instruments such as sound level meter and noise dosimeter. The method used to measure THD is a free field method using a full anechoic chamber with narrow band analysis. Measurand to determine THD is sound pressure level (SPL) with output of loudspeaker are 94 dB, 104 dB, and 114 dB. From result of measurement was found THD value of fundamental frequencies of 125 Hz and 1000 Hz. For the former frequency, the maximum THD was found at SPL of 94 dB where its value was 1,86 %. Meanwhile the later, the maximum value of THD was 1,94 % also at SPL 94 of dB. The results of this measurement can be used into uncertainty budget for either calibration or testing of acoustical instruments, and also support for validation of calibration of noise dosimeter based on percentage of noise exposure dose using acoustic comparison coupler that still under research and development in this year.</p>

Effect Of Value Of Resistance Announcement To Thd In Electrical System Faculty Of Engineering University Udayana Denpasar

AC (Air Conditioner), TV, lamp, LCD and others are categorized as nonlinear load generating harmonics. The high content of harmonics has a negative impact on the quality of electrical power. The result of measurement of THD (Total Harmonic Distortion) current at 9 ohm ground resistance value at phase R = 9,8%, phase S = 11,0%, phase T = 7,5% exceed from standard value IEEE 519 Year 2014 equal to ? 5 , 0%, THD measurement of phase voltage R = 1.4%, phase S = 1.2%, phase T = 1.3%, meet the maximum THDv standard of ? 5%. To overcome this problem, it was observed the effect of the value of ground resistance to THDi and THDv on the electrical system of the College of Engineering Faculty of Denpasar. This method of analysis with ETAP software simulation. With grounding system ? 3 ohm only effect on current THD only with decreasing value of THDi become: phasa R = 4,2%, phase S = 5% and phase T = 4,3%, meaning with grounding system ? 3 ohm THD current fulfill IEEE 519 - 2014 standard <5%. while THD voltage has no effect (THD value of fixed voltage). Several studies have suggested that THD repair can be done by filter installation. However in this study the installation of grounding system ? 3 ohms can reduce the value of current THD.

ANALYSIS OF THREE-PHASE SVPWM MICROCONTROLLED INVERTER WITH FOCUS ON HARMONICS GENERATION

This work presents SVPWM modulation technique concepts in a simple and direct way, aiming at the level of harmonics generated measurement, in order to evaluate its performance and to compare with another method of modulation widely used and known as SPWM. It also presents the generation algorithm, implemented and simulated in an 8-bit microcontroller. PWM is a technique used by inverters to control induction motors, aiming to control rotation and torque. Several techniques have been developed, the most famous being SPWM, due to its simplicity and performance, and the most recent being SVPWM, which has gained the confidence and preference of designers, mainly due to its performance characteristics. A bibliographic study was necessary to implement the SVPWM with simulations in EXCEL, PSIM, MATHLAB and PROTEUS for a better understanding of the algorithm concepts and construction. Performances of SPWM and SVPWM modulations were evaluated under the same conditions in harmonics generation, by total harmonic distortion measurement, and the SVPWM method presented better results. On the other end, by increasing the number of vectors, this technique may be impracticable when acting with low cost conventional microprocessors. In both techniques, inverters dead times were realized in hardware, by dedicated integrated circuits, so that, besides avoiding crossed conductions, they didn´t influence distortions.

A DC-90-GHz 4- $V_{\mathrm{ pp}}$ Modulator Driver in a 0.13- $\mu \text{m}$ SiGe:C BiCMOS Process

In this paper, a linear driver for optical modulators in a 0.13- $\mu \text{m}$ SiGe:C BiCMOS technology with $f_{T}/f_{\text {max}}$ of 300/500 GHz is presented. The design is implemented following a distributed amplifier topology in a differential manner. The driver features a small-signal gain of 12.5 dB and a 3-dB bandwidth of 90 GHz and delivers a maximum output amplitude of $4~V_{\text {pp}}$ to a 100- $\Omega $ differential load. Delivering the maximum output swing, the large-signal gain is 10.5 dB. Time-domain measurements are performed, showing the maximum output swing with ON–OFF keying (OOK) eye-diagrams up to 64 Gb/s and pulse amplitude modulation-4 up to 45 Gbaud (90 Gb/s). Moreover, OOK eye-diagrams up to 120 Gb/s are reported with an output swing of $3~V_{\text {ppd}}$ . Total harmonic distortion measurements are also conducted demonstrating a value of 5% at 1 and 8 GHz up to an input amplitude of 800 mVppd. Using a reduced number of stages in the design, the power dissipation of the integrated circuit is 550 mW, resulting in an output power to power dissipation ratio of 3.6%. To the best knowledge of the authors, this is the first time a linear driver for optical modulators demonstrates such high bandwidth and efficiency for the demonstrated data-rates.

Power quality experimental analysis of grid-connected photovoltaic systems in urban distribution networks

This paper presents the analysis of the impact of dispersed source production on the electric distribution network. The focus is on the production of electric energy by photovoltaic systems in public distribution networks. Photovoltaic systems may in certain cases influence voltage quality in public distribution networks, which is determined by the EN 50160 standard. Photovoltaic systems affect the voltage profile and harmonic distortion of current and voltage. Ensuring the appropriate voltage profile is especially important in radial networks because of eventual huge voltage drops. Many photovoltaic systems on a radial network with relatively high short-circuit impedance and relatively low short-circuit power can be problematic with regard to the permitted level of harmonic distortion, particularly at lower power. The analysis of power quality is based on real measurements of total harmonic distortion (THD) on four existing photovoltaic systems and two transformer stations in the urban electric distribution networks.

Affordable headphones for accessible screening audiometry: An evaluation of the Sennheiser HD202 II supra-aural headphone

Objective: Evaluation of the Sennheiser HD 202 II supra-aural headphones as an alternative headphone to enable more affordable hearing screening. Design: Study 1 measured the equivalent threshold sound pressure levels (ETSPL) of the Sennheiser HD 202 II. Study 2 evaluated the attenuation of the headphones. Study 3 determined headphone characteristics by analyzing the total harmonic distortion (THD), frequency response and force of the headband. Study sample: Twenty-five participants were included in study 1 and 15 in study 2 with ages ranging between 18 and 25. No participants were involved in study 3. Results: The Sennheiser HD 202 II ETSPLs (250–16000 Hz) showed no significant effects on ETSPL for ear laterality, gender or age. Attenuation was not significantly different (p > 0.01) to TDH 39 except at 8000 Hz (p < 0.01). Maximum permissible ambient noise levels (MPANL) were specified accordingly. The force of the headband was 3.1N. THD measurements showed that between 500 and 8000 Hz intensities of 90 dB HL and higher can be reached without THD >3%. Conclusion: Sennheiser HD 202 II supra-aural headphones can be used as an affordable headphone for screening audiometry provided reported MPANLs, maximum intensities and ETSPL values are employed.

High speed BiCMOS linear driver core for segmented InP Mach-Zehnder modulators

A hybrid arrangement for an optical transmitter sub-system comprising a linear driver fabricated in IHP SiGe 0.13 µm BiCMOS technology with an InP segmented Mach-Zehnder modulator is described. The proposed scheme, with direct interface to the digital to analog converter, is suitable for coherent high order modulation formats intended for data transmission over optical fiber at a wavelength of 1550 nm. In this paper, a partial prototype, consisting of a single driver core and modulator segment is demonstrated. The driver core features an output differential voltage of 2.5 Vpp, a gain of 9 dB and a 3 dB bandwidth of 32 GHz. Linearity is evaluated through total harmonic distortion measurements. With on---off-keying modulation, electro-optical eye diagram measurements of the single segment demonstrate successful operation up to 40 Gb/s data rate. While exhibiting clear capability for high speed operation, these results serve also to explore the boundaries of the proposed hybrid configuration.

Power quality analysis of grid-connected solar photovoltaic generators in Brazil

The typical electrical distribution system shows a passive characteristic in relation to power flows (i.e. unidirectional power flows from substation to loads along the feeder). However, with the inclusion of solar photovoltaic (PV) generators along the feeder, this behavior is changed, and characteristics related to power quality, such as voltage level and total harmonic distortion (THD), may be affected. This paper presents the analysis of power quality in a feeder of the urban grid in the city of the Florianopolis, Brazil, with the integration of grid-connected PV systems as distributed generation. The analysis of power quality is based on real measurements of THD on an existing 12kWp PV pilot plant installed in the urban environment, and power flow simulations of a hypothetical PV system of 4.2MWp distributed in the same area, using the ANAREDE software. The power flow simulations allowed assessing the voltage level, the direction of power flow and loading of the distribution lines. The introduction of limited amounts of PV generation as distributed generation in the urban environment was found to be beneficial in several aspects: better voltage profile; power loss reduction and improvement in total harmonic distortion of the voltage (THDv). Furthermore, photovoltaics as a distributed generation source can also postpone feeder capacity upgrading investments.

A 330 MHz 11 bit 26.4 mW CMOS Low-Hold-Pedestal Fully Differential Sample-and-Hold Circuit

A new technique for realizing a very-high-speed low-power low-voltage fully differential CMOS sample-and-hold circuit with low hold pedestal is presented. To achieve high sampling linearity the circuit utilizes linearized input switches. The fully differential design relaxes the trade-off between sampling speed and the sampling precision. The circuit design of major building blocks is described in detail. A prototype circuit in a 0.35-μm CMOS process is designed and experimental results are presented. The sample-and-hold circuit operates up to 330 MHz of sampling frequency with less than −68.3 dB of total harmonic distortion, corresponding to 11 bits for an input 80.24 MHz sinusoidal amplitude of 1.2V pp at a 3 V supply. This total harmonic distortion measurement reflects the held values as well as the tracking components of the output waveform. In these conditions, a differential hold pedestal of less than 0.8 mV, 0.8 ns acquisition time at 1.2 V step input, and 1.2V pp full-scale differential input range are achieved. The circuit dissipates 26.4 mW with a 3 V power supply.

A microelectromechanical systems-based piezoelectric microphone for aeroacoustic measurements.

This paper describes the packaging and characterization of micromachined piezoelectric microphones designed as aircraft fuselage instrumentation for full-scale noise characterization flight tests. An important requirement for such microphones is a high maximum sound pressure level (SPL) &amp;gt;150 dB coupled with noise floor &amp;lt;45 dB SPL (narrow bin) and flat frequency response in the audio band (20 Hz–20 kHz). In contrast to many past micromachined piezoelectric microphones that use PZT and ZnO for piezoelectric transduction, aluminum nitride (AlN) was used due to inherent advantages in dielectric loss and signal-to-noise ratio. The microphone structure includes a 500–900-μ m diameter circular diaphragm composed of a structural layer and an annular AlN/metal film stack on a silicon substrate. Promising microphone die were selected via laser vibrometer measurements followed by packaging of the microphones and associated electronics in individual 1/4 in. tubular housings. Characterization of the packaged microphones included frequency response, noise floor, and total harmonic distortion measurements. Early results for a packaged microphone reveals a sensitivity of 27 μV/Pa, dynamic range of 36–157 dB, and resonant frequency of 176 kHz.

A Bit-Stream-Based PWM Technique for Sine-Wave Generation

A new method for the generation of high-quality sinusoidal signals is presented. Multibit binary signals are represented using uniformly weighted single bit streams that can then be processed by digital logic. Building blocks that are useful for the construction of the sinusoidal generator are also presented. The bit-stream representation has the advantage of having the characteristics of a classical pulsewidth-modulation signal and hence can be used to drive high-power switching devices with minimal conditioning. The technique is simple and can easily be implemented using digital logic on a field-programmable gate array (FPGA). The operation of a single-phase inverter using the proposed technique is demonstrated using an Altera Stratix FPGA and a custom-built power stage. The complete digital design uses less than 200 logic elements. The performance of this technique is quantified using simulations and practical measurements. Practical implementations lead to total harmonic distortion measures ranging between 0.75% and 4.92%.

A 250 MHz 11 bit 22 mW CMOS low-hold-pedestal fully differential sample-and-hold circuit

A new technique for realizing a very-high-speed low-power low-voltage fully differential CMOS sample-and-hold circuit with low hold pedestal is presented. To achieve high sampling linearity the circuit utilizes improved bootstrapped input switches. The fully differential design relaxes the trade-off between sampling speed and the sampling precision. The circuit design of major building blocks is described in detail. A prototype circuit in a 0.35-μm CMOS process is integrated and experimental results are presented. The sample-and-hold circuit operates up to 250 MHz of sampling frequency with less than ?70 dB of total harmonic distortion corresponding to 11 bits for an input 60.8 MHz sinusoidal amplitude of 1.8 V pp at a 3 V supply. The total harmonic distortion measurement reflects the held values as well as the tracking components of the output waveform. In these conditions, a differential hold pedestal of less than 0.8 mV, 0.8 ns acquisition time at 1.8 V step input, and 1.8 V pp full-scale differential input range are achieved. The circuit dissipates 22 mW with a 3 V power supply.

Total Harmonic Distortion Measurement System of Electronic Devices up to 100 MHz With Remarkable Sensitivity

This paper describes a system for measuring total harmonic distortion (THD) signal components between 1 and 100 MHz at levels down to 130 dBc, which has not been previously achieved. This system consists of mechanically sturdy passive bandpass (BPF) and passive band-elimination (BEF) filters with carefully selected parts. The BPF is used to create a pure sinusoidal signal input to the device under test, whereas the BEF removes the fundamental frequency component of the output signal to overcome dynamic range limitations of a spectrum analyzer that is used to measure the output. We describe design concepts and implementation of these filters, as well as measurement results that show the performance achieved. We also propose to use our BPF to provide a pure sine wave output from signal generators that use analog-to-digital converters (ADCs) as the signal source. A high-precision THD measuring system can be used to measure the ac linearity of electronic devices (such as operational amplifiers, ADCs, and digital-to-analog converters) that operate at frequencies up to several tens of megahertz.