Waveform Distortion Research Articles

Calibration System for High-Voltage Transformers With Multiharmonic Distorted Waveforms

Calibration System for High-Voltage Transformers With Multiharmonic Distorted Waveforms

Modern Control of a Power Supply Based on a Matrix Converter for Water Disinfection by UVC Radiation

Water, an essential resource, has been facing gradual deterioration in quality over an extended period. Water treatment has emerged as a critical concern, with a long-standing acknowledgment of the importance of preserving and appreciating this precious resource. UV-C technology has proven to be an ideal solution that effectively addresses these twin needs. The core principle of UV bactericidal treatment revolves around generating ultraviolet rays within a treatment chamber filled with water. Consequently, ensuring a dependable power source for low-pressure mercury-argon discharge lamps has become imperative to guarantee the efficiency of UV-C disinfection.The primary goal of this study is to supply our discharge lamp with a current source that produces a sinusoidal current at its output, featuring a frequency of 50 kHz and an effective value of 0.65 A. Electronic ballasts enable lamps to enhance radiation quality by operating at high frequencies, and the selection of a power supply is a response to this specific challenge.The aim of this research centers on the utilization of a single-phase matrix converter. The bidirectional switching cells within this converter offer frequency-related advantages. To achieve the desired magnitude and frequency, we employed a PWM control strategy. Subsequently, we implemented a linear current adjustment approach using two controllers: a Proportional-Integral (PI) controller and a Generalized Predictive Control (GPC) in the RST polynomial form. This was done to ensure a high-quality current source with the desired waveform and low Total Harmonic Distortion (THD).The research outcomes have led to environmental simulations conducted using Matlab/Simpower system and Matlab/Simulink.

Electromagnetic Forces in Induction Motor With Nonsinusoidal Power Supply.

Magnetic flux density and electromagnetic forces of induction motors at sinusoidal and nonsinusoidal power supply are analyzed. On the basis of asymptotic small parameter expansions depending on the level of higher time harmonics in the supply current waveform the most essential components of radial and tangential forces are singled out. With the given current waveform preliminary estimations of the relation of electromagnetic forces and torques of geometrically similar motors are obtained. It is shown that even insignificant distortions in the supply current waveform may bear negative effect on increase in vibrations due to some additional torques and forces. These forces are conditioned by interaction of the main field and linear load waves from the current first and higher time harmonics. In relative units they are comparable with forces of interaction of the field tooth harmonics. Increase in the current harmonics leads to proportional increase in electromagnetic forces. At significant current harmonics some additional rise of the total level and enrichment of the spectrum of forces due to interaction of the field higher time harmonics between themselves takes place. The computation results are compared with the experimental data for an induction motor power supplied from a pulse-width frequency converter.

DENOISING THE SHOCKWAVE PRESSURE SIGNAL OF UNDERWATER EXPLOSION BASED ON EMD-CEEMDAN IN CONSIDERATION OF THE SIGNAL CURVE CURVATURE

The measured signal of shockwave pressure of underwater explosion is usually disturbed by many objective factors such as the disturbance of the environment surrounding the sensors, the complexity of wave propagation and wave reflection in complex environments, the formation and fluctuation of air bubbles, especially analog signals always have noise due to the influence of electronic noise from the A/D converter and circuit board error embedded in measuring devices, etc. These are the main causes of initial waveform distortion, obscuring important characteristics of the signal, and making it difficult to use and further analyze underwater explosion shockwave pressure. Based on two algorithms Empirical Mode Decomposition (EMD) and Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN), this article combines the two algorithms above into one denoising model called EMD-CEEMDAN model with Python codes. Three evaluation criteria such as the average curvature of the signal curve, signal-to-noise ratio (SNR) and mean squared error (MSE) are applied to establish the most suitable denoising model. Applying this model to experimentally measured signal of underwater explosion shockwave pressure, the results show that high-frequency noise is eliminated, the denoised signal is transformed into a typically smooth explosion signal while its peak pressure value differs only about 2% from that of the initial signal.

NUMERICAL AND LABORATORY SIMULATION OF TRANSFORMER SATURATION DEPENDING ON THE INITIAL PHASE OF THE CURRENT

In case of short circuits in electric power systems, emergency modes are possible, accompanied by saturation of transformers. With them, significant distortion of current signals occurs in the secondary winding of the transformer with the appearance of an aperiodic component and harmonics, the level of which is comparable to the signal at the main industrial frequency. The requirements for relay protection and automation devices imply the need to determine the time from the onset of the transient process to the onset of distortion of the current signal in the secondary winding.
 
 The purpose of the study is to analyze the saturation of the transformer depending on the initial phase of the transition process.
 
 Materials and methods. The PSCAD platform was used to model the power system section. The model makes it possible to qualitatively describe the saturation of a step-down transformer in the event of a short circuit on the low side, taking into account hysteresis phenomena in the magnetic system. Experimental verification was carried out in laboratory conditions using a measuring (intermediate) current transformer.
 
 Results. It is shown that, depending on the phase of the current at the moment of the beginning of the transient process, the pattern of saturation and, accordingly, the distortion of the current changes significantly. The distortion of the time waveform of the current signal in the secondary winding of the transformer can begin both after fractions of the period of the power frequency signal, and after several periods.
 
 Conclusions. The assessment of transformer saturation modes should be carried out taking into account the fact that the initial conditions for transient processes during short circuits are random. In the analysis of such processes, it is necessary to take into account the phase shift between current and voltage.

Performance analysis of fluorescent and LED lighting sources

"Artificial lighting is a necessity in the conduct of activities, especially at night. The use of fluorescent and LED lighting sources has led to a decrease in electricity consumption compared to incandescent lighting sources. The paper presents a case study highlighting the voltage and current waveforms in the operation of the analyzed sources. A considerable distortion of the current waveform is found, identifying the need for measures to improve power quality. The photometric measurements showed that for some light sources the luminous flux on the box is higher than the luminous flux actually emitted. Keywords: lighting sources, electrical and photometric measurements, waveforms, efficiency"

High accuracy and resolution damage detection for concrete based on novel virtual correlation imaging method and embedded piezoelectric sensing technology

This paper presents a novel virtual correlation imaging (VCI) method to reduce the adverse effects of stress wave distortion and realize high accuracy and resolution damage imaging based on the sparse stress wave data collected by embedded piezoceramic transducers. Specifically, a compensation function is first constructed in the VCI method based on the frequency response characteristic of damage-induced scattering signals. Then, the constructed compensation function is emitted as the virtual excitation signal in the simulation space via virtual channels. To automatically compensate for the effect of waveform distortion, a virtual correlation operator is developed based on the scattering signal and its corresponding virtual received signal to design the imaging function. Finally, the practicability of the proposed VCI method is investigated on a concrete specimen with two successively drilling holes under laboratory conditions. The results indicate that, compared with the conventional damage imaging methods, the proposed VCI method can effectively decrease the adverse effect of distorted probing stress waves on damage localization accuracy and spatial resolution during the imaging process.

Analysis of Reactive Power in Electrical Networks Supplying Nonlinear Fast-Varying Loads

This study concerns problems related to the assessment of reactive power in power networks with nonlinear fast-varying loads, such as electric arc furnaces, rolling mill drives, etc. The operation of this type of load is characterized by the introduction of interharmonic currents (including higher harmonics) into the power supply network and a relatively low power factor. Rapid changes in the RMS value of the current also cause voltage fluctuations and the related phenomenon of light-flickering. Therefore, there is a need to evaluate the power selection of compensating devices, taking into account the random nature of load changes and the distortion of current and voltage waveforms, in particular, interharmonic components, the impact of which has not been fully investigated so far. To analyze the random nature of load changes, autocorrelation functions were used, which allowed for the estimation of the expected values of the arc furnace current distortion coefficient (based on the recorded waveforms). In order to determine the parameters of reactive power compensating devices, and in particular capacitor banks, an autocorrelation function in the exponential-cosine-sine form was used, which meets the conditions of differentiation. This study contains comparative results of the reactive power of capacitor banks determined using different methods. The criterion for selecting capacitor bank parameters was the minimization of energy losses in the power supply network. The calculations presented in this study show that by taking into account higher harmonics and interharmonics in the voltage and currents of fast-varying loads, the installed power of the capacitor bank can be reduced by approximately 7%, and energy losses in the power grid can be reduced by 3–5%.

Time of Flight Measurement Method Combining Threshold Method and Cross-Correlation Method

With various benefits such as a large range ratio, suitability for large-diameter measurement, and lack of excess pressure drop, ultrasonic flowmeters (UFMs) have been widely adopted in natural gas measurement. The accuracy of flow measurement in transit-time UFMs is mostly dependent on the accurate measurement of time of flight (TOF). The threshold method, the cross-correlation (CC) method, and the model-based method are examples of traditional TOF calculation techniques. However, the threshold method is susceptible to such factors as waveform distortion, amplitude attenuation, and noise, the CC method is constrained by the sampling frequency, and the model-based method necessitates a significant investment in calculation time and resources. Based on the analysis of the shortcomings of traditional TOF measurement methods, a TOF measurement method that combines the threshold method and CC method is presented. This method integrates the advantages of the high measurement resolution of the threshold method and the strong robustness of the CC algorithm. The results demonstrate that the flow rate accuracy and the repeatability of the TOF are greatly improved by this method.

Dynamic Dead-Time Compensation Method Based on Switching Characteristics of the MOSFET for PMSM Drive System

In order to effectively avoid the shoot-through issue of the semiconductor device (such as the power metal-oxide-semiconductor field-effect transistor (MOSFET)) adopted in the phase leg of the motor drives, a dead-time zone should be inserted. However, the nonlinearity caused by the dead-time effect will bring about voltage/current distortion, as well as high-order harmonics, which largely degrades the performance of motor drives, especially in low-speed operations with slight loads. In this paper, a dead-time compensation method is proposed to suppress such side effects caused by dead-time zones and improve the performance of motor drives. Compared with other existing methods, the proposed method is mainly focused on the switching characteristics of the power MOSFET, which is directly relative to the compensation time in each pulse-width modulation (PWM) period. Firstly, a detailed derivation process is elaborated to reveal the relationship between compensation time and the switching performance of the MOSFET. Meanwhile, the switching process of the MOSFET is also well analyzed, which summarizes the variations in the switching time of the MOSFET with a varied load current. Then, the multipulse test (MPT) is carried out to obtain accurate values of the switching time with the varied load current in a wide range (0–80 A) and form a 2D lookup table. As a result, the compensation method can easily be realized by combining the lookup table and linear interpolation based on the phase current of the motor dynamically. Finally, the effectiveness of the proposed method is verified based on a 12 V permanent magnet synchronous machine (PMSM) drive system. According to the relative experiment results, it can be clearly observed that the time-domain waveform distortion, high-order harmonics, and total harmonic distortion (THD) value are reduced significantly with the proposed dynamic compensation method.

Estimation of central blood pressure waveform from femoral blood pressure waveform by blind sources separation.

Central blood pressure (cBP) is a better indicator of cardiovascular morbidity and mortality than peripheral BP (pBP). However, direct cBP measurement requires invasive techniques and indirect cBP measurement is based on rigid and empirical transfer functions applied to pBP. Thus, development of a personalized and well-validated method for non-invasive derivation of cBP from pBP is necessary to facilitate the clinical routine. The purpose of the present study was to develop a novel blind source separation tool to separate a single recording of pBP into their pressure waveforms composing its dynamics, to identify the compounds that lead to pressure waveform distortion at the periphery, and to estimate the cBP. The approach is patient-specific and extracts the underlying blind pressure waveforms in pBP without additional brachial cuff calibration or any a priori assumption on the arterial model. The intra-arterial femoral BPfe and intra-aortic pressure BPao were anonymized digital recordings from previous routine cardiac catheterizations of eight patients at the German Heart Centre Berlin. The underlying pressure waveforms in BPfe were extracted by the single-channel independent component analysis (SCICA). The accuracy of the SCICA model to estimate the whole cBP waveform was evaluated by the mean absolute error (MAE), the root mean square error (RMSE), the relative RMSE (RRMSE), and the intraclass correlation coefficient (ICC). The agreement between the intra-aortic and estimated parameters including systolic (SBP), diastolic (DBP), mean arterial pressure (MAP), and pulse pressure (PP) was evaluated by the regression and Bland-Altman analyses. The SCICA tool estimated the cBP waveform non-invasively from the intra-arterial BPfe with an MAE of 0.159 ± 1.629, an RMSE of 5.153 ± 0.957 mmHg, an RRMSE of 5.424 ± 1.304%, and an ICC of 0.94, as well as two waveforms contributing to morphological distortion at the femoral artery. The regression analysis showed a strong linear trend between the estimated and intra-aortic SBP, DBP, MAP, and PP with high coefficient of determination R2 of 0.98, 0.99, 0.99, and 0.97 respectively. The Bland-Altman plots demonstrated good agreement between estimated and intra-aortic parameters with a mean error and a standard deviation of difference of -0.54 ± 2.42 mmHg [95% confidence interval (CI): -5.28 to 4.20] for SBP, -1.97 ± 1.62 mmHg (95% CI: -5.14 to 1.20) for DBP, -1.49 ± 1.40 mmHg (95% CI: -4.25 to 1.26) for MAP, and 1.43 ± 2.79 mmHg (95% CI: -4.03 to 6.90) for PP. The SCICA approach is a powerful tool that identifies sources contributing to morphological distortion at peripheral arteries and estimates cBP.

Ultrafast pump-probe spectroscopy via chirped-pulse up-conversion with dispersion compensation.

In this study, ultrafast transient signals were detected on a single-shot basis using chirped-pulse up-conversion spectroscopy with dispersion compensation. Unlike in the conventional time-encoding technique using chirped pulses, distortion of the ultrafast waveform was reduced by applying dispersion compensation to the chirped probe pulses and using sum-frequency generation with the chirped readout pulses. The method was applied to terahertz time-domain spectroscopy and near-infrared pump-probe spectroscopy, providing ultrafast observations with an improved temporal resolution comparable to the transform-limited pulse durations. Terahertz waveforms, Kerr rotation signals, and phonon-polariton oscillations were measured accurately with no significant waveform distortion, thereby showing the proposed scheme to be promising for single-shot pump-probe spectroscopy in a wide range of spectroscopic applications.

Acoustic diode realized by asymmetric filter

Devices of one-way transport for acoustic waves are called acoustic diodes. They are able to promote the advancement of noise isolation, acoustic communication, and acoustic signal processing. A lot of designs of acoustic diodes based on various mechanisms have been given. However, most designs have problems of one kind or another, such as low efficiency, instability, bulky volume, complex structure, frequency change, waveform distortion, and so on. An asymmetric acoustic filter with only three layers is proposed in this work. The total length of the acoustic diode is less than half the wavelength. Its backward transmission is almost completely stopped. For the forward transmission, the amplitude of the transmitted wave is almost proportional to the driving voltage. This characteristic is better than its electronic counterpart which is often annoyed by the unavoidable nonlinearity at high driving voltage. A simple, compact, stable, broadband, frequency-preserved, highly efficient, linear acoustic diode is realized.

A generalized canine transfer function accurately reconstructs central aortic pressure waveforms to enable enhanced pulse wave analysis

Routine preclinical blood pressure evaluation is an important risk assessment tool. Although proximal aortic pressure is most relevant for key target organs, abdominal aortic pressures are more commonly recorded. Pulse pressure amplification and waveform distortion in abdominal waveforms make it inappropriate for central hemodynamic analytical methods without the use of a mathematical transfer function. Clinical transfer functions have been developed to estimate ascending aortic waveforms from brachial or radial artery waveforms in humans, but no preclinical analogues exist. The aim of this study was to develop a canine-specific transfer function to reconstruct thoracic aortic pressure waveforms from abdominal aortic data to enable the application of central hemodynamic analytical methods. Simultaneous abdominal and thoracic blood pressures were recorded from seven conscious, male beagle dogs administered 3 well-characterized pharmacologic standards and animals were appointed to a training (n = 3) or validation (n = 4) group at baseline and during dosing. A generalized transfer function was developed from the training group data and evaluated for its ability to synthesize thoracic pressure waves in the training and validation groups. Select hemodynamic parameters were evaluated in measured and synthesized thoracic data. There was a high degree of correlation between measured and synthesized thoracic parameters (r2 = 0.74–0.99). There was no difference between indices computed from synthesized or actual thoracic waveforms at baseline or after administration of pharmacologic standards. This work demonstrates that a generalized preclinical transfer function can reproduce thoracic pressure waves across a range of hemodynamic responses thus enabling the application of central hemodynamic analytical methods.

A novel voltage sag detection method for analyzing charging quality of electric vehicle

Electric car charging quality is severely impacted by voltage sag in the distribution network. Voltage sag events frequently occur in conjunction with other power quality disturbances, which leads to signal waveform distortion, making it difficult to identify voltage sag characteristics in composite power quality disturbance signals. The voltage sag amplitude, phase angle jump, and duration are all accurately detected in the composite power quality disturbance signal thanks to the method's two-stage waveform decomposition model, which eliminates the interference of the transition segment by pinpointing the beginning and ending points of the voltage sag using DQ transform. Moreover, the designed simulation experiments further verify that our proposed method outperforms other mainstream approaches, and it can be well used to effectively detect voltage sags of different causes under various signals that disturb the composite power quality, with an average accuracy rate of over 98.86 %.

FPGA-based pulsed laser with high modulation depth from Mach-Zehnder electro-optic modulator and its application

Mach-Zehnder electro-optic modulator as the essential component of high-speed modulation in the optical fiber communication and sensing system, its stability control of operating bias-point plays a key role in determining the transmission signal quality. Based on the output characteristic principle of Mach-Zehnder electro-optic modulator, researches on its bias-point drifting for causing the reduction mechanism of modulation depth and extinction ratio are analyzed. Switching its internal state machine from FPGA is proposed to automatically adjust the bias voltage in real time realizing the operating bias-point control of Mach-Zehnder electro-optic modulator, which is studied through the theoretical investigation. A pulsed laser with the temperature sensing system of fiber Bragg grating ring-down cavity based on FPGA is established experimentally to demonstrate its effectiveness. The experimental results show the modulation depth and the extinction ratio of pulsed laser are improved by 40.45% and 32.85 dB, respectively. Output characteristic curve of the sensing system is optimized, which includes the phenomenon of initial curve rise of ring-down signals and the distortion of ring-down waveform are eliminated. The good linearity, repeatability, stability and accuracy of sensing system are investigated at the continuous variation temperature from −30℃ to 30℃.

Analysis of Control Strategy of Arc Plasma Power Supply Inverter Module

The inverter module serves as a critical component in the conversion of electrical energy within arc plasma power sources, exerting a profound influence on the overall performance and stability of the power supply. Consequently, the meticulous design and precise control of the inverter module are of paramount importance in ensuring the effective operation and application of arc plasma power sources. This paper introduces a dual-closed-loop control system, integrating a voltage outer loop with a current inner loop, as the cornerstone of its inverter module design. It also undertook a comprehensive comparative analysis of various voltage-control strategies, encompassing four control methods (PI, PID, PR, QPR) and two modulation techniques (bipolar modulation and unipolar, carrier-based modulation) under diverse operating conditions. Additionally, simulation experiments were conducted on a prototype 10 kW inverter module using the Matlab/Simulink simulation platform, with evaluation criteria including waveform tracking performance, voltage waveform distortion rate, and steady-state error. The results indicate that in low-frequency operating conditions, the voltage-control strategy employing QPR control plus unipolar, carrier-based modulation, and in high-frequency operating conditions, the voltage-control strategy utilizing PI control plus unipolar, carrier-based modulation exhibited superior waveform tracking performance. The waveform distortion rates were measured at below 0.47% and 4.2%, respectively, aligning perfectly with the stringent standards of IEEE 519. This research provides valuable theoretical support and practical guidance for future engineering endeavors in the field of inverters.

Output Waveform Distortion Suppression Method of Asymmetric Sine Wave Inverter Based on Online Identification and Linearization of System Transmission Characteristics

Limited by the switching frequency of an insulated gate bipolar transistor (IGBT), the system bandwidth of high-power inverters is low. If the amplitude and phase changes of each harmonic from the reference signal to the output waveform are defined as transmission characteristics, it can be concluded that the limited bandwidth will result in nonlinear system transmission characteristics. This results in the amplitude and phase distortion of each harmonic of the asymmetric sine wave, which in turn leads to severe distortion of the output waveform. Therefore, this article proposes a method to linearize transmission characteristics. This method effectively offsets the nonlinear effect of transmission characteristics, which is caused by the limited bandwidth, by causing distortions with respect to each harmonic in the reference signal, thereby suppressing the distortion of the output waveform. In addition, an online identification method of transmission characteristics based on a state observer is proposed to achieve the online linearization of system transmission characteristics. This method does not rely on closed-loop system control, has no stability problems, and can be used for a variety of control methods. Simulation and experiments verify the effectiveness of this method.

Analysis of output characteristics of wireless power transfer system based on LCC/S-S hybrid compensation structure

PurposeTo simplify the circuit design and control complexity of the magnetic coupling resonant wireless charging system, the radio energy transmission constant current and constant voltage charging is realized.Design/methodology/approachThe purpose of this study is to simplify the circuit design and control complexity of the magnetic coupling resonance wireless charging system, in order to achieve constant current and constant voltage charging for wireless energy transmission. First, the principle of LCC/S-S compensation structure is analyzed, and the equivalent mathematical model is established; then, the system characteristics under constant current and constant voltage mode are analyzed, and the design method of system parameters is given; finally, a simulation and experimental system is built to verify the correctness and feasibility of the theoretical analysis.FindingsThe results show that the proposed hybrid topology can achieve a constant current output of 2 A and a constant voltage output of 30 V under variable load conditions, and effectively suppress the current distortion problem under light load conditions. The waveform distortion rate of the inverter current is reduced from 33.97% to 10.45%.Originality/valueBy changing the high-order impedance characteristics of the compensation structure, the distortion of the current waveform under light load is suppressed, and the overall stability and efficiency of the system are improved.

Effects of magnet shapes on total harmonic distortion and cogging torque in a permanent magnet synchronous generator for wind turbines

Abstract This paper explores and theoretically reports the effects of different magnet structures on the cogging torque and the total harmonic distortion of the output waveforms from a permanent magnet generator. The generator is a radial flux machine and four different structures are considered for the magnet arrangement in the rotor component and modelled in the Ansys/Maxwell electromagnetic simulation program. This three-phase machine exhibits different behaviours towards various magnet structures, i.e. rectangular, inclined slotted rectangular, skewed double rectangular and inclined slotted skewed double rectangular, respectively. It has been proven by finite element analysis and Fourier analysis that both the cogging and total harmonic distortion values vary significantly for all models. The cogging torque values change in the range of 89.95 to 436.75 mNm and the lowest cogging torque is measured for the inclined slotted skewed double rectangular magnet geometry, while the conventional rectangular magnet geometry yields the worst value with 436.75 mNm. Furthermore, the total harmonic distortion values varies between 1.63 and 3.55 for different magnetic orientations. While the worst total harmonic distortion value is obtained from the inclined slotted rectangular magnet, the best total harmonic distortion is acquired from the skewed double rectangular magnet. All these results will provide scientists and engineers with important information in order to obtain more efficient machines.