Voltage dip generator for testing wind turbines connected to electrical networks

Voltage source inverter (VSI) had been used in dc traction power substation to deliver the trains braking energy back to the utility grid. To mitigate low order harmonics components, pulse-width-modulation (PWM) technique is commonly used in VSI controlled. As a result, the ac voltage and current waveforms may contain high frequency ripples. This paper proposes to mitigate the high frequency harmonics using LCL-filter with series <em>R</em>-damper. This filter offers good attenuation on harmonics with smaller size compare to other passive filter topologies. Theoretical analysis and simulation verification are conducted in designing the proposed filter. System level simulation had also been carried out. Sinusoidal grid current and voltage waveforms are recorded (THD<2%). This paper also includes damping losses analysis in conjunction with resonance peak suppression in designing the <em>R</em>-damper.

Non-Intrusive Load Monitoring (NILM) relies on the extraction of meaningful features from electrical signals to effectively disaggregate power consumption. Traditional NILM methods often focus on low-frequency power features, while recent advancements explore more sophisticated signal processing techniques. This study investigates two feature extraction approaches based on sinusoidal current and voltage waveforms. First, the impact of using only apparent power and phase angle is analyzed, followed by an evaluation of harmonic components alone. The experimental setup included both linear and non-linear electrical appliances to ensure that the proposed approach could handle a wide range of load characteristics and accurately reflect realistic operating conditions. The results indicate that the best performance is achieved by combining these features into a single method, which constitutes the first approach. The findings provide insights into the effectiveness of these feature sets and their potential advantages over existing NILM techniques.

This paper proposes the design, mathematical modeling, and performance evaluation of a three-phase switched-capacitor multilevel inverter (SCMLI) using a capacitor-grounded switched cell in a transformer-less (CGSCTL) arrangement. The proposed topology improves output voltage quality while reducing component count, voltage stress, and system complexity, making it well-suited for renewable energy systems, electric mobility, and grid-connected applications. The $\mathbf{d}-\mathbf{q}$ reference frame uses a proportionalintegral (PI) controller for accurate current regulation, a phase locked loop (PLL) for grid synchronization, and an LC filter to suppress harmonics. The simulation results show wellsynchronized sinusoidal voltage and current waveforms with minimal distortion. FFT analysis reveals a Total Harmonic Distortion (THD) of 0%, suggesting high power quality. The inverter achieves 96% peak efficiency at a rated power of 10 kW and optimized capacitor sizing. Comprehensive performance assessment covering THD, efficiency, and transient response validates the effectiveness of the proposed system, which further features soft-switching and a modular framework supporting scalability and reliability.

Minimization of the total harmonic distortion (THD) at the output of an inverter is essential to reach the ideal case, i.e. a pure sinusoidal. So far, very intensive studies about this topic have been carried out. In this study, a fully rectified version of a sinusoidal voltage waveform at an utility amplitude and frequency obtained from a well-known buck–boost regulator has been converted to a sinusoidal AC voltage waveform with a simple inverter operation. The purpose of this innovative circuit is to generate an approximate sinusoidal voltage waveform with a quite low THD at the inverter output without invoking the harmonic elimination techniques. Since distortions in the AC link voltage in this circuit fully depend on how well the capacitor current is regulated to its reference, the value of the load current is a critical component in this regulation.

The objective of this paper is to present an approach for isolating the harmonic contents in both voltage and current waveforms of the montage feeder of Gharb Talkha substation (60/11 KV). A novel technique using Discrete Wavelet transform (DWT) for the analysis of the waveforms harmonics content At the beginning the substation is simulated using Simulink toolbox in Matlab program with and without the presence of capacitor bunk. The obtained voltage and current waveforms are compared to the actual data. The proposed model is used to study the effect of replacing the capacitor bank with single tuned parallel passive filter. The resulting current and voltage waveforms are analyzed using the proposed DWT technique. The analysis showed that the Total Harmonic Distortion (THD) of both voltage and current waveforms is improved as well as the power factor.

Investigations into machining accuracy and quality in wire electrochemical micromachining under sinusoidal and triangular voltage pulse condition

Active ripple decoupling technique of single-phase inverter is a popular topic to minimize the dc-link capacitance. However, the existing control methods are based on tracking sinusoidal or predetermined voltage waveform of compensation capacitor, where they assume the inverter outputs are pure sinusoidal voltage and current. Therefore, the performance of existing methods degrades when the inverter output voltage and current are not purely sinusoidal. Furthermore, the limited dynamic performance threatens the safety of dc-link capacitor when the load changes, because the inrush ripple power is injected into dc link with small capacitance and the dc-link voltage will suddenly rise up when the ripple power is not buffered during transients. In this paper, a direct instantaneous power predictive control is proposed to buffer ripple power of single-phase inverter, which combines instantaneous ripple power control with model predictive control to overcome the issues above. The proposed method tracks instantaneous ripple power rather than voltage or current waveform. In this way, it can fully buffer all ripple powers in the system even for distorted output voltage and current of the inverter; the voltage waveform of the capacitor has the different shape in different operation cases, which enables the full utilization of storage capacitor. Model predictive control makes the proposed method have fast dynamic and perfectly compensate ripple power during transients and steady states. The buck-type active ripple decoupling circuit is chosen by comparing with another typical topology to implement the proposed method. Simulation and experimental results on a 3-kW prototype verify the theoretical analysis and the proposed control method.

Pantograph arcing with AC supply generates transients, cause asymmetries and distortion in supply voltage and current waveforms and can damage the pantograph and the overhead contact line. The asymmetry generates a net dc component and harmonics, which propagate within the traction power and signalling system and causes electromagnetic interference. Unlike DC-fed systems (Part I), the arcing in ac supply is complex because of the zero crossing of currents and voltages. In this paper, we discuss the mechanisms of sliding contact and arcing between pantograph-contact wire using the experimental setup described in Part I. Influences of various parameters and test conditions on arcing phenomenon and their signature patterns on the supply voltage and current waveforms are presented. It is shown how the arcing mechanism and corresponding asymmetry in the voltage and current waveforms are governed by line speed, current, supply voltage, inductive load, and pantograph material. The asymmetry in the current waveform is mainly due to the difference in the duration of successive zero-current regions and uneven distortion of the waveshapes. This, in turn, creates the asymmetry in the voltage waveform. The findings presented in this paper could be beneficial for coming up with appropriate mitigation techniques from the electromagnetic interference due to pantograph arcing in AC traction systems.

An analytical method to study the discharge-radiation dynamics (DRD) in alternating current plasma display panels was developed. The input parameters for this DRD analysis were experimentally determined panel voltage and current wave forms. Discharge voltage, current, and power wave forms in the discharge volume of a cell were first obtained from the measured panel voltage and current wave forms using known geometrical configurations and electric circuit calculations. Intrinsic discharge parameters, such as electron temperature and density, were then determined to satisfy these discharge wave forms under the assumption of a hydrodynamic approach. A one-dimensional discharge structure with two regions (cathode fall and positive column) and several other assumptions which are plausible from the discharge physics point of view were also adopted. These assumptions took account of known cross sections and energies of electron-impact excitation and ionization of discharge gas atoms, and a secondary electron emission coefficient of the dielectric surface at the cathode side induced by ion bombardment. Radiation intensities from the discharge were calculated using the determined intrinsic discharge parameters, and the results were compared with those measured for the respective panel conditions used in the calculations, yielding a fair agreement. The luminous efficiency, defined as the radiation intensity divided by the discharge power, was also determined using the intrinsic discharge parameters. Discussion on the luminous efficiency change for different panel operating conditions revealed that the efficiency improvement at a lower voltage was attributable to a lower electron temperature for this condition.

In this chapter, we shall discuss techniques used to fit faulted current and voltage waveforms, each to a sinusoidal waveform containing a fundamental component, a decaying/constant direct current (DC) component and/or harmonics.These techniques use the least squares (LSQ) method to minimise the fitting error, and all have the common goal of extracting the fundamental components of voltage and current waveforms, to calculate the impedance to the fault or the comparison of current-based signals in digital differential protection.

An experimental investigation of a TRAPATT diode with its oscillator circuit is presented. The measurements of current and voltage waveforms were made with a sampling oscilloscope (3 dB bandwidth, 14 GHz)and an improved capacitive voltage-divider probe. Design information is given for this type of probe which can have an almost unlimited bandwidth. Voltage and current waveforms across the semiconductor chip are presented for a diode that oscillated at 1 GHz with an efficiency of 49%. It is shown that the mode of operation and the waveforms are explained well by a simple theoretical model that has been developed.

This paper presents optimal third harmonics in both permanent magnet (PM) shaping and current waveform to improve the output torque of five-phase surface-mounted PM (SPM) machines. The optimal value of third harmonic injected into the sinusoidal PM shape and current waveform for maximum torque improvement is analytically derived and validated by both finite element (FE) analyses and experiments. It is found that the optimal third harmonic is 1/6 of the fundamental one for both PM shape and current waveform. For the five-phase SPM machines having rotors without shaping, Sine shaping, or Sine shaping with third harmonic injected, the electromagnetic performance including the back EMF waveform, cogging torque, average torque, torque ripple, copper loss, iron loss, impact on power inverter, and demagnetization withstand capability are compared. It is demonstrated that, although the copper loss and iron loss increase due to additional third harmonic in the winding current and magnet shape, the average torque with optimal third harmonics injected in PM shaping and current waveform can be improved by >30% while the torque ripple and remains similar to that of the one with Sine shaping. In addition, this will reduce the dc bus voltage while maintaining the machine torque density. Furthermore, the machine with Sine and Sine+3rd rotors presents much better demagnetization withstand capability performance than conventional rotor.

The analysis and test results are given for an experimental single-phase controlled-current PWM (pulse-width-modulated) rectifier that operates at unity power factor with near sinusoidal current waveform and that has power reversal capability. The twice-line-frequency AC power is identified as a source of voltage harmonics in the DC link. The harmonics enter into the voltage regulation feedback loop to distort the AC current waveform. These undesirable harmonics can be removed by a low-pass filter. It is noted that the overall design must address the possibility of instability due to the low-pass filter in the feedback path. >

Modular Multilevel Converter (MMC) system has many advantages over conventional voltage source converters and therefore they can play major role in Direct Current power transmission, micro grid, or renewable energy applications and recently it attracted attention to use in smart transformers. MMC’s distinctive topology offers many new features, it also offer a sophisticated topology to deal with high frequency requirements of generating a sinusoidal voltage waveform for smart transformers. In this work we will make a comparison between T-cell Submodule based MMC and Half-Bridge Submodule based MMC when generating 1kHz voltage waveform as we will investigate capacitor voltages, AC voltage and current THD as generating high frequency sinusoidal voltage waveform is essential for the size of Smart Transformers. Simulation analysis has been done using MATLAB/Simulink and the results are verified.

A XeCl dielectric barrier discharge (DBD) excilamp applied by pulsed and sinusoidal voltage waveforms is simulated using a 1-D drift–diffusion model. In both waveforms, the light output power depends not only on the gas mixture composition but also on the electrical parameters of each voltage waveform such as the frequency, the duty cycle, etc. At the same amplitude of the applied voltage and frequency, the light ultraviolet output efficiency of a pulsed voltage is higher than that of a sine voltage. These results obtained in this paper permit us to find out an appropriate power supply for a DBD excilamp.