Harmonic Elimination using Discrete Wavelet Transform (Dept.E)

Multi-level inverter used in applications that require high power. The important factor in multi-level inverter is Total Harmonic Distortion (THD). This study discuss nine level cascaded H-bridge multilevel inverter. Also, proposed the effects of using filter on waveform and Total Harmonic Distortion (THD) of output voltage and current. Discussed LC low pass filter and sinusoidal pulse width modulation as control technique of switches. Comparison THD of nine level cascaded H-bridge multilevel inverter with and without filter. The proposed level and filter are design and simulate by MATLAB 2010 Version 7.11.0. The simulation results show the effects of using filter on THD and waveform of output voltage and current. Different methods for choosing filter value are used to illustrate the filter effect.

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.

The use of wireless charging technology for Electric Vehicles (EVs) is gaining increasing significance due to its ability to charge batteries safely and conveniently without the need for physical connectors. This paper presents the design and implementation of the transmitter-side power conversion system for a wireless EV charging station. The proposed system architecture integrates a front-end Power Factor Correction (PFC) rectifier, an Interleaved Resonant DC-DC converter, and a three-level Neutral Point Clamped (NPC) inverter, providing a highly efficient and stable power transmission path for battery charging. The Interleaved Resonant DC-DC converter, designed with a Zero Voltage Switching (ZVS) mechanism, minimizes switching losses and enhances overall efficiency. Its operation under Constant Current (CC) and Constant Voltage (CV) control modes ensures smooth and reliable mode transition through an auxiliary controller incorporated alongside a conventional PI controller. The inverter stage adopts a Modified Space Vector Pulse Width Modulation (MSVPWM) strategy that significantly reduces Total Harmonic Distortion (THD) in both voltage and current waveforms, thereby maintaining compliance with power quality standards. The complete system's performance has been evaluated through both simulation and experimental validation. MATLAB/Simulink-based analysis demonstrates stable converter dynamics with a regulated output voltage of 325 V and negligible transient disturbances during mode transitions. A 0.2 kW laboratory prototype was developed to confirm the simulation results using PIC24F16KA102 and FPGA-SPARTAN-7 controllers for power and switching signal generation, respectively. Experimental measurements indicate that the proposed Interleaved Resonant DC-DC converter achieved an efficiency of approximately 95.35% at rated load, which aligns closely with theoretical predictions. The three-level NPC inverter produced a 320 V output with voltage and current THD levels of 4.8% and 5.6%, respectively. A 2:1 air-core transformer designed for high-frequency operation (100-200 kHz) effectively transfers power to the EV receiver side. The influence of coupling coefficient and air-gap variation on transfer efficiency was systematically investigated, revealing an optimal separation distance of 10-20 mm. The overall results confirm the efficacy of the proposed design for high-efficiency wireless EV charging. Future work will concentrate on optimizing the receiver-side converters to further enhance system efficiency and dynamic performance.

Harmonics are one of the key power quality issues on the front burner in the power system. Advancements in solid-state technology in recent times have resulted in the proliferation of non-linear loads which are the main sources of harmonics. Harmonics penetration in power system networks is detrimental to effective system operation and can result in frequent failures and damage to electrical equipment. This, therefore, creates the need for harmonic mitigation in power system networks for power quality enhancement. This work examined the impact of a shunt passive filter (SPF) in minimizing harmonic distortion on an electrical distribution network considering the power network layout of 7-Up Industry Plc as a case study. The indices for quantifying the level of harmonic distortion and shunt passive filter design for harmonic mitigation in power networks were respectively analysed and presented. The considered 7-Up Industry Plc power network was modelled and simulated with and without SPF in MATLAB/Simulink software environment R2020a. The voltage and current total harmonic distortion, VTHD and ITHD, from the two system states, were evaluated. The observed voltage and current waveforms from the simulation of the test network without any filter applied were distorted, signifying the harmonics’ presence. The estimated VTHD and ITHD values with no filter used were 6.084 and 19.79 % respectively. SPF application on the test network mitigated the VTHD and ITHD to 0.7802 and 2.448 %, giving an improvement of 5.304 and 17.342 % respectively in the minimization of voltage and current total harmonic distortion compared to the no filter case. This study established that a shunt passive filter is suitable for power quality enhancement in an electrical distribution network. Keywords: Electrical distribution network, harmonics, non-linear load, power quality, shunt passive filter, total harmonic distortion

The continual growth of renewables in the distribution scale is converting the conventional arrangement of power grid into a modern arrangement in which the Distribution Generation (DG) units are included within the distribution section of any power system. These renewable units include power electronics-based converters in their construction and the advent of these new technologies deteriorates the Power Quality (PQ) and introduces serious issues of harmonic distortion in both voltage and current waveforms. This research attempts to alleviate the problem of harmonic distortion in low voltage distribution networks containing solar PV modules through the proper sizing of adaptive Passive Harmonic Filters (PHFs). For this purpose, a real distribution network is simulated by ETAP environment, and the harmonic's load flow study is performed to specify the harmonic content at various busbars in the network. Hence PHF models based on the frequency scan performed are proposed to minimize the Total Harmonic Distortion (THD) in the network. The results of the simulations performed have shown that this approach reduces the THD significantly to comply with the permissible limits specified by the international standards IEEE STD 519 and IEC STD 61,000–3–6.

This paper presents the implementation of the Grid-Forming (GFM) control technique in renewable energy source inverters to synchronize with the grid and provide frequency support. Specifically, the GFM Droop Control technique, based on the Power–Frequency relationship, is employed. The proposed model was developed and validated in the Matlab-Simulink environment. By using electromagnetic transient (EMT) simulations, we were able to precisely monitor and analyze voltage and current waveforms, thereby confirming the approach’s effectiveness in enhancing grid stability and power quality. The implementation of the GFM control technique in islanded mode demonstrated high system frequency stability. In response to sudden load changes up to 5 MW (equivalent to over 30% of the total load), a maximum frequency deviation of 0.04 Hz and a maximum Rate of Change of Frequency (RoCoF) of 4 Hz/s were observed. The system ensured the frequency’s return to its nominal value of 60 Hz, thanks to the virtual inertia and frequency regulation provided by the GFM. The total harmonic distortion (THD) of current and voltage in steady-state operation consistently remained below 1%, thus complying with IEEE 1547 standards. In tests with the GFM interconnected to the grid, the droop+LPF control provided dynamic support to the external system, effectively mitigating both frequency deviations and RoCoF. The GFM contributes to the grid’s frequency stability by providing virtual inertia. The power quality at the point of common coupling (PCC) was excellent, as the voltage distortion was maintained below 0.5%, confirming that the injection of harmonic currents does not violate established limits.

This paper introduces the power quality analysis of unidirectional and bidirectional ac voltages controllers. An AC voltage regulator coupled between the power supply and the load is a device having major components of two thyristors connected in inverse parallel manner and the power flow is controlled by varying the firing angle of thyristors. For each configuration, the experimental setup is implemented on Feedback Power Electronics Trainer and simulation is done using MATLAB/Simulink. The simulated and experimental waveforms of current and voltage in case of resistive and inductive loads are obtained by taking different firing angles and are correlated, which demonstrate the effectiveness of model and its configurations. Due to switching operations of power electronic converters, they contain nonlinearities and generate harmonics which not only disturb the performance of converters but also the quality of input power system is badly affected. The power quality factor is observed by Fluke Power Quality Analyzer that can monetize the cost of energy waste due to poor quality. In this research, the performance evaluation of controller with industrial inductive loads under different delaying angle is investigated and detailed comparative analysis is done by experimental readings and simulation results. Total Harmonic Distortion (THD) analysis for different waveforms of voltage and current, its calculation and comparison for change in loads have been presented in this paper.

Matrix-based high-frequency linked (MBHFL) bidirectional dc–ac converters are getting much interest in grid-tied applications due to their high efficiency and the compacted footprint. This paper proposes a new PWM switching technique of the MBHFL dc–ac converters based on phase shift angle considering compensation of the LC filter current at the grid side in order to realize accurate unity power factor and to reduce the total harmonic distortion (THD) of the grid current waveform. The proposed technique estimates the phase shift angle error between the grid voltage and current waveforms due to the capacitor injected current that reduces the power factor at the grid side. It considers two operational modes based on the patterns of three-phase grid voltage and current waveforms. Therefore, it provides the matrix converter switches with different duties according to the pattern of the detected grid voltage and the reference grid current to compensate the phase shift angle error. Also, grid LC filter design and the system controllable limit of the matrix converter output voltage are presented. In addition, the PWM switching technique of the H-bridge circuit is modified to realize safe operation of the converter during step changes at the grid voltage. The effectiveness of the proposed PWM switching technique and its related mathematical model have been investigated experimentally using laboratory prototype based 200 V, 2 kW.

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.

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.

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.

This work presents the development and implementation of four control configurations for photovoltaic inverter. These configurations are: Proportional Integral plus Resonant controller, Proportional Integral plus Repetitive controller, Proportional Integral-Proportional plus Resonant Controller and Two Degrees of Freedom plus Repetitive control with the aim of reducing the Total Harmonic Distortion in Voltage. These techniques are useful in island mode operation of an inverter when it is working as a voltage source in microgrid. In this operation mode, these control techniques are successfully applied when the inverter feeds linear and nonlinear loads. The purpose is to keep the output voltage waveform, frequency and amplitude according to the standard IEEE 519. It is use is justified because currently most of the loads have nonlinear characteristics which increase considerably the Total Harmonic Distortion in voltage. A comparative analysis derived from inverter simulations with nonlinear loads has been performed in order to validate those control techniques, considering that its application to feed line loads proves to be effective.

Harmonics in current and voltage waveforms produced by nonlinear loads in a distribution system can be minimised using passive filters; however, implementing these filters requires the calculation of several suitable parameters for filter components. This work aimed to simulate and analyse the harmonics in the Al-Itihad 11 kV distribution system that branches off from Zubayr substation (33/11 kV) in Basra in Iraq using MATLAB/SIMULINK. Five non-linear loads were simulated to generate harmonics in the simulated Al-Itihad distribution system, and for each non-linear load three types of filters were tested: a single tuned filter (STF), double tuned filter (DTF), and C-type filter. The objectives of these filters to minimise the total harmonic distortion (THD) in the voltage and current waveforms, to minimise the total current, and to improve the power factor of the distribution system. The simulation results showed a reduction in total harmonic distortion, a reduction in the current at the main distribution feeder, and an improvement in the power factor of the feeder.

When the soil invaded by water as the grounding medium in green power generation sites near river basins, on the coast, is dominantly characterized in terms of its resistivity, the characteristics of the voltage and current waveforms on transient discharges such as the soil can be experimentally investigated using the liquid gap, reproducing the resistivity of the soil. The transient discharge characteristics is available information on the surge withstand rating of surge protective devices used in the green power generation sites. Experimental results on the behaviour of lightning impulse discharges in a tap-water gap are reported; these results show that the resistivity of tap water is nearly equal to those of a river and cultivated and marshy land. Further, (1) the discharge voltage and current waveforms indicate the periodic attenuated waveforms for one period, and the voltage waveforms indicate amplitude distortions; (2) the discharge impedance obtained using the fitting curves to the discharge waveforms ranges from 1 to 2.5 times that of the tap-water resistance, i.e., 80Ω, and from 8 to 3.2 times that for positive and negative rod discharges.

In the past decade, wind power capacity has experienced tremendous surge for a growing electrical energy demand. With generation of wind power, wind power can be made in usable form with the help of prominent technology named permanent magnet synchronous generator (PMSG) which is directly driven by back to back converters. However, grid integration with wind brings the problems of harmonic distortion and fluctuations present in voltage. This paper aims to reduce the total harmonic distortion (THD) which are present in current and voltage waveforms. For reducing THD, artificial technology (AI) such as artificial neural network (ANN) and (FLC) fuzzy logic control-based techniques have been modeled, simulated and analyzed. The AI-based harmonic filter is placed between the network and wind system which enhances the power quality during disturbances. The AI-based filter with wind turbine, model of PMSG and model power electronic converters are implemented in MATLAB/Simulink environment.