Total Harmonic Distortion (thd)

This paper researched relationship between Power of adapter and total harmonic distortion of the open-type earphone. In the power of adapter, even harmonic component is extremeley less and only the odd harmonics component is found. When analysed THD of leaking sound open-type earphone far from 1m, as a result, even harmonic component was 2% and odd harmonic component was 35.5%. THD of the diaphragm was affected by THD of electric signal.

Abstract— A neural network based space vector modulation (SVM) of voltage source inverter is proposed. The voltage source converter (VSC) is highly used in high voltage direct current (HVDC) transmission so that a detailed analysis and transmission of this system is carried out. In addition, a non-linear neural network controller is proposed to control the space vector pulse width modulation (SVPWM) to reduce the total harmonic distortion (THD) of the converter (inverter) output voltage. The inverter outputcurrent is analyzed with two switching frequency 1050Hz and1450Hz with and without proposed ANN controller. The results show a THD enhancement about 0.74 % for 1050Hz and 0.68 % for 1450Hz.

been reported by B. Muralidhara [1]. In the year 1924, Alger [2] has reported the Voltage harmonics that exists in an inverter fed IM drive system, results in shaft voltage and bearing current. In the year 2006, A.Ramachandran [3] discussed about the mitigation of Conducted Electro-magnetic interference (EMI) in three-phase Induction motor driven by inverter. The voltage at shaft loop induces harmonics that is due to the asymmetrical flux as reported in [4], [5]. Hence it is necessary to minimize the total harmonic distortion (THD) [4], [5], EMI [6] within limits for the reduction in bearing current and heating of IM winding.

Inverter is necessary for DC to AC conversion for uninterrupted AC power supply and utilization of many types of AC electrical equipment in our day to day life. Square wave inverter and modified sine wave (actually a cascaded square wave) inverter is available which includes total harmonic distortion (THD). In fact the generation of a pure sinusoidal AC voltage is a big challenge with minimum amount of total harmonic distortion. This paper deals with the design of a project which is the hardware implementation of a two level PWM driver to achieve close approximated sinusoidal waveform for DC to AC conversion with low harmonic distortion in unloaded condition.

The function of a single tuned filter is to filter out specific frequency by creating a low-impedance path to ground. The dominant harmonics currents will flow out of the load resulting in a lower total harmonic distortion (THD). A single tuned filter can be tuned on a specific frequency by making the inductive and capacitive cancel each other out. The most dominant frequency is usually selected to obtain better harmonic mitigation from the single tuned filter. The double tuned filter design is an improvement from the single tuned filter design. It is designed to improve the performance of the single tuned filter [7].

In this paper the performance of a proposed three level cascaded MLI-DSTATCOM is analyzed using Synchronous Reference Frame based control scheme with neural network controller for %THD reduction in distribution network. The operation of proposed system is analyzed using MATLAB/SIMULINK software. It can be concluded that Three level Cascaded Multilevel inverter Distribution Static Compensator using Synchronous Reference Frame Theory control scheme with neural network controller effectively improves the power quality in distribution networks. Using neural network, it improves the trustworthiness of the reduction in Total Harmonic Distortion in Distribution Networks. The simulation results show that current perturbations caused by non-linear load can be compensated effectively by the proposed control strategy and thus the prediction error obtained by Neural Network model is very plausible. So the Neural Network model produces reliable estimates of current THD. The results have also pointed out that Neural Network can implement many other data prediction efforts easily and successfully, the ANN controllers are very effective and efficient compared to the PI and PID controllers, because the steady state error in case of ANN control is less and the stabilization of the system is better in it. In the ANN methodology the time taken for computation is since there is no mathematical model .

Abstract: This paper presents the study of total harmonic distortion in permanent magnet synchronous motor (PMSM) using space vector modulation (SVM) technique. SVM generates low Total Harmonic Distortion (THD) and it is well suitable for motor control. Harmonics is one of the major power quality issues occurring in most of the application. SVM holds the major advantage that only one switch is turned on at a time. The proposed model shows the effect of eliminating the lower order harmonics in SVM. MATLAB/Simulink is used develop the model.

Abstract- The worldwide installation of solar photovoltaic (PV) system has proliferated in the last decades. This will inevitably introduce power quality issues to the grid as the solar PV penetration increases. The high switching frequency from the solar inverter has produced unwanted electrical signals that will eventually injected into the power grid. Thus, this paper aims to investigate the total harmonic distortion (THD) performance of the solar inverters under real operating conditions. More specifically, it focuses on the THD performance of the single-phase grid-tie inverters which are installed at Universiti Teknikal Malaysia Melaka (UTeM). The well-established K-Means clustering technique has been utilised to perform the characterization of THD current from the collected data. In addition, the correlation between the THD current with the solar irradiance and the inverter’s output power ratio were also presented and discussed. The findings of this study suggest that the THD current from a solar inverter is highly dependent on the solar irradiance of which the recorded THD current values can be as high as over 60% during the starting-up and shutting-down of the inverter. Furthermore, the THD current values can be broadly categorised into four different categories, depending on the level of solar irradiance.

A table is created in Double Precision Floating Point. The following commands make a 256 point sine wave and measure its total harmonic distor- tion when sampled first on the points and then by jumping with a delta of 2.5 points per step using linear interpolation. For frequency-based appli- cations, spectral purity can be more important than absolute error in the table. The M-file is used for calculating total harmonic distortion (THD) for digital sine wave generation with or without inter- polation. This THD algorithm proceeds over an integral number of waves to achieve accurate re- sults[4]. The number of wave cycles used is A.

Abstract:- When using nonlinear loads, affects the quality of supply power ,which leads to a number of issues like harmonics, voltage sag, voltage swell, flicker, voltage imbalance etc. These issues affect the performance and the lifetime of the utilities. In order to overcome issues arises due to nonlinear loads power filters were developed. This work proposed an active filter which is controlled by PI controller and Fuzzy logic controller to reduce the THD (total harmonic distortion). Here we compared the results of active filter results, without controller and with PI and Fuzzy controller. Results show that performance of fuzzy controller is better than PI controller.

This paper presents a genetic algorithm (GA) optimization technique to find the optimum switching angles of 11-level inverter with minimum number of dc sources and switches in comparison with the cascade multilevel inverter in order to minimize the total harmonic distortion (THD) of their output voltage waveform. Theoretical and simulation results for an 11-level converter show the efficiency of the proposed algorithm to determine the optimum angles in order to decrease the undesired harmonics and produce very high quality output voltage waveform.

Multilevel inverters have been widely used in medium and high voltage applications. Different modulation techniques have been proposed to control the multilevel inverter. This paper presents a switching strategy for cascaded multilevel inverters, based on space vector modulation. The SVPWM can be applied practically in hybrid multilevel inverters with different voltage steps; it can be applied to most multilevel topologies. This paper proposes a new algorithm for hybrid multilevel inverters with unequal voltage steps under the space vector pulse width modulation (SVPWM). The proposed algorithm offers an intuitive method for minimizing the total harmonic distortion (THD) of the output voltage of the inverter and uses simple arithmetic for determining the sector and does not require lookup tables. The proposed techniques lead to a significant reduction in THD. Finally, the algorithm was implemented on a Digital Signal Processor (DSP) and the scheme is explained for a seven level inverter, and experimental results are presented for a seven level inverter.

Abstract---This paper deals with analysis of Total harmonic distortion (THD) for grid connected photovoltaic (PV) systems. In the utility grid, four different inverter topologies like Z-Source Inverter, Voltage Source Inverter, Current Source Inverter, and Multi-level Inverter are connected together and Total Harmonic Distortion (THD) analysis are obtained in MATLAB SIMULINK and simulation outputs are presented.

Abstract - This paper deals with reduction of total harmonic distortion in new Cascaded H-bridge multilevel inverter topology with artificial neural network technique. This topology consists of lower blocking voltage on switches and it requires less number of dc voltage sources, power switches which results in decrease the complexity and total cost of the inverter. Moreover, a new algorithm is used to determine the magnitude of dc voltage sources for generation of all voltage levels. Artificial Neural Network (ANN) is trained by the back-propagation algorithm of the Mean Square Error (MSE) between the output and the desired value. The performance and functional accuracy of the proposed topology using ANN technique in generating all voltage levels for 31-level inverter are simulated using MATLAB simulink.

In Power System applications one major problem in output is distortion. For mitigation of this different methodologies have been used. With advances in Solid-State Power Electronics Devices, various Pulse Width Modulation (PWM) techniques have been developed for Industrial applications. Shao-Liang An, Xiang-Dong Sun, Member, IEEE, Qi Zhang, Yan-Ru Zhong, and Bi-Ying Ren has been studied SVPWM Technique and this paper shows further study and talk about reduction of total harmonic distortion. PWM is a means of transmitting information in a series of pulses, where the data being transmitted is encoded in the width of the transmitted pulse. In the Space Vector Pulse Width Modulation technique, the duty cycles are computed rather than derived through comparison as in Sine Pulse Width Modulation. The SVPWM technique can improve the fundamental component by up to 27.39% than SPWM. This paper discusses the studies of Space Vector PWM technique (SVPWM). The simulation results show that the SVPWM technique has lower total harmonic distortion than the PWM technique.

Power Electronic Cycloconverter circuits use in different application for example, ship propulsion and cement mill. These applications require adjustable speed to do their job. Changing number of pole of motor is quite difficult. So, Cycloconverter circuit play important role to adjustable speed higher or lower than synchronous speed. In this paper, single phase mid-point Cycloconverter will be investigated. MOSFET, IGBT and GTO will be used as power devices in Cycloconverter circuit. Harmonics and total harmonics distortion(THD) for Cycloconverter circuit will be compared between these power devices. Pulse width modulation technique PWM will be used as gate drive for all power devices. MATLAB software will be used in this project.

It is important, therefore, in a simulation model to include the nonlinear core model to ensure that the transformer does not degrade the performance of the system as a whole. This paper concentrates on this aspect of the transformer design, with inves- tigations carried out into the tradeoffs of material characteristics and air gaps, the effect of core size and number of windings on performance, and comparisons between different winding configurations and core types. Previous work [26] describes the basic design procedure for DSL transformers, but relies on “rule of thumb” calculations and simplification of the THD figures. It is proposed in this paper to apply circuit simulation to more ac- curately predict the effect of nonlinear ferrite cores on the trans- former’s performance. The proposed model will have a similar parasitic model to that described previously, but will include an accurately characterized nonlinear core model. In this case, the original Jiles–Atherton [27]–[29] model has generally been used. The modifications to the Jiles–Atherton model that have been proposed previously by Wilson et al. [30]–[33] generally refer to heavily saturated cores, and in general the ADSL trans- formers operate at low signal levels implying minor – loops. D. Distortion Performance Criteria

Fig. 8. Under healthy operation at no-load. (a) Measured flux linkage. (b) Frequency spectrum of flux linkage Figure 8a shows the measured magnetic flux linkage induced in a search coil, under healthy operation at no-load. According to this figure, it can be seen that, under ideal conditions, the machine has an air-gap magnetic field which varies sinusoidally in space and time. Its frequency spectrum is shown in Fig. 8b. Also, Fig. 9a shows the measured magnetic flux linkage induced in a search coil, under faulty operations at no-load and its frequency spectrum is shown in Fig. 9b. According to this figure, it can be seen that, faulty operation will cause a distortion of this sinusoidal waveform. Due to the high circulating current in the fault areas, magnitude of magnetic flux linkage under fault condition in these areas is higher. Comparing Fig. 8b and Fig. 9b, the THD increases from 1.8% to 25.7% after the fault has happened. This large increase in the THD that indicates the fault has occurred. Therefore by analyzing magnetic flux linkage of the machine, inter turn faults can be detected. In fact, a fault indicator based on harmonic analysis of the magnetic flux linkage is achieved.

è under critical conditions (like air or fuel starvation) the whole polarization curve shifts and there is an harmonic distortion of the cell voltage response.. è THD = effective [r]

Also the lightning ballasts connected to the lamp may produce large harmonic distortions and third harmonic currents in the neutral. The newer rapid start ballast has a much lower harmonic distortion and can be filtered with a filter circuit implementation. Table below shows the harmonic spectrum of a fluorescent lamp with a magnetic ballast. Harmonic currents are shown as the percentage of the fundamental component.