Thd

The electric drives and its application requires advanced power electronic converter to meet the high power demands. As a result, multilevel inverter structure has been introduced for high power and medium voltage applications. A multilevel inverter improves the performance of the system in terms of harmonics, dv/dt stress and Electro Magnetic Compatibility (EMC). The multilevel topologies are (1) Diode clamped (2) Flying capacitor and (3) Cascade H-bridge. According to literature review, Cascade H-bridge multilevel inverter with separate DC source is most commonly used for medium voltage and high power application. This configuration has several identical single phase H-bridge cells which are cascaded in series at its output side. In this project different level of cascade H-bridge multilevel inverter are simulated by using MATLAB software and analysis of total harmonic distortion (THD) is calculated.

In this paper, the author proposes a sensorless direct torque control (DTC) of an induction motor (IM) fed by seven-level NPC inverter using artificial neural networks (ANN) and fuzzy logic controller. Fuzzy PI controller is used for controlling the rotor speed and ANN applied in switching select stator voltage. The control method proposed in this paper can reduce the torque, stator flux and total harmonic distortion (THD) value of stator current, and especially improve system good dynamic performance and robustness in high and low speeds.

A Dual active bridge converter is a high efficiency power converter. This converter is provided isolation with use of solid state transformer. DAB converter consists of two H-bridges of active power control along with one high-frequency transformer. High frequency transformer (SST) provides galvanic isolation and act as energy storage device. The leakage inductance of transformer at primary and secondary side acts as energy storage component. DAB converter has considerable amount of harmonics. The aim is to reduce the harmonics. This paper discusses sinusoidal pulse width modulation technique (SPWM) to achieve harmonics reduction. Solid state transformer is a high frequency transformer can be used as power electronic converter. The three stage SST configuration includes ac to dc rectifier, isolated dc to dc dual active bridge converter, dc to ac inverter. The switching frequency of inverter part is greater than DAB part so inverter stage is model for double line frequency i.e. at 120 Hz. The second harmonics are dominant at this frequency. For better performance of DAB converter PI control is used but at 120 Hz it has limited gain. To proposed methods are PI plus feed forward and PI plus Resonant controller. Keywords: Dual Active Bridge converter (DAB), Sinusoidal Pulse Width Modulation (SPWM), THD, Feed Forward Controller _______________________________________________________________________________________________________

This paper present a asymmetrical cascaded 7 level multiinverter using fixed frequency carrier based pulse width modulation technique.The multilevel inverter is used to reduce harmonics. Here we are comparing single phase 7 levels and 3 phase seven level topology and thus reducing THD less than 5%. In asymmetical cascaded single phase MLI by using only 2-H bridges with 8 switches we can get 7 level output voltage where as cascaded three phase MLI 7 level output voltage is obtained by using 6-H bridges with 24 switches.

This Paper investigates the impact of power system harmonics on the performance of over-current relays. Simulation is performed on the IEEE 30-Bus system with heavy penetration of non-linear loads using ETAP software. Simulation results show that with significant harmonic contents in the power network, a relay malfunction will occur and they will trip in a wrong sequence when there is a fault in the system.

Distance relay is the main protection of power transmission lines and make an important role in power system stabilization if it operates selective and instantaneous. In this paper, the trajectory of the fault impedance is determined. It is shown that in the end of the first zone or in the middle of the second zone, distance relay could not make a correct decision for operating if the fault occurs with arc. So to overcome this problem, in this paper a novel technique using total harmonic distortion (THD) is proposed. The proposed method makes the distance relay more selective and instantaneous.

A worldwide system was developed for solar photovoltaic (PV) applications. The demand for "clean" power generation is primarily powered here. The grid-based PV systems would become most important player in prospect mixed power systems, combined with multiple power electronic converters. Strict demands on the entire PV network have been made to achieve consistent & effective power generation from PV systems. Development of power converters in PV systems is being built in response. This paper offers a description of the latest power electronic converters used widely in residential applications, in three-phase PV systems. This paper also discusses demands for three-stage grid-connected PV systems and common systems management strategies.

A number of reference current generation have been developed for analysis of shunt active power filter to mitigate the load compensation. Depending upon the type of load the technique have to be chosen. In this paper, six reference current generation techniques viz. instantaneous reactive power theory(IRP), Synchronous reference frame theory(SRF), Perfect harmonic cancellation(PHC), Unity power factor method(UPF), Self tuning filter method(STF), Predictive filtering method(PFM) are compared for different operating conditions. The harmonic are introduced because of non-linear loads in system. These harmonics are eliminated using above techniques. The results and performance of system simulated on MATLAB/Simulink platform. The system is experimentally implemented using DS1104 card of dSPACE system.

Multilevel inverter is an important alternative technique in high power, medium voltage power control. Multilevel inverter topology is classified in to diode clamped multilevel inverter (DCMLI), flying capacitors multilevel inverter, cascaded inverter with separate dc source. This project presents diode clamped multilevel inverter with sinusoidal pulse width modulation (SPWM) framework. The carrier based SPWM technique is developed to facilitate its implementation in diode clamped multilevel inverter. Diode clamped multilevel inverter using MOSFET as switching device is used in this particular project. Furthermore, in this study reduction of harmonics has been stressed on using diode clamped multilevel inverters. It also states the adverse effects of Total Harmonic Distortion (THD) on generation and transmission equipments. It also explains about Common Mode Voltage and its effects in brief. Multilevel Inverters have been designed, modeled and simulated and the output results have been depicted in the form of waveforms, THD analysis modules using MATLAB SIMULINK and the results are systematically tabulated.

A worldwide system was developed for solar photovoltaic (PV) applications. The demand for "clean" power generation is primarily powered here. The grid-based PV systems would become most important player in prospect mixed power systems, combined with multiple power electronic converters. Strict demands on the entire PV network have been made to achieve consistent & effective power generation from PV systems. Development of power converters in PV systems is being built in response. This paper offers a description of the latest power electronic converters used widely in residential applications, in three-phase PV systems. This paper also discusses demands for three-stage grid-connected PV systems and common systems management strategies.

Low rating wind power generators have attracted the general public for distribution of power. Generally smaller rating wind turbines are fed to single phase inverters in which there is reduced power extraction. However there is need to develop three phase inverters for various applications such as irrigation systems, small scale industries, domestic applications and variable frequency drives. In view of this a three phase voltage source inverter is designed and fabricated for 1.5kW wind turbine installed at B. E.C Energy Park. SPWM and SVPWM techniques are employed for the proposed three phase inverter. The performance of both SPWM and SVPWM are compared in terms of power quality. The above results are validated by experimental setup.

This paper presents a reconfigurable architecture for coherent built-in self-testing (BIST) of high speed analog-to-digital converters (ADCs) with moderate resolutions. The proposed system is suited to be fully integrated with the ADC and, besides a low jitter clock reference, no other external high quality generators are required. The complete system comprises two synchronized phase-locked loops (PLLs), one based on a two-integrator oscillator capable of providing low distortion outputs and another based on a relaxation oscillator providing low jitter squared output, to allow coherent sampling. A detailed description of the building blocks of both PLLs is given as well as the techniques used to minimize area of the loop filters (LFs), to stabilize the output amplitude of the two-integrator oscillator to a known value, and to improve the total harmonic distortion (THD) of this oscillator. Post-layout simulations, in a 0.13 μm CMOS technology, of the proposed BIST scheme applied to a case-study 6-bit 1 GS/s ADC are shown and validate the proposed test methodology.

The multilevel inverters have drawn tremendous interest in the power industry. The unique structure of multilevel voltage source inverter allows them to reach high voltages with low harmonics without the use of transformers or series-connected synchronized switching devices. A diode clamped multilevel inverter is used .For these type of inverters as the number of levels is high enough ,the harmonic content will be low enough to avoid filters. The inverter efficiency is higher and it is having simple control methods than all other types of multilevel inverters. A nine level multilevel inverter is used here. A comparative study on the THD of nine level diode clamped inverter has been carried out. The diode clamped inverter provides multiple voltage levels from a nine level unidirectional voltage balancing method. Multicarrier SPWM control is used to obtain high quality sinusoidal output voltage with reduced harmonics. It is an effective replacement for the conventional method which has high switching losses and poor drive performance. It reduces the total harmonic distortion and enhances performance of any drive system. Variation in the performance characteristics of the induction motor has been done by connecting it with multilevel inverter. The effectiveness of the system is verified through simulation using MATLAB Simulink package and hardware implementation has been done.

The paper presents the study of high harmonics influence on power metering by static
meters for active and reactive energy. The review and analysis of manufacturer’s documents
and standards in the field of electricity meters testing was conducted and mathematical
models for calculating active and reactive energy were identified. Various electronic meters
were tested at the experimental stand. As a result, the errors of active and reactive energy
metering in the presence of high harmonics were determined. It is shown that the implemented
in static meters equations for the active and reactive energy calculation can lead to unfair
payments for electrical energy in the presence of high harmonics.

Researchers have found interest in the multilevel inverters (MLI) owing to the low total harmonic distortion (THD) associated with their output voltage, as well as their low electromagnetic interference (EMI). The MLI represents an effective and feasible solution for enhancing power demand and minimizing AC waveforms' harmonics as they generate a preferred level of output voltage as inputs from varying levels of DC voltages. In this paper, the performance of a seven-level cascaded H-bridge MLI with an asymmetrical number of power switches was evaluated. The simulation performance is shown to validate the operating principle of the single-phase cascaded H-bridge inverter. To control the MLI, a pulse width modulation approach was utilized. The operating principle of the MLI was verified via simulation using PSIM software.

Nowadays power electronics circuits are embedded to most of electrical application areas. This approached offers a great control mechanism with simple and easy circuit configuration. Switched Reluctance Motor (SRM) is one of the most recent apparatus which draws a great number of researchers’ interests. Previously several attempts are made to use the power converters as driver for SRM such as Voltage Source Inverter (VSI) and bridge converters. This paper presents an analysis study of three level inverter to control the SRM. The inverter is controlled using space vector modulation SVM. The aim of this paper is to report the use the multilevel inverter to be fed into the SRM. The implementation of the multilevel inverter is abl to reduce the Total Harmonics Distortion (THD). Performance comparison are made between the multilevel and previous power electronics circuits that applied to the SRM. The simulation results have been conducted by MATLAB/SIMULINK software.

The paper presents the study of high harmonics influence on power metering by static meters for active and reactive energy. The review and analysis of manufacturer's documents and standards in the field of electricity meters testing was conducted and mathematical models for calculating active and reactive energy were identified. Various electronic meters were tested at the experimental stand. As a result, the errors of active and reactive energy metering in the presence of high harmonics were determined. It is shown that the implemented in static meters equations for the active and reactive energy calculation can lead to unfair payments for electrical energy in the presence of high harmonics.

In recent days multilevel inverter(MLI) hold attractive features, in the area of high power medium voltage energy control though multilevel inverter has a number of advantages it has drawbacks in the vein of higher levels because of using more number of semiconductor switches. So in order to overcome this problem the new multilevel inverter is proposed with reduced number of switches. Switch topologies using carrier-based PWM techniques. These pulse width modulating (PWM) techniques include the phase disposition (PD) strategy, alternate phase opposition disposition (APOD) strategy. The modulating indices are evaluated for total harmonic distortion, form factor, crest factor, VRMS (fundamental) and distortion factor. This paper proposed the different carrier arrangement in order find out the less total harmonics distortion. The results are validated using MATLAB/SIMULINK software.

There are various types of Multilevel Converters (MCs) in addition to various types of modulation techniques for these types of MCs; the challenges in selecting the best one of them with regard to the amount of the required of components, and its harmonics content. So, a comparison study among these types has been done in this paper. For comparison study, the simulation of seven level of two popular topologies of MCs: Neutral Point Clamped (NPC) converter, and Cascaded-MCs were carried out with Matlab/Simulink software program. These converters are used to drive a single phase capacitor start motor drive. Multicarrier modulation control techniques are used for controlling the MCs; these techniques involve two main type: Level Shifted Carrier (LSC), and Phase Shifted Carrier (PSC). The comparison is made with respect to the performance factors as, the amplitude of the Total Harmonic Distortion (THD), and the DC-bus utilization performance which measured by Root Mean Square of the output voltage Vrms at variable modulation indices and variable carrier frequency. Based on simulation results it's found, that the cascaded-MC with PSC modulation method gives best results, in addition to the Alternative Phase Opposition Disposition APOD-LSC modulation technique (with even number of modulation frequency) generate the output voltage with a lower harmonic content compared with the other techniques.