Effect of duty cycle on THD for multilevel inverter based on selective harmonic elimination technique

Multilevel inverters controlled suffers from the issue of harmonic distortion in the output voltage. Selective Harmonic Elimination (SHE) technique plays an effective role to eliminate these harmonics. The undesirable odd harmonics can be eliminated by having optimized the switching angles in SHE signal. To optimized and obtained these switching angles, a number of nonlinear equations should be solved using a numerical method. In addition to the modulation index, by changing the value of the duty cycle the Total Harmonics Distortion (THD) will also change. In this paper, a novel Optimization Harmonic Elimination Technique (OHET) based on SHE scheme is proposed in order to minimize Total Harmonic Distortion (THD). To evaluate and investigate the performance of the proposed scheme, a seven-level cascaded inverter is simulated by MATLAB and PSIM software

Harmonics elimination based on curve fitting method for modular multilevel converters

This paper presents the additional ways to figure out the switching angles for eliminating harmonic in Modular Multilevel Converters, MMCs. The switching angles equation is written in terms of nonlinear equation system, in general, one of the numerical method, named Newton-Raphson method, is used for this calculation procedure but the Newton-Raphson method takes more time for calculation that is difficult to implement the MMCs in a real-time control application. So that, numerous previous calculation methods are proposed to address this issue. To reduce the calculated time of switching angles, the Curve Fitting method is selected to assist the Newton-Raphson method and the idea of this combination method is presented in this paper. The calculation result of this combination and original Newton-Raphson method are compared and implemented in the 3-phase 7-level MMCs simulation to validate the calculation results. The Curve-Fitting can be used for calculation assisting of Newton-Raphson Method and obtains the calculation results faster than the using of lone Newton-Raphson method

Integrated renewable energy micro-grid for meeting peak hours demand

In the TNB-based conventional system, the power demand varies randomly depending upon seasons and months of the year including festive occasions, reaching peak in some hours of days of some months. Sometime a heavy demand (in MW) falls at a time of a day. Such heavy energy demands need to be transported from far-away power stations over long lengthy transmissions causing energy loss not less than 20% in most of the cases. This paper presents load demand variation scenario, identifying peaks, and finally suggesting a strategy for meeting the peak demand from Renewable Energy Sources (RES) of solar and wind. An integrated RES-based microgrid is suggested with analytical and simulation results showing how the peak demand is being met from alternative sources of solar. The results of this paper find applications in suggesting RES-based generations for distributed locations within the low-voltage distribution network of Malaysian Electric Utility Tenaga Nasional Berhad

Comparison of selective harmonic elimination and SPWM techniques for unipolar inverters

Several modulation schemes are used to operate power electronics devices MOSFETs and IGBTs in power converters and are also utilized to reduce the influence of Total Harmonic Distortion (THD) in the output voltage of these inverters. Selective Harmonic Elimination (SHE) and Sinusoidal Pulse Width Modulation (SPWM) are the most popular techniques used in this regard. Number of notches and modulation index (m) are the important parameters used to design both techniques. Total Harmonic Distortion is utilized as a standard to measure the signal quality for both schemes. This paper discusses a comparison study of using SHE and SPWM techniques in full bridge inverter. MATLAB and PSIM tools are used to estimate and verify the performance of both techniques and the results are obtained experimentall

Input-series output-parallel full-bridge DC-DC converter for high power applications

Input-series and output-parallel (ISOP) connected DC-DC converters are suitable for high input voltage and high output current applications by using a low voltage rating power switches. This paper proposes an input-series-output-parallel Full-Bridge DC-DC converter with low-voltage switches under high frequency operation with low losses switching, low harmonic spikes with high efficiency and high power density. In this proposed work, Arduino mega microcontroller has been used to generate Pulse Width Modulation (PWM) for ISOP configuration. Under different duty cycle PWM and switching frequency, the simulation and experimental results with appropriate theoretical analysis of an ISOP full-bridge converter topology are presented

A novel optimization harmonic elimination technique for cascaded multilevel inverter

The main goal of utilizing Selective Harmonic Elimination (SHE) techniques in Multilevel Inverters (MLI) is to produce a high-quality output voltage signal with a minimum Total Harmonic Distortion (THD). By calculating N switching angles, SHE technique can eliminate (N-1) low order odd harmonics of the output voltage waveform. To optimized and obtained these switching angles, N of nonlinear equations should be solved using a numerical method. Modulation index (m) and duty cycle play a big role in selective harmonic elimination technique to obtain a minimum harmonic distortion and desired fundamental component voltage. In this paper, a novel Optimization Harmonic Elimination Technique (OHET) based on SHE scheme is proposed to re-mitigate Total Harmonic Distortion. The performance of seven-level H-bridge cascade inverter is evaluated using PSIM and validated experimentally by developing a purposely built microcontroller-based printed circuit board

On quality energy management in a third world country: the case study of war torn Libya

The ever growing energy demands and the negative environmental impacts associated with global warming have pushed the policy makers toward adopting renewable energy sources. Unfortunately, the management of energy resources in many countries still fall short of optimizing the depleting nature of conventional energy sources and balancing them with untapped and abundant renewable energy sources. This calls for a detailed study on quality management of energy with the objective of minimizing losses and capitalizing on more efficient conversion methods of energy transfer for use in important industry applications. A good case study is in war torn country like Libya. Libya is one of the countries that recently struggles to satisfy its energy demand, although, the country has a high potential for solar energy. One major sector is electricity generation, which uses gas and fuel-fire to operate the turbines in the generation stations. Libya currently produces 33 TWH of energy to meet the demand of the local electricity market. The demand on energy will substantially increase in the near future as a result of economic development in order to build new infrastructure in Libya after the massive destruction that happened during the last four years. This will lead to more consumption of oil and gas, which causes a reduction in the national economical revenues, and more carbon dioxide emission. Therefore, Libya should use its alternative energy supplies to cover some of its load requirements. In this paper, we investigate the current energy situation in Libya while exploring the use of renewable energy to improve the current poor situation through some example scenarios. A quality management program of the energy landscape may be necessary as a way forward for the country to sustain any form of economic development amidst the shortage of energy resources in the country

Mitigation of Harmonics Using Novel Sector-Based Switching Pattern Space Vector Pulse Width Modulation

Pulse Width Modulation (PWM) driven power converters are widely used in realizing the function of rectification and inversion in renewable and emerging power applications. They play a key role in tying renewable energy sources of solar and wind to conventional energy grid systems. Such emergying styles of power systems are referred to as Distributed Generation (DG) or energy mix. The PWM-based switching devices are also sources for injecting harmonics to degrade the quality level in this emerging style of DG systems causing steady-state waveform distortion. Thus power converters operated by finely tuned PWM play an important role in mitigating the voltage waveform distorting harmonics and consequently improving the stability of the system. This paper presents the mitigation of harmonic contents by reproducing as a novel space vector-based switching pattern of SVPWM. In this work, the proposed switching pattern will have a DC link RMS current equal to or less than that of a conventional SVPWM current under the same switching frequency (SF), load, L-C filter, DC bus voltage, and Modulation Index (MI). The results include a 13.43% improvement in Total Harmonic Distortion (THD) at relatively high modulation indices. The Weighted Total Harmonic Distortion (WTHD) has also improved by 47.37% and the number of thyristors has been reduced lowering switching losses. The Matlab-Simulink simulation results have been experimentally verified with an Advanced Digital Analog Learning Module (ADALM M2k)-based experimental setup, improving the proposed SVPWM THD by 13.49%. The conventional and proposed SVPWM performance comparison is done by obtaining Fast Fourier Transform (FFT) by driving a two-level three-phase voltage source inverter

Effects of switching frequency to series loaded series resonant circuit

This paper analyses the effect of switching frequency on series loaded series resonant (SLSR) converter. SLSR converter is a well-known topology typically used for applications in kilowatt-range power supplies and can operate in either continuous or discontinuous conduction modes. The modes are determined according to the relationship between the switching frequency and resonant frequency. The analysis results in a set of equations with solutions presented graphically. The development of a SLSR converter is described along with the results of computer simulation. The output waveforms obtained for each switching frequency are compared

Low spikes and low harmonic distortion multilevel inverter for induction motor implementation

Different Modulation techniques are suggested for use in electronic converters’ applications for getting minimized Total Harmonic Distortion (THD). One of such techniques a Selective Harmonics Elimination Pulse Width Modulation (SHE-PWM) scheme. Specific odd harmonics can be mitigated by operating the semiconductor switches in H-bridge inverters at optimized switching angles of the PWM signals. These switching angles are determined by calculating a set of nonlinear equations. Multilevel converters operated by PWM, suffer from the issue of harmonic spikes in the output voltage. In this paper, an improved scheme of SHE-PWM is proposed for multilevel converter to mitigate THD and supress the harmonic spikes of the system. To investigate and confirm the proposed technique, a five-level cascade multilevel inverter is simulated, and experimentally implemented. It is seen that the simulation results are verified experimentally by eliminating low- order harmoinics in getting a THD of 23.20% without using filter. The experimental results of the developed multilevel converer is validated with the simulation results under different performance conditions which show a complete agreement between them in terms of shapes and values