Asymmetric DC source multilevel inverter

An asymmetrical multilevel inverter with harmonic profile improvement and lower voltage stress is presented in this paper. The multilevel inverter is a power electronic circuit that produces sinusoidal output voltage waveform from several levels of dc input voltages, which reduces Electromagnetic Compatibility (EMC) and Total Harmonic Distortion (THD). Four modules are connected in series together with its dc source is configured in asymmetrical configuration to produce 31 output voltage levels. Asymmetrical Multilevel Inverter offers more advantages compared to the conventional multilevel (symmetrical Multilevel Inverter) and the two-level inverters itself. This work focuses on the cascaded multilevel inverter with it dc source configured in asymmetrical configuration. The proposed topology will be developed and simulated in MATLAB/Simulink software package. For comparison purposes, normal two-level inverter also developed. The results such as the output voltage, voltage stress across the power switch, the THD content have been analyzed and discussed

Extensively used conventional and selected advanced maximum power point tracking techniques for solar photovoltaic applications: an overview

The lower output efficiency of the solar PV panel is due to the deviation of its operating point from the maximum power operation. And the change in the maximum power point (MPP) with the change in uncontrolled environmental conditions such as temperature and isolation make it difficult to withstand the MPP operation of the system. Different techniques and maximum power point tracking algorithms have been developed to address the issue. This paper presents a critical overview of widely used maximum power tracking techniques for photovoltaic system applications. Conventional, as well as advanced developed methods, which are less complex, robust and reliable, are discussed. However, some complexity occurs while selecting the appropriate MPPT method for a particular application. One of the contributions of this review article is to provide an outline for the selection of appropriate technique suitable for a particular application. Comparative analysis and classification of the selected MPPT methods based on various features such as type of control strategies, control variables, a converter circuit, and practical/commercial applications are presented. This review article is envisioned to serve as a useful reference for future MPPT users and PV system design engineers

Maximum Power Point Tracking Charge Controller for Standalone PV System

The depletion of conventional energy sources and global warming has raised worldwide awareness on the usage of renewable energy sources particularly solar photovoltaic (PV). Renewable energy sources are non-polluting sources which can meet energy demands without causing any environmental issues. For standalone PV systems, a low conversion efficiency of the solar panel and high installation cost due to storage elements are the two primary constraints that limit the widespread use of this system. As the size of the system increases, the demand for a highly efficient tracking and charging system is very crucial. Direct charging of battery with PV module will results in loss of capacity or premature battery degradation. Furthermore, most of the available energy generated by the PV module or array will be wasted if proper tracking technique is not employed. As a result, more PV panels need to be installed to provide the same output power capacity. This paper presents selection, design and simulation of maximum power point tracker (MPPT) and battery charge controller for standalone Photovoltaic (PV) system. Contributions are made in several aspects of the whole system, including selection of suitable converter, converter design, system simulation, and MPPT algorithm. The proposed system utilizes direct duty cycle technique thus simplifying its control structure. MPPT algorithm based on scanning approach has been applied by sweeping the duty cycle throughout the I-V curve to ensure continuous tracking of the maximum power irrespective of any environmental circumstances. For energy storage, lead acid battery is employed in this work. MATLAB/Simulink® was utilized for simulation studies. Results show that the propose strategy can track the MPPs and charge the battery effectively

Switching modulation strategies for multilevel inverter

There is always a need to create efficient and optimized converters to deliver the best possible results to achieve a better THD profile in the waveform output. One way is by controlling the switching of the power switches of the converters using appropriate modulation schemes. While numerous works have been done in proposing new switching modulation strategies for multilevel inverters, this work will compare multicarrier PWM and near-to-level control (NLC) modulation schemes. In this paper, multicarrier PWM variants, namely, PD-PWM, POD-PWM, and APOD-PWM, are designed and simulated. Their voltage THD and spectrum performance are discussed when applied to single-phase 7, 9, and 11-level cascaded multilevel inverters. Then NLC modulation will be designed and applied to similar multilevel inverter circuits. It will be shown that the NLC exhibits some superior performances compared to PWM-based but with several drawbacks that can be optimized

New asymmetrical modular multilevel inverter topology with reduced number of switches

In this article, a new single-phase multilevel inverter is introduced with a reduced number of power switches and reduced voltage stress on power switches. The proposed topology consists of four input dc sources and nine semiconductor switches (eight unidirectional and one bidirectional switch). The topology can be used for asymmetrical voltage source configuration to generate seventeen voltage levels. The extended topology is constructed by a series connection of the topology circuit to produce higher voltage levels with less voltage stress on the switches without modifying the existing structure. Comparison is made with traditional and recently introduced topologies based on the number of power switches, dc sources, total blocking voltage of switches, and gate driver circuits, to prove the proposed topology's superiority. A simple nearest level modulation has been deployed as the switching scheme. Validation on the viability of the proposed topology has been carried out through simulation and hardware experimental setup

Voltage instability analysis for electrical power system using voltage stabilty margin and modal analysis

Voltage instability analysis in electric power system is one of the most important factors in order to maintain the equilibrium of the power system. A power system is said to be unstable if the system is not able to maintain the voltage at all buses in the system remain unchanged after the system is being subjected to a disturbance.The research work presented in this paper is about the analysis of voltage instability of electric power system by using voltage stability margin (VSM), load real power (P) margin, reactive power (Q) margin, reactive power-voltage (QV) and real power-voltage (PV) modal analysis. IEEE 30-bus system has been chosen as the power system. The load flow analysis are simulated by using Power World Simulator software version 16. Both QV and PV modal analysis were done by using MATLAB application software

A community scale hybrid renewable energy system for sustainable power supply during load shedding

Load shedding is an operating condition in which the electrical grid is temporarily disconnected from the load. The objective is to minimize the gap between available generation capacity and load demand while maintaining an equitable supply for all consumers. Load shedding is a prominent problem for many developing countries. To address this issue, this paper explores the potential of a hybrid energy system (HES) to provide uninterrupted power supply at the distribution feeder despite load shedding from electrical grid. The proposed HES in this work combines photovoltaic (PV) array, battery storage system (BSS) and diesel generator (DG). The HES is equipped with energy management scheme (EMS) that ensures continuous power supply, improves energy efficiency, and minimizes the electricity cost. To accomplish these tasks, the EMS operates the system in one of three modes: grid mode, renewable energy source mode and the diesel generator mode. Besides, the proposed methodology allows injecting surplus PV energy into the grid, thus maximizing PV utilization and improving power system’s reliability. The results of this study will assist policymakers to determine the prospect of renewable based hybrid system to supply sustainable power and eliminate the energy problems in the power deficit countries

Kejuruteraan penggerudian telaga minyak: prinsip dan praktik

Teks baru yang dibentangkan di sini menerangkan tentang teknik-teknik penggerudian yang moden dan meliputi semua operasi telaga yang dijangkakan berlaku serta masalah yang selalu dijumpai. Teori dan praktik disepadukan dengan membentangkan contoh-contoh kerja untuk membantu pembaca memahami sepenuhnya penggerudian telaga minyak. Berdasarkan kepada pengalaman ikhtisas dan kemudiannya diadunkan dengan nasihat serta manfaat daripada syarikat pembuatan dan syarikat minyak, Kejuruteraan Penggerudian Telaga Minyak akan menjadi bahan yang sangat bernilai kepada penggerudi, jurutera lapangan, pelatih dan pelajar kejuruteraan petroleum. Selain daripada itu, ia juga sesuai untuk dijadikan bahan rujukan kepada ahli kajibumi dan ahli geofizik yang sama-sama berkecimpung dalam bidang ini. Unit imperial dan metrik digunakan dengan menyeluruh dan teks ini dipenuhi dengan banyak gambar rajah untuk memudahkan rujukan

Field programmable gate array (FPGA) based fuzzy logic controller for boost converter

This project presents the application of the Single Input Fuzzy Logic Controllers (SIFLC) to regulate the output voltage of a Boost (step-up) DC to DC power converter. The SIFLC is derived from the Signed Distance Method which reduces the multi-input Fuzzy Logic Controller (FLC) with Toeplitz rule table structure to a sinngle input FLC. Effectively, it allows for the rule table to be approximated to a one dimensional piecewise liner control surface. To validate the effectiveness of the SIFLC compared to the Conventional FLC, simulation and experimental works are carried out. The results show that the Boost converter performance is exactly identical when subjected to both controllers. However SIFLC requires nearly an order of magnitudeless time to execute its algorithm