Comparative performance of modular with cascaded H-bridge three level inverters

The conventional two-level inverter becomes no longer has the ability to cope with the high-power requirement, so this paper discusses two very common topologies of multilevel inverter like modular multi-level converter (MMC) and cascaded H-bridge (CHB) multi-level inverter for induction motor drive applications. This work attempts to investigate the comparison between MMC and CHB. The comparison is done in aspects of the configuration, concept of operation, advantages and disadvantages, the comparison is also consider output voltage (line to line) waveform, total harmonic distortion (THD) of the output line voltage waveform and the current drawn by both inverters. The performance of the inverters under carrier-based pulse width modulation (PWM) technique and mainly in-phase disposition (IPD), level shifted pulse width modulation is viewed. The paper discusses the comparison between the two multilevel inverters (MLIs) with motor drive applications especially induction motor. The operation of the motor is studied under certain value of load torque. The simulation results for the induction motor with the two inverters (modular multi-level and Cascaded H-bride) for three numbers of levels using MATLAB/Simulink are provided). The obtained results are encouraging and promising especially in the improvement of the THD% results

Near to DC level multilevel inverter

The purpose of this study is to investigate the application of genetic algorithm (GA) in modelling linear and non-linear dynamic systems and develop an alternative model structure selection algorithm based on GA. Orthogonal least square (OLS), a gradient descent method was used as the benchmark for the proposed algorithm. A model structure selection based on modified genetic algorithm (MGA) has been proposed in this study to reduce problems of premature convergence in simple GA (SGA). The effect of different combinations of MGA operators on the performance of the developed model was studied and the effectiveness and shortcomings of MGA were highlighted. Results were compared between SGA, MGA and benchmark OLS method. It was discovered that with similar number of dynamic terms, in most cases, MGA performs better than SGA in terms of exploring potential solution and outperformed the OLS algorithm in terms of selected number of terms and predictive accuracy. In addition, the use of local search with MGA for fine-tuning the algorithm was also proposed and investigated, named as memetic algorithm (MA). Simulation results demonstrated that in most cases, MA is able to produce an adequate and parsimonious model that can satisfy the model validation tests with significant advantages over OLS, SGA and MGA methods. Furthermore, the case studies on identification of multivariable systems based on real experiment t al data from two systems namely a turbo alternator and a continuous stirred tank reactor showed that the proposed algorithm could be used as an alternative to adequately identify adequate and parsimonious models for those systems. Abstract must be bilingual. For a thesis written in Bahasa Melayu, the abstract must first be written in Bahasa Melayu and followed by the English translation. If the thesis is written in English, the abstract must be written in English and followed by the translation in Bahasa Melayu. The abstract should be brief, written in one paragraph and not exceed one (1) page. An abstract is different from synopsis or summary of a thesis. It should states the field of study, problem definition, methodology adopted, research process, results obtained and conclusion of the research. The abstract can be written using single or one and a half spacing. Example can be seen in Appendix 1 (Bahasa Melayu) and Appendix J (English)

Single phase asymmetrical multilevel inverter topology with reduced device count

Multilevel Inverters (MLIs) are vital components for medium voltage and high-power applications. However, the number of components will increase with increased output voltage levels. It leads to high power losses. In this thesis, a new single-phase asymmetrical multilevel inverter topology used for medium and high voltage applications is proposed. The topology is capable of producing n-level output voltage with reduced device counts. It is achieved by arranging available switches and direct current (dc)-sources to obtain the maximum combinations of addition and subtraction of the input dc-sources. A comprehensive literature review has been carried out, and the proposed topology is compared with the topologies available in the literature. Comparison based on the number of switches utilized, the number of dc sources used, and the total number of devices is made. To verify the viability of the proposed topology, circuit models for 9-level, 25-level, and 67-level inverters are developed and simulated in Matlab-Simulink software first. Voltage and current waveforms and THD for resistive and inductive loads are obtained from the simulation model and validated with the experimental setup. Experimental results of the proposed inverter prototype for 9-level and 25-level output, developed in the laboratory, are presented. A low-frequency and high-frequency switching strategy for the proposed inverter topology are also presented in this work. Thermal modelling of the proposed topology is done in PLECS software, and detailed loss analysis for 9-level as well as 25-level topologies is carried out. The fundamental topology utilizes 9 switches with a total standing voltage (TSV) of 6.75 per unit while the 25-level topology structure has 12 switches with the TSV of 6.92 per unit only. Comparison with the other multilevel topologies shows that the proposed circuit requires fewer power switches and dc-sources to produce the same output levels. Due to the low switching frequency requirement, the proposed topology is applicable for high and medium voltage applications, resulting in lower switching losses

A Novel Multi-Level Cascade Inverter with Reduced Switching Devices to Connect Renewable Energy Sources to the Grid

Multi-level inverters (MLIs) have now become an essential component for medium and high power applications with medium voltage levels. Low switches multi-level inverters are very popular due to their high efficiency, low cost, and easy control for output with higher levels. In this paper, a new multi-level inverter structure based on a switched DC voltage source is proposed by reducing the number of switches for single-phase applications. The proposed structure can be used in grid-connected applications, such as grid connections for renewable energy sources. The proposed structure is developed with a higher number of levels at the output using a smaller number of devices. The proposed topology can also be used in symmetric and asymmetric configurations. Two switching methods including pulse width modulation (PWM) switching and ladder switching based on selective harmonic elimination (SHE) have been used to generate the output voltage. Comparative studies with multilevel inverters were presented recently to show the advantage of the proposed structure in terms of reducing the number of devices. Simulation and experimental results are presented to confirm the performance of the proposed topology. In addition, the performance of the proposed multilevel structure for energy transfer from renewable sources to the low-power grid has also been investigated

A New Topology of Cross-Switched Multilevel Inverter

This study proposed a Multilevel Inverter (MLI) topology that generates a high number of output voltage levels with a reduced number of components. The proposed topology was configured with symmetrical, asymmetrical, and hybrid configurations. Each configuration generates a different level of output voltage. In parallel to the increased output level, the output voltage has a better output quality (i.e., a lower percentage of total harmonic distortion), simple design and less demanding operation

Model Predictive Control Methods for Photovoltaic Electrical Energy Conversion Systems

Solar photovoltaic energy systems (PV) have had a consistently increasing market penetration over the past seven years, with a total global installed capacity of over 500 GW. A PV installation must harvest the maximum possible electrical energy at the lowest cost to be economically justifiable. This presents many engineering challenges and opportunities within power electronics amongst which include low-cost power converter implementation, high reliability, grid-friendly integration, fast dynamic response to track the stochastic nature of the solar resource, and disturbance rejection to grid transient and partial shading. This dissertation investigates the controls of the power electronic interface with the objective to reduce cost, increase reliability, and increase efficiency of PV energy conversion systems. The overall theme of this dissertation involves exploring the theory of model predictive control (MPC) within a range of applications for PV systems. The applications within PV energy conversion systems are explored, ranging from cell to grid integration. MPC-based maximum power point tracking (MPPT) algorithm is investigated for the power electronics interface to maximize the energy harvest of the PV module. Within the developed MPC based MPPT framework, sensorless current mode and adaptive perturbation are proposed. The MPC framework is expanded further to include inverter control. The control of a single-phase H-bridge inverter and sub-multilevel inverter are presented in this dissertation to control grid current injection. The multi-objective optimization of MPC is investigated to control the dc-link voltage in microinverters along with grid current control. The developed MPC based MPPT controller is shown to operate with a single-stage impedance source three-phase inverter with PID based grid-side control