Ziaur Rahman Khan

Bio: Ziaur Rahman Khan is an academic researcher from Bangladesh University of Engineering and Technology. The author has contributed to research in topics: Inverter & Pulse-width modulation. The author has an hindex of 3, co-authored 8 publications receiving 35 citations.

Physics-Based Generalized Threshold Voltage Model of Multiple Material Gate Tunneling FET Structure

Abstract: A generalized 2-D analytical model of gate threshold voltage for multiple material gate Tunneling FET (TFET) structures is derived. The model can also be used for calculating threshold voltage of a single metal gate TFET. Surface potential model of a triple material double gate TFET has been developed by applying Gauss's law in the device. From the potential model, physics-based model of gate threshold voltage has been derived by exploring the transition between linear to quasi-exponential dependence of drain current on applied gate bias. The model includes the effect of gate and drain bias, gate material workfunction, oxide thickness, silicon film thickness, gate dielectric, and other device parameters. The accuracy of the proposed model is verified by comparing the results predicted by the proposed model to the results of the numerical model developed in Silvaco, Atlas.

Fixed Point Implementation of Grid Tied Inverter in Digital Signal Processing Controller

Abstract: Power inverters are one of the devices of great importance used in power grids to convert DC to AC, especially for grids with attached solar panels or wind turbines. The world is getting warmer due to coal- and oil-based power generation. So human existence is threatened due to the increased amount of carbon-dioxide in the air. As a result, integration of renewable energy sources (RESs) with the grid became mandatory. So, the demand of grid-connected inverters is increasing as more RESs are connecting with the grid; this necessitates developing a low-cost grid connected inverter system. This paper presents a comprehensive study and hardware implementation of a grid tied inverter. In this research, we have demonstrated a cost-efficient grid tied inverter design using low cost DSP controller applying fixed point arithmetic. The fixed-point arithmetic and Digital Signal Processing (DSP) implementation results in superior performance over conventional methods of calculation. This paper also proposes a hardware model of such a bi-directional grid tied inverter. A current controlled Voltage Source Inverter(VSI) is used in the paper and a PI controller is suggested for current error compensation. To generate gating pulse for appropriate voltage, Space Vector Pulse Width Modulation (SVPWM) technique is employed. Synchronous Reference Frame Phase Locked Loop (SRF-PLL) is chosen for performing grid synchronization. The feasibility of the hardware model is verified by performing simulations on Simulink.

Amended THD with modified phase-shifted PWM for micro-grid connected multilevel inverter

Abstract: In this work, the phase shifted carrier pulse width modulation (PSC PWM) technique is applied as the most favorable modulation scheme for a photovoltaic (PV) fed cascaded multilevel-micro-grid connected inverter (CM-MGCI), with consideration of the total harmonic distortion (THD) of the output voltage In addition to this, a modified PSC PWM method named as variable amplitude PSC-PWM (VA-PSC-PWM) is proposed To verify the performance of proposed PSC PWM method, MATLAB/Simulink simulations are performed with nine-level CM-MGCI To feed the CM-MGCI required voltage, a PV array is designed and a maximum power point tracking (MPPT) technique is demonstrated in MATLAB/Simulink environment From the voltage profile of VA-PSC-PWM technique, it is observed that the proposed method gives better THD profile than classical PSC PWM method Our proposed modified PSC-PWM also provides better THD profile compared to other recently proposed PSC-PWM technique

A Single-Phase Grid-Connected Inverter using Phase Control Method

Abstract: The design of a single-phase grid-connected inverter (GCI) using the phase-control technique is presented here. The circuit has fewer harmonics and a simpler design than traditional GCI technology. The performance of GCI has a direct influence on the entire distributed generation system. The control architecture of GCI must ensure the capability of matching inverter output voltage and frequency with continuously fluctuating grid voltage and frequency. The dynamic sinusoidal pulse width modulation technique (SPWM) has been used to control the power switches of the inverter. The finished design is simulated in MATLAB/SIMULINK to ensure output results.

Transient anode voltage modeling of IGBT and its carrier lifetime dependence

Abstract: This work presents a minority carrier lifetime estimation technique through investigation into transient anode voltage modeling of Non-punch Through (NPT) Insulated Gate Bipolar Transistor (IGBT). Parabolic approximation has been used for derivation of minority carrier concentration within the base. With the help of derived expression, an analytical model has been developed for turn-off voltage of IGBT in all minority carrier lifetime conditions. Better agreements with experimental data have been found compared to the linear model generally used. Finally, the implications of carrier lifetime dependence on the anode voltage are discussed, including implementation of such a carrier lifetime measurement technique.

Modular Cascaded H-Bridge Multilevel PV Inverter with Distributed MPPT for Grid-Connected Applications

Abstract: Due to the possibility of providing energy with much less dependence on the fossil fuels, renew-competent energy sources, in specified sun photovoltaic (PV) conversion have received elevated acceptance and progress in latest times. Big benefits of PV panels comprise easy and trustworthy power production and suitability for disbursed iteration. In addition the costs for photovoltaic modules is drastically lowering. To comprehend this issue, a control plan with modulation compensation scheme is likewise proposed. An exploratory three-stage seven-level cascaded H-bridge inverter has been manufactured using nine H-bridge modules (three modules for each stage). Each H-bridge module is associated with a 185-W solar panel. Simulation results are introduced to confirm the practicality of the proposed approach.

Design and Hardware Implementation Considerations of Modified Multilevel Cascaded H-Bridge Inverter for Photovoltaic System

Abstract: Inverters are an essential part in many applications including photovoltaic generation. With the increasing penetration of renewable energy sources, the drive for efficient inverters is gaining more and more momentum. In this paper, output power quality, power loss, implementation complexity, cost, and relative advantages of the popular cascaded multilevel H-bridge inverter and a modified version of it are explored. An optimal number of levels and the optimal switching frequency for such inverters are investigated, and a five-level architecture is chosen considering the trade-offs. This inverter is driven by level shifted in-phase disposition pulse width modulation technique to reduce harmonics, which is chosen through deliberate testing of other advanced disposition pulse width modulation techniques. To reduce the harmonics further, the application of filters is investigated, and an LC filter is applied which provided appreciable results. This system is tested in MATLAB/Simulink and then implemented in hardware after design and testing in Proteus ISIS. The general cascaded multilevel H-bridge inverter design is also implemented in hardware to demonstrate a novel low-cost MOSFET driver build for this study. The hardware setups use MOSFETs as switching devices and low-cost ATmega microcontrollers for generating the switching pulses via level shifted in-phase disposition pulse width modulation. This implementation substantiated the effectiveness of the proposed design.

PWM Common Mode Reference Generation for Maximizing the Linear Modulation Region of CHB Converters in Islanded Microgrids

Abstract: Microgrid-interactive converters are increasingly expected to provide auxiliary services, particularly during islanded microgrid operation. Unbalanced, non-sinusoidal pulse width modulation (PWM) references may be required when converters provide auxiliary services, such as negative-sequence compensation. Since PWM references cannot exceed dc-bus voltage defined limits without causing overmodulation, the maximum positive-sequence voltage producible by microgrid-interactive converters may be diminished unless reference waveforms are adjusted. In this paper, a technique for maximizing the linear modulation region by injecting a common mode component into PWM references is proposed for microgrid-interactive cascaded H-bridge (CHB) converters. The technique presented can be implemented in real-time without lookup tables, is controller independent, is compatible with any carrier-based PWM method, enabling its use for symmetric and asymmetric CHB, and enables continued operation after internal fault events when utilized with fault tolerant PWM schemes. Experimental data verify the common mode injection technique.

An advanced control technique for power quality improvement of grid-tied multilevel inverter

Abstract: The use of different control techniques has become very popular for controlling the performance of grid-connected photovoltaic (PV) systems. Although the proportional-integral (PI) control technique is very popular, there are some difficulties such as less stability, slow dynamic response, low reference tracking capability, and lower output power quality in solar PV applications. In this paper, a robust, fast, and dynamic proportional-integral resonance controller with a harmonic and lead compensator (PIR + HC + LC) is proposed to control the current of a 15-level neutral-point-clamped (NPC) multilevel inverter. The proposed controlled is basically a proportional-integral resonance (PIR) controller with the feedback of a harmonic compensator and a lead compensator. The performance of the proposed controller is analyzed in a MATLAB/Simulink environment. The simulation result represents admirable performance in terms of stability, sudden load change response, fault handling capability, reference tracking capability, and total harmonic distortion (THD) than those of the existing controllers. The responses of the inverter and grid outlets under different conditions are also analyzed. The harmonic compensator decreases the lower order harmonics of grid voltage and current, and the lead compensator provides the phase lead. It is expected that the proposed controller is a dynamic aspirant in the grid-connected PV system.