Akbar Ahmad

Analysis and implementation of multicarrier modulation techniques for Marx multilevel inverter

Several control strategies have been proposed for diode clamped and flying capacitor multilevel inverters topologies which have their advantages. The observation for multicarrier modulation is quite similar for the above mentioned topologies, where as phase disposition technique has a superior line-to-line harmonic performance over alternative phase opposition disposition and phase opposition disposition techniques. Marx multilevel inverter derived from the Marx generator topology with the features of voltage balancing and boosting capability may find various applications in the field of renewable applications. This paper analyzes and propose the most suitable control strategy for the aforementioned topology. The detailed mathematical analysis and simulation results for various control algorithms for Marx inverter are presented in the paper.

Embedded system design for digital control of single phase Z-Source inverter using FPGA

Z-Source inverter comprises of two port impedance network with a small value dc link capacitor. Suitable control of the switching pattern provides the desired output ac voltage. Automated HDL code from MATLAB/Simulink with Xilinx integrated environment minimizes the effort of the system developer and researcher in modeling and design of the system. The attractive features of Z source inverter in the field of renewable energy developed the attention of researchers in the recent years. The paper presents the development of embedded system design using Altium Nanoboard FPGA kit for generation of suitable control signal for Z source inverter. FPGA board is chosen for real time hardware prototyping with higher level of abstraction for digital control due to its ability to produce accurate results with high computational speed and software portability. Xilinx system generator, a plug in tool in MATLAB/Simulink with integrated block set library based pulse width modulation for increased resolution without unnecessarily increasing the clock frequency is used.

Digital PWM of cascaded multilevel voltage source inverter using FPGA

Multilevel inverter finds its application in high voltage and high power converters. Various topologies of multilevel inverter provides several advantages including lower voltage stress, higher efficiency, lower EMI, better waveform and improved THD. This paper presents the development of Altium FPGA as a control circuit for generation of the digital pulse width modulation (DPWM) signal for the single-phase cascaded H-bridge multilevel inverter. The FPGA chip is chosen for the hardware implementation due to its ability to produce accurate results at a high computational speed. Counter based digital pulse width modulation (DPWM) for increased resolution without unnecessarily increasing the clock frequency is used. In addition to Altium Nanoboard FPGA, Xilinx System Generator/MATLAB software has been used for simulation and verification of the proposed circuit before implementation. The simulation and experimental results are in close agreement.

Photovoltaic System-Based Marx Multilevel Converter for Hybrid Modulation Strategy

The multicarrier modulation strategy seems to be the most common thread for multilevel topologies. The harmonic observations for phase-shifted and phase disposition multicarrier strategy are different for cascaded and neutral-point-clamped topologies. The novel application of the photovoltaic implementation of self-boost capable of Marx multilevel inverter with an added feature of capacitor voltage balancing is proposed in this paper. The comparison of harmonic performance with fundamental and total harmonic distortion is shown to verify the claim. The analysis and implementation of the proposed hybrid carrier-based control strategy technique show superiority over harmonic performance on different techniques for the aforementioned topology. The exemplification of mathematical analysis and control modulation of Marx multilevel inverter for photovoltaic application are presented and discussed.

Hardware in Loop Control of Switched Capacitor Multilevel Inverter for Bus Clamping Modulation

The modified structure of multilevel inverter including a capacitor in series and parallel, providing voltage boost feature, is suitable for both symmetrical and asymmetrical cascaded operations. It produces a more number of voltage levels at the output with reduced number of switching devices when compared to the three basic multilevel inverters, namely diode-clamped, flying capacitor, and cascaded multilevel inverters. The hardware in loop switched capacitor multilevel inverter has been simulated and verified with the most popular and widely used sinusoidal pulse width modulation and space vector-based bus clamping modulation techniques. The vector modulation techniques have advantages of high output voltages and reduced harmonic distortion as they utilize the DC bus effectively. Bus-clamped pulse width modulation has the ability to reduce the switching losses of the converter and has reduced harmonic distortion. This paper provides a comparison between various control algorithms and bus clamping techniques for modified multilevel inverter.

Real-Time Implementation of Maximum Power Point Methods for Photovoltaic Systems

The eco-friendly solution to the ever expanding demands of the energy supplies has seen a substantial growth of installed renewable energy integration to the grid in the last decade. The major portion of the installed capacity is from the photovoltaic system due to several factors like reduction in capital investment, an increase in efficiency of modules and converters, favorable government policies. The maximum power point tracking enables the maximum utilization of the available power with a constant change in environmental conditions. These techniques are judged on accuracy, speed, efficiency and fewer oscillations. Several strategies have been proposed in the last decade to maximize the power output. The article provides an overview of the operational principle of such techniques. The simulation and real-time hardware implementation have been done using Atmega328 microcontroller to verify the several performance features.

Analytical Modelling and Verification of Bus-Clamping Modulation Technique for Switched-Capacitor Converter

Space vector modulation techniques have advantages of high output voltages and reduced harmonic content as they utilize the dc bus effectively. Bus-clamped pulse width modulation classified in space vector techniques has the ability to reduce the switching losses of the converter and has reduced harmonic distortion. This paper provides mathematical analysis for 60-degree bus-clamping strategy to obtain the complete closed-form solution for finding the harmonic coefficients using double Fourier integral expression. The effectiveness of the bus-clamped approach on switched capacitor based multilevel inverter has been shown with comparison to Sinusoidal PWM. The DSP controller TMS320F240 has been chosen for the real-time implementation of 60-degree bus-clamping modulation technique. Simulation and experimental results of the prototype are presented for RL load at different modulation indices showing the superiority of the configuration to cascaded multilevel inverter.

Switching loss reduction of switched capacitor multilevel inverter using bus clamping modulation

In this paper simulation of three phase structure for recently proposed topology based on self-voltage balancing capability with step up switched capacitor multilevel inverter has been performed in PSCAD software. This topology has simplified gate circuit since number of active switches are less when compared with other switched capacitor topologies. Another advantage is the voltage boost capability with only one voltage source per phase. Sinusoidal Pulse Width Modulation and Bus Clamped Pulse Width Modulation techniques have been considered for both R and RL loads and results have been compared at different modulation indices for both 50 Hz and 400 Hz output voltage. Bus Clamped Pulse Width Modulationis capable of reducing switching losses and gives reduced harmonic distortions even at modulation indices close to unity.