Mahrous Ahmed

Switched inductor boost converter for PV applications

This paper introduces a boost converter with high dc gain as a solution for partial shading of photovoltaic (PV) module. Switched inductor boost converter (SIBC) is introduced by replacing the inductor of the boost converter with a switched inductor branch. As a result, the conversion gain ratio can be increased. The proposed converter is used as an interface between the PV system and the load. A Maximum Power Point Tracking (MPPT) control is applied to extract the maximum power of the PV module. Analyses, simulation, and experimental results are provided to validate the operation of the converter.

A single stage SEPIC PFC converter for LED street lighting applications

Light Emitting Diodes (LEDs) with their current performances have been proved to be the most suitable solution for street lighting applications. Nowadays, a topic of interest in this context is the design for electronic driver in order to take the advantage of LEDs performances. However, requirements such as high power factor, long life time, accurate current control and high efficiency pose challenges to the design of LED driver circuits. Single-stage power factor correction (PFC) topologies are preferred here for their advantages of lower cost and near unity power factor, while adding a separated PFC stage will surely increase the cost. This paper presents a high efficiency single-stage LED lamp driver for street lighting applications based on SEPIC PFC converter topology operating in continuous conduction mode (CCM). This converter has achieved high efficiency and high power factor all over the operating range with low total harmonic distortion (THD). Simulation results are provided to demonstrate the effectiveness of the proposed driver. Then, a laboratory prototype is built to verify the feasibility of the proposed LED lamp driver.

High gain single-stage inverter for photovoltaic AC modules

In this paper, a high gain single-stage buck-boost grid-connected system is proposed. The proposed system consists of a high voltage gain — high efficiency — switched inductor buck-boost converter (SIBBC) and a folded cascade H-bridge inverter. The proposed converter switch is derived with a sinusoidal modulation, so that the converter output voltage is a rectified sine wave which requires only a folded cascade as a second stage. Therefore, H-bridge is used to fold converter output voltage at fundamental frequency that eliminates the switching loss. The proposed system is used to connect the PV module to the grid with achieving maximum Power Point Tracking (MPPT) control; AC module. The converter operates in DCM to inject a sinusoidal current into the grid with unity power factor. The proposed dc-ac system has some advantages such as low cost, small size and simple control. In addition, the grid connection, MPP, and unity power factor controls are executed through only one switch, the converter switch. A prototype has been built and tested for validation. Some selected simulation and experimental results have been provided.

Development of high gain and efficiency photovoltaic system using multilevel boost converter topology

This paper presents the analysis and operation of a PV system using multilevel dc-dc topology as a high gain converter in addition to applying Maximum Power Point Tracking (MPPT) technique. The multi-level boost converter parameters have been adjusted to achieve the high efficiency and high gain target results. In addition, a full bridge inverter is used to connect the generated power from the PV into the grid. The total system has been analyzed and then simulated using MATLAB to prove the idea. Then, a set-up of experimental results has been provided to validate the simulation results using FPGA control.

New Three-Phase Symmetrical Multilevel Voltage Source Inverter

This paper presents a new design and implementation of a three-phase multilevel inverter (MLI) for distributed power generation system using low frequency modulation and sinusoidal pulse width modulation (SPWM) as well. It is a modular type and it can be extended for extra number of output voltage levels by adding additional modular stages. The impact of the proposed topology is its proficiency to maximize the number of voltage levels using a reduced number of isolated dc voltage sources and electronic switches. Moreover, this paper proposes a significant factor (FC/L), which is developed to define the number of the required components per pole voltage level. A detailed comparison based on FC/L is provided in order to categorize the different topologies of the MLIs addressed in the literature. In addition, a prototype has been developed and tested for various modulation indexes to verify the control technique and performance of the topology. Experimental results show a well-matching and good similarity with the simulation results.

Development of high-gain high-efficiency grid-connected inverter for PV Module

This paper proposes a high gain and high efficiency power conditioning system for grid connected PV module. The system consists of a one module of PV, boost converter with high gain transformation ratio, and singlephase H-bridge inverter. The system is suitable for using less number of PV modules or using only one PV module for the grid connection applications which called ac modules. Since the controller will disconnect the whole string of PV modules in case of one PV module is affected by, for example, the shadow. As a result, the proposed system can avoid this phenomenon which results in increasing the whole system efficiency. The paper also proposes an accurate PV cell model which considers the environmental conditions such as temperature and shadow effects. A modified maximum power point tracking (MPPT) algorithm based on the conductance MPPT will be proposed. Additionally, the system will be connected to the utility grid at unity power factor. The proposed system have been studied, analyzed, and simulated for the validation. Also some selected of the experimental results have been provided.

Fuzzy Logic Speed Controller of 3-Phase Induction Motors for Efficiency Improvement

The paper presents an accurate loss model based controller of an induction motor to calculate the optimal air gap flux. The model includes copper losses, iron losses, harmonic losses, friction and windage losses, and stray losses. These losses are represented as a function of the air gap flux. By using the calculated optimal air gap flux compared with rated flux for speed sensorless indirect vector controlled induction motor, an improvement in motor efficiency is achieved. The motor speed performance is improved using a fuzzy logic speed controller instead of a PI controller. The fuzzy logic speed controller was simulated using the fuzzy control interface block of MATLAB/SIMULINK program. The control algorithm is experimentally tested within a PC under RTAI-Linux. The simulation and experimental results show the improvement in motor efficiency and speed performance.

Modified MPPT with using model predictive control for multilevel boost converter

This paper proposes a modification in the maximum power point tracking (MPPT) by using model predictive control (MPC). The modification scheme of the MPPT control is based on the perturb and observe algorithm (P&O). This modified control is implemented on the dc-dc multilevel boost converter (MLBC) to increase the response of the controller to extract the maximum power from the photovoltaic (PV) module and to boost a small dc voltage of it. The total system consisting of a PV model, a MLBC and the modified MPPT has been analyzed and then simulated with changing the solar radiation and the temperature. The proposed control scheme is implemented under program MATLAB/SIMULINK and the obtained results are validated with real time simulation using dSPACE 1103 ControlDesk. The real time simulation results have been provided for principle validation.

Design considerations of a single-stage LED lamp driver with power factor correction

Light emitting diodes (LEDs) with their current performances have become the most convenient solution to replace conventional lighting sources. LEDs are current driven devices with low equivalent dynamic resistance. This causes instabilities and bifurcations in the driver. Therefore, this paper provides the analysis and design considerations of the stability boundaries of the LED lamp model in comparison with resistive loads. Single stage power factor correction converters are cost effective solution to drive LED lamps with a near unity power factor and high efficiency. Unfortunately the single stage converters suffer from two main problems: the increased voltage stresses and bifurcations during line cycle. The proposed LED lamp driver is based on a modified SEPIC converter which is well known by its reduced voltage stresses. If the system is operated in discontinuous conduction mode (DCM), the input current will follow automatically the input voltage profile. This paper describes the fast-scale instability in a power-factor-correction (PFC) modified SEPIC converter operating in DCM for driving LED lamps. This work provides a convenient mean of designing a high performance LED lamp driver and predicting stability boundaries which can facilitate the selection of practical parameters values for maintaining stable operation. In this paper, it will be shown that, with improper choice of system parameters, the converter can suffer from fast-scale instability for some intervals of time during the line cycle. Simulation results of exact cycle-by-cycle system equations are presented to demonstrate the effectiveness of the proposed design method. Then, a laboratory prototype is built to verify the feasibility of the proposed LED lamp driver and design considerations.

A switched inductor multilevel boost converter

This paper presents a new single stage dc-dc boost converter topology with very large gain conversion ratio as a switched inductor multilevel boost converter (SIMLBC). It is a PWM-based dc-dc converter which combines the Switched-Inductor Structures and the switching capacitor function to provide a very large output voltage with different output dc levels which makes it suitable for multilevel inverter applications. The proposed topology has only single switch like the conventional dc-dc converter which can be controlled in a very simple way. In addition to, two inductors, 2N+2 diodes, N is the number of output dc voltage levels, and 2N-1 dc capacitors. A high switching frequency is employed to decrease the size of these components and thus much increasing the dynamic performance. The proposed topology has been compared with the existence dc-dc boost converters and it gives a higher voltage gain conversion ratio. The proposed converter has been analyzed, simulated and a prototype has been built and experimentally tested. Simulation and experimental results have been provided for validation.