A. Elnady

A comparative study for the common current regulators of multilevel and cascaded inverters

This paper presents an innovative comparative study for the most commonly used current regulators of the multilevel inverters. This study describes the most widely used hysteresis versions of the current controller utilized in multilevel inverters. The common hysteresis versions under investigation in this paper are nested multi-band hysteresis, offset multi-band hysteresis, time-based hysteresis and improved time-based hysteresis applied to the diode clamped and cascaded five-level inverters. This paper demonstrates the important characteristics for each hysteresis version, advantages and disadvantages of each version in comparison with other hysteresis versions. The comparison is verified by simulation results for all aforementioned versions.

AN EFFICIENT CURRENT REGULATOR FOR MULTILEVEL VOLTAGE SOURCE CONVERTER BASED ON A SIMPLE ANALOG CONTROL CIRCUIT

This paper presents an innovative driver circuit for a new current regulator of the multilevel inverters. The proposed regulator has a PI controller to guarantee the optimum tracking for the refere...

A power conditioner versus a DSTATCOM for compensation of flicker in distribution systems

This paper presents a simple and effective control strategy for a custom power conditioner, (mitigation device), to improve the voltage and the current in the arc furnace environment. The new strategy depends on a recursively innovative implementation of the second-order digital notch filter. It is the first time to utilize the regular notch filter for power quality improvement. The performance of the proposed control is compared to the performance of the traditional control strategies those are used to improve the voltage and current of the arc furnaces. The presented ideas are conveyed and approved through simulation results using MATLAB/SIMULINK for a real time-domain model of the arc furnace.

Decoupled State-Feedback Based Control Scheme for the Distributed Generation System

Abstract This article presents a new development for the decoupled state-feedback control to operate the distribution generation unit (DGU) within an efficient distribution generation system (DGS). The developed decoupled state-feedback is better than the conventional voltage vector control and sliding mode control for dealing with active and reactive power. Therefore, it is embraced to form a new control scheme, which is employed to effectively decouple and precisely control the injected active and reactive power to the distribution system. A five-level diode-clamped inverter is adopted to build the DGU in order to minimize the injected harmonics, facilitate the operation of the proposed control scheme, and ease the design of its passive filter. The proposed control scheme enables the DGS to be functional in several operational modes such as grid-connected, intentional islanding, unintentional islanding, anti-islanding, and ride-through modes. The effectiveness of the proposed control scheme is proved through the simulation results for all foregoing modes. Experimental results are provided to show how the proposed concepts are practically implemented to control the voltage of the DGU so that the active power and reactive power are exchanged between the power grid and the DGS in the grid-connected mode.

Multilevel inverter operated by voltage orientation control

This paper presents an innovative control scheme for the multilevel inverter that is connected to the power grid as a Distributed Generation unit, DG. The paper demonstrates novel application for the voltage orientation control, also called voltage vector control, so as to precisely control active and reactive power injected by the distributed generation units in a normal operation of the system, (grid-connected mode), and it works as a voltage source in an islanding mode. The adopted topology for the DG is the diode clamped multilevel inverter structure in order to minimize the injected harmonics and get rid of a sophisticated passive filter. The utilization of the voltage vector control scheme is optimized so that the DG unit can precisely control the instantaneous power injected to the power grid. The presented simulation results verify the capability of the suggested control to precisely adjust the active and reactive power based on set-values.

A novel multilevel DC chopper supplying DC motor

This paper deals with controlling DC motor speed and/or torque through the multilevel Chopper circuit. The proposed switching circuit consists of four cascaded switching elements with three clamping diodes and four equal or different voltage sources connected in series. The configuration provides a constant five levels of voltage and has the ability to generate and track any reference input voltage within the source voltage range. The generated voltage has relatively very small harmonic and ripples compared to the traditional step down chopper. The profile of the generated voltage positively affects the performance of the motor armature current, the generated dynamic torque and the rotor. The simulation results show adequate voltage reference tracking, smooth speed response and reduced current and torque ripples, which normally reflect in smaller mechanical vibration and acoustic noise.

Experimental and simulation analysis for the 5-level diode clamped inverter

This paper investigates the performance of the multilevel, (5-level), diode clamped inverter in terms of the magnitude of the output voltage and harmonic spectrum of its output. This paper presents simulation results for the output voltage and how it can be controlled to get variable output voltage. Moreover, it introduces the harmonic content of the output voltage. In addition, the experimental results are also provided to prove and validate the simulation results. Finally, the correlation between the simulation results and experimental results are also presented.

An efficient current regulator for a power conditioner operated by an innovative strategy

This paper presents an innovative implementation of the recursive Gauss-Newton (GN) algorithm for extraction of the common current quality problems such as the current harmonics and current fluctuation. This paper introduces also the utilisation of the adaptive notch filters to efficiently track the unknown frequencies of the current disturbances. The paper exhibits the mitigation results for these current disturbances using a shunt power conditioner. Furthermore, the adopted shunt power conditioner is operated by the ramp-comparison current regulator. Also, the paper proves that the utilisation of the ramp-comparison current controller, (the linear current controller), is more meritorious than the commonly used current controller, which is the hysteresis current controller, (HCC). The effectiveness of the developed extraction technique with the employed current controller is verified by the simulation and experimental results.

Current Improvement in Distribution Systems Using a Modeless Formulation

Abstract This article presents a new modeless technique to extract current disturbances and shows a modular compensation strategy to mitigate these disturbances. The main advantage of this technique is that it does not require any model or state-space formulation to extract current disturbances like other commonly used state-space techniques. In addition, it is very simple for practical implementation compared to the time-domain and frequency-domain methods. The proposed extraction technique depends on the Wiener filtering theory. The proposed Wiener filter can be utilized to design a modeless generalized compensation strategy for extracting and mitigating the most common current disturbances such as current harmonics and different current fluctuations. The suggested strategy is validated by digital simulation results using MATLAB/SIMULINK (The MathWorks, Natick, Massachusetts, USA) on the most common stationary current quality problems.