Hulusi Karaca

A novel compensation method based on fuzzy logic control for matrix converter under distorted input voltage conditions

Matrix converter (MC) is a direct energy conversation device without dc-link components. Therefore, the output of the converter is directly affected by the disturbances in the input voltages. Many researchers have made an effort to overcome this problem. In this paper, the behaviors of the MC have been investigated under the distorted input voltage conditions. A fuzzy logic control (FLC) based novel compensation method is proposed, which performs close loop control of the output current to improve the output performance of the MC. Some results are presented to prove the effectiveness of the proposed compensation technique.

Modelling and simulation of matrix converter under distorted input voltage conditions

Abstract Matrix converter is an energy conversion device which directly connects a three-phase voltage source to a three-phase load without dc-link components. Therefore, the output of the matrix converter is directly affected by the disturbance or imbalance in the input voltages. Many researchers have made an effort to overcome this problem in recent years. In this paper, the behaviors of the matrix converter controlled with the optimum-amplitude Venturini method are investigated and a novel compensation technique based on fuzzy logic controller is proposed to eliminate the undesirable influences of the input voltage under the distorted input voltage conditions. The proposed technique is based on closed loop control of the three-phase output current to enhance the output performance of the matrix converter. The mathematical model of the proposed system is developed. The simulation of the development model is performed in Matlab&Simulink. Some results demonstrating validity of the proposed compensation technique are presented.

Analysis of a Multilevel Inverter Topology with Reduced Number of Switches

Multilevel inverter is energy conversion device that is generally used in medium-voltage and high-power applications. It offers lower total harmonic distortion, switching losses and voltage stress on switches than conventional inverter. In this chapter, the topologies of the conventional multilevel inverters are discussed and a novel multilevel inverter topology with the reduced number of power switches is proposed. Also, a modulation technique for the proposed multilevel inverter is introduced. This multilevel inverter structure consists of the level module units to enhance the level of the output voltage. Since a level module unit consists of only a DC voltage source and a bidirectional switch, this structure allows a reduction of the system cost and size. Effectiveness of the proposed topology has been demonstrated by analysis and simulation.

Simulation and analysis of SVPWM based VSI for wind energy systems

Space Vector Pulse Width Modulation (SVPWM) technique is extensively used to control the three-phase voltage source inverter (VSI) of wind energy systems. The main advantages of SVPWM method are fixed switching frequency, low harmonic content and higher DC bus utilization. In terms of the use of the DC bus voltage compared to conventional PWM method provides 15.15% more efficient usage. This paper focuses on SVPWM controlled three-phase VSI simulated under MATLAB/SIMULINK.

Selective Harmonic Elimination Technique Based on Genetic Algorithm for Multilevel Inverters

Multilevel inverters have been used in medium or high voltage levels of the power applications to get low total harmonic distortion (THD). Several techniques have been emerged to decrease the THD of the output voltage in multilevel inverter. One of these techniques is Selective Harmonic Elimination (SHE) that has an extensive research area in the field of power electronics. In addition, it is an alternative to usual PWM techniques and includes nonlinear equations of stepped voltage waveform. In this paper, conventional multilevel inverter structures have been analyzed and it is concluded that cascaded H-bridge topology needs lower device component. According to this implication a multilevel inverter topology with reduced number of switches which resembles the cascaded H-bridge topology and enables a reduction in the system cost has been proposed, and solution of SHE equations have been optimized using Genetic Algorithm (GA). The results of analysis and simulation obtained have evidently proved that proposed GA based SHE technique eliminates desired harmonic order.

Simulation of three-phase grid interactive inverter for wind energy systems

Electrical energys transfer, obtained from the wind energy systems, directly to the grid or load is not possible in terms of efficiency and usability. For these reasons, grid interactive inverters are largely used for wind energy systems. In this study, three phase grid interactive Voltage Source Inverter (VSI) controlled by Space Vector Pulse Width Modulation (SVPWM) has been performed. The current controller model, Proportional-Integral (PI) controller regulated the injected grid current, has been implemented as the grid interactive VSI control model. In order to operate between inverter and grid synchronously, the phase angle of grid voltage is detected by using Phase Locked Loop (PLL) in dq-synchronous reference frame. This system has been simulated under MATLAB/SIMULINK. Simulation results illustrate that inverter output voltages are in same phase and frequency with grid voltages.

Dynamic simulation of SVM based direct AC/AC converter

In this study, direct AC/AC converters controlled with space vector modulation (SVM) method are modelled in Matlab&Simulink. Direct AC/AC converters produce directly the three-phase load voltages which have variable frequency and variable amplitude, without rectifying the fixed three-phase input voltages. Simulation results are analyzed for output voltages with various frequency and amplitude.