El Madjid Berkouk

A Novel Space-Vector Current Control Based on Circular Hysteresis Areas of a Three-Phase Neutral-Point-Clamped Inverter

This paper presents a novel space-vector current-control strategy for three-phase neutral-point (NP)-clamped inverters. The main task of this control technique is to force the actual current vector to reach the reference current vector. This original strategy consists in defining three circular hysteresis bands around the error vector. Then, according to the location of this error vector, a selection process of the next applied vector is used to minimize the error vector. The NP voltage is balanced by using the redundant inverter switching states. Simple lookup tables are required for area and sector detection, as well as for vector selection. The performance of the proposed control technique is demonstrated through simulation and experimental investigations.

Study and control of two two-level PWM rectifiers-clamping bridge-two three-level NPC VSI cascade. application to double stator induction machine

In this paper, the authors present a study of the stability problem of the input DC voltages of the three-level neutral point clamping (NPC) voltage source inverter (VSI). They remind the model of the double stator induction machine (DSIM). Then, they develop a knowledge and a control models of this inverter using the connection functions of the semiconductors. After that, they propose a PWM strategy to control his converter. To analysis the instability problem of the input DC voltages of the inverter, the authors study a cascade constituted by two two-level PWM rectifiers-two three-level NPC VSI-DSIM. The results obtained show that the input DC voltages of the inverters are not stables. To remedy to this problem, the authors propose, in this paper, a solution which uses a clamping bridge. The results obtained with this solution confirm the good performances of the proposed solution.

Ripple Reduction in DTC Drives by Using a Three-Level NPC VSI

A direct torque control strategy of a three-level neutral point clamped inverter-fed induction machine is presented. Three-level inverters are an emerging technology and are commonly applied to high power motion drives instead of the standard two-level voltage source inverters (VSI). In three-level inverters the blocking voltage of each switch is half of the DC bus voltage, lower dV/dt is generated and the output voltage and current have lower harmonic distortion. In this paper the application of the direct torque control (DTC) strategy is studied for this particular topology. In the three-level inverter the voltage selection possibilities are enhanced since more inverter states are available. In the simulation results, the three-level DTC system shows reduction in torque ripple and harmonic distortion in the stator currents and voltages. Both features are important for applications in motion control where smooth movement and high efficiency are necessary.

Direct generalized modulation of electrical conversions including self stabilization of the DC-link for a single phase multilevel inverter based AC grid interface

The output voltage waveform of a multilevel inverter is composed of several intermediary voltage levels, which are obtained from capacitor voltage sources. If the number of levels reaches infinity, the total harmonic distortion of the modulated voltage becomes practically zero. However, the numbers of the achievable voltage levels are limited by voltage unbalance problems, voltage clamping requirement, circuit layout, and packaging constraints. This paper presents a modulation strategy that enables to copy directly a modulated multilevel waveform on to output voltages of a (n+1) level inverter. The redundancies of different switch configurations are used to perform the voltage balancing of the DC link. The obtained modelling shows that high voltage multi levels are obtained by combination of n different three-level functions, which are called modulation functions. Therefore, a novel PWM strategy is designed to generate n fictive modulated voltage systems via the direct width modulation and the position setting of modulation functions. Simulation results are presented for a five-level inverter. Experimental results are given for a three-level inverter.

A five-level diode clamped inverter with self-stabilization of the DC-link voltage for grid connection of distributed generators

In this paper, a new control system for single phase five-level diode clamped inverters (DCI) is presented. The obtained modeling shows that high voltage multilevels are obtained by combination of four different three-level functions, which are called conversion functions. Therefore a novel PWM strategy is designed by a particular modulation for creating four fictive modulated voltage systems via the direct width modulation and the position setting of both conversion functions. Redundancies of different switch configurations for the generation of intermediate voltages are used to limit the deviations of capacitor voltages. A correct filtered AC output is obtained with a classical closed loop control. Experimental and simulation results for a three-level and five-level diode clamped inverter are presented to demonstrate the validity of the proposed balancing modulation.

Development of real time Wind Turbine Emulator based on DC Motor controlled by hysteresis regulator

In this paper, a Wind Turbine Emulator will be designed, developed and built. During this phase of the project, the experimental implementation of the Wind Turbine Emulator (WTE) for Wind Energy Conversion Systems (WECS) would consist of separately-excited DC motor. The DC motor is controlled by regulator hysteresis. The model of the wind turbine and the control of the DC motor, which emulate the wind turbine, are implemented in MATLAB/Simulink. The developed WTE allows a WECS to be analyzed or reconfigured for design studies without need of real wind turbines. The DC Motor and its control actuate as the WT. The proposed approach was implemented on DS1104 real-time interface card and Matlab/Simulink real-time control programming. The experimental results verify the performance of proposed WTE.

Sliding mode control of the active and reactive power of DFIG for variable-speed wind energy conversion system

The present research paper deals with a study of a variable speed wind energy conversion system (VSWECS) based on a Doubly Fed Induction Generator (DFIG).A direct control of doubly fed induction generator (DFIG) with a variable structure control based on a sliding mode controller (SMC). Our aim is to make the stator active and reactive power control track their reference variations. The use of the nonlinear sliding mode control gives very good active and reactive power performance when it applies to DFIG. Simulation results and improvement of the behaviour of the DFIG are presented, using Matlab/Simulink software, and discussed to validate the proposed control strategy. Simulation results illustrate the good performance of the controller and prove feasibility of the power control strategy.

Redundant states in five-level inverter using selective harmonics elimination PWM

This study deals the problem of DC-link capacitor voltages balance in five-level inverter. The proposed solution is based on the redundant switching vectors using the selective harmonics elimination SHEPWM instead of space vector modulation [3]. The inverter supplies a high power induction motor of 20MW. The obtained results prove that the balancing of the dc capacitor is kept with canceling the most undesirable harmonics row 5th, 7th, and 11th.

An improved sliding mode controller for a multifunctional photovoltaic grid tied inverter

This paper proposes a robust control algorithm for a photovoltaic (PV) multifunctional grid tied inverter (MFGTI). The MFGTI is used to simultaneously inject the active power of a PV panel and enhance the power quality of a microgrid. The proposed algorithm will estimate the positive fundamental component of the source current even under strongly disturbed main voltage and load conditions. First, a Sliding Mode Controller is used to estimate the magnitude of the source current. Then, a positive fundamental component estimator is used to estimate the unity vector of the main voltage. By multiplying the output of the two blocks, we obtain a pure sinusoidal source current in phase with the main voltage. Using this algorithm, the MFGTI will inject the active power, compensate the reactive power, and enhance the power quality of the microgrid. Thus, the main grid will only supply some amount of active power with a unity power factor. The proposed algorithm is compared with the conventional method to verify its...

DTC-SVM control of induction machine fed by three level NPC matrix converter

This work proposes a DTC-SVM control algorithm based on Stator coordinate transformation to control an induction machine fed by a three level Neutral point clamped matrix converter. The algorithm is simulated on Matlab Simulink to verify its performance. It gives good performance in general. The results are discussed and a study of the effect of the variation of stator resistance is proposed also.