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Stabilization of multi DC bus link voltages of multilevel NPC VSI. Application to double stator induction motors

Beriber D., Talha A., Boucherit M. S.

Archives of Control Sciences

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2012

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Vol. 22, no. 1

107-120

EN

Voltage source multilevel inverters have become very attractive for power industries in power electronics applications during last years. The main purposes of studying multilevel inverters are the generation of output voltage signals with low harmonic distortion and reduction of switching frequency. An important issue of the multilevel inverter is the capacitor voltage-balancing problem. The unbalance of different DC voltage sources of multilevel neutral point clamped (NPC) voltage source inverter (VSI) constitutes the major limitation for the use of this new power converter. In this paper, we present study on the stability problem of the input DC voltages of the three-level Neutral Point Clamping (NPC) voltage source inverter (VSI). This inverter is useful for application in high voltage and high power area. In the first part, we remind the model of double stator induction motors (DSIM). Then, we develop control models of this inverter using the connection functions of the semi-conductors. We propose a Pulse Width Modulation (PWM) strategy to control this converter. The inverter is fed by constant input DC voltages. In the last part, we study the stability problem of the input DC voltages of the inverter. A cascade constituted by two three-level PWM rectifiers - two three-level NPC VSI - DSIM is discussed. The results obtained show that the input DC voltages of the inverters are not stable. To solve this problem, we propose to use a half clamping bridge. This solution is very promising in order to stabilize the input DC voltages of this converters.

2

Evaluation of maximum power point tracking methods for photovoltaic systems

Talha A., Boumaaraf H., Bouhali O.

Archives of Control Sciences

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2011

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Vol. 21, no. 2

151-165

EN

The output characteristics of photovoltaic (PV) arrays are nonlinear and change with the solar irradiance and the cell's temperature. Therefore, a maximum power point tracking (MPPT) technique is needed to draw peak power from the solar array to maximize the produced energy. Among the hill climbing methods, the perturb and observe (P&O) method tracks the maximum power point (MPP) by repeatedly increasing or decreasing the output voltage at the MPP of the PV module. The implementation of the method is relatively simple, but it cannot track the MPP when the irradiance varies quickly with time. In addition, itmay cause system oscillation around the peak power points due to the effect of measurement noise. The incremental conductance (IncCond) method is also often used in PV systems. This method tracks the MPPs by comparing the incremental and instantaneous conductances of the solar array. This method requires longer conversion time, and a large amount of power loss results. In addition, extra hardware circuitry is required to implement the system. In this paper, it is shown that the negative effects associated with such a drawback can be greatly reduced if the intelligent method is used to improve P&O and IncCond algorithms. The perturbation step is continuously approximated by using fuzzy logic controller (FLC). By the digital simulation, the validity of the proposed control algorithm is proved.

3

Novel digital PWM strategies of multilevel voltage source inverters

Beriber D., Talha A., Berkouk E. M., Francois B., Boucherit M. S.

Archives of Control Sciences

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2009

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Vol. 19, no. 1

43-57

EN

In this paper, two novel algorithms of algebraic PWM strategies for seven-level Neutral Point Clamped (NPC) Voltage Source Inverter (VSI) are presented. These algorithms use a control model of the inverter. In the first part, the authors develop a model of this inverter, without assumption on its control, by using design method associated to Petri nets and switching functions. In the second part, knowledge and control models of this converter are reviewed by using respectively instantaneous and continuous equivalent switching functions. In the last part, two algebraic PWM control strategies of the inverter are proposed. The obtained results are full of promise to use these digital strategies to control seven - level NPC VSI used in high voltage and high power applications as electrical traction.

4

Feedback and control cascade using seven - Level NPC voltage source inverter

Talha A., Berkouk E-M., Boucherit M. S.

Archives of Control Sciences

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2005

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Vol. 15, no. 2

159-174

EN

In this paper, the authors present a study of the stability problem of the input DC voltages of the seven-level neutral point clamping (NPC) voltage source inverter (VSI). In the first part, a knowledge model of this converter isdeveloped by using connection functions. In the second part, The authors propose a PWM strategy which uses six bipolar carriers to control the converter. In this part, The inverter is fed by constant input DC voltages. In the last part of the paper, the authors study the stability problem of the input DC voltages of the inverter. Thus, a cascade is studied constituted by three two-level PWM rectifiers - clamping bridge - seven-level NPC VSI. The obtained results show that the input DC voltages of the inverter are not stable. To improve the performances of the proposed cascade and stabilize the input DC voltages, the authors propose in this paper a solution which uses a linear feedback control of this cascade. This study allows to find a solution for the instability problem of the input DC voltages of the inverter. The results obtained with this solution confirm a good performance of the system.