L. Zarri

Theoretical and experimental investigation on the stability of matrix converters

Matrix converters perform a direct coupling between two ac sources without the need for energy storage components. This characteristic, together with the presence of L-C input filters and the feedforward compensation of the input voltage variations, may determine unstable operation as the power delivered to the load exceeds a limit value. In this paper, a theoretical analysis of the stability of matrix converters is presented with the aim of predicting possible critical operating conditions. It is verified that all of the system parameters affect more or less the stability, including the delay introduced by the digital controller and the power losses. The theoretical analysis is supported by numerical simulations and experimental results carried out on a matrix converter prototype.

Theoretical and experimental analysis for the RMS current ripple minimization in induction motor drives controlled by SVM technique

In this paper, an analytical approach useful for predicting the current ripple in induction motor drives controlled by space-vector modulation (SVM) technique is presented. The analysis is applied to determine the optimal modulation technique that minimizes the rms value of the current ripple. The minimization procedure is based on the analysis of the locus described by the current ripple in the /spl alpha/--/spl beta/ reference frame. As a result, a simple equation has been obtained, which allows the online calculation of the optimal SVM switching pattern. It has been verified that it is possible to obtain a current ripple lower than that of symmetric modulation, and with a reduced number of commutations. Experimental results are provided to confirm the theoretical approach.

A novel modulation strategy for matrix converters with reduced switching frequency based on output current sensing

The performance of matrix converters is strictly related to the modulation strategy adopted to control the state of the switches. In this paper a novel modulation strategy, based on the measurement of the output currents, is presented and discussed. The proposed strategy allows sinusoidal input and output currents to be obtained, like the well-known space vector modulation or Alesina-Venturini Modulation. However, compared to those modulation strategies, it requires a lower number of switch commutations for cycle period, thus leading to a sensible reduction of the converter switching losses and of the effects related to the switching dead time. Furthermore, the maximum voltage transfer ratio can be preserved. The modulation strategy is theoretically derived using the duty-cycle space vector theory that represents a systematic approach towards the modulation problem for matrix converters. Simulation results are also given.

Cascaded multilevel inverter modulation strategies: a novel solution based on duty-cycle space vector approach

In this paper the problem of the modulation strategy of a cascaded multilevel inverter is solved using the duty-cycle space vector (DCSV) approach, which is based on the space vector representation of the switch state. This approach simplifies the study of the modulation strategies and leads to a general solution of the problem, providing an intuitive graphical representation of the modulation properties. Starting from the general solution, a great number of particular modulation strategies, having different characteristics, can be immediately derived. An example of application to a 5-level inverter is presented. The effectiveness of the proposed approach is tested by numerical simulations.

A robust method for flux weakening operation of DTC induction motor drive with on-line estimation of the break-down torque

A method for the flux weakening operation of DTC induction motor drives is proposed. The flux reference is adjusted on the basis of the torque error, thus determining a spontaneous flux weakening. For implementing this algorithm, it is necessary to estimate the maximum torque that the induction machine is able to generate at any speed. The main features of the proposed system are little dependency on machine parameters and smooth transition into and out of the flux weakening operation mode. Experimental tests demonstrate the effectiveness of the control scheme

Experimental analysis of a matrix converter prototype based on new IGBT modules

This paper describes the design and the solutions adopted for a matrix converter prototype of 10 kW based on new power modules manufactured by International Rectifier Corporation Italy. Experimental results are presented along with the comparison among different design possibilities.

Theoretical and Experimental Analysis of the Line Current in Matrix Converters

In this paper a general approach for the determination of the line current harmonic content in matrix converters is presented. The input disturbances, such as voltage unbalance and voltage harmonics, are considered as perturbations of the fundamental component, and a small-signal analysis is used to determine the spectrum of the line current. The proposed analytical approach has a general validity, because it takes into account the effects of the line and filter impedance, the supply harmonics and the input current modulation strategy as well. Hence, it could be usefully employed to evaluate the line current quality in the point of common coupling for different filter topologies and supply distortions. Experimental results are given to confirm the analytical solution.