Carlos Ortega

Improved Waveform Quality in the Direct Torque Control of Matrix-Converter-Fed PMSM Drives

Despite the ability of matrix converters (MCs) to generate a higher number of voltage vectors compared with standard voltage-source inverters, most of the applications reported in the literature utilize only those having larger amplitudes. This paper investigates the use of MC input voltages with different amplitudes in order to reduce the inherent torque ripple that appears when direct torque control (DTC) is used to drive ac machines, particularly permanent-magnet synchronous motors, as its stator inductance is typically half of that of an induction machine of similar ratings. Utilizing a wider range of input voltage vectors for the MC, but not using the rotating vectors, a new lookup table that distinguishes between small and large torque errors is developed, leading to an enhanced MC-fed DTC. The enhancement enables a reduction in the electromagnetic torque ripple and output-current total harmonic distortion. Furthermore, the proposed control strategy improves the MC voltage transfer ratio up to 86.6% compared with 50% achieved by the conventional DTC using MCs at the expense, however, of slightly decreasing the input power factor control capability. The proposed enhanced MC DTC was tested experimentally, and results comparing its performance with MC DTC using an adapted lookup table are shown.

Reduction of Output Common Mode Voltage Using a Novel SVM Implementation in Matrix Converters for Improved Motor Lifetime

This paper presents the study of an alternative space vector modulation (SVM) implementation for matrix converters (MCs), which reduces the output common mode (CM) voltage. The strategy is based on replacing the MC zero vectors with rotating ones. In doing this, the CM voltage (CMV) can be reduced, which, in turn, reduces the CM leakage current. By reducing the CM current, which flows inside the motor through the bearings and windings, the induction motor (IM) deterioration can be slowed down. This paper describes the SVM pattern and analyzes the CMV and the leakage current paths. Simulation and experimental results based on an MC-IM drive are provided to corroborate the presented approach.

Speed Anti-Windup PI strategies review for Field Oriented Control of Permanent Magnet Synchronous Machines

The work presented in this paper addresses the unwanted windup phenomenon reviewing and comparing different PI anti-windup strategies employed in speed control of electric drives. The tuning process of PI controllers is usually carried out considering the system as linear and therefore disregarding its physical limits such as maximum current and voltage. To safeguard the systems integrity, the PI output is normally limited eventually causing the windup phenomenon characterized by long periods of overshoots which may even result in instability.

Common Mode EMI Model for a Direct Matrix Converter

This paper presents an electromagnetic interference (EMI) model to evaluate the conducted common mode (CM) disturbances produced by matrix converters (MCs). The model is based on obtaining a high frequency (HF) equivalent circuit with HF sources representing the switching devices. The circuit resolution in the frequency domain allows the calculation of any EMI parameter with very low computational burden and avoids convergence problems, which are common in time domain methods. The original contribution lies in the source model implementation and placement. The simulation and experimental results for CM leakage currents validate the EMI model.

The Use of Small Voltage Vectors of Matrix Converters in Direct Torque Control of Induction Machines

The effects on torque performance when using small voltage vectors of Matrix Converters is investigated in this paper. These vectors are used in order to reduce the electromagnetic torque ripple which appears when Direct Torque Control technique is used in Induction Motors. Direct Torque Control for Induction Motors using Matrix Converters is reviewed and it is pointed out the problem of the electromagnetic torque ripple which is one of the most important drawbacks of the Direct Torque Control. A new look-up table for Direct Torque Control using small vectors of Matrix Converters is developed. With the new look-up table, the system will differentiate between small and large torque errors and consequently reduce the electromagnetic torque ripple. A comparison between the classical Direct Torque Control using Matrix Converters and the proposed method is carried out. Results which demonstrate the improvement of the novel Direct Torque Control are shown.

Common mode voltage in DTC drives using matrix converters

The paper analyzes the common mode voltage at the output of matrix converters. Based on the theoretical analysis, an approach to reduce the common mode voltage for direct torque control drives using matrix converter is then proposed. The proposed method can be easily implemented without increasing computational requirements and it has been shown to achieve a reduction of 42% in the peak value of the common mode voltage. The functionality of the proposed method is validated by experimental results and compared to the conventional direct torque control.

Sensorless Direct Torque Control of a Surface Mounted PMSM using High Frequency Injection

This paper proposes the high frequency (hf) voltage injection technique to DTC drives with the objective of extending their performance to the low and zero speed region. The simplicity of the original DTC algorithm is not compromised. The hf carrier is introduced by the direct modification of the fundamental voltage vectors. The position signal is then obtained from the direct demodulation of the resulting hf currents. Both simulation and experimental results are shown

Predictive Direct Torque Control of Matrix Converter fed Permanent Magnet Synchronous Machines

A predictive Direct Torque Control method for Matrix Converters fed Permanent Magnet Synchronous Machines drives is proposed in this paper. The voltage vector from the Matrix Converter which ensures minimum torque ripple is selected based on a predictive algorithm. A look-up table for Direct Torque Control using Matrix Converters has been developed which delivers a set of three vectors, at every sample period, that fulfil the torque and flux demands. The predictive algorithm computes the torque error that would be present applying each vector and selects the one that contributes with the minimum error. Simulation results, which confirm the good performance of the proposed predictive Direct Torque Control using Matrix Converters are shown.

Predictive vector selector for Direct Torque Control of Matrix Converter fed Induction Motors

In this paper, a Direct Torque Control method for Matrix Converters fed Induction Motors is proposed. A predictive algorithm which ensures minimum torque ripple is employed for the selection of the appropriate voltage vector from the Matrix Converter. A new look-up table for Direct Torque Control using Matrix Converters has been developed which delivers a set of three vectors, at every sample period, that fulfil the torque and flux demands. The predictive algorithm computes the torque error that would be present applying each vector and selects the one that contributes with the minimum error. Simulation results, which confirm the good performance of the novel predictive Direct Torque Control using Matrix Converters are shown.

High Frequency injection in a Matrix Converter DTC Drive for sensorless operation of a PMSM

A sensorless Direct Torque Control (DTC) of a Permanent Magnet Synchronous Motor (PMSM) drive using a high frequency hf hf voltage injection technique without compromising the simplicity of the original DTC algorithm, is proposed in this paper. A new hf hf injection algorithm, in which the hf hf carrier is introduced by the direct modification of the fundamental voltage vectors of a Matrix Converter (MC), is developed and explained in detail. The position signal is then obtained from the direct demodulation of the resulting hf hf currents. Experimental results showing the effectiveness of the proposed method are shown.