Antoni Arias

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.

Novel direct torque control (DTC) scheme with fuzzy adaptive torque-ripple reduction

Investigations were carried out on a novel direct torque control system, which not only reduces the undesirable torque ripple by up to 98% by means of introducing a modulation between the selected active state and a zero state, but also maintains constant switching frequency. Additionally, this two-state modulator is fuzzy adaptive and may be applied to any induction motor. Simulation and the results of experiment illustrate the operation and performance of the proposed fuzzy-logic-based controller.

Elimination of Waveform Distortions in Matrix Converters Using a New Dual Compensation Method

Matrix converters are becoming a real alternative to traditional topologies for many ac-ac power conversion applications. One of the less well-known advantages is the potential for reduced waveform distortion that arise from device characteristics and commutation delays. This paper describes the origin of distortion effects for a matrix converter with current sign-based commutation and gives a novel approach to the method that can, in principle, eliminate the distorting effects to give a power converter having excellent linear behavior. The effectiveness of compensation techniques are illustrated for both an open-loop matrix converter driving a passive load and a matrix converter as part of a vector-controlled drive.

Direct Torque Control of Induction Motors Utilizing Three-Level Voltage Source Inverters

A new control strategy for induction motors based on direct torque control is presented which employs a three-level inverter instead of the standard two-level inverter. The controller is designed to achieve a torque ripple reduction by taking advantage of the increase in the number of inverter states available in a three-level inverter. The harmonic distortion in the stator currents and the switching frequency of the semiconductor devices are also reduced in the new control system presented.

Use of a matrix converter to enhance the sensorless control of a surface-mount permanent-magnet AC motor at zero and low frequency

This paper addresses the use of a matrix converter (MC) with high-frequency voltage injection for zero- and low-speed sensorless control of surface mount permanent magnet alternating current motors. This paper also proposes a dual compensation technique that can practically eliminate zero-current-crossing distortions in MCs, discusses the effect of such distortions on sensorless control using injection techniques, and presents experimental results that illustrate the enhanced low-speed sensorless performance that can be obtained from exploiting the effective linearity of the MC operation.

Fuzzy logic direct torque control

A brief review of the different induction motor drives is done and its reason of being such a high matter of interest is summarised. Next, the direct torque control (DTC) in induction motors with its fundamental principles and schemes is described. Once the DTC is described, its main drawbacks are introduced. One of the goals of the paper is to overcome one of the worst disadvantages of the DTC, which is the existence of a considerable ripple in its torque response. The previously explained DTC limitations involve plenty of nonlinear functions. Therefore, artificial intelligence is suggested to overcome the DTC limitations. Hence, a fuzzy logic DTC controller, which is based on the classical DTC but includes a fuzzy logic controller, is described. Finally an optimised method of calculating the stator reference flux value is presented, which can be applied in any kind of induction motor drive. This optimised stator flux reference value not only improves the torque ripple, but also reduces the power consumption from the mains. Simulated results are shown to corroborate all the presented work and the updated workbench where all the experimentation is realised is also described.

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.

Overview of maximum power point tracking control techniques used in photovoltaic systems

Nowadays power supply systems based on photovoltaic cells have two main drawbacks even the primary energy is free and renewable. They are production cost and efficiency. In order to increase their efficiency should be interesting that the energy transfer between cells and load was done at maximum level. In this paper an overview of control techniques oriented to obtain the maximum power point tracking (MPPT) is presented. Then a specific method is fully developed and finally, some simulation and experimental results are also included.