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Recently, model-based predictive current control (MB-PCC) has been presented as a good alternative to classical control algorithms in terms of simplicity and performance reliability. However, MB-PCC suffers from the high dependence on system parameters, which may deteriorate its performance under parameters variations. On the other hand, Synchronous Reluctance Motors (SynRMs) are susceptible to suffer from inductances variations due to the magnetic saturation. Accordingly, in this paper a new model-free predictive current control of SynRMs based on a recurrent neural network (RNN-PCC) is developed and proposed. The proposed RNN-PCC relies on the identification of the SynRM currents without considering any parameters. Simulation and experimental results show that both RNN-PCC and MB-PCC have similarly excellent dynamics, while better control performance and tracking errors can be achieved thanks to the proposed RNN-PCC.

Inter-turn short-circuit faults are one of the most (if not the most) harmful electrical machine failures, that if not detected and mitigated at a very incipient stage of development may involve serious consequences, both in terms of repair costs and safety. This paper proposes a novel inter-turn fault diagnostic technique for Synchronous Reluctance Machines based on the Luenberger state observer and currents second-order harmonic. The superiority of the proposed approach over the conventional model-based techniques is the ability to evaluate the severity of the fault as well as the efficiency in detecting faults in early stages and under various operating conditions. The effectiveness of the proposed method is demonstrated and validated through several experimental tests.

Direct model predictive control (DMPC) of permanent magnet synchronous generators with full-scale back-to-back (BTB) converters plays an important role in improving the power quality injected to the grid and to comply with grid codes. However, DMPC suffers from the excessive computational burden since all the feasible voltage vectors (VVs) of the BTB converter are used for the prediction and evaluation. Moreover, the weighting factor in the cost function may affect the control performance and tuning it is a complex process. Accordingly, benefiting from the simplicity of the direct control techniques, new direct model predictive flux and power control are proposed in this article, in combination with the direct torque and power control (DTC and DPC), respectively. By defining new DTC and DPC switching tables, only three out of the eight predictions are required to select the best VV for each converter of the BTB topology, which significantly reduces the algorithm computations. To avoid the weighting factor, the electromagnetic torque is simply converted into an equivalent stator flux and only the latter one is considered in the cost function. Experimental results prove that the execution time can be reduced by 26.9%, while the best control performance can be achieved.

Power converters are complex devices subject to failures that can lead to undesired stops. For this reason, many fault-tolerant topologies and strategies have been deeply studied, mainly focusing on improving the electromechanical behavior of the reconfigured drive after the fault. However, it is also very important to evaluate the possible increase of power losses. In this paper, a power loss analysis is performed on a current-controlled three-phase inverter supplying a permanent-magnet synchronous motor (just chosen as an example), for all the operating modes, starting from the fault occurrence until the faulty operation mode is established. This is particularly important because the effectiveness of a fault-tolerant control strategy depends on the possibility to maintain a continuous operation. The latter is ensured only if there is no such increment of the losses that the survival of the component is at risk. The simulations are validated by means of experimental tests, and the results are discussed. The method can be easily applied to other topologies and reconfiguration strategies.

The widespread use of electric drives has led to an increasing interest in their condition monitoring and fault diagnostics. With respect to power-switch open-circuit fault diagnosis, the majority of the proposed voltage-based approaches require additional hardware, increasing the system cost. As a result, industry acceptance may be low. This paper proposes a new voltage-based approach-without additional sensors-for open-circuit fault diagnosis in closed-loop controlled pulsewidth-modulation (PWM) ac voltage source converters, by using the information contained in the reference voltages available from the control system. The robustness against false alarms of the proposed technique is improved by employing a voltage observer, in order to estimate the actual converter voltages. It has been proven that the algorithm is insensitive to parameter errors; thus, its effectiveness is not compromised. In order to assess the applicability of the diagnostic technique, it is integrated into the control system of a permanent-magnet-synchronous-machine drive, with regenerative capabilities, together with three of the most widely used PWM control strategies: hysteresis current control, direct torque control, and space vector modulation. The technique performance is analyzed in detail by means of several experimental results.

Reliability and availability levels are crucial aspects for assessing the economic viability of wind energy conversion systems. Therefore, fault-tolerant systems can make a valuable contribution. This paper presents a fault-tolerant permanent-magnet synchronous generator (PMSG) drive employing new direct control techniques. For postfault operation, a direct power control (DPC) of a four-switch three-phase converter and a direct torque control of a three-switch three-phase rectifier are proposed. Switching tables are theoretically formulated for both control techniques. Two alternative tables are obtained for the DPC of the grid-side converter, permitting the choice between implementation simplicity and enhanced performance. All necessary reconfigurations to handle open-circuit faults are triggered by a reliable fault diagnostic method, which has a low computational demand, without requiring additional measurements. Experimental results are presented, demonstrating the feasibility of the proposed fault-tolerant PMSG drive.

Condition monitoring and fault diagnosis are currently considered crucial means to increase the reliability and availability of wind turbines and, consequently, to reduce the wind energy cost. With similar goals, direct-drive wind turbines based on permanent magnet synchronous generators (PMSGs) with full-scale power converters are an emerging and promising technology. Numerous studies show that power converters are a significant contributor to the overall failure rate of modern wind turbines. In this context, open-circuit fault diagnosis in the two power converters of a PMSG drive for wind turbine applications is addressed in this paper. A diagnostic method is proposed for each power converter, allowing real-time detection and localization of multiple open-circuit faults. The proposed methods are suitable for integration into the drive controller and triggering remedial actions. In order to prove the reliability and effectiveness of the proposed fault diagnostic methods, several simulation and experimental results are presented.

Three-phase inverters are currently utilized in an enormous variety of industrial applications, including variable-speed ac drives. However, due to their complexity and exposure to several stresses, they are prone to suffer critical failures. Accordingly, this paper presents a novel diagnostic algorithm that allows the real-time detection and localization of multiple power switch open-circuit faults in inverter-fed ac motor drives. The proposed method is quite simple and just requires the measured motor phase currents and their corresponding reference signals, already available from the main control system, therefore avoiding the use of additional sensors and hardware. Several experimental results using a vector-controlled permanent-magnet synchronous motor drive are presented, showing the diagnostic algorithm effectiveness, its relatively fast detection time, and its robustness against false alarms.

This paper deals with the use of the instantaneous active and reactive power signature analyses and their derived signals-the instantaneous power factor and phase angle - for discriminating broken rotor bars and airgap eccentricity conditions (rotor faults) from mechanical load oscillation effects in operating three-phase squirrel cage induction motors. Both simulation and experimental results are presented to show the effectiveness and the merits of the proposed approach that offers the possibility to distinguish between the three conditions by comparing the signature analyses of two different quantities for each abnormality condition.

This paper presents a new diagnostic technique for the diagnosis of open-circuit faults in matrix converters operating with an Optimum Alesina-Venturini modulation scheme. Compared to previous diagnostic techniques developed for matrix converters, the technique proposed in this paper has the major advantage of not requiring the installation of any additional sensors in the converter besides the ones already present for control purposes. Hence, it can be easily integrated into the control platform of the converter at no additional cost. In addition to the diagnostic approach, a new fault-tolerant switching strategy is also presented so that after the appearance of an open-circuit fault, the matrix converter can continue to run although with degraded performance, until a repair action can be taken. Several simulation and experimental results are presented, demonstrating the effectiveness and applicability of the developed techniques.

The monitoring of power converters is critical for obtaining systems with self-diagnostic capabilities and fault-tolerant features. This paper presents an analytical work concerning the operation of matrix converters (MCs) under the presence of open-circuit faults and discusses the applicability of a method for the diagnosis of this type of failures. The proposed method uses the absolute values of nine modulated error voltages for the continuous monitoring of the condition of the bidirectional switches of an MC. This method allows a fast detection and location of the faulty switches, independent of the modulation strategy of the converter, its voltage transfer ratio, output frequency, or type of load connected to it, both in steady-state and transient regimes. The theory, validated by simulation and experimental results, demonstrates the applicability of the proposed technique for the diagnosis of faults in MCs.

In this paper, a new detection technique based on the instantaneous-reactive-power signature analysis is proposed for the diagnosis of rotor-cage faults (RCFs) in operating three-phase induction motors (IMs). This technique has been tested through the simulation of two different IMs using a mathematical model based on the winding-function approach. In order to demonstrate the capability of the proposed tool for rotor-condition monitoring, these simulations are complemented by the experimental results obtained from two IMs with several faulty rotors, powered from sinusoidal and nonsinusoidal supply voltages. The results obtained by the fast-Fourier-transform algorithm and the Welch method show the merits of the proposed approach for the detection of RCFs. A suitable fault-severity factor is also proposed as an indicator of the motor condition. Moreover, the inductive reactive effect of RCFs is underlined to demonstrate the effectiveness and convenience of this new technique for the diagnosis of RCFs in three-phase IMs.

This paper presents a very simple technique to estimate the condition of aluminum-electrolytic-capacitors. The aging of aluminum-electrolytic-capacitors is expressed by the increase of their equivalent series resistance (ESR) and the reduction of their capacitance. Thus, the proposed technique is based on the estimation of both the ESR and capacitance values. To implement the proposed technique, the capacitor is fed by a sinusoidal voltage with the required power. The resultant impedance vector defined by the capacitor voltage and current gives enough information to estimate the condition of the capacitor.

This paper proposes a new model-based diagnostic technique, which is the so-called virtual current technique (VCT), for the diagnosis of rotor faults in direct rotor field oriented controlled (DRFOC) induction motor drives. By measuring the oscillations at twice the slip frequency found in the rotor flux of the machine, and by conjugating this information with the knowledge of some motor parameters, as well as the parameters of the flux and current controllers, it is possible to generate a virtual magnetizing current which, after normalization, allows the detection and quantification of the extension of the fault. The proposed method allows one to overcome the major difficulties usually found in the diagnosis of rotor faults in closed-loop drives by providing information about the condition of the machine in a way that is independent of the working conditions of the drive such as the load level, reference speed, and bandwidth of the control loops. Although the VCT was primarily developed for traction drives used in railway applications, it can be incorporated in any DRFOC drive at almost no additional cost. Several simulation results, obtained with different types of DRFOC drives, as well as experimental results obtained in the laboratory, demonstrate the effectiveness of this new diagnostic approach.

This paper deals with the use of the signature analysis of the complex apparent power modulus as a new technique for the diagnostics of mixed airgap-eccentricity condition in operating three-phase squirrel-cage induction motors. First, a modeling and simulation study concerning the occurrence of airgap eccentricity in three-phase induction motors is presented. For that purpose, the winding function approach is considered. Then, both simulation and experimental results are presented to illustrate the effectiveness of the proposed approach. A suitable fault-severity factor is also proposed as an indicator of the condition of the machine.

This paper presents a comparative analysis involving several fault-tolerant operating strategies, applied to three-phase induction-motor drives, that intend to compensate for inverter faults. The results presented show the advantages and the inconveniences of several fault-tolerant drive structures, under different control techniques, such as the field-oriented control and the direct torque control. Experimental results concerning the performance of the three-phase induction motor, based on the analysis of some key parameters, like induction-motor efficiency, motor power factor, and harmonic distortion of both motor line currents and phase voltages, will be presented