A. M. S. Mendes

Voltage source inverter fault diagnosis in variable speed AC drives, by the average current Park's vector approach

This paper introduces a new approach, based on the average motor supply current Parks vector monitoring, for diagnosing voltage source inverter faults in variable speed AC drives. Both simulation and laboratory tests results demonstrate the effectiveness of the proposed on-line diagnostic technique.

Fault-Tolerant Operating Strategies Applied to Three-Phase Induction-Motor Drives

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

Analysis and Diagnosis of Open-Circuit Faults in Matrix Converters

This paper presents a new diagnostic technique, known as the Modulated Error Voltages (MEV), for the diagnosis of open-circuits faults in the power switches of matrix converters. The proposed technique is based on the monitoring of nine modulated output error voltages, each one associated to a bidirectional switch of the converter. For each output phase, an error voltage is calculated and subsequently modulated by the gate signals of each one of the three bidirectional switches connected to that specific phase. Each modulated signal is subsequently averaged over a certain period of time. If at the end of this averaging period the obtained value is higher than a threshold limit, it will trigger the indication of an open-circuit fault in the power switch associated to the monitored signal. By using the MEV it is possible to concurrently detect and locate open-circuit faults, independently of the type of load of the matrix converter or its operating conditions, namely amplitude and frequency of the output voltages, both in steady-state and transient regimes. Moreover, the MEV allows to speed up the diagnostic process when compared to other diagnostic techniques, and can easily deal with the presence of multiple faults occurring simultaneously.

Real-Time IGBT Open-Circuit Fault Diagnosis in Three-Level Neutral-Point-Clamped Voltage-Source Rectifiers Based on Instant Voltage Error

This paper presents a real-time diagnostic algorithm for insulated-gate bipolar transistor open-circuit faults in three-level neutral-point-clamped rectifiers. This algorithm is based on the instant voltage error in the converter and requires only signals already available to the control system, avoiding the use of additional hardware. The algorithm is independent from the load and from the used control strategy and provides very fast detection and identification of the fault, with diagnostic times as low as two sample periods (in favorable conditions). Experimental results are presented for the operation of the rectifier with two distinct control and modulation strategies and in different conditions. Results show the algorithms speed, effectiveness, and robustness.

A New Fault Diagnosis Method and a Fault-Tolerant Switching Strategy for Matrix Converters Operating With Optimum Alesina-Venturini Modulation

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.

Fault diagnosis on a pwm rectifier ac drive system with fault tolerance using the average current Park's Vector approach

Motor drives reliability is becoming a fundamental aspect of their general performance due to the widespread use of motor-drive systems in numerous critical applications. Therefore, strategies able to operate under faulty conditions are of extreme importance. However, for them to operate there is the obvious need of detecting, identifying and locating the fault.

Thermal Performance of a Three-Phase Induction Motor Under Fault Tolerant Operating Strategies

This paper presents the thermal behavior of a three-phase induction motor under direct torque control, when supplied by a three-phase voltage source inverter with fault tolerant capabilities. For this purpose, a fault tolerant operating strategy based on the connection of the faulty inverter leg to the dc link middle point was considered. The motor thermal profile is obtained through the use of nine thermocouples positioned in both stator and rotor circuits. The experimental results obtained under fault compensated operation show that, as far as the motor thermal characteristics are concerned, it is not necessary to reinforce the motor insulation properties since it is already prepared for such an operation.

Experimental study of the effect of positive sequence voltage on the derating of induction motors under voltage unbalance

This paper presents the results of an experimental study on derating of an induction motor under different voltage unbalanced conditions and its comparison with the NEMA standard MG1 voltage unbalance derating graph. During the derating tests the 4 kW squirrel cage induction motor temperature rise was kept constant at the rated value and the windings temperature was measured on-line by means of an accurate digital thermal monitoring system with nine thermocouples positioned in both stator and rotor circuits. The obtained results show that the positive sequence voltage plays an important role in the derating performance of the induction motor under unbalanced conditions, and that the unbalance voltage indices currently used do not allow for accurately measuring this influence.

Thermal Behavior of a Three-Phase Induction Motor Fed by a Fault-Tolerant Voltage Source Inverter

This paper presents the results of an investigation regarding the thermal behavior of a three-phase induction motor when supplied by a reconfigured three-phase voltage source inverter with fault-tolerant capabilities. For this purpose, a fault-tolerant operating strategy based on the connection of the faulty inverter leg to the dc link middle point was considered. The experimentally obtained results show that, as far as the motor thermal characteristics are concerned, it is not necessary to reinforce the motor insulation properties since it is already prepared for such an operation

Performance analysis of three-phase induction motor drives under inverter fault conditions

This paper presents a comparative analysis involving several fault tolerant operating strategies applied to three-phase induction motor drives. The paper exploits the advantages and the inconveniences of using remedial operating strategies under different control techniques, such as the field oriented control and the direct torque control. Global results are presented concerning the analysis of some key parameters like efficiency, motor line currents harmonic distortion, among others.