Reliability in the electrical drives is becoming an important issue in many applications. In this context, the reliability associated to the switched reluctance machine ( SRM ) is also an important area of research. One of the major problems, that strongly affect its operation, are drive power semiconductors faults. Typical power converter topologies used in SRM drives cannot handle faults in their power semiconductors. So, this paper presents a power converter topology that provides fault-tolerant capabilities to the drive under a switch fault. This power converter will be used considering that a change in the direction of the current that flows in the SRM windings does not affect the behavior of the machine. Besides that, the proposed power converter will allow to generate multilevel phase voltages in order to apply different voltage levels as function of the SRM speed. A laboratory power converter was developed to test the SRM drive in normal and faulty conditions. From the obtained results it was possible to verify the fault-tolerant capability of the drive under switch faults in different devices and failure modes. It was also possible to confirm the multilevel operation of the drive.

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A Multilevel Fault-Tolerant Power Converter for a Switched Reluctance Machine Drive

This article proposes a new asymmetric neutral-point diode-clamped (NPC) multilevel converter for a four-phase switched reluctance motor drive. The inbuilt NPC clamping capacitors are used for both voltage level clamping and also as dc rail voltage-boosting capacitors to increase the output power of the motor, particularly for high-speed electric vehicle applications. The new converter allows regenerative energy to be recovered back to the dc supply for rapid machine braking, thus increasing overall drive efficiency. Analysis of the different modes of converter operation, along with design equations for sizing the voltage-boosting capacitors, is detailed. The effect of capacitance on boost voltage and increased motor base speed is presented. Simulation and experimental results confirm the effectiveness of the proposed converter.

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A Neutral-Point Diode-Clamped Converter With Inherent Voltage-Boosting for a Four-Phase SRM Drive

The use of power electronic converters is essential for the operation of Switched Reluctance Machines (SRMs) Many topologies and structures have been developed over the last years considering several specific applications for this kind of machine, improving the control strategies, performance range, fault-tolerant operation, among other aspects Thus, due to the great importance of power electronic converters in such applications, this paper is focused on a detailed review of main structures and topologies for SRM drives The proposed study is not limited to the classic two-level power converters topologies dedicated to the SRMs; it also presents a review about recent approaches, such as multilevel topologies and based on impedance source network Moreover, this review is also focused on a new class of topologies associated to these machines, namely the ones with fault-tolerant capability This new category of topologies has been a topic of research in recent years, being currently considered an area of great interest for future research work An analysis, taking into consideration the main features of each structure and topology, was addressed in this review A classification and comparison of the several structures and topologies for each kind of converter, considering modularity, boost capability, number of necessary switches and phases, integration in the machine design, control complexity, available voltage levels and fault-tolerant capability to different failure modes, is also presented In this way, this review also includes a description of the presented solutions taking into consideration the reliability of the SRM drive

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A Review of the Power Converter Interfaces for Switched Reluctance Machines

This paper proposes several modifications of the conventional Asymmetric Half-Bridge (ABH) topology for switched reluctance motor (SRM) drives with the aim of increasing its reliability to safety critical applications. This solution intends to achieve fast changing between main and standby redundant devices in fault-tolerant ABH topologies through the combination of mechanical commutators and semiconductors. With those modifications, the energy processing capability can be maintained for the most common failure modes. A survey of previously developed fault tolerant topologies for SRM drives and several aspects of failure modes, detection and isolation mechanisms are also included. The theoretical validity of one the proposed solutions is confirmed by several experimental results.

Fault-Tolerant Voltage-Source-Inverters for Switched Reluctance Motor Drives

In this work it is proposed a switched reluctance machine (SRM) drive supplied by a renewable source (PV array) to operate a water pumping system. To improve the speed of the commutation between phases it is proposed the use of a multilevel converter for the SRM drive. This converter was designed to reduce the number of controlled power semiconductors, reducing the cost of the system. To obtain the maximum power extraction of the PV system is proposed the use of an algorithm based on the product of the time derivative of power with the time derivative of voltage. A control system to ensure the balance between the power generated by the renewable source and the water pumping system is also proposed. The operation and characteristics of the system will be verified by several numerical tests.

Multilevel Converter Fed SRM Drive for Single Stage PV Array Based Water Pumping

This paper presents a quasi-Z-source (qZS) converter that allows to supply multilevel voltages for the switched reluctance machine (SRM) drive. The use of qZS converter in SRM drives allows obtaining better high speed operation characteristics since higher voltages can be achieved. The proposed drive uses a qZS converter but designed in order to be possible to apply, to the SRM, different voltage levels on the magnetizing and demagnetizing stages. The presented converter also allows to regulate the output voltages and the difference between the voltage levels. Thus, it is possible to improve the efficiency of the drive, by reducing the switching frequency, as well as having better characteristics for high-speed operation. Different configurations of the converter are presented and the modulator associated to the SRM drive is described. In order to verify the features of the proposed system several results are also presented and discussed.

V. Feraao Pires

Papers

A Quasi-Z-Source Converter to Feed a Switched Reluctance Drive with Multilevel Voltages