A Scalable System Architecture for High-Performance Fault Tolerant Machine Drives

When targeting mission critical applications, the design of the electronic actuation systems needs to consider many requirements and constraints not typical in standard industrial applications. One of these is tolerance to faults, as the unplanned shutdown of a critical subsystem, if not handled correctly, could lead to financial harm, environmental disaster, or even loss of life. One way this can be avoided is through the design of an electric drive systems based on multi-phase machines that can keep operating, albeit with degraded performance, in a partial configuration under fault conditions. Distributed architectures are uniquely suited to meet these challenges, by providing a large degree of isolation between the various components. This paper presents a system architecture suitable for scalable and high-performance fault tolerant machine drive systems. the effectiveness of this system is demonstrated through theoretical analysis and experimental verification on a six-phase machine

Common Architectures and Devices for Current Source Inverter in Motor-Drive Applications: A Comprehensive Review

When compared to the much more common voltage-source inverter (VSI), the current-source inverter (CSI) is rarely used for variable speed drive applications, due to its disadvantages: the need of a constant DC-link current, typically realized with a front-end converter, and the need for reverse-voltage blocking (RVB) devices, typically implemented with in-series diodes. This limits the overall efficiency of the architecture. This paper investigates latest progress of the CSI research, with the aim of demonstrating why CSI could come back in the near future. Different architectures based on modern wide-bandgap (WBG) switches are analyzed, with an emphasis on why CSI can be advantageous compared to VSI

Improved Speed Extension for Permanent Magnet Synchronous Generators by Means of Winding Reconfiguration

With the increased development of electrical subsystems onboard modern transportation platforms, e.g., more electric aircrafts or more electric ships, the need for electric generation systems has increased. Since many motors require electric starting capability, the application of the starter/generator has been the focus of several studies. The peculiarity of such a system is its requirement for high torque at low speed (for the starting) as well as an extended operation range during the normal generation operations. This mismatch between maximum torque and speed comes at the expense of the power density of the electronic converter, which needs to be designed for the worst case situation and, due to the electric machine optimization, often requires field weakening operations. A new winding reconfiguration is proposed to achieve speed extension and provide more potentiality for high-speed applications. This work compares different power trains in terms of efficiency current stress for electric machines. Hardware-in-the-loop results are adopted to verify the practical implementation of the control systems

Multistress characterization of fault mechanisms in aerospace electric actuators

The concept behind the More Electric Aircraft (MEA) is the progressive electrification of on-board actuators and services. It is a way to reduce or eliminate the dependence on hydraulic, mechanical and the bleed air/pneumatic systems and pursue efficiency, reliability and maintainability. This paper presents a specialised test rig whose main objective is to assess insulation lifespan modelling under various stress conditions, especially investigating the interaction between ageing factors. The test set-up is able to reproduce a multitude of environmental and operational conditions at which electric drives and motors, used in aerospace applications, are subjected. It is thus possible to tailor the test cycle in order to mimic the working cycle of an electrical motor during real operation in aircraft application. The developed test-rig is aimed at projecting the technology readiness to higher levels of maturity, in the context of electrical motors and drives for aerospace applications. Its other objective is to validate and support the development of a comprehensive insulation degradation model

csi and csi7 current source inverters for modular transformerless pv inverters

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Sampling-time harmonic control for cascaded H-bridge converters with thermal control

Cascaded H-bridge converter (CHB) is a multilevel topology that is a well-suited solution for multiple applications such as flexible ac transmission systems or motor drives. This paper is focused on a CHB where the cells present an aging mismatch. This can be caused by the maintenance operation which forces the replacement of some damaged cells of the converter with new or repaired ones. In this paper, a new improved approach of the active thermal control (ATC) of the CHB using discontinuous pulsewidth modulation (PWM) (D-PWM) is presented. The D-PWM technique is used to reduce the power losses of one cell reducing its average temperature in order to increase its remaining lifetime. However, the combination of D-PWM with traditional phase-shifted PWM (PS-PWM) introduces high harmonic distortion in the output voltage of the CHB converter at twice the carrier frequency. A detailed harmonic distortion analysis of the CHB output voltage when the D-PWM based ATC is active is presented. From this analysis, a modification of the traditional PS-PWM is derived to eliminate the harmonic distortion at twice the carrier frequency. Experimental results show how the ATC using D-PWM is achieved whereas the harmonic distortion around twice the carrier frequency is eliminated. © 1982-2012 IEEE

Multistress characterization of fault mechanisms in aerospace electric actuators

The concept behind the More Electric Aircraft (MEA) is the progressive electrification of on-board actuators and services. It is a way to reduce or eliminate the dependence on hydraulic, mechanical and the bleed air/pneumatic systems and pursue efficiency, reliability and maintainability. This paper presents a specialised test rig whose main objective is to assess insulation lifespan modelling under various stress conditions, especially investigating the interaction between ageing factors. The test set-up is able to reproduce a multitude of environmental and operational conditions at which electric drives and motors, used in aerospace applications, are subjected. It is thus possible to tailor the test cycle in order to mimic the working cycle of an electrical motor during real operation in aircraft application. The developed test-rig is aimed at projecting the technology readiness to higher levels of maturity, in the context of electrical motors and drives for aerospace applications. Its other objective is to validate and support the development of a comprehensive insulation degradation model

Common-mode voltage mitigation of dual three-phase voltage source inverters in a motor drive application

Electric variable speed drives (VSDs) based on two VSDs connected to a multiphase machine are an attractive solution to replace high-power mechanic and hydraulic systems in many sectors of industry and transportation because they present high performance with reduced cost, volume and weight. Among the causes which affect the reliability of dual VSDs, the common-mode current flowing through the machine bearing is an important issue. This paper faces the mitigation of the common-mode current by reducing the common-mode voltage (CMV) generated by the operation of a dual VSD. The CMV reduction is carried out without introducing any extra device and/or passive filtering method. This CMV reduction is performed by applying a specific phase-displacement between the modulation strategies of each single inverter drive. The proposed technique has been evaluated in a down scaled experimental setup in order to test its effectivenes

Common dc-link capacitor harmonic current minimization for cascaded converters by optimized phase-shift modulation

This paper investigates the influence of a constant carrier phase shift on the DC-link capacitor harmonic current of cascaded converters used in fuel-cell and mild-hybrid electric vehicles. In these applications, a DC-DC converter can be adopted between the battery and the motor drive inverter in a cascaded structure, where the two converters share the same DC-link. Since the DClink capacitor of such a system represents a critical component, the optimization of the converter operation to limit the current stress and extend the lifetime of the capacitor is an primary objective. This paper proposes the use of a carrier phase shift between the modulations of the two converters in order to minimize the harmonic current of the DC-link capacitor. By harmonic analysis, an optimal carrier phase shift can be derived depending on the converter configuration. Analytical results are presented and validated by hardware-in-the-loop experiments. The findings show that the pulse width modulation carrier phase shift between the interleaved boost converter and the voltage source motor drive inverter has a significant influence on the DC-link capacitor current and thus on its lifetime. A case study with two-cell and three-cell interleaved boost converters shows a possible DC-link capacitor lifetime extension of up to 390%.peer-reviewe

Detection Method of the DC bias in Distribution Power Transformers

Non-linear loads such as AC drives switch-mode power supplies and grid-connected converters can cause, besides the generation of unwanted current harmonics, a DC current component injection into the grid. This DC current component can lead to magnetic saturation of the distribution power transformers, leading to higher current distortion and overheating. This paper presents a method to detect the DC current component flowing into the distribution power transformer with a precise measurement of the DC voltage component at the transformer winding. A magnetic sensor has been developed and implemented in a closed-loop control system to achieve a high sensitivity and guarantees a good linearity with a high rejection ratio to grid voltage variations. Simulation and experimental results confirm the effectiveness of the proposed approach