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A low input current total harmonic distortion (THD) rectifier is presented, tailored around an open-end winding permanent magnet synchronous generator. Specifically, a six-level converter topology is obtained by connecting the generator stator winding to a three level T-type unidirectional rectifier on one side, and to an auxiliary two-level inverter on the other side. The T-type rectifier manages the entire active power stream and operates at the line frequency in order to minimize the switching power losses. The auxiliary inverter is instead driven by a standard PWM technique, being tasked to sinusoidally shape the input current and to actively balance the voltage across the dc-bus capacitors of the T-type rectifier. Such an inverter, being rated at a lower power and at a lower voltage than the T-type rectifier, can exploit low-cost power mosfets. The proposed topology, featuring a very low input current THD, could well supplement in aircraft, portable or distributed generation applications, modern high-speed permanent magnet synchronous generators featuring a quite small stator impedance. Simulation and experimental results confirm the effectiveness of the proposed configuration. [ABSTRACT FROM AUTHOR]

Multiple-motor fed by multiple-converter systems feature a set of electric motor drives sharing the load through a common mechanical coupling. Such a coupling is exploited in this paper to build up a sensorless field oriented control, based on a quite common back-EMF technique to estimate the rotor flux angular position and an original approach to correct estimation errors. The technique is based on the injection of a suitable, very low frequency, sinusoidal signal on the current reference of one of the motor drives. If the estimated rotor flux position is correct, the drive output torque does not show variations. Differently, a torque ripple is generated at the frequency of the injected signal, whose effects on the system speed are easily compensated by the main speed controller. However, due to the mechanical coupling, an additional component of the reference torque current at the frequency of the injected signal is generated on all the other drives. By minimizing such a component, the estimated rotor flux position can be corrected online. The proposed method can also be exploited to estimate actual values of the stator resistance and of the rotor time constant. [ABSTRACT FROM AUTHOR]

An open-end winding machine configuration and a suitable control strategy for medium-voltage ac motor drives applications are proposed in this paper in order to reduce the distortion of phase voltages in multilevel inverters (MLIs). Differently than standard open-end winding configurations, where two inverters provide active power to both sides of the stator winding, a main MLI supplies in this case the machine on one side, while an auxiliary two-level inverter acts as active power filter on the other side. A high efficiency step modulation manages the MLI, while the auxiliary unit is pulse width modulation (PWM) operated. As the phase current harmonic content is improved, the torque ripple is reduced and the drive efficiency is increased. By exploiting the proposed approach, the apparent switching frequency of the system is that typical of a PWM inverter, although the main unit is operated according to a voltage step modulation strategy. Simulation and experimental results confirm the consistency of the proposed methodology. [ABSTRACT FROM PUBLISHER]

A strong demand for even more compact and reliable power electronic devices has powered the development of advanced design techniques. A key role is played in these techniques by the reliability assessment, a procedure that estimates the expected lifetime according to given mission profiles. The reliability assessment of a low voltage MOSFET working in avalanche mode is considered in this paper through an experimental approach based on the Coffin–Manson law. Differently from previously proposed techniques, based on a thermodynamic analysis, a direct measurement of the thermal strain over the source aluminum layer is instead exploited. The consistence of the proposed technique is evaluated by comparing estimation of the progressive increment of the on-state resistance with results of endurance tests and estimation obtained from previously presented reliability models. The described technique can be applied to assess the reliability of MOSFETs in applications typical of the automotive field, where they are tasked to power inductive loads in unclamped mode. More in general, the method can be exploited to characterize the front metal of MOSFET devices subjected to power cycling, or short-circuit stress tests. [ABSTRACT FROM AUTHOR]

Introduces the industrial applications of sensorless control for permanent-magnet synchronous motor (PMSM) drives. Industry applications of sensorless drives; Features of the sensorless control of PMSM drives; Rotor position detection at standstill; Experimental results.

In this paper, an innovative converter topology is presented that allows to improve the performance of electronically commutated motor drives, aimed to equip home appliances. The proposed topology is based on a modified C-dump converter configuration, where the energy recovery stage acts as an active power factor controller (PFC) for offline operation. This is made possible by introducing a new technique to manage the free-wheeling energy that is recovered back to the dc bus by a suitable high frequency (HF) transformer. The proposed approach allows to omit the PFC stage that is included in motor drives devoted to home appliance applications in order to comply with power quality requirements. Moreover, the proposed converter topology features only low side or high side configuration switches, allowing to simplify the design of the drive and easily integrate the power semi-conductors in a single chip exploiting smart power technologies. Simulations and experimental results confirm the validity of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper presents a new technique to detect the slip angular frequency in induction motor drives with indirect field-oriented control (IFOC). Slip frequency is calculated by processing the effects exerted by an additional high-frequency signal on the zero-sequence stator voltage. By measuring such a zero-sequence voltage, it is possible to evaluate the air-gap flux and detect the slip frequency in order to implement an IFOC algorithm. According to the proposed approach, rotor time constant errors are not influent as in conventional field-oriented control schemes, thus, complex tuning or compensation techniques are not required. Simulations and experimental tests are performed to evaluate, the consistency of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper aims to demonstrate that, exploiting the sensorless zero-sequence (SZS) air-gap flux estimation technique, it is possible to realize field-oriented induction motor drives without speed and current sensors, able to operate down to zero speed. According to the SZS technique a zero-sequence stator voltage component is generated as a result of the injection of a suitable high-frequency signal on the stator voltage. By manipulation of such a zero-voltage component, that is unaffected by speed and load changes, it is possible to detect both the amplitude and the angular position of the air-gap flux. In the present paper, it is shown that such a technique allows for the estimation of the motor speed and the phase currents, enabling implementation of a field-oriented control as well as speed and current closed control loops using a simple hardware which, with minor modifications, resembles that of an inexpensive constant Volt/Hertz drive. Experimental tests are shown in order to practically confirm the expected features of the proposed approach. [ABSTRACT FROM AUTHOR]

Although sensorless techniques are among the preferred topics of many researchers around the world, the challenge they represent in terms of finding a robust and effective solution for sensor elimination in ac machine drives has not yet been completely solved. This is especially true for induction motor (IM) drives that still remain the "drive choice" for most of the low- and mediumperformance applications. This paper discusses how standard control methods of IM drives can be improved by adopting a sensorless flux estimation procedure. [ABSTRACT FROM AUTHOR]

Voltage wave reflection phenomena along power cables are particularly threatening on ac motor drives equipped with silicon carbide power mosfets due to very short switching times and high switching frequency. Overvoltage suppression resistance inductance capacitance (RLC) networks are usually added but leading to extra cost and a lower efficiency. A completely different overvoltage mitigation approach is presented in this paper exploiting an open-end winding motor configuration. Overvoltage occurring on the terminals of motor phase windings are, in fact, mitigated by simply coordinating the operations of the two inverters; thus, no passive RLC networks are required. The proposed approach is intended as a mean to provide a further valuable feature to open-winding systems at no extra cost, but it can be also valued as an alternative to conventional bridge inverters equipped with overvoltage mitigation devices. [ABSTRACT FROM AUTHOR]

A novel approach of exploiting the stator-temperature-monitoring system to perform sensorless rotor-position estimation is described in this paper. The rotor position is, in fact, estimated by processing the voltages induced in thermistor cablings, which are modified in order to work as search coils (SCs). Using SCs, some typical drawbacks of sensorless position-estimation techniques based on the manipulation of fundamental components of stator voltages and currents, such as those related to inverter non-linearities, stator-resistance voltage drops, magnetic saturation and cross-coupling, can be overcome or mitigated. According to the proposed approach, a rotor-position-tracking technique for synchronous reluctance motor drives is developed independently from motor parameters. Such a sensorless rotor-position-estimation technique can be directly used to build up a sensorless controller or to improve the performance of conventional model based sensorless control systems. Simulations and experimental tests confirm the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper deals with the development and implementation of an on-line technique for the identification of the stator resistance and permanent magnet flux linkage on three-phase, open-end winding, permanent magnet synchronous motor (PMSM) drives. The stator resistance and permanent magnet flux linkage are independently determined by exploiting a special current vector control strategy, which holds one of the phase currents at zero while suitably modifying the other two in order to keep the magnetomotive force unchanged. As will be demonstrated, no additional sensors or special tests are required by the proposed technique; moreover, motor electrical parameters can be on-line estimated in a wide operating range, avoiding any detrimental impact on the torque capability of the PMSM drive. Finally, the electrical machine thermal status can be also estimated from obtained values of the stator resistance and permanent magnet flux linkage. [ABSTRACT FROM AUTHOR]

An optimal current control strategy for asymmetrical hybrid multilevel inverters (MLIs) is proposed in this paper enabling their use on motor drives, static synchronous compensators, and photovoltaic and wind generators, where a fast and precise current regulation is required. A key feature of these highly efficient converters is that an ac machine (motor or transformer) operates according to an open-end winding configuration, connected on one side to a main MLI and, on the other side, to an auxiliary two-level inverter (TLI). The first efficiently controls the main power stream operating at a low switching frequency, while the TLI acts as an active power filter, exploiting a conventional high-frequency two-level pulsewidth modulation (PWM) technique. The proposed control scheme optimally exploits the key features of the two inverters by suitably sharing the control task. In fact, a predictive current control is assigned to the MLI, which can be accomplished by low switching frequency operations, while the high switching frequency of the PWM-operated TLI is exploited to accomplish a fast and precise closed-loop current control, processing only a part of the power stream flowing through the system, thus producing low power losses. Simulations and experimental results confirm the consistency of the proposed approach. [ABSTRACT FROM AUTHOR]

Due to their inner structural redundancy, ac multidrive systems (MDSs) can achieve a fault-tolerance capability with minor circuit modifications. However, some additional components are generally required in order to create emergency current paths. According to a recently presented approach, the amount of additional components can be reduced by exploiting healthy drives to support faulty drives. This can be obtained by connecting together the neutral points of motor stator windings and suitably sharing the neutral current of faulty units among some, or all, healthy units. Following such an approach, three current-sharing methodologies for fault-tolerant MDSs are presented in this paper, which are able to cope with single or multiple failures. They are first theoretically introduced and then validated by mean of simulations and experimental test results. [ABSTRACT FROM PUBLISHER]

This paper analyzes different aspects of the maximum-torque-per-ampere (MTPA) vector control of interior permanent-magnet synchronous motors at steady state and transient. Two different implementations are considered: a nonlinear-model-based MTPA profile including saturation and cross-saturation effects and a technique based on the maximization of the motor input power versus stator current. Furthermore, this paper analyzes the torque evolution during a transient under an MTPA control strategy on motors with different characteristics. Useful modifications of the current loop are suggested to improve the drive performance. The effects of the torque transient on the sensorless rotor position estimation are also taken into consideration, in case a sensorless MTPA implementation is required. Experimental results confirm the theoretical analysis, showing the benefits of the new control schemes. [ABSTRACT FROM AUTHOR]

In this paper, the rotor position of a synchronous reluctance motor is estimated exploiting the natural saliency of the machine through an addition of a small high-frequency sinusoidal voltage to the stator voltage reference. Due to rotor saliency, a stator voltage component is generated orthogonal to the added signal, whose amplitude depends on the phase displacement between the d-axis and the direction of the injected signal. A robust rotor position tracking can be accomplished by adjusting the direction of the carrier voltage in order to minimize the amplitude of the generated orthogonal voltage. The proposed technique allows zero-speed operation, does not require additional voltage or current sensors, and can easily correct the influence of the armature reaction. Experimental results confirm the validity of the proposed sensorless technique. [ABSTRACT FROM AUTHOR]

This paper exploits the interaction between the low-frequency and the high-frequency fields created by signal-injection techniques during sensorless estimation of the air-gap flux position in induction machines. Such an interaction causes new phenomena that can be summarized in a modulation of the machine saturation level and creation of harmonics that contain information about the position of the flux. This paper analyzes the issues related to the presence of additional fields and predicts the resulting harmonic content using three different approaches such as analytical calculations, computer simulation, and finite element analysis. Experimental measurements confirm the conclusions of this paper. [ABSTRACT FROM AUTHOR]

The paper presents a method to compute the air-gap flux position in induction motors at very low including zero-stator frequency. A low-frequency (50 ÷ 100 Hz) sinusoidal stationary signal is added to the normal stator variables to provide the machine with a suitable permanent excitation. Such an additional excitation modulates the saturation level of the magnetic core of the machine according to the angular position of the air-gap flux. As a result, a new zero-sequence stator-voltage component is generated that contains useful information about the position of the air-gap flux unaffected by load variation. Such a zero-sequence voltage can be easily employed to provide a wide bandwidth measurement of the air-gap flux position. A key feature of the proposed approach is that a low-frequency (0 ÷ 5 Hz) signal is demodulated, thus avoiding any drawback featured by previous sensorless techniques operating with high-frequency signal injection. [ABSTRACT FROM AUTHOR]

In this paper, a new approach is presented aimed at improving the power factor of pulsewidth-modulation inverters that equip low-power electric motor drives for household appliances. The key feature of the proposed approach consists of exploiting the dc-bus current as a suitable dither generator by means of a high-frequency transformer. Such a strategy is used to force the diode rectifier to draw current from the mains in those periods when, in conventional systems, the diodes are reverse biased, i.e., when the dc-bus capacitor voltage exceeds the ac input voltage. The proposed method allows for elimination of the power-factor controller (PFC) front end, traditionally used to comply with power quality requirements. In comparison with standard PFCs based on a dc/dc converter, the proposed approach represents a cheaper and more feasible solution, not using additional power devices and control circuits. Simulation and experimental results confirm the consistency of the proposed approach. [ABSTRACT FROM AUTHOR]