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Three phase inverters with switching frequencies above 100 kHz have recently become feasible thanks to the significant progress made in wide band gap (WBG) semiconductor technology. The main drivers behind the intense research and development of these ultrahigh switching frequency pulsewidth modulation (PWM) inverters are the extraordinary gravimetric and volumetric power densities that can be achieved. On the other hand, not as much attention has been devoted to the loads that these inverters supply, quite frequently consisting in ac motors. The impact of sub-MHz PWM and of the associated tens of nanoseconds range switching transients on motor terminal overvoltage, common mode currents, and losses are still to be discussed exhaustively. The authors have thus decided to investigate what happens to induction motors (IM) supplied by inverters having switching frequencies up to 350 kHz. After an introduction on WBG semiconductor devices, the article presents some interesting experimental observations conducted on a 1.1 kW four-pole IM fed by a silicon carbide (SiC) inverter. Further insight is provided by tests on a laminated steel toroid, supplied by a single-phase full bridge SiC inverter. Discussions on the experimental results highlight the previously unreported impact of common mode losses, which become a predominant part of the PWM harmonic losses. [ABSTRACT FROM AUTHOR]

This paper deals with the study and implementation of a losses minimization control strategy for an integrated multidrive (IMD) topology used in the drivetrain of parallel hybrid electric vehicles. In this IMD, the stator sections of a multiwinding induction machine are interfaced to the storage units through standard three-phase inverters. The goal of this study is to optimize the management of multidirectional power flows in an IMD configuration, reducing both the power losses of the induction machine and the energy storage units while keeping the computational complexity suitably low. To this aim, the proposed approach consists in a control strategy that continuously searches for the best compromise between the torque response and the power capability of each storage unit while minimizing the overall power losses. Using such an approach, a significant improvement in the overall efficiency is obtained. Simulations and experimental tests confirm the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, it is shown how to obtain a low-cost, high-resolution, and fault-robust position sensing system for permanent-magnet synchronous motor drives operating in safety-critical systems, by combining binary Hall-effect sensors with high-frequency signal injection. It is shown that the position error signal obtained via signal injection can be merged easily into the quantization-harmonic-decoupling vector-tracking observer that is used to process the Hall-effect sensor signals. The resulting algorithm provides accurate, high-resolution estimates of speed and position throughout the entire speed range; compared to the state-of-the-art drives using Hall-effect sensors alone, the low-speed performance is greatly improved in healthy conditions and also following position sensor faults. It is envisaged that such a sensing system can be successfully used in applications requiring IEC 61508 SIL 3 or ISO 26262 ASIL D compliance, due to its extremely high mean time to failure and to the very fast recovery of the drive following Hall-effect sensor faults at low speeds. Extensive simulation and experimental results are provided on a 3.7-kW interior permanent-magnet drive. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of a three-phase permanent magnet synchronous motor (PMSM) drive operating under a single fault, adopting a low cost and fault-tolerant control based on deadbeat-direct torque and flux control (DB-DTFC). Under faulty operation, this fault-tolerant DB-DTFC offers an independent regulation of the electromagnetic torque and the stator flux linkage by using the same torque line equation, stator flux linkage, and current observers adopted during healthy conditions, requiring very limited hardware reconfigurations. In particular, it has been demonstrated that in a fault situation, the same drive model equations adopted for the healthy electric drive can be exploited with very limited detrimental effects on the drive performance simply by applying a suitable reference frame transformation set in the torque and flux control structure. The proposed fault-tolerant DB-DTFC has been validated by experimental tests, confirming that the proposed fault-tolerant DB-DTFC ensures satisfactory faulty operations and drive stability, without significant degradation of parameter sensitivity, keeping limited the increment of computational efforts. [ABSTRACT FROM PUBLISHER]

The paper deals with the analysis and implementation of a vector control strategy devoted to integrated multidrive systems used in starter alternator applications with several dc buses at different voltage levels. The electromechanical system of the considered multidrive topology is obtained by splitting the conventional stator winding of an induction machine into different n three-phase subunits, maintaining the same magnetomotive force distribution and sharing the same rotor. Each stator unit together with rotor can be considered a submotor, thus the entire electromagnetic system behavior can be considered as the combination of all submotors contributions. The submotors are suitably supplied through standard three-phase inverters whose technical specifications are also established according to the storage unit voltage levels. First, a detailed mathematical representation of the electromagnetic system has been developed, then the conditions to carry out the field orientation in each generic subdrive are determined. Addressing a starter-alternator system, the integrated multidrive configuration has been experimentally tested, highlighting the capability of the proposed approach to efficiently handle multidirectional power flows among the storage units and mechanical system while ensuring high dynamic performance. [ABSTRACT FROM AUTHOR]

In this paper, binary Hall-effect sensor faults are investigated in rectangular-current-fed brushless dc (BLDC) drives and a very effective methodology for their detection, identification, and compensation is explored. It is shown that these faults cause erroneous commutation, generally leading to unstable operation. Using a fault detection and identification technique proposed by the authors in a recent paper on low-cost field-oriented drives, it is possible to pinpoint the faulty sensors. In this paper, it is demonstrated that the destabilizing effect of these faults on motion-state estimation can be compensated for in any position and speed estimation algorithm, as long as it is properly readapted. To this end, it is shown how to incorporate such fault-compensation in three state-of-the-art estimation algorithms: 1) the zeroth-order algorithm (ZOA); 2) the hybrid observer (HO); and 3) the vector-tracking observer (VTO). Comparative experimental tests are performed and it is verified that stable operation is achieved with three, two, or only a single Hall-effect sensor functioning correctly. These results show that the classical BLDC drive with three Hall-effect sensors has an inherent double redundancy to position-sensor faults. With the proposed method, this property can be exploited in systems that require very high reliability, such as in aerospace and automotive applications. Redundancy can be increased, using more than three Hall-effect sensors; reduced using two sensors; or eliminated using a single sensor, in ultra low-cost applications where redundancy is not a requirement. [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 proposes a novel Maximum Power Point Tracking (MPPT) method suitable for any application in which very fast changing and not uniform shading conditions continuously occur, as in case of photovoltaic systems (PVs) installed in the roof of electric vehicles. Basically, an Artificial Neural Network (ANN) based approach is utilized to automatically detect the global maximum power point of the PV array by using a preselected number of power measurements of the PV system. The method requires only the measure of PV voltages and currents, thus avoiding the use of additional sensors providing information about the environmental operating conditions and temperature of PV modules. The time interval required to achieve the maximum power generation from the PV modules is about constant and established a priori . The greater the number of power–voltage characteristic scansions, the greater the ANN’s ability to meet the maximum and its prediction accuracy. The algorithm is cost-effective, with no additional hardware requirements and limited dependence on system parameter variations. Numerical simulations have validated the effectiveness of the proposed method, and have highlighted the tradeoff between the preselected number of power–voltage characteristic scansions, the size of the ANN and its prediction accuracy. [ABSTRACT FROM AUTHOR]

High-resolution position and velocity estimation algorithms based on binary Hall-effect sensors for low-cost vector control drives have been the subject of significant research in recent years. While different estimation algorithms have been proposed and analyzed, no contribution so far has dealt with Hall-effect sensor faults and their repercussion on the drive. Here, single and multiple Hall-effect sensor faults are analyzed, and a method to detect, identify, and mitigate such faults is investigated. The method is general, and it ensures proper operation of the drive and is not dependent on the particular estimation algorithm that is used; by way of example, here it will be applied to a vector-tracking observer. Limitations on the performances of the faulty system are discussed, and experimental results are reported to confirm the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper deals with the analysis and implementation of a new scalar control technique for industrial interior permanent-magnet synchronous motor drives that exploits energy-saving capability. In particular, the proposed control strategy forces the conditions of maximum torque per ampere (MTPA), flux weakening (FW), and maximum torque per voltage (MTPV) simply by assigning polynomial relationships between the operating angles of the machine. Although the dynamic performance of the drive is worsened compared to that of vector control schemes, the modified scalar control allows us to work in energetic conditions, very close to those obtained with vector-controlled drives exploiting MTPA, FW, and MTPV strategies. The control techniques are implemented without using any speed and voltage measurement and with only a single current feedback. This paper provides a detailed study of the control strategy, showing the effectiveness and limitations of the method through simulations and experimental results. [ABSTRACT FROM PUBLISHER]

This paper deals with modeling and control of three-phase permanent-magnet synchronous motors (PMSMs) under open-phase fault conditions. Suitable reference frame transformations are introduced in order to obtain a q–d axis model similar to that normally used for machines working in healthy conditions. Adoption of such a model also allows implementing vector control strategies for PMSM drives under open-phase fault conditions in a wide operating range. Simulations and experimental tests confirm the validity of the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper deals with the study and development of new control solutions of permanent-magnet synchronous motor (PMSM) drives specifically aimed to operate under sensorless vector control even during fault conditions. The phase imbalance produced by an open-phase fault leads to the failure of several sensorless estimation algorithms based on either machine models or high-frequency signal injection. Exploiting a recently proposed machine model for three-phase faulted PMSM drives, the practical implementation of sensorless vector controls for such drives under asymmetric conditions due to a single-phase open-circuit fault is performed. The effects of the magnetic/geometrical asymmetries during the fault are studied, and the techniques able to mitigate such effects on the rotor position information are provided. The rotor position estimation is achieved in a wide operating range during the fault as it is confirmed by experimental tests. [ABSTRACT FROM AUTHOR]

Global maximum power point tracking (GMPPT) in case of rapidly variable irregular shading conditions is a complex task, which is exacerbated in case of inexpensive solutions where sensors for acquiring environmental conditions are excluded, that is there is not any information about irradiance and temperature distribution along the photovoltaic system. In such a context, the paper deals with the feasibility study and implementation of a novel easy and cost-effective hybrid two-stages GMPPT algorithm. The first stage synergically combines two different methods to predict the optimal operating condition: an artificial neural network based algorithm and a segmentation-based approach. A traditional hill-climbing method is used in the second stage to finely track the maximum power point. The theoretical aspects of the proposed solution are firstly described, then a wide simulative and experimental tests campaign have been executed to validate the effectiveness of the GMPPT method, confirming that a very simple artificial neural network structure combined with a standard segmentation based method leads to excellent performance for applications where the environmental conditions vary very frequently. [ABSTRACT FROM AUTHOR]

This paper deals with a novel hybrid transformer configuration for MV/LV three-phase distribution systems. The configuration involves a standard distribution transformer with an open-end secondary winding, which is connected to the LV grid and a four-legged inverter with a floating DC bus. Unlike previous hybrid transformers, the proposed configuration eliminates the need for a bidirectional converter and auxiliary transformer windings as well. The fourth leg of the inverter is exploited to manage the neutral line current. The main advantage of the proposed configuration is its ability to provide phase voltage control at the distribution grid edge. This enables the compensation of various grid voltage anomalies such as sags, swells and some kinds of interruptions. The effectiveness of the proposed configuration is demonstrated through simulation and experimental results, highlighting its promising performance in real-world scenarios. [ABSTRACT FROM AUTHOR]

The paper presents a self-sensing control technique for a special type of multilevel motor drive featuring an Open-end Winding Permanent-Magnet Synchronous Motor fed on one side by a main multilevel inverter (MLI) and on the other side by an auxiliary two-level inverter (TLI). In order to minimize the power losses, the MLI manages the machine active power operating at a low-switching frequency. The TLI instead acts as an active power filter and operates at a higher switching frequency and a lower DC-Bus voltage than the MLI. The current control task is shared between the two inverters, as a predictive action is exerted by the MLI, while a feedback action is accomplished by the TLI. Common sensorless rotor position estimation techniques cannot be straightforwardly applied on such a system, due to the particular drive structure. Therefore, a specific technique has been carried out, able to ensure satisfactory efficiency and control performance in all the operating speed ranges by optimally exploiting the different features of the two inverters. Simulation and experimental results confirm the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

The development and the validation of an averaged-value mathematical model of an asymmetrical hybrid multi-level rectifier is presented in this work. Such a rectifier is composed of a three-level T-type unidirectional rectifier and of a two-level inverter connected to an open-end winding electrical machine. The T-type rectifier, which supplies the load, operates at quite a low switching frequency in order to minimize inverter power losses. The two-level inverter is instead driven by a standard sinusoidal pulse width modulation (SPWM) technique to suitably shape the input current. The two-level inverter also plays a key role in actively balancing the voltage across the DC bus capacitors of the T-type rectifier, making unnecessary additional circuits. Such an asymmetrical structure achieves a higher efficiency compared to conventional PWM multilevel rectifiers, even considering extra power losses due to the auxiliary inverter. In spite of its advantageous features, the asymmetrical hybrid multi-level rectifier topology is a quite complex system, which requires suitable mathematical tools for control and optimization purposes. This paper intends to be a step in this direction by deriving an averaged-value mathematical model of the whole system, which is validated through comparison with other modeling approaches and experimental results. The paper is mainly focused on applications in the field of electrical power generation; however, the converter structure can be also exploited in a variety of grid-connected applications by replacing the generator with a transformer featuring an open-end secondary winding arrangement. [ABSTRACT FROM AUTHOR]

The main aim of this work is to present a step-by-step procedure to model and analyze the power loss distribution of three-level Gallium Nitride (GaN) inverters. It has been applied to three distinct three-phase three-level voltage source inverters utilized in electric traction drives: Active Neutral Point Clamped, Neutral Point Clamped and T-Type Neutral Point Clamped. The proposed analytical power loss modelling, combined with an equivalent representation of the electrical machine proved to be a viable solution to achieve a time-saving and low computational burden simulation platform, leading to satisfying accurate results. This has been confirmed by comparing the results carried out from the simulations of a 110 kW permanent magnet synchronous motor drive and those determined by considering a simplified circuital representation based on the proposed analytical power loss modelling. [ABSTRACT FROM AUTHOR]

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]

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]

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]

Recent articles demonstrate that sensorless drives for induction motors can operate at zero-electrical and mechanical frequencies with the aid of high-frequency signal injection techniques and processing the zero-sequence voltage signals. The paper presents some practical implementation issues affecting the performance of such a technique and shows how to improve the quality of the estimated angle. All the assessments are experimentally proved and have a general value that can be extended to other sensorless techniques injecting high-frequency signal. [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]

Temperature monitoring is a major issue in induction motor drives, because temperature variations under working conditions may affect the machine lifetime and the control performance as well. The paper presents a technique for on-line monitoring the rotor and stator temperature on field-oriented induction motor drives, based on a new approach to estimate the rotor and stator winding resistances. The proposed approach exploits the injection of small additional current signals to extract the thermal status of the electrical machine, without affecting the normal drive operation. Moreover, it features a low computational effort, does not require other transducers than these already present in a standard field-oriented controlled drive and can be applied on both conventional and sensorless induction motor drives. The stator and rotor temperature estimation can be used either to prevent dangerous overheating and for on-line tuning of the control system. The practical effectiveness of the proposed approach is demonstrated by simulations and experimental tests. [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]

Electrochemical batteries used in energy storage systems provide a significant contribution to the development of smart grids and green transportation. In recent years, intensive research activities have been oriented to the optimal management of energy storage systems for power electronics applications in fast growing industrial sectors as EVs and HEVs. The accurate modeling of electrochemical batteries is fundamental in the design of control algorithms applied to energy storage systems. Focusing on automotive applications, in this paper a comprehensive analysis of ESS models based on equivalent electric circuits using a multi-criteria approach is presented. An extensive experimental validation has been carried out to evaluate the performance of battery models in automotive applications. [ABSTRACT FROM AUTHOR]

The potential benefit of coupling hydraulic and electronic regulation to maximize the energy production of a cross-flow turbine in hydraulic plants is analyzed and computed with reference to a specific case. Design criteria of the cross-flow turbine inside hydraulic plants are first summarized, along with the use of hydraulic regulation in the case of constant water head and variable discharge. Optimal turbine impeller rotational speed is derived, and traditional as well as innovative systems for electrical regulation are presented. A case study is analyzed to evaluate the potential energy production according to the expected monthly mean flow distribution and two possible choices: CFT1 with the hydraulic regulation, and CFT2 with coupled hydraulic and electric regulations. The return time of capital investment (RCI), computed for both the solutions, showed that the CFT2 solution provides an increment of the total produced energy, along with an increment of approximately 30% of the corresponding RCI. The sensitivity of the results to water head variability and to possible different pipe design criteria in future scenarios is finally discussed. [ABSTRACT FROM AUTHOR]

To obtain a full exploitation of battery potential in energy storage applications, an accurate modeling of electrochemical batteries is needed. In real terms, an accurate knowledge of state of charge (SOC) and state of health (SOH) of the battery pack is needed to allow a precise design of the control algorithms for energy storage systems (ESSs). Initially, a review of effective methods for SOC and SOH assessment has been performed with the aim to analyze pros and cons of standard methods. Then, as the tradeoff between accuracy and complexity of the model is the major concern, a novel technique for SOC and SOH estimation has been proposed. It is based on the development of a battery circuit model and on a procedure for setting the model parameters. Such a procedure performs a real-time comparison between measured and calculated values of the battery voltage while a PI-based observer is used to provide the SOC and SOH actual values. This ensures a good accuracy in a wide range of operating conditions. Moreover, a simple start-up identification process is required based on battery data-sheet exploitation. Because of the low computational burden of the whole algorithm, it can be easily implemented in low-cost control units. An experimental comparison between SOC and SOH estimation performed by suggested and standard methods is able to confirm the consistency of the proposed approach. [ABSTRACT FROM AUTHOR]

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]

A novel control algorithm devoted to remove undesired low-order current harmonics in AC motor drives is presented in this article. The proposed control algorithm combines a suitable multiple reference frame synchronous harmonic estimator and multiple reference frame vector control implementation to suppress the undesired harmonics contained in the motor stator currents. This control technique can handle positive-, negative-, and zero-sequence sets, keeping a satisfying dynamic behavior. The control technique has been evaluated by numerical simulations and experimentally tested on a permanent magnet synchronous motor drive. [ABSTRACT FROM PUBLISHER]

Power generation systems (PGSs) based on hybrid renewable energy are one of the promising solutions for future distributed generation systems. Among different configurations, hybrid photovoltaic-wind turbine (PV-WT) grid connected PGSs are the most adopted for their good performance. However, due to the complexity of the system, the optimal balance between these two energy sources requires particular attention to achieve a good engineering solution. This paper deals with the optimal sizing of PV-WT by adopting different multicriteria decision analysis (MCDA) optimization approaches. Sensitivity of MCDA algorithms has been analyzed, by considering different weighting criteria techniques with different fluctuation scenarios of wind speed and solar radiation profiles, thus highlighting advantages and drawbacks of the proposed optimal sizing approaches. The following study could be assumed as a powerful roadmap for decision makers, analysts, and policy makers. [ABSTRACT FROM PUBLISHER]

In order to precisely define the harmonic content of the main flux and stator voltage of an induction motor that is fed by a high-frequency carrier in addition to the normal set of stator voltages, this paper performs the analytical calculation of the zero-sequence components of the air-gap flux and stator voltage. The calculations are made by defining suitable winding functions to derive the self- and mutual inductances and by adopting a new inverse air-gap function to model the variation of the saturation level of the machine produced by the additional magnetomotive force. Analysis of the calculated expressions that are confirmed by experimental tests shows that the proposed analytical technique can be suitably applied to quantify the effects of high-frequency carriers on the air-gap flux and offers useful hints to understand sensorless control mechanisms. [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]

A technique to improve the performance of grid-connected induction motors by exploiting an auxiliary winding set is proposed in this paper. This auxiliary winding features the same distribution of the main winding, although with a reduced number of turns and it is fed by an inverter a fraction of the power in comparison with the rated size of the induction motor. As shown in the paper, through the auxiliary winding, it is possible to set the machine power factor, increasing the efficiency of the power conversion system and mitigating speed oscillations due to torque disturbances. A mitigation of the grid current peaks due to motor start-up is obtainable. First, the proposed technique is theoretically introduced, then a feasibility assessment is accomplished by simulations. [ABSTRACT FROM AUTHOR]

A three-phase multi-level multi-input power converter topology is presented for grid-connected applications. It encompasses a three-phase transformer that is operated on the primary side in an open-end winding configuration. Thus, the primary winding is supplied on one side by a three-phase N-level neutral point clamped inverter and, on the other side, by an auxiliary two-level inverter. A key feature of the proposed approach is that the N-level inverter is able to perform independent management of N − 1 input power sources, thus avoiding the need for additional dc/dc power converters in hybrid multi-source systems. Moreover, it can manage an energy storage system connected to the dc-bus of the two-level inverter. The N-level inverter operates at a low switching frequency and can be equipped with very low on-state voltage drop Insulated-Gate Bipolar Transistor (IGBT) devices, while the auxiliary inverter is instead operated at low voltage according to a conventional high-frequency two-level Pulse Width Modulation (PWM) technique and can be equipped with very low on-state resistance Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) devices. Simulations and experimental results confirm the effectiveness of the proposed approach and its good performance in terms of grid current harmonic content and overall efficiency. [ABSTRACT FROM AUTHOR]

In this paper, a procedure to simulate an electronic power converter for control design and optimization purposes is proposed. For the addressed application, the converter uses SiC-MOSFET technology in bidirectional battery chargers composed of two power stages. The first stage consists of a single-phase AC/DC power factor correction synchronous rectifier. The following stage is a DC/DC dual active bridge. The converter has been modulated using a phase-shift technique which is able to manage bidirectional power flows. The development of a model-based simulation approach is essential to simplify the different design phases. Moreover, it is also important for the final validation of the control algorithm. A suitable tool consisting of a system-level simulation environment has been adopted. The tool is based on a block diagram design method accomplished using the Simulink toolbox in MATLAB™. [ABSTRACT FROM AUTHOR]

Distributed power converters represent a technical solution to improve the performance of large or utility-scale photovoltaic (PV) plants. Unfortunately, evaluation of the yield obtained in large PV fields by using distributed converters is a difficult task because of recurring partial unavailability, inaccuracy of power analyzers, operating constraints imposed by the Power Plant Controller and so on. To overcome such issues in real operating scenarios, a new modeling strategy has been introduced and validated in terms of computational complexity and accuracy. This approach is based on the state-space averaging technique which is applied to large PV plants with multiple conversion stages by performing some elaborations in order to get a final integrated model. The new modeling strategy has been tested in MatLab Simulink environment using data coming from a 300 MW PV plant located in Brazil representing the case study of this work. In this plant, one subfield is equipped with central inverters while another is with string inverters. The proposed model, whose accuracy is in the range from 2.2 to 2.7% with respect to the measured energy, effectively supports data analysis leading to a consistent performance assessment for the distributed conversion system. Final results highlight that string inverters ensure a gain of about 2% in terms of produced energy. [ABSTRACT FROM AUTHOR]

A multi-level open-end winding converter topology for multiple-motor drives is presented featuring a main multi-level inverter processing the power delivered to the motors and an active filter based on an auxiliary two-level inverter. The main inverter operates at the fundamental frequency in order to achieve low switching power losses, while the active filter is Pulse Width Modulation (PWM) operated to suitably shape the motor currents. The proposed configuration features less phase current distortion than conventional multi-level inverters operating at the fundamental frequency, while achieving a higher efficiency compared to PWM multi-level inverters. Experimental results confirm the effectiveness of such a configuration on both multiple motors-single converter and multiple motor-multiple converter drives. [ABSTRACT FROM AUTHOR]