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A new approach to obtain an integrated battery charger is described in this paper, based on the Asymmetrical Hybrid Multilevel Converter topology. Such a particular open-end winding motor configuration, which has proved to be more efficient than conventional inverter topologies in EV motor drive applications, can be turned in an on-board battery charger only by acting on the control system. Thus, no circuit reconfiguration through electro-mechanical switches is required. Moreover, by introducing a single extra power switch, a bilateral power flow can be managed enabling vehicle to grid operations. The obtained integrated battery charger can be supplied either by a standard ac single-phase grid, either by a dc power source for direct connection to domestic energy resources. The proposed approach enables a new remarkable function to the asymmetrical hybrid multilevel converter at a marginal extra cost, thus mitigating the larger complexity and cost of such an inverter if compared with conventional topologies.

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.

Voltage wave reflection phenomena along power cables are particularly threatening on ac motor drives equipped with silicon carbide power mosfet s 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.

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.

Wheat (Triticum spp. L.), rye (Secale cereal L.), and barley (Hordeum vulgare L.) seeds contain peptides toxic to celiac patients. Maize (Zea mays L.) and rice (Oryza sativa L.) are distant relatives of wheat as well as sorghum (Sorghum bicolor (L.) Moench) and are known to be safe for celiacs. Both immunochemical studies and in vitro and in vivo challenge of wheat-free sorghum food products support this conclusion, although molecular evidence is missing. The goal of the present study was to provide biochemical and genetic evidence that sorghum is safe for celiac patients. In silico analysis of the recently published sorghum genome predicts that sorghum does not contain peptides that are toxic for celiac patients. Aqueous/alcohol-soluble prolamins (kafirins) from different sorghum varieties, including pure lines and hybrids, were evaluated by SDS-PAGE and HPLC analyses as well as an established enzyme-linked immunosorbent assay (ELISA) based on the R5 antibody. These analyses provide molecular evidence for the absence of toxic gliadin-like peptides in sorghum, confirming that sorghum can be definitively considered safe for consumption by people with celiac disease.

Some of DC actuators used in home automation, office automation, medical equipment and automotive systems require a position sensor. In low power applications, the introduction of such a transducer remarkably increases the whole system cost, which justifies the development of sensorless position estimation techniques. The well-known AC motor drive sensorless techniques exploiting the fundamental component of the back electromotive force cannot be used on DC motor drives. In addition, the sophisticated approaches based on current or voltage signal injection cannot be used. Therefore, an effective and inexpensive sensorless position estimation technique suitable for DC motors is presented in this paper. This technique exploits the periodic pulses of the armature current caused by commutation. It is based on a simple pulse counting algorithm, suitable for coping with the rather large variability of the pulse frequency and it leads to the realization of a sensorless position control system for low cost, medium performance systems, like those in the field of automotive applications.

Modified space-vector modulations (MSVMs) that reduce the variations of common mode voltage (CMV) for decreasing common mode currents (CMCs) are a low cost interesting approach. Unfortunately the lack of full utilisation of the DC bus voltage is a severe drawback that can limit the exploitation of such modulation techniques, unless special overmodulation methods are adopted. In this study, some solutions are presented that make a trade-off between the DC bus voltage exploitation and CMCs reduction and make MSVMs appealing to most electrical drives on the market. Furthermore, the influence of dead time in CMV generation is considered thus modifying the switching patterns according to the sign of the load currents. Experimental results are presented in order to confirm the feasibility of the proposed approach.

The on state resistance of power MOSFETs tasked to perform repetitive avalanche operations is subject to modifications caused by the growth of voids and cracks in the source metallization. Endurance tests are the traditional way to monitor these changes in order to assess the device reliability. However, they are very time expensive, requiring even months of uninterrupted operations. An interesting alternative consists in the assessment of the reliability through a suitable model, but no standard techniques have been developed up to now to accomplish this task. A possible approach is followed in this paper exploiting a dynamic analysis of the temperature distribution over the source metal. Coupling the thermodynamic analysis with a reliability model, carried out from the Coffin-Manson law, the device degradation over the time can be estimated and the level of reliability as well. The consistence of the obtained reliability prediction is confirmed by comparison with results of endurance tests. The described approach can be usefully applied to assess the reliability of MOSFETs in a large set of applications in the automotive field.

Photo Voltaic (PV) generators today find application in the domestic field, where the decentralized power conversion concept has proven to be more advantageous than the conventional string architecture. According to the decentralized power conversion concept, PV modules are connected to a single phase AC grid through a two stage converter composed of a DC/DC converter and an inverter. The DC/DC converter accomplishes the Maximum Power Point Tracking (MPPT) and boosts the voltage. It must also include a suitable capacitor bank to solve the unbalance between the DC power generated by the modules and the AC power drawn by the grid. Such a power unbalance in fact generates a voltage ripple that negatively affects the MPPT, forcing the system to work only around its optimal operating point. On the other hand, electrolytic capacitors are highly disliked in PV systems for reliability reasons. Therefore, active current ripple reduction techniques have been proposed in the past, exploiting active filters that increase the complexity and the cost of the system. An alternative approach is proposed in this paper where an active filter is integrated into a Double Interleaved Boost Converter, without introducing extra power devices. According to the proposed approach the size of the electrolytic capacitor bank can be largely reduced, thus improving the reliability and the efficiency of PV systems.

Small photo-Voltaic generators for residential applications are rapidly spreading all over the world in an effort to reduce polluting emissions. In this kind of applications the AC solar module concept has recently proven to be more advantageous than the conventional string architecture. According to the AC solar module concept, single PV modules are directly connected to the AC grid through a DC/DC converter and an inverter. However, in this case a periodical power unbalance is generated because the power drawn by a single-phase residential grid features a large ripple at twice the fundamental frequency, while PV modules generate a DC power. Such a power unbalance affects the Maximum Power Point Tracking and forces the system to operate under suboptimal conditions and is faced with the introduction of bulky electrolytic capacitors. In this paper a alternative approach is presented enabling a standard DC/DC converter to also act as a power ripple damper, without the introduction of extra power devices. A hybrid PWM/unfolder approach has been also developed to reduce the switching power losses of the inverter connecting the DC/DC converter to the grid.

Fuel cell stacks represent a quite promising technology for the realization of small electrical generators for distributed generation. Key advantages of fuel cells over combustion based generators are the absence of polluting emissions and a high efficiency even on small size systems and partial loads. A typical application of distributed generators is in the residential field, where they are connected to single phase AC grids. In these cases a power unbalance is generated because the power drawn by the grid features a large ripple at twice the fundamental frequency, while the power produced by the stack is essentially constant. A large capacitor bank is then used to solve such a power unbalance, that however causes a ripple on the stack output current. This ripple is shortens the fuel cell lifetime, to worsen the stack efficiency and to reduce the available peak power. Active current ripple reduction techniques have been proposed in the past exploiting expensive active filters. An alternative approach is proposed in this paper where an active filter is integrated into the converter, without introducing extra power devices. Moreover, the auxiliary power supply is integrated in the main converter partially compensating the power unbalance. According to the proposed approach the size of the electrolytic capacitor bank can be largely reduced, thus improving the reliability, while lowering costs and size.