A hybrid modulation technique for the dc-bus voltage balancing in a three-phase npc converter

In this paper a new pulse width modulation technique for three-phase neutral point clamped (NPC) converter is presented, with the aim to actively control the dc-bus capacitors' voltages. To meet this requirement, usually NPC modulation techniques are either based on the sole common mode voltage injection (CM1) or on the sole multi-step (MS) switching mode of operation. Contrarily, the presented approach combines these two strategies, taking advantages of all their main benefits while keeping the switching transitions to the minimum required number. The approach has been numerically tested and compared with some of the other strategies, showing an overall better behaviour, especially for high modulation indices

Hybrid Modulation Technique with DC-Bus Voltage Control for Multiphase NPC Converters

The article presents a novel carrier-based pulsewidth modulation technique for multiphase neutral point clamped converters. The technique is aimed to actively control the neutral point (NP) potential while supplying the desired set of line-to-line voltages to the load. Standard techniques are either based on the sole common mode voltage injection or on the sole multistep switching mode; contrarily, the proposed algorithm combines these two approaches to take advantage of their main benefits. The technique performs well for each number of phases, for each modulation index, and for each type of load. It can control in closed-loop the NP voltage to any desirable value with a reduced number of switching transitions. The proposed approach has been experimentally validated and compared with other carrier-based algorithms

General Approach for Modeling and Control of Multiphase PMSM Drives

This article presents a modeling approach and a control strategy for multiphase surface-mounted permanent magnet synchronous machine drives. The mathematical model is completely general with respect to the machine parameters and to the winding configuration. It also intrinsically considers the effects of eventual constraints for the phase currents, generated from the electrical connections among the phase windings or resulting from faults. The current controller is entirely formalized in the phase variables domain. It is based on a pseudoinverse decoupling algorithm and on a linear decoupled controller. The current references are computed by means of a maximum-torque-per-ampere strategy, which can be also easily adapted for torque sharing purposes. The proposed controller requires minimum changes with respect to system reconfigurations or parameters variations and, therefore, it is suited both for healthy and for faulty operations. An extensive set of experimental results has been conducted to validate the proposed approach in several testing scenarios

Risk assessment of atmospheric emissions using machine learning

Supervised and unsupervised machine learning algorithms are used to perform statistical and logical analysis of several transport and dispersion model runs which simulate emissions from a fixed source under different atmospheric conditions. <br><br> First, a clustering algorithm is used to automatically group the results of different transport and dispersion simulations according to specific cloud characteristics. Then, a symbolic classification algorithm is employed to find complex non-linear relationships between the meteorological input conditions and each cluster of clouds. The patterns discovered are provided in the form of probabilistic measures of contamination, thus suitable for result interpretation and dissemination. <br><br> The learned patterns can be used for quick assessment of the areas at risk and of the fate of potentially hazardous contaminants released in the atmosphere

Hybrid modulation technique with dc-bus voltage control for multiphase NPC converters

The paper presents a novel Carrier-Based Pulse Width Modulation (CBPWM) technique for multiphase Neutral Point Clamped (NPC) converters. The technique is aimed to actively control the Neutral Point (NP) potential while supplying the desired set of line-to-line voltages to the load. Standard techniques are either based on the sole Common Mode Voltage Injection (CMI) or on the sole Multi-Step (MS) switching mode; contrarily, the proposed algorithm combines these two approaches to take advantage of their main benefits. The technique performs well for each number of phases, for each modulation index and for each type of load. It can control in closed-loop the NP voltage to any desirable value with a reduced number of switching transitions. The proposed approach has been experimentally validated and compared with other carrier-based algorithms

Optimal Third-Harmonic Current Injection for an Asymmetrical Nine-phase PMSM with Non-Sinusoidal back-EMF

The paper investigates an optimal strategy to exploit the third harmonic current injection for the torque enhancement in a nine-phase permanent magnet synchronous machine (PMSM). The machine is with asymmetrical winding configuration and has a single isolated neutral point. The optimization follows the minimization of the average power losses for a given reference torque or, equivalently, the maximization of the developed torque for a given current RMS. It is shown that, in contrast to the situation for a symmetrical configuration, the optimal ratio between the fundamental and the third harmonic components does not correspond to the ratio between the corresponding back-EMF components. It is demonstrated that this is due to the fact that the phase currents have to sum to zero; consequently, the third harmonic current injection in different three-phase sets has to be different with regard to the magnitude and phase shift. The strategy is introduced using an entirely analytical approach and its effectiveness has been successfully validated through numerical simulations

A hybrid modulation technique for the DC-bus voltage balancing in a three-phase NPC converter

In this paper a new pulse width modulation technique for three-phase neutral point clamped (NPC) converter is presented, with the aim to actively control the dc-bus capacitors’ voltages. To meet this requirement, usually NPC modulation techniques are either based on the sole common mode voltage injection (CMI) or on the sole multi-step (MS) switching mode of operation. Contrarily, the presented approach combines these two strategies, taking advantages of all their main benefits while keeping the switching transitions to the minimum required number. The approach has been numerically tested and compared with some of the other strategies, showing an overall better behaviour, especially for high modulation indices

The pgip family in soybean and three other legume species: evidence for a birth-and-death model of evolution

Polygalacturonase-inhibiting proteins (PGIPs) are leucine-rich repeat (LRR) plant cell wall glycoproteins involved in plant immunity. They are typically encoded by gene families with a small number of gene copies whose evolutionary origin has been poorly investigated. Here we report the complete characterization of the full complement of the pgip family in soybean (Glycine max [L.] Merr.) and the characterization of the genomic region surrounding the pgip family in four legume species. Results: BAC clone and genome sequence analyses showed that the soybean genome contains two pgip loci. Each locus is composed of three clustered genes that are induced following infection with the fungal pathogen Sclerotinia sclerotiorum (Lib.) de Bary, and remnant sequences of pgip genes. The analyzed homeologous soybean genomic regions (about 126 Kb) that include the pgip loci are strongly conserved and this conservation extends also to the genomes of the legume species Phaseolus vulgaris L., Medicago truncatula Gaertn. and Cicer arietinum L., each containing a single pgip locus. Maximum likelihood-based gene trees suggest that the genes within the pgip clusters have independently undergone tandem duplication in each species. Conclusions: The paleopolyploid soybean genome contains two pgip loci comprised in large and highly conserved duplicated regions, which are also conserved in bean, M. truncatula and C. arietinum. The genomic features of these legume pgip families suggest that the forces driving the evolution of pgip genes follow the birth-and-death model, similar to that proposed for the evolution of resistance (R) genes of NBS-LRR-type

Optimal Third-Harmonic Current Injection for Asymmetrical Multiphase Permanent Magnet Synchronous Machines

This article proposes a modeling approach and an optimization strategy to exploit a third-harmonic current injection for the torque enhancement in multiphase isotropic permanent magnet synchronous machines with nonsinusoidal back electromotive forces. The modeling approach is based on a proper vector space decomposition and on the associated rotational transformation, aimed to properly select a set of stator current space vectors to be controlled. It is presented for a generic (i.e., asymmetrical, with an arbitrary angular shift) winding configuration. The injection strategy is related to the choice of a constant synchronous current set aimed at minimizing the average stator winding losses for a given reference torque by using the first and the third spatial harmonics of the air-gap flux density. The optimal solution has been found analytically and has been developed in detail for a selected set of asymmetrical winding configurations. Both the numerical and experimental results are in good agreement with the theoretical analysis