Hybrid Modulation and Optimal Neutral-Point Voltage Control for Three-Level NPC Inverters

A preliminary review of advanced carrier based modulation techniques for three-phase three-level NPC inverter is reported, focusing the attention to double signal and hybrid modulations. The problem of the neutral-point balancing is considered and reference to previous proposals recalled. A general analytical approach for the calculation of conduction and switching losses in NPC 3-level inverter is proposed, emphasizing the role of the adopted modulation strategy on the calculations. Finally simulation results are reported based on the model of a grid-connected three-phase three-level neutral-point-clamped inverter

Design of a high efficiency 22 kW wireless power transfer system for EVs fast contactless charging stations

The technology of wireless charging, also referred to as wireless power transfer (WPT) or inductive power transfer (IPT), has been successfully applied at the low power level, such as applications in the medical field or in small devices such as smart phones Along with the fast growing interest in electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs), wireless charging is becoming a new way of charging batteries. In this paper, the design of a WPT system for electrical bus fast wireless charging stations will be presented. The system is composed by a two stage switching power supply, i.e. a multiphase soft-switching buck converter controlling the output power and a high-frequency resonant full-bridge converter connected to a series-series compensation topology. The input DC voltage is around 700V and the maximum output power is 22kW. An analytical description of the system is reported, as well as simulations and experimental results based on a TMS320F28335 DSP are presented to confirm the effectiveness of the proposed syste

Modulation Techniques for Three-Phase Three-Level NPC Inverters: a Review and a Novel Solution for Switching Losses Reduction and Optimal Neutral-Point Balancing in Photovoltaic Applications

A number of modulation strategies have been proposed in literature in the particular case of three-phase three-level NPC inverter, each one focusing on the optimization of specific aspects and performance of the converter. Nevertheless a comprehensive analysis of state-of-art techniques and their specific features suitable for a photovoltaic (PV) applications is still missing, such a study being highly desirable. Both carrier-based and space vector modulation techniques are analyzed in this paper, highlighting specific features and limitations, especially related to PV applications. Basic issues are considered and compared among modulation strategies, namely: switching losses, low-frequency oscillations of the neutral-point (NP) voltage, total harmonic distortion (THD) and weighted total harmonic distortion (WTHD) of the phase currents and line voltages, dynamic response of the neutral-point voltage control loop under imbalance conditions and modulation algorithm complexity. A hybrid modulation strategy assisted by an optimal neutral-point voltage controller is then proposed aiming at both the reduction of the switching losses with a limited deterioration of the output voltage/current quality and fast dynamics control of the neutral point voltage. Those features allow the development of reduced dc bus capacitance PV inverters with optimized efficiency and quality of the output waveforms. Simulation and experimental results based on a TMS320F28069 DSP controller and a PV inverter are presented to confirm the effectiveness of the proposal

Bidirectional PMSM Drive Employing a Three Level ANPC Inverter and a Multi-Phase Interleaved DC/DC Converter for Hybrid Electric Vehicles

A proposal for a two-stage bidirectional electric drive for hybrid electric vehicle is presented in this paper. The system comprises a synchronous PM electrical machine (EM) directly connected to a Diesel internal combustion engine. The EM is fed by a three-level active neutral point clamped (ANPC) inverter connected to a bi-directional multi-phase interleaved DC/DC converter interfacing the high voltage dc-link with a low voltage battery. The electric drive design issues, control topics and the power converter prototype description are reported in this work. Simulation and experimental results are based on a prototype test bench, composed by two external rotor permanent magnet synchronous machines with the same speed/torque/power rating and connected to the same shaft, intended to emulate a hybrid traction system. The drive system is controlled by multiple digital signal controllers based on TMS320F28035 DSP

Novel Interleaved Multiphase Proposal for a Three Level Neutral Point Clamped Buck Converter

This paper introduces a new multiphase phase interleaved three-level neutral point clamped (NPC) buck converter. Compared to the conventional three phase buck, this new topology allows to split the output current between two inductors, increasing the energy density and thus reducing the inductor size. Furthermore, the output voltage and current ripple can be significantly reduced and the ripple frequency is fourth times the switching one, allowing to employee a smaller output capacitance. The operating modes and switching intervals of the proposed topology are presented and discussed. A simulation model of the converter has been developed in the standalone PLECS tool, including conduction and switching loss models, based on commercial silicon carbide power devices. Extensive simulation have been performed in order to verify the effectiveness of the proposal and to highlight the specific features of this converter, mainly phase and output current ripple reduction, nested current/voltage control scheme and current sampling issues, losses and efficiency

Active Torque Ripple Damping in Direct Drive Range Extender Applications: A Comparison and an Original Proposal

The conventional internal combustion engine (ICE) produces an inherent oscillating torque which causes a significant amount of vibration and noise and also reduces the power train life time. An opportunity for ICE used as range extender is to reduce the speed pulsation by using the electric machine (EM) for active damping of the torque ripple by applying an inverse torque sequence to crankshaft. This paper presents three different solutions for torque damping control system, i.e. a conventional proportional integral controller, an observer-based torque feed-forward technique and an original approach based on an adaptive multi-resonant controller. In order to better understand the torque engine oscillation phenomena an effective ICE model has been implemented aiming at comparing the effectiveness of the different techniques by simulation analysis. Experimental investigations are based on a dedicated laboratory test bench composed by an actual ICE connected to the EM. Obtained results show that a appreciable reduction of speed ripple and noise is achieved with the proposed active damping techniqu

Natural leukocyte interferon alfa for the treatment of chronic viral hepatitis in heart transplant recipients

Background. A more rapid and aggressive course of hepatitis B virus (HBV)-related and hepatitis C virus (HCV)-related infection in organ transplant recipients has been described. Interferon alfa is the most accepted drug for treating HBV and HCV chronic infections. However, the use of interferon alfa-N3 has been contraindicated in heart transplant (HTx) recipients because of the hypothesized greater risk of triggering acute cellular rejection. The aim of this clinical pilot study was to evaluate tolerability, safety, and efficacy of natural leukocyte interferon alfa in the treatment of chronic HBV and HCV in HTx recipients. Methods. Seven HTx recipients were enrolled in the study: two with HBV, four with HCV, and one with combined HBV-HCV chronic infection. The patients had a mean follow-up after heart transplantation of 8.5±3 years, before starting interferon alfa-N3 treatment at a dose of 6 MU three times per week, intramuscularly for 12 months. Results. All patients completed the treatment with no major side effects. No unexpected episodes of acute cellular rejection were observed during the treatment. Mean aminotransferase serum levels were significantly lower than before transplantation at 3 (P<0.03), 6 (P<0.02), and 12 (P<0.02) months of treatment and at the 12-month follow-up (P<0.02). A complete and sustained response was achieved in all subjects with HBV-related chronic hepatitis, whereas sustained virologic response was observed in one of four HCV patients. Conclusions. The preliminary data emerging from our study indicate that natural leukocyte interferon alfa-N3 can be safely administered in HTx recipients with chronic HBV or HCV viral hepatitis. Further studies with larger numbers of patients are needed to assess the efficacy of interferon alfa-N3 on HCV virologic response