1,721,010 research outputs found
Tecniche di modulazione per convertitori a quadruplo inverter trifase in condizioni di guasto
No full textL’attività di ricerca nel settore degli inverter multifase multilivello, già intrapresa dall’Unità di Bologna alcuni anni or sono, è stata ulteriormente sviluppata estendendo l’analisi alle problematiche della sincronizzazione delle tecniche di modulazione ed al funzionamento in caso di guasto di una o più unità del sistema di conversione.
Per quanto riguarda la sincronizzazione della modulazione, finalizzata essenzialmente alla riduzione o eliminazione delle sub-armoniche nella tensione di uscita, sono state sviluppate alcune tecniche di modulazione per la configurazione multifase multilivello a quadruplo inverter [1]-[2], in collaborazione con il Gruppo di Ricerca del Dr. V. Oleshuk del Institute of Power Engineering, Academy of Sciences of Moldova.
Per quanto riguarda l’analisi della configurazione a quadruplo inverter in caso di guasto, sono state esaminate le casistiche di malfunzionamento di uno, due e tre inverter, prevedendo per ciascuna di queste una modalità di funzionamento post-guasto a prestazioni ridotte [3].
L’analisi è basata sulla considerazione che il guasto, se pur limitato ad un solo componente di un singolo inverter trifase, compromette tipicamente il funzionamento dell'intero inverter. Per consentire al convertitore a quadruplo inverter di poter operare anche in caso di guasto, è quindi necessario isolare dal sistema l’intera unità trifase avariata. Con riferimento alla situazione più comune di un solo inverter guasto, sono state introdotte tecniche di modulazione tali da ripartire uniformemente la potenza sui tre inverter attivi (stessa potenza sulle alimentazioni) o di ripartire egualmente la potenza tra i due sistemi trifase di uscita (minimizzazione delle perdite di inverter e motore) [4]. Lo studio ha riguardato l’analisi teorica, la verifica con simulazioni numeriche in ambiente Matlab/PLECS, ed alcune verifiche speri- mentali sul prototipo di convertitore realizzato presso il Laboratorio del DIE
The Combined use of the Instantaneous Fault Frequency Evolution and Frequency Sliding for Advanced Rotor Fault diagnosis in DFIM Under Time-Varying Condition
No full textThe paper introduces a new monitoring and diagnostic technique for the detection of rotor electrical faults in Doubly Fed Induction Machine (DFIM) for wind power systems. Operating in aggressive environments, with plans onshore or offshore, the detection of anomalies at an incipient stage is a crucial step to decide about the operating continuity of the machines. Discrete Wavelet Transform (DWT) with High Multiresolution Analysis (HMRA) of stator currents is here proposed in order to detect rotor faults. The instantaneous fault frequency evolution (IFFE) and frequency sliding (FS) are proposed for improving the ability of DWT in extracting the contribution of each left side harmonic dynamically over time. Moreover the mean power at different resolution levels was introduced as a diagnostic index for fault quantification. Simulations and experimental results show the effectiveness of this new method in discriminating healthy from faulty rotor in time-varying operating condition
Doubly Fed Induction Machine stator fault diagnosis under time-varying conditions based on frequency sliding and wavelet analysis
No full textThe paper introduces a monitoring and diagnostic technique for the detection of incipient stator electrical faults in Doubly Fed Induction Machine (DFIM) for wind power systems. Operating in aggressive environments, the detection of anomalies at an incipient stage is crucial to decide about the operating continuity of the machines. Discrete Wavelet Transform (DWT) is used to detect stator faults under time varying-condition in two mainly different contexts: Transient-Speed conditions and Fault-Varying conditions. A frequency sliding (FS) with High Multiresolution Analysis (HMRA) approach is proposed for improving the ability of DWT in extracting the most relevant stator fault frequency component dynamically over time thereby. A dynamic mean power calculation at different resolution levels was introduced as a diagnostic index to quantify the fault extent. Simulation and experimental results show the effectiveness of the proposed approach in discriminating stator fault severities leading to an effective diagnostic procedure for stator faults in DFIM
Stator Fault Analysis Based on Wavelet Technique for Wind Turbines Equipped with DFIG
No full textThe paper introduces a monitoring and diagnostic technique for the detection of incipient stator electrical faults
in Doubly Fed Induction Generators (DFIGs) for wind power systems. Depending on wind speed, the induction
machine operates continuously in non stationary conditions. In this context, traditional Fourier Analysis fails to
discriminate between healthy and abnormal stator operating conditions. To overcome this limitation a wavelet
based analysis of rotor currents is here proposed in order to detect stator faults. This technique allows extracting
fault frequencies dynamically over time providing an effective fault detection. Moreover the mean power at
different resolution levels was introduced as a diagnostic index to quantify the extent of the fault.
Simulation and experimental results show that wavelet decomposition allows good discrimination between
healthy and faulty cases even in time-varying conditions leading to an effective diagnostic procedure for stator
faults in DFIG
Advanced Doubly Fed Induction Machine Diagnosis Under Time-Varying Condition
No full textThis paper introduces a new diagnostic
technique for the detection of incipient electrical faults in
Doubly Fed Induction Machine for wind power systems. In the
considered application, the rotor is supplied by a static
converter for the control of active and reactive power flows
from the generator to the electrical grid. A new diagnostic
method based on the rotor modulating signals pre-processing
by Frequency Sliding and Discrete Wavelet Transform thereby
is here proposed to detect stator and rotor faults dynamically
over time. Experimental and simulation results demonstrate the
effectiveness of the proposed approach under time-varying
conditions
Experimental Investigation of Fault-Tolerant Control Strategies for Quad-Inverter Converters
No full textFault-tolerant control strategies for quad-inverter based multiphase-multilevel converters are proposed and experimentally verified in this paper. Explicitly, the conversion scheme consists of four standard 2-level three-phase voltage source inverters (VSIs), able to supply a dual three-phase induction motor in open-end stator winding configuration (asymmetric six-phase machine), quadrupling the utility power of a single VSI within given voltage and current ratings. The developed modulation scheme has the capability to generate multilevel output voltage waveforms in healthy conditions, equivalent to the one of a 3-level VSI, and to share the total motor power among the four dc sources in each switching cycle. This sharing potentiality is investigated under post-fault operating conditions, when one VSI completely insulated due to a severe failure on it. In such circumstances, the quad-inverter system can perform with reduced power rating by a proper modulation of the remaining three healthy VSIs. The complete multiphase-multilevel conversion system with the proposed control algorithm under healthy and post-fault operating conditions has been verified by experimental implementation in open-loop control aspect using two dsp TMS320-F2812 processors with two three-phase passive loads in openend configuration
Fault-tolerant operating analysis of a quad-inverter multiphase multilevel AC motor drive
Full text linkThis paper investigates a new fault-tolerant strategy of a multi-phase multi-level ac motor drive. The proposed approach is based on four conventional 2-level threephase voltage source inverters (VSIs) supplying the open-end windings of a dual three-phase motor (asymmetric six-phase machine), quadrupling the power capability of a single VSI with given voltage and current ratings. The developed faulttolerant control algorithm is able to generate multi-level voltage waveforms, equivalent to the ones of a 3-level inverter, and to share the total motor power among the four dc sources within each switching period. The investigated ac motor drive has been numerically implemented and a complete set of simulation results, under healthy and for three degraded modes of the system, are given to prove the effectiveness of the whole strategy
Fault-Tolerant Control Strategies for Quad Inverter Induction Motor Drives with One Failed Inverter
No full textIn this paper post-fault-tolerant control strategies
for quad-inverter multiphase-multilevel induction motor
drives are investigated. More specifically, four standard 2-
level three-phase voltage source inverters (VSIs) supplying the
open-end windings of a dual three-phase induction motor
(asymmetric six-phase machine) is considered, quadrupling
the power capability of a single VSI with given voltage and
current ratings. In healthy conditions, the control algorithm is
able to generate multilevel voltage waveforms, equivalent to
the ones of a 3-level inverter and to share the total motor
power among the four dc sources in each switching period.
This sharing capability is investigated under post-fault
operating conditions, when one VSI must be completely
insulated due to a severe failure on it. In this case, the
conversion power units can operate with a reduced power
rating by a proper modulation of the remaining three VSIs.
The whole ac motor drive has been numerically implemented
to verify the effectiveness of the proposed control strategies
under healthy and post-fault operating conditions
Advanced Doubly Fed Induction Machine Rotor Fault Diagnosis Based on Wavelet Analysis in Closed Loop Operation Under Time-varying condition
No full textThis paper introduces a new diagnostic technique
for the detection of incipient electrical rotor faults in doubly fed
induction Machine (DFIM) for wind power systems. In the
considered application, the rotor is supplied by a static
converter for the control of active and reactive power flows
from the generator to the electrical grid. A new diagnostic
method based on the rotor modulating signals pre-processing by
Frequency Sliding (FS) and Discrete Wavelet Transform
(DWT) thereby is here proposed to detect rotor faults
dynamically over time. Experimental and simulation results
demonstrate the effectiveness of the proposed approach under
time-varying conditions
Fault detection and quantification of stator high-resistance connection for induction machines
No full textThe paper introduces diagnostic technique for the detection of intermittent stator High-Resistance connection in Wound Rotor Induction Machines. In this context, traditional Fourier Analysis (FA) fails to quantify the extend of fault propagation over time. To overcome this limitation a wavelet based analysis of rotor currents is here proposed in order to detect stator faults. This technique allows extracting fault frequencies dynamically over time providing effective fault detection. A periodical quantification of the fault, issued from the wavelet analysis, has been introduced for accurate stator fault detection. Simulation and experimental results show the validity of the proposed method, leading to an effective diagnosis procedure for intermittent stator electrical faults in wound rotor induction machines
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