31 research outputs found
Medium voltage three-level converters for the grid connection of a multi-MW wind turbine
Three-level (3L) neutral point clamped (NPC), flying capacitor (FC), and H-bridge (HB) voltage
source converters (VSCs) as a grid-side full-scale medium voltage (MV) converter are modeled,
controlled, and simulated for the grid connection of a hypothetical 6MW wind turbine. Via the
converter topological features and the simulation results demonstrating the converter performance,
these three 3L-VSCs are discussed and compared in terms of power density and reliability, which can
be considered as two of the most important criteria for the converters placed in wind turbine nacelles.
Given the grid connection circuit (without capacitive switching ripple filters), the 3L-HB-VSC is
expected to be superior with respect to power density and reliability over the 3L-NPC- and -FC-VSCs.Peer ReviewedPostprint (published version
Converter structure-based power loss and static thermal modeling of the press-pack IGBT-based three-level ANPC and HB VSCs applied to Multi-MW wind turbines
In this
study, the converter-structure based power loss and thermal
models are developed for the medium voltage full-scale 3LANPC-
VSC and 3L-HB-VSC utilizing press-pack IGBT-diode
pairs and interfacing a 6MW wind turbine to a medium voltage
grid. The switching power loss models are built using the
experimentally obtained switching power loss data from a fullscale
3L-ANPC-VSC leg. The static thermal models are
developed considering the double-sided cooling of the switches
by the cooling plates. For the experimental model verifications, a
test setup with a single-phase full-scale 3L-ANPC-VSC is introduced.Peer ReviewedPostprint (published version
Geoeconomic variations in epidemiology, ventilation management, and outcomes in invasively ventilated intensive care unit patients without acute respiratory distress syndrome: a pooled analysis of four observational studies
Background: Geoeconomic variations in epidemiology, the practice of ventilation, and outcome in invasively ventilated intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) remain unexplored. In this analysis we aim to address these gaps using individual patient data of four large observational studies. Methods: In this pooled analysis we harmonised individual patient data from the ERICC, LUNG SAFE, PRoVENT, and PRoVENT-iMiC prospective observational studies, which were conducted from June, 2011, to December, 2018, in 534 ICUs in 54 countries. We used the 2016 World Bank classification to define two geoeconomic regions: middle-income countries (MICs) and high-income countries (HICs). ARDS was defined according to the Berlin criteria. Descriptive statistics were used to compare patients in MICs versus HICs. The primary outcome was the use of low tidal volume ventilation (LTVV) for the first 3 days of mechanical ventilation. Secondary outcomes were key ventilation parameters (tidal volume size, positive end-expiratory pressure, fraction of inspired oxygen, peak pressure, plateau pressure, driving pressure, and respiratory rate), patient characteristics, the risk for and actual development of acute respiratory distress syndrome after the first day of ventilation, duration of ventilation, ICU length of stay, and ICU mortality. Findings: Of the 7608 patients included in the original studies, this analysis included 3852 patients without ARDS, of whom 2345 were from MICs and 1507 were from HICs. Patients in MICs were younger, shorter and with a slightly lower body-mass index, more often had diabetes and active cancer, but less often chronic obstructive pulmonary disease and heart failure than patients from HICs. Sequential organ failure assessment scores were similar in MICs and HICs. Use of LTVV in MICs and HICs was comparable (42\ub74% vs 44\ub72%; absolute difference \u20131\ub769 [\u20139\ub758 to 6\ub711] p=0\ub767; data available in 3174 [82%] of 3852 patients). The median applied positive end expiratory pressure was lower in MICs than in HICs (5 [IQR 5\u20138] vs 6 [5\u20138] cm H2O; p=0\ub70011). ICU mortality was higher in MICs than in HICs (30\ub75% vs 19\ub79%; p=0\ub70004; adjusted effect 16\ub741% [95% CI 9\ub752\u201323\ub752]; p<0\ub70001) and was inversely associated with gross domestic product (adjusted odds ratio for a US$10 000 increase per capita 0\ub780 [95% CI 0\ub775\u20130\ub786]; p<0\ub70001). Interpretation: Despite similar disease severity and ventilation management, ICU mortality in patients without ARDS is higher in MICs than in HICs, with a strong association with country-level economic status. Funding: No funding
High Performance Harmonic Isolation By Means of The Single-phase Series Active Filter Employing The Waveform Reconstruction Method
This paper proposes the Waveform Reconstruction Method (WRM), which is utilized in the single-phase Series Active Filter's (SAF's) control algorithm, in order to extract the load harmonic voltage component of voltage harmonic type single-phase diode rectifier loads. Employing WRM and the line current sampling delay reduction method (SDRM), a single-phase SAF compensated system provides higher harmonic isolation performance and higher stability margins compared to the system using conventional synchronous reference frame based methods. The analytical, simulation, and experimental studies of a 2.5 kW single-phase SAF compensated system prove the theory
Converter structure-based power loss and static thermal modeling of the press-pack IGBT three-level ANPC VSC applied to multi-MW wind turbines
Wind turbine converters demand high power density due to nacelle space limitation and high reliability due to high maintenance cost. Depending on the converter structure, the converter thermal performance determines the converter power density and reliability. To estimate the converter thermal performance, the converter structure-based power loss and thermal models are developed in this study for the medium-voltage (MV) three-level active neutral-point-clamped voltage source converter (3L-ANPC-VSC) utilizing 4500 V-1800 A press-pack insulated-gate bipolar transistor-diode pairs and interfacing a 6 MW wind turbine to a MV grid. The switching power loss models are built using the experimental switching power loss data acquired via the double-pulse tests conducted on a full-scale 3L-ANPC-VSC prototype. The converter static thermal model is developed based on the double-sided water-cooled press-pack switches. Via a single-phase test setup with two full-scale 3L-ANPC-VSC legs, the developed power loss and thermal models are validated experimentally. Employing the validated models, the 3L-ANPC-VSC's thermal performance is demonstrated on simulation for a 6 MW wind turbine grid interface. Hence, these converter structure-based models developed and validated in this study are proven to be suitable for the converter power density and reliability studies based on converter thermal performance.Peer ReviewedPostprint (published version
Conference on the condition monitoring and corrosion prevention in refineries and petrochemical plant
Proceedings of a conference held London (GB), 1-2 Jun 1992SIGLEAvailable from British Library Document Supply Centre- DSC:q92/13544(Conference) / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Electro-thermal modeling for junction temperature cycling-based lifetime prediction of a press-pack IGBT 3L-NPC-VSC applied to large wind turbines
Reliability is a critical criterion for multi-MW
wind turbines, which are being employed with increasing
numbers in wind power plants, since they operate under harsh
conditions and have high maintenance cost due to their remote
locations. In this study, the wind turbine grid-side converter
reliability is investigated regarding IGBT lifetime based on
junction temperature cycling for the grid-side press-pack IGBT
3L-NPC-VSC, which is a state-of-the art high reliability
solution. In order to acquire IGBT junction temperatures for
given wind power profiles and to use them in IGBT lifetime
prediction, the converter electro-thermal model including
electrical, power loss, and dynamical thermal models is
developed with the main focus on the thermal modeling
regarding converter topology, switch technology, and physical
structure. Moreover, these models are simplified for their
practical implementation in computation platforms. Finally, the
converter lifetimes for wind power profiles are predicted using
the IGBT lifetime model available. Hence, the developed electrothermal
model’s suitability for the lifetime predictions is shown.Peer Reviewe
Power capability investigation based on electrothermal models of press-pack IGBT three-level NPC and ANPC VSCs for multimegawatt wind turbines
Wind turbine power capability is an essential set of
data for both wind turbine manufacturers/operators and transmission
system operators since the power capability determines
whether a wind turbine is able to fulfill transmission system reactive
power requirements and how much it is able to provide
reactive power support as an ancillary service. For multimegawatt
full-scale wind turbines, power capability depends on converter
topology and semiconductor switch technology. As power capability
limiting factors, switch current, semiconductor junction temperature,
and converter output voltage are addressed in this study
for the three-level neutral-point-clamped voltage source converter
(3L-NPC-VSC) and 3L Active NPC VSC (3L-ANPC-VSC) with
press-pack insulated gate bipolar transistors employed as a gridside
converter. In order to investigate these VSCs’ power capabilities
under various operating conditions with respect to these
limiting factors, a power capability generation algorithm based on
the converter electrothermal model is developed. Built considering
the VSCs’ operation principles and physical structure, the model is
validated by a 2MV·A single-phase 3L-ANPC-VSC test setup. The
power capability investigations regarding a sample grid code’s reactive
power requirement showthat 3L-ANPC-VSC results in 32%
better power capability than 3L-NPC-VSC at the switching frequency
of 1050 Hz. Furthermore, 3L-ANPC-VSC with 57% higher
switching frequency (1650 Hz) and 33% smaller switching ripple
filter can yield close power capability compared to 3L-NPC-VSC
with 1050 Hz.Peer ReviewedPostprint (published version