12,414 research outputs found
Multilevel Converters: An Enabling Technology for High-Power Applications
| Multilevel converters are considered today as the
state-of-the-art power-conversion systems for high-power and
power-quality demanding applications. This paper presents a
tutorial on this technology, covering the operating principle and
the different power circuit topologies, modulation methods,
technical issues and industry applications. Special attention is
given to established technology already found in industry with
more in-depth and self-contained information, while recent
advances and state-of-the-art contributions are addressed with
useful references. This paper serves as an introduction to the
subject for the not-familiarized reader, as well as an update or
reference for academics and practicing engineers working in
the field of industrial and power electronics.Ministerio de Ciencia y Tecnología DPI2001-3089Ministerio de Eduación y Ciencia d TEC2006-0386
Power Quality Enhancement in Electricity Grids with Wind Energy Using Multicell Converters and Energy Storage
In recent years, the wind power industry is experiencing a rapid growth and more wind farms with larger size wind turbines are being connected to the power system. While this contributes to the overall security of electricity supply, large-scale deployment of wind energy into the grid also presents many technical challenges. Most of these challenges are one way or another, related to the variability and intermittent nature of wind and affect the power quality of the distribution grid. Power quality relates to factors that cause variations in the voltage level and frequency as well as distortion in the voltage and current waveforms due to wind variability which produces both harmonics and inter-harmonics. The main motivation behind work is to propose a new topology of the static AC/DC/AC multicell converter to improve the power quality in grid-connected wind energy conversion systems. Serial switching cells have the ability to achieve a high power with lower-size components and improve the voltage waveforms at the input and output of the converter by increasing the number of cells. Furthermore, a battery energy storage system is included and a power management strategy is designed to ensure the continuity of power supply and consequently the autonomy of the proposed system. The simulation results are presented for a 149.2 kW wind turbine induction generator system and the results obtained demonstrate the reduced harmonics, improved transient response, and reference tracking of the voltage output of the wind energy conversion system.Peer reviewedFinal Accepted Versio
The Essential Role and the Continuous Evolution of Modulation Techniques for Voltage-Source Inverters in the Past, Present, and Future Power Electronics
The cost reduction of power-electronic devices, the increase in their reliability, efficiency, and power capability, and lower development times, together with more demanding application requirements, has driven the development of several new inverter topologies recently introduced in the industry, particularly medium-voltage converters. New more complex inverter topologies and new application fields come along with additional control challenges, such as voltage imbalances, power-quality issues, higher efficiency needs, and fault-tolerant operation, which necessarily requires the parallel development of modulation schemes. Therefore, recently, there have been significant advances in the field of modulation of dc/ac converters, which conceptually has been dominated during the last several decades almost exclusively by classic pulse-width modulation (PWM) methods. This paper aims to concentrate and discuss the latest developments on this exciting technology, to provide insight on where the state-of-the-art stands today, and analyze the trends and challenges driving its future
Direct control strategy for a four-level three-phase flying-capacitor inverter
A direct predictive control strategy is proposed for a three-phase four-level flying-capacitor (FC) inverter in this paper. The balancing of the FC voltages, a challenge in applications with small capacitors and low switching frequencies, is done without any modulation, simply using tables calculated offline. These allow the realization of fast-dynamics output currents with reduced dv/dt in the output voltages and reduced switching frequencies. Moreover, no interharmonics are created when operating at low switching frequencies and with reference currents containing multiple harmonic components, which is a key feature for active power filters. Simulations and experimental results are presented to demonstrate the excellent performance of the direct control strategy in comparison with a conventional pulsewidth-modulation control technique, mostly for operation at low switching frequencies
Postfault operation strategy for cascaded H-bridge inverters driving a multiphase motor
Multiphase motor drives based on a cascaded
H-bridge (CHB) voltage source inverter (VSI) are suitable
for fault-tolerant applications because a damaged H-bridge
can be safely bypassed without interrupting the drive operation. This bypass has the effect of an undesired dclink voltage shortage that multiphase motors can effectively
tolerate if appropriate x-y components are injected in the
stator voltages. These degrees of freedom, which are not
available in three-phase motors, permit to reach higher
speeds without field weakening nor torque oscillations during the fault. However, no specific strategies exploiting this
particular advantage of multilevel multiphase drives have
been proposed so far, albeit resorting to strategies devised
for three-phase VSIs would reduce the drive performance.
This paper proposes a post-fault strategy for multiphase
CHBs with bypassed H-bridges that better uses its dc
link by injecting appropriate x-y components in the modulation reference signals, without altering the α-β ones.
Experimental results, obtained with a five-level five-phase
motor drive, show that the proposed strategy manages to
run the motor at rated speed with negligible torque ripple
when an H-bridge is bypassed. It is also recognized that
the continuous operation in this situation requires using a
circulating-current filter to mitigate the extra stator copper
losses that ariseAgencia Estatal de Investigación | Ref. PID2021-124136OB-I0
Analysis of the power balance In the cells of a multilevel cascaded H-Bridge converter
Multilevel cascaded H-Bridge converters (CHB)
have been presented as a good solution for high power applications.
In this way, several control and modulation techniques
have been proposed for this power converter topology. In this
paper the steady state power balance in the cells of the single
phase two cell CHB is studied. The capability to be supplied with
active power from the grid or to deliver active power to the grid
in each cell is analyzed according to the dc-link voltages and
the desired ac output voltage value. Limits of the maximum and
minimum input active power for stable operation of the CHB are
addressed. Simulation results are shown to validate the presented
analysis
The Age of Multilevel Converters Arrives
This work is devoted to review and analyze the most relevant characteristics of multilevel converters, to motivate possible solutions, and to show that we are in a decisive instant in which energy companies have to bet on these converters as a good solution compared with classic two-level converters. This article presents a brief overview of the actual applications of multilevel converters and provides an introduction of the modeling techniques and the most common modulation strategies. It also addresses the operational and technological issues
An open-phase fault detection method for six-phase induction motor drives
Malaga (Spain), 4th to 6th April, 2017
Comunicaciones del Congreso Publicadas en: Renewable Energy and Power Quality Journal (RE&PQJ) ISSN 2172 038X, No.15 April 2017Induction machines (IM) with multiple sets
of three-phase windings are a real alternative in safety-
critical applications due to their inherent redundancy
and extra number of freedom degrees. These
properties
can be used to devel
op
a fault-tolerant system without
extra hardware. The fault detection is mandatory
in
the creation of a fault tolerant system. Since, the fault
localization allows to adapt the control scheme of this
anomalous mode of operation. Nowadays, open-phase
faults (OPFs) and six-phase IMs are hot topics in the
literature
of fault-tolerant drives. Thus, this paper
presents an open-phase fault detection method for
a
six-phase IM drive
. The detection method is based o
n
the vector space decomposition (VSD), taking the
components of the secondary orthogonal subspace to
localize the open-phase fault. The goodness of the
proposed method is validated with simulation resultsMinisterio de Ciencia e Innovacion ENE2014-52536-C2–1-
Energy Pulsation Reduction in Modular Multilevel Converters Using Optimized Current Trajectories
In power electronics, the modular multilevel converter (MMC) is an easily scalable topology with an high output voltage quality. It is suitable for the transmission of large amounts of electrical power over long distances, which supports the realization of the ongoing energy transition. State-of-the-art methods require a comparatively large total cell capacitance in the system for energy pulsations during operation. In the present paper, in order to minimize this total capacitance, first a new method is developed to model the system, and second, by help of this model, optimal current trajectories are calculated. These currents are used for control to reduce the energy pulsation over the complete operating range, and thus, to better utilize the hardware. The new method independent on the Clarke transformations is implemented on a laboratory scale setup, and measurement results are presented which validate the new method. Furthermore, the new method is compared to the state-of-the-art method of the compensation of the 2nd harmonic and outperforms the latter significantly. This applies to the entire operating range for different power factors. A total reduction of up to 44% of the energy pulsations is achieved
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