Rolan, A.; Corcoles, F.; Bogarra, S.; Monjo, L.; Pedra, J. IEEE transactions on energy conversion Vol. 31, num. 2, p. 566-577 DOI: 10.1109/TEC.2015.2504793 Data de publicació: 2015-12-01 Article en revista
This paper develops a study of reduced-order models for squirrel-cage induction generators used in the fixed-speed wind turbines. The squirrel-cage of these generators must be modeled with a double-cage for accuracy purposes. These proposed reduced-order models are valid for unbalanced grid conditions (unsymmetrical faults), which require flux and current decomposition into positive-and negative-sequences. Three reduced-order models are obtained: R2 model, where the derivative of the positive and negative-sequences of the stator fluxes are neglected (the usual approach in the literature); R1 model, where the derivative of the negative-sequence of the rotor fluxes are also neglected (proposed model); and R0 model, where all the stator and rotor fluxes are neglected (steady-state electrical model). The analytical models are validated with simulations carried out in the MATLAB and with experimental tests. The results show that R1 model (proposed model) shows a good performance (similar to the full-order model) under unbalanced conditions.
Eduardo Prieto-Araujo; Junyent-Ferré, A.; Lavemia, D.; Gomis-Bellmunt, O. IEEE transactions on energy conversion Vol. 30, num. 3, p. 1103-1112 DOI: 10.1109/TEC.2015.2412550 Data de publicació: 2015-09-01 Article en revista
This paper presents a decentralized current control approach for a nine-phase wind turbine generator. This type of generator has three different three-phase stators sharing the same machine yoke and connected to the grid by means of three different voltage source back-to-back power converters. Due to the machine configuration, magnetic couplings are present between the three stators, complicating the design and implementation of the machine current controllers. Rather than a centralized control approach, this paper proposes a methodology to design a decentralized machine control to regulate the active and reactive power flowing through each stator independently. A complete dynamic analysis is performed in order to design the controller to reduce the coupling effects within the machine, while ensuring a proper dynamic performance. The control strategy is validated through simulation and experimental results.
A new parameters determination method for squirrel-cage induction motors is presented. As a main contribution, the method uses the instantaneous electrical power and the mechanical speed measured in a free acceleration test to estimate the double-cage model parameters. The parameters are estimated from the machine impedance calculated at several points. At speed points where the double-cage effect is significant, i.e., between the zero speed point and the maximum torque point, the machine impedance is evaluated by the instantaneous power method, and at speed points where the double-cage effect is not significant, i.e., between the maximum torque point and synchronism, the machine impedance is evaluated by a dynamic-model-based linear least-square method. The proposed method has been applied to obtain the parameters of three motors tested in the laboratory. To check the method accuracy, the steady-state torque and current-slip curves predicted by the estimated parameters are successfully compared with those measured in the laboratory.
This paper presents amethod for squirrel-cage induction motor parameter estimation using a phase-to-phase standstill variable frequency test. The measured resistance and reactance at different frequencies are the data of the minimization error function to be minimized for single-and double-cage model parameters estimation. It is observed that the single-cage model is unable to fit the measured data for frequencies above several tenths of Hertz, whereas the double-cage model fits the measured data accurately in all the frequency ranges (from 0 to 150 Hz). The single-and double-cage estimated parameters are validated by comparison with data from two additional tests: 1) steady-state torque and current measurement test at different speeds; and 2) dynamic free-acceleration test. Again, the agreement between measured and predicted torque (in the first test) and current (in both tests) is satisfactory only for the double-cage model.
Medjmadj, S.; Diallo, D.; Mostefai, M.; Delpha, C.; Arias, A. IEEE transactions on energy conversion Vol. 30, num. 1, p. 349-358 DOI: 10.1109/TEC.2014.2354075 Data de publicació: 2015-03-01 Article en revista
High-frequency injection (HFI) is an alternative method to estimate permanent magnet synchronous motor (PMSM) rotor position using magnetic saliency. Once the maximum fundamental electrical frequency and the power converter switching frequency are set, the HFI voltage amplitude tuning is generally based on trial and error. This paper proposes a methodology to select the appropriate high-frequency signal injection voltage amplitude for rotor position estimation. The technique is based on an analytical model taking into account the noise in the voltage supply to derive the resulting currents containing the information on the rotor position. This model allows setting the injection voltage amplitude that leads to the maximum acceptable position error for a given signal-to-noise ratio and a speed range. The approach is validated with the analytical and the global drive models through extensive simulations. Experimental results on a 1-kW PMSM drive confirm the interest of the proposed solution.
This paper presents the development and experimental results of a supervisor strategy and a sliding mode control setup to improve the performance of hybrid generation systems. The topology in this study is conformed by a core comprising a fuel cell module and a supercapacitor module, in combination with an alternative energy source module and an electrolyzer. In particular, a wind power turbine is considered as alternative power source to attain a hybrid generation system fully relying on renewable energy. First, a supervisor strategy is proposed to manage the power flows of the subsystems and coordinate the system as a whole. Subsequently, a sliding mode control setup for combined operation of the dc/dc power converters of the fuel cell/supercapacitor core is presented to track the power references synthesized by the supervisor control. Both control levels, supervisor strategy and sliding mode controllers, are implemented and assessed through extensive experimental tests under different wind conditions and heavy-load changes.
Bianchi, F.; Ocampo-Martinez, C.A.; Kunusch, C.; Sánchez, R.S. IEEE transactions on energy conversion Vol. 30, num. 1, p. 307-315 DOI: 10.1109/TEC.2014.2351838 Data de publicació: 2015 Article en revista
The article addresses the implementation of a data-driven control strategy in a real test bench based on proton exchange membrane fuel cells (PEMFCs). The proposed control scheme is based on Unfalsified Control (UC), which allows adapting in real-time the control law by evaluating the performance specifications based only on measured input-output data. This approach is especially suitable to deal with non-linearity, model uncertainty and also possible faults that may occur in PEMFCs. The control strategy has been applied to several experimental practical situations in order to evaluate not only the system performance but also different fault scenarios. The experimental results have shown the effectiveness of the proposed approach to regulate the oxygen stoichiometry in real-time operation as well as to maintain a proper system performance under fault situations. Also, a start-up mass-flow controller is added in order to bring the system towards its normal operating conditions.
In this paper, a new method for modeling converterbased power generators in ac-distributed systems is proposed. It is
based on the concept of electrostatic synchronous machines. With this new concept, it is possible to establish a simple relationship between the dc and ac side and to study stability in both the small and large signals of the microgrid by considering a dc-link dynamic
and high variation in the power supplied. Also, for the purpose of illustration, a mathematical and electrical simulation is presented, based on MATLAB and PSCAD software. Finally, an experimental
test is performed in order to validate the new model.
A new method for determination of the steady-state
equivalent circuit parameters of wound-rotor induction motors using experimental data from starting transient measurements is presented. The algorithm data are the stator currents and voltages andmechanical speed. The algorithm uses the least-square method and motor dynamic equations in the synchronous reference frame.
Moreover, an approximation of the rotor flux that improves the accuracy of the estimation method, as well as a detailed study of errors, is included. The estimation method is applied to starting
transient measurement data of a 2 kW wound rotor induction motor, and the accuracy of the obtained parameters is verified by comparing steady-state torque- and current-slip curves calculated
with the estimated parameters and those measured in the laboratory
A new method for determination of the steady-state equivalent circuit parameters of wound-rotor induction motors using experimental data from starting transient measurements is presented. The algorithm data are the stator currents and voltages
andmechanical speed. The algorithm uses the least-square method and motor dynamic equations in the synchronous reference frame.
Moreover, an approximation of the rotor flux that improves the accuracy of the estimation method, as well as a detailed study of
errors, is included. The estimation method is applied to starting transient measurement data of a 2 kW wound rotor induction
motor, and the accuracy of the obtained parameters is verified by comparing steady-state torque- and current-slip curves calculated with the estimated parameters and those measured in the laboratory
This paper deals with the design and the experimental validation in scale-lab test benches of an energy management algorithm based on feedback control techniques for a flywheel energy storage device. The aim of the flywheel is to smooth the net power injected to the grid by a wind turbine or by a wind power plant. In particular, the objective is to compensate the power disturbances produced by the cycling torque disturbances of the wind turbines due to the airflow deviation through its tower section. This paper describes the control design, its tuning, as well as the description of the experimental setup, and the methods for the experimental validation of the proposed concepts. Results show that the fast wind power fluctuations can be mostly compensated through the flywheel support.
Ceballos, S.; Rea, J.; López, I.; Pou, J.; Robles, E.; Osullivan, D. IEEE transactions on energy conversion Vol. 28, num. 3, p. 553--564 DOI: 10.1109/TEC.2013.2265172 Data de publicació: 2013-09 Article en revista
The Wells turbine is a bidirectional air turbine which operates efficiently over a restricted range of air flow. The optimization of its efficiency requires control of rotational velocity in order to maintain the ratio between airflow and tip speed within the high efficiency range. This paper introduces two generator control strategies that optimize the power take-off efficiency for low inertia turbine systems in which instantaneous control of the turbine air flow to tip speed ratio is a realistic goal. The first control strategy requires measurement of turbine rotational speed and air chamber pressure, and the second strategy removes the requirement for air pressure measurement. The implementation issues associated with this level of control are examined and the simulation results are validated in an experimental test rig.
This paper measures and analyzes the saturation
effects on torque- and current–slip curves of three squirrel-cage induction
motors.Motor saturation is illustrated by three sets of measurements:
I) torque and current for each slip measured at three
voltage levels; II) short-circuit impedance measured at different
current levels; and III) no-load impedance measured at different
voltage levels. In test I, torque and current measured at reduced
voltage are prorated to full voltage for comparison purposes. A
double-cage model is used to model the motors, and the nonlinearity
of their reactances is examined. In order to evaluate the individual
weight of every nonlinear reactance on the observed saturated
behavior, we try to fit the measurements considering that only one
reactance of the double-cage model is nonlinear. Good agreement is
obtained only when the stator leakage reactance is considered nonlinear.
On the contrary, when magnetizing or remaining leakage
reactances are considered nonlinear, they predict machine behaviors
inconsistent with measurements. In otherwords, the saturation
of the stator leakage reactance is the main contributor to torque
and current behavior, while the saturation of the remaining reactances
has a negligible influence. Consequently, when all voltage
levels are considered, the squirrel-cage induction motors can be
accurately modeled (with reasonable accuracy) with a double-cage
modelwhere only the stator leakage reactance is considered nonlinear.
When only a constant voltage level is considered, the paper also
proves that a linear double-cage model (all reactances are linear)
accurately predicts machine behavior at such voltage level.
This paper develops and analyzes an online methodology to detect demagnetization faults in surface-mounted permanent magnet synchronous motors. The proposed methodology, which takes into account the effect of the inverter that feeds the machine, is based on monitoring the zero-sequence voltage component of the stator phase voltages. The theoretical basis of the proposed method has been established. Attributes of the method presented here include simplicity, very low computational burden, and high sensibility. Since the proposed method requires access to the neutral point of the stator windings, it is especially useful when dealing with fault tolerant systems. A simple expression of the zero-sequence voltage component is deduced, which is proposed as a fault indicator parameter. Both simulation and experimental results presented in this paper show the potential of the proposed method to provide helpful and reliable data to carry out an online diagnosis of demagnetization failures in the rotor permanent magnets.
This paper addresses a detailed design of a wind
power plant and turbine slope voltage control in the presence of
communication delays for a wide short-circuit ratio range operation.
The implemented voltage control scheme is based upon the
secondary voltage control concept, which offers fast response to
grid disturbances, despite the communication delays, i.e., this concept
is based on a primary voltage control, located in the wind turbine,
which follows an external voltage reference sent by a central
controller, called secondary voltage control, which is controlling
the voltage at the point of connection with the grid. The performance
has been tested using PSCAD/EMTDC program. The plant
layout used in the simulations is based on an installed wind power
plant, composed of 23 doubly fed generator wind turbines. The resulting
performance is evaluated using a compilation of grid code
voltage control requirements. The results show that fast response
to grid disturbances can be achieved using the secondary voltage
control scheme, and the fulfillment of the design requirements can
be extended for a wide range of short-circuit ratios.
The aim of this paper is to analyze the dynamic behavior
of the doubly fed induction generator (DFIG) subject to
symmetrical voltage sags caused by three-phase faults. A simple
control algorithm is considered and assumed ideal: the rotor current
irf in the synchronous reference frame is kept constant. This
hypothesis allows the electrical transient to be solved analytically,
providing a comprehensive description of DFIG behavior under
symmetrical sags. The fault-clearing physics of symmetrical sags is
also analyzed. That is, the fault is cleared in the successive natural
fault-current zeros, leading to a voltage recovery in one, two, or
three steps. This clearing process, called discrete fault clearing in
this paper, results in a more accurate sag modeling than the abrupt
or instantaneous fault clearing (the usual modeling in the literature).
The fault-clearing process has a strong influence on the rotor
voltage required to control the rotor current after fault clearing. To
compare the effects of both abrupt and discrete sags, different wind
turbine (WT) operating points, which determine different generated
powers, are considered. This study helps in the understanding
of WT fault ride-through capability.
An experimentally validated control-oriented model that reproduces the most typical features of a laboratory proton exchange membrane fuel cell generation system, is presented in this paper. The proposed representation is a 7th order fully analytical nonlinear model of ordinary differential equations, primarily focused on the system gases dynamics. The complete model is developed following a modular procedure, combining theoretical modeling techniques and empirical analysis based on experimental data. The presented methods can be used as a general modeling guideline for control-oriented purposes, being possible to adapt to other fuel-cell-based systems with similar characteristics.
Wind farm harmonic emissions are a well-known
power quality problem, but little data based on actual wind farm
measurements are available in literature. In this paper, harmonic
emissions of an 18MWwind farm are investigated using extensive
measurements, and the deterministic and stochastic characterization
of wind farm harmonic currents is analyzed. Specific issues
addressed in the paper include the harmonic variation with the
wind farm operating point and the random characteristics of their
magnitude and phase angle.
Castilla, M.; Miret, J.; Matas, J.; Borrell, A.; Garcia de Vicuña, J. IEEE transactions on energy conversion Vol. 25, num. 3, p. 722-731 DOI: 10.1109/TEC.2010.2052105 Data de publicació: 2010-09 Article en revista
Garcia, A.; Rosero, J.; Cusido, J.; Romeral, L.; Ortega, J.A. IEEE transactions on energy conversion Vol. 25, num. 2, p. 312-318 DOI: 10.1109/TEC.2009.2037922 Data de publicació: 2010-06 Article en revista
This paper presents a novel method to diagnose demagnetization
in permanent-magnet synchronousmotor (PMSM).
Simulations have been performed by 2-D finite-element analysis in
order to determine the current spectrum and the magnetic flux
distribution due to this failure. The diagnostic just based on motor
current signature analysis can be confused by eccentricity failure
because the harmonic content is the same. Moreover, it can
only be applied under stationary conditions. In order to overcome
these drawbacks, a novel method is used based upon the
Hilbert–Huang transform. It represents time-dependent series in a
2-D time–frequency domain by extracting instantaneous frequency
components through an empirical-mode decomposition process.
This tool is applied by running the motor under nonstationary
conditions of velocity. The experimental results show the reliability
and feasibility of the methodology in order to diagnose the demagnetization
of a PMSM.
Gomis-Bellmunt, O.; Junyent-Ferré, A.; Sumper, A.; Bergas, J. IEEE transactions on energy conversion Vol. 23, num. 4, p. 1036-1045 DOI: 10.1109/TEC.2008.2001440 Data de publicació: 2008-12 Article en revista