This work presents a control strategy of a dynamic voltage restorer (DVR) to improve the stability in wind farms based on squirrel-cage induction generators. The DVR controller is tailored to work ...under unbalanced conditions, which allows overcoming most faults in the power grid. The proposed strategy is capable of balancing voltages at wind farm terminals obtaining several advantages. Firstly, negative-sequence currents are eliminated; thus, overheating, loss of performance, and decreasing of generator useful life are avoided. Secondly, by nullifying negative-sequence voltages, 2ω pulsation in the mechanical torque is prevented, reducing high stress in the turbine mechanical system, especially in the gearbox. The proposed control strategy for the DVR is compatible with farms which already have installed a static VAR compensator. Several scenarios and disturbances, carefully chosen to provide a realistic assessment, have been tested showing the adequacy of the proposed arrangement and controllers.
Owing to the competitive advantages of cost reduction, system downsizing, and reliability enhancement, position sensorless control methods for permanent magnet synchronous machine drives have drawn ...increasing attention from academia to industrial applications. In this article, a survey of the major sensorless control techniques for a wide speed range from low to high speeds is presented. The different high frequency signal injection schemes, fundamental pulsewidth modulation excitation methods, and model-based sensorless control are displayed and compared, which is able to facilitate the sensorless control implementation.
Multilevel current-source inverters have proved to be a high-performance option for industrial applications due to reliability, fault-tolerant capabilities, quasi soft switching, and the use of lower ...filter capacitor values. One of its major challenges is to balance the internal currents that feed each module. Imbalances could be caused by manufacturing deviations of the reactive components, temperature drift or aging, nonlinear loads, and modulation errors, among others. Using the well-known phase-shift carrier sinusoidal pulse width modulation, a slight change in the amplitude of the carrier signals produces a variation in the average value of the internal currents. In this paper, we introduce a control strategy to balance the current of the inductors and its implementation in a prototype. Simulation and experimental results at different operating conditions show a robust behavior of the control system along with a low distortion in the output voltages and currents of the converter.
A medium voltage power interface for a variable speed Wind Turbine is presented in this paper. The converter topology consists on the Back-to-Back connection of two medium voltage Diode Clamped ...Multilevel Inverters (
DCMI) in the full power path. This mitigates traditional tradeoffs around the low voltage connection between the generator and the grid on the megawatt range. Also, this configuration allows for higher control versatility for grid codes compliance. The converter controllers are based on a Finite-States Model Predictive Control approach, leading to fast dynamic response and
DC bus voltage equalization. The control scheme can be used with converters of an arbitrary number of levels with reduced computational effort. This is based on necessary switching restrictions which allow the reliable operation of converter legs. The performance of the control scheme is evaluated through computer simulations.
► Multilevel Converters in Wind Energy Conversion Systems. ► The back to back converter topology enhances grid codes compliance. ► Multilevel converters allows for transformerless connection to the grid and present low current distortion. ► The conversion system addresses high power wind turbine design tradeoffs.
A transformer less Shunt Active Power Filter (SAPF) for medium voltage distribution networks based on Multilevel Diode Clamped Inverter is presented in this paper. Converter current control is based ...on a Model Predictive strategy, which gives very fast current response. Also, the algorithm includes voltage balancing capability which is essential for proper converter operation. The presented current control algorithm is naturally applicable to converters with an arbitrary number of levels with reduced computational effort by virtue of the incorporation of switching restrictions which are necessary for reliable converter operation. The performance of the proposed algorithm is evaluated by means of computer simulations.
Multilevel Current-Source Inverter With FPGA Control Aguirre, M. P.; Calvino, L.; Valla, M. I.
IEEE transactions on industrial electronics (1982),
2013-Jan., 2013-01-00, 20130101, Letnik:
60, Številka:
1
Journal Article
Recenzirano
In this paper, a multilevel current-source inverter (MCSI) topology is analyzed. The issue of constructing a novel modular single-rating inductor MCSI is explored, taking advantage of the features of ...field-programmable gate arrays (FPGA) for control and gate signal generation. The proposed topology is built with identical modules where all inductors carry the same amount of current, simplifying the construction and operation of industrial applications with higher efficiency. A new state-machine approach, which is easy to implement in an FPGA, and a proper implementation of the phase-shifted carrier sinusoidal pulse width modulation (PSC-SPWM) allow both current balance in all modules and effective switching-frequency minimization. The performance of the MSCI proposed is simulated with Matlab and is verified by constructing a prototype.
The problem of reactive power and harmonics in the medium voltage level of a power distribution system is considered in this paper. Reconfiguration of the power delivery network imposes new ...constraints in a distribution substation so that the reactive compensation should be increased. The alternative of a shunt hybrid active filter connected to the 13.8-kV level to enhance the power quality is analyzed in this paper. This proposal uses the existing capacitor bank to build a hybrid filter in which the complementary compensation is performed by the active filter. The performance of the hybrid filter is evaluated with extensive simulations considering reactive power, harmonics, and unbalance compensation. It shows very good behavior in steady-state and transient conditions.
This paper deals with the problem of reactive power and harmonics in a standard medium-voltage (MV) distribution network. It proposes a simple and inexpensive solution to enhance power quality when a ...particular connection to the high-voltage transmission network is required. It presents the design of a hybrid active filter topology connected to the MV level of a power distribution system. Its main task is to regulate a 132-kV voltage level. Reconfiguration of the power delivery network imposes new constraints in a distribution substation so that the reactive compensation should be increased. The topology of a shunt hybrid active filter is analyzed. It is built with the series connection of a passive filter and a low-rated active filter. The proposed filter is directly connected to a 13.8-kV level with no need of a step-down transformer. The possibility of different levels of reactive power compensation is implemented. The proposal shows very good performance for different load demands.
In this paper, a model-based strategy for stator-interturn short-circuit detection on induction motors is presented. The proposed strategy is based on the generation of a vector of specific residual ...using a state observer. The vectorial residual is generated from a decomposition of the current estimation error. This allows for a fast detection of incipient faults, independently of the phase in which the fault occurs. Since the observer includes an adaptive scheme for rotor-speed estimation, the proposed scheme can be implemented for online monitoring, by measuring only stator voltages and currents. It is shown that the proposed strategy presents very low sensitivity to load variations and power-supply perturbations. Experimental results are included to show the ability of the proposed strategy for detecting incipient faults, including a low number of short-circuited turns and low fault current.
A sensorless control strategy for a doubly fed (wound rotor) induction machine working in variable-speed stand-alone power systems without using mechanical sensors is presented in this paper. Stator ...voltage magnitude and frequency are regulated using two field-oriented control loops. A Luenberger observer is used to estimate the stator flux, while an adaptive scheme modifies the rotor position required in the stator flux estimation. Stator voltage magnitude and frequency control loops behave very well for steady state as well as for transient states like startup, speed variations, or electric load changes. Experimental results are presented to validate this proposal.
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