The Experts below are selected from a list of 22644 Experts worldwide ranked by ideXlab platform
Manel Velasco - One of the best experts on this subject based on the ideXlab platform.
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Negative-Sequence Voltage elimination for distributed generators in grid-feeding operation mode
IET Power Electronics, 2020Co-Authors: Juan M. Rey, Miguel Castilla, Jaume Miret, Manel Velasco, Pau Marti, Eduardo Mojica-navaAbstract:A major concern of the power quality in distributed systems is related to the mitigation of Voltage imbalances. This function can be implemented directly in the control system of the distributed generation power converters working simultaneously with the standard operation modes. This study presents a negative-Sequence Voltage elimination technique for distributed generators in grid-feeding operation mode. The proposal guarantees a complete elimination of the negative-Sequence Voltage, while operating without a priori in-depth knowledge of the grid configuration and its characteristics. The proposed control architecture is presented together with its pseudocode, a controller flowchart and a discussion of the implementation aspects. A closed-loop modelling is derived based on a complex transfer function approach, which is used to determine stability margins and control design guidelines. A laboratory setup was implemented to verify the performance of the proposed strategy.
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Enabling Grid-Feeding Converters With a Dissonant-Resonant Controller for Negative-Sequence Voltage Elimination
IEEE Transactions on Power Electronics, 2020Co-Authors: Manel Velasco, Juan M. Rey, Jaume Miret, Pau Marti, Antonio Camacho, Miguel CastillaAbstract:The mitigation of the adverse effects of Voltage unbalance in equipment and power quality can be performed by the power electronic converters that interface distributed generators to the grid. Inspired in a resonant controller, this article presents a dissonant-resonant controller for negative-Sequence Voltage elimination for a grid-feeding converter connected to the grid. The controller eliminates the negative-Sequence Voltage at the converter output with a regulable precision, it does not require knowing the grid impedance for successful operation, and it can be a good candidate for parallel operation because it operates not like an integrator, but like an “untuned” integrator. Using the stationary $\alpha \beta$ frame, a closed-loop model is developed in a complex space vector built from the complexification of the stationary components. This allows extracting stability conditions for safe closed-loop operation as well as deriving design guidelines for the controller parameters. Numerical and experimental results show the ability of the proposed controller to meet its design goals, thus, corroborating the theoretical approach.
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IECON - Maximizing positive Sequence Voltage support in inductive-resistive grids for distributed generation inverters during Voltage sags
IECON 2016 - 42nd Annual Conference of the IEEE Industrial Electronics Society, 2016Co-Authors: Antonio Camacho, Miguel Castilla, Jaume Miret, Pau Marti, Manel VelascoAbstract:Grid codes are continuously evolving to improve the ride-through services during Voltage sags. The main reason for this evolution is the increasing flexible capabilities of distribution generation inveters. The problem of selecting an appropriate strategy during grid faults is an open research topic that depends on many aspects. Among the possible solutions, this paper solves an optimization problem based on the maximization of the Voltage support during grid faults. The control strategy is based on raising as much as possible the positive Sequence Voltage. This strategy allows to reduce the risk of disconnection by under-Voltage that can led to a blackout. The problem is related to two main issues: the amount of injected current and the grid impedance. Regarding the injected current, it should be desirable to develop the references so as to inject the rated current of the inverter. Therefore the Voltage support could be improved while keeping the inverter within a safety operation mode. Regarding the impedance, the strategy for inductive or resistive grids should be different. For a combination of both impedances, an optimal solution should exist in order to maximize the Voltage increment. This solution is related to the amount of active and reactive current injected by the inverter. The work proposes a Voltage support control strategy intended to increase as much as possible the positive Sequence Voltage and to inject the maximum rated current of the grid-connected distributed generation inverter. The problem is mathematically solved for any type of grid impedance, even resistive, inductive or a combination of both. Simulation results are presented to corroborate the theoretical solution.
Miguel Castilla - One of the best experts on this subject based on the ideXlab platform.
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Negative-Sequence Voltage elimination for distributed generators in grid-feeding operation mode
IET Power Electronics, 2020Co-Authors: Juan M. Rey, Miguel Castilla, Jaume Miret, Manel Velasco, Pau Marti, Eduardo Mojica-navaAbstract:A major concern of the power quality in distributed systems is related to the mitigation of Voltage imbalances. This function can be implemented directly in the control system of the distributed generation power converters working simultaneously with the standard operation modes. This study presents a negative-Sequence Voltage elimination technique for distributed generators in grid-feeding operation mode. The proposal guarantees a complete elimination of the negative-Sequence Voltage, while operating without a priori in-depth knowledge of the grid configuration and its characteristics. The proposed control architecture is presented together with its pseudocode, a controller flowchart and a discussion of the implementation aspects. A closed-loop modelling is derived based on a complex transfer function approach, which is used to determine stability margins and control design guidelines. A laboratory setup was implemented to verify the performance of the proposed strategy.
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Enabling Grid-Feeding Converters With a Dissonant-Resonant Controller for Negative-Sequence Voltage Elimination
IEEE Transactions on Power Electronics, 2020Co-Authors: Manel Velasco, Juan M. Rey, Jaume Miret, Pau Marti, Antonio Camacho, Miguel CastillaAbstract:The mitigation of the adverse effects of Voltage unbalance in equipment and power quality can be performed by the power electronic converters that interface distributed generators to the grid. Inspired in a resonant controller, this article presents a dissonant-resonant controller for negative-Sequence Voltage elimination for a grid-feeding converter connected to the grid. The controller eliminates the negative-Sequence Voltage at the converter output with a regulable precision, it does not require knowing the grid impedance for successful operation, and it can be a good candidate for parallel operation because it operates not like an integrator, but like an “untuned” integrator. Using the stationary $\alpha \beta$ frame, a closed-loop model is developed in a complex space vector built from the complexification of the stationary components. This allows extracting stability conditions for safe closed-loop operation as well as deriving design guidelines for the controller parameters. Numerical and experimental results show the ability of the proposed controller to meet its design goals, thus, corroborating the theoretical approach.
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IECON - Maximizing positive Sequence Voltage support in inductive-resistive grids for distributed generation inverters during Voltage sags
IECON 2016 - 42nd Annual Conference of the IEEE Industrial Electronics Society, 2016Co-Authors: Antonio Camacho, Miguel Castilla, Jaume Miret, Pau Marti, Manel VelascoAbstract:Grid codes are continuously evolving to improve the ride-through services during Voltage sags. The main reason for this evolution is the increasing flexible capabilities of distribution generation inveters. The problem of selecting an appropriate strategy during grid faults is an open research topic that depends on many aspects. Among the possible solutions, this paper solves an optimization problem based on the maximization of the Voltage support during grid faults. The control strategy is based on raising as much as possible the positive Sequence Voltage. This strategy allows to reduce the risk of disconnection by under-Voltage that can led to a blackout. The problem is related to two main issues: the amount of injected current and the grid impedance. Regarding the injected current, it should be desirable to develop the references so as to inject the rated current of the inverter. Therefore the Voltage support could be improved while keeping the inverter within a safety operation mode. Regarding the impedance, the strategy for inductive or resistive grids should be different. For a combination of both impedances, an optimal solution should exist in order to maximize the Voltage increment. This solution is related to the amount of active and reactive current injected by the inverter. The work proposes a Voltage support control strategy intended to increase as much as possible the positive Sequence Voltage and to inject the maximum rated current of the grid-connected distributed generation inverter. The problem is mathematically solved for any type of grid impedance, even resistive, inductive or a combination of both. Simulation results are presented to corroborate the theoretical solution.
J P De Arruda - One of the best experts on this subject based on the ideXlab platform.
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a method for extracting the fundamental frequency positive Sequence Voltage vector based on simple mathematical transformations
IEEE Transactions on Industrial Electronics, 2009Co-Authors: H E P De Souza, F A S Neves, M C Cavalcanti, Fabricio Bradaschia, Gustavo M S Azevedo, J P De ArrudaAbstract:In this paper, a novel scheme for obtaining the fundamental-frequency positive-Sequence grid Voltage is proposed. The method is based on four simple mathematical transformations; two of them are in the stationary reference frame, which are able to eliminate odd harmonics from the original signals. The other two transformations are implemented in a synchronously rotating reference frame in order to eliminate even harmonics. The output of the last transformation block is the input to a synchronous reference-frame phase-locked loop for detecting the frequency and position of the positive-Sequence Voltage vector. The proposed algorithm was verified through simulations and experiments by applying distorted and unbalanced signals, containing positive and negative-Sequence components. The results are in agreement with those theoretically predicted and indicate that the proposed scheme has a great potential for use in grid-connected converter synchronization algorithms.
Josep Pou - One of the best experts on this subject based on the ideXlab platform.
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Instantaneous Zero Sequence Voltage for Grid Energy Balancing Under Unbalanced Power Generation
2019 IEEE Energy Conversion Congress and Exposition (ECCE), 2019Co-Authors: Ricardo P. Aguilera, Pablo Acuna, Christian A. Rojas, Georgios Konstantinou, Josep PouAbstract:An instantaneous zero Sequence Voltage injection method is presented in this paper. The key novelty of this method lies in the ability to provide instantaneous zero Sequence Voltage references using stationary abc-framework variables with no numerical iterations and no phase-locked loops. This paper discusses its applicability, especially in the field of large-scale photovoltaic power plants integration, where the efforts are made to achieve grid energy balancing. As an application example, the proposed method is used to find suitable zero Sequence Voltage references to extract unbalanced power from each phase in star-connected cascaded H-bridge multilevel converters. Under same conditions, the proposed method allows reactive power control, in contrast to traditional approaches that only consider unity power factor operation. Experimental results are provided to verify the effectiveness of the proposed zero Sequence Voltage injection method.
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A Carrier-Based PWM Strategy With Zero-Sequence Voltage Injection for a Three-Level Neutral-Point-Clamped Converter
IEEE Transactions on Power Electronics, 2012Co-Authors: Josep Pou, Jordi Zaragoza, Salvador Ceballos, Maryam Saeedifard, Dushan BoroyevichAbstract:Performance of a carrier-based pulsewidth modulation (CB-PWM) strategy can be improved by the inclusion of a zero-Sequence Voltage in the modulation-reference signal. This paper proposes a new CB-PWM strategy for a three-level neutral-point-clamped (NPC) converter, which is based on a zero-Sequence Voltage injection. By inclusion of the zero-Sequence Voltage, the sinusoidal-modulation reference is modified to 1) carry out the Voltage-balancing task of the dc-link capacitors, with no additional control effort, 2) reduce the switching losses, and 3) reduce the low-frequency Voltage oscillations of the neutral point. The proposed strategy is an alternative approach to the nearest three-vector (NTV) space-vector modulation (SVM) strategy and is obtained by the analysis of the NTV-SVM strategy and establishing a correlation between the NTV-SVM and the CB-PWM strategies. The salient features of the proposed scheme, as compared with the NTV-SVM strategy, are: 1) its reduced computational processing time which is attractive for digital implementation and 2) its reduced switching losses. Compared with the existing CB-PWM strategies, the proposed strategy offers 1) capability to balance the capacitor Voltages and reduce the NP Voltage oscillations and 2) reduced switching losses. Performance of the proposed CB-PWM strategy for a three-level NPC converter based on time-domain simulation studies in the MATLAB/SIMULINK environment is evaluated and also experimentally verified.
Huang Jisheng - One of the best experts on this subject based on the ideXlab platform.
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On-Line Detection of Voltage Transformer Insulation Defects Using the Low-Frequency Oscillation Amplitude and Duration of a Zero Sequence Voltage
Energies, 2019Co-Authors: Hongwen Liu, Ke Wang, Qing Yang, Huang JishengAbstract:The insulation degradation of a Voltage transformer winding is not easy to find, but it may ultimately cause the transformer to explode, leading to accidents such as phase-to-phase short circuits. At present, power transformers, lightning arresters, and other equipment have on-line methods to detect the insulation state. However, there is no mature method for the on-line monitoring of Voltage transformer winding insulation. In this study, a small current disturbance method based on a zero-Sequence loop is proposed. The characteristic parameters of the low-frequency oscillation of zero-Sequence Voltage after a disturbance are used to evaluate the insulation state of the winding and detect faults. Theoretical modeling, simulation tests, and field tests show that when the insulation resistance of the Voltage transformer winding is in the range 0–40 kΩ, a low frequency oscillation of about 10 Hz can be detected on the zero-Sequence Voltage, and its amplitude and duration are proportional to the degree of damage to the insulation. This can hence be used as a criterion for the on-line detection of Voltage transformer winding insulation defects.
