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Papers by pedro rodriguez

IEEE Transactions on Industrial Electronics, 2007

The increasing penetration of distributed power generation into the power system leads to a conti... more The increasing penetration of distributed power generation into the power system leads to a continuous evolution of grid interconnection requirements. In particular, active power control will play an important role both during grid faults (lowvoltage ride-through capability and controlled current injection) and in normal conditions (reserve function and frequency regulation). The aim of this paper is to propose a flexible active power control based on a fast current controller and a reconfigurable reference current selector. Several strategies to select the current reference are studied and compared using experimental results that are obtained during an unsymmetrical voltage fault. The results of the analysis allow selection of the best reference current in every condition. The proposed methods facilitate multiple choices for fault ride through by simply changing the reference selection criteria.

IEEE Transactions on Power Electronics, 2009

Abstract—This paper discusses the evaluation of different cur-rent controllers employed for grid-... more Abstract—This paper discusses the evaluation of different cur-rent controllers employed for grid-connected distributed power generation systems having variable input power, such as wind tur-bines and photovoltaic systems. The focus is mainly set on linear controllers such as ...

This paper proposes a new technique for grid synchronization under unbalanced and distorted condi... more This paper proposes a new technique for grid synchronization under unbalanced and distorted conditions, i.e., the dual second order generalised integrator - frequency-locked loop (DSOGI-FLL). This grid synchronization system results from the application of the instantaneous symmetrical components method on the stationary and orthogonal alphabeta reference frame. The second order generalized integrator concept (SOGI) is exploited to generate in-quadrature signals used on the alphabeta reference frame. The frequency-adaptive characteristic is achieved by a simple control loop, without using either phase-angles or trigonometric functions. In this paper, the development of the DSOGI-FLL is plainly exposed and hypothesis and conclusions are verified by simulation and experimental results

The distributed power generation based on renewable energy sources such as wind and sun experienc... more The distributed power generation based on renewable energy sources such as wind and sun experiences a high penetration in the power systems around the world, having in some countries a large contribution to the total energy production. In order to protect the distribution and transmission systems, the grid operators are more and more talking about the ability of the distribution systems (mainly wind turbines WT systems) to behave as a conventional power plant. This paper discusses the possibilities of the distributed power generation systems (DPGS) to deliver power when grid disturbances are present in the utility network. The focus is set more on the control strategies for active power generation, and mainly on the creation of the reference currents which fulfill the demanded output power. Considerations about reactive power are also stated. Experimental results are presented in order to validate the theory behind the proposed control strategies on faulty grid

This work aims to present a generalized vector-based formulation for calculating the grid-side cu... more This work aims to present a generalized vector-based formulation for calculating the grid-side current reference of distributed power generation systems in order to independently control active and reactive power delivered to the grid. Strategies for current reference generation were implemented on the abc stationary reference frame and their effectiveness was demonstrated experimentally, perhaps validating the theoretical analysis even under grid fault conditions

This work presents the construction of a model for a PV panel using the single-diode five-paramet... more This work presents the construction of a model for a PV panel using the single-diode five-parameters model, based exclusively on data-sheet parameters. The model takes into account the series and parallel (shunt) resistance of the panel. The equivalent circuit and the basic equations of the PV cell/panel in Standard Test Conditions (STC) 1 are shown, as well as the parameters extraction from the data-sheet values. The temperature dependence of the cell dark saturation current is expressed with an alternative formula, which gives better correlation with the datasheet values of the power temperature dependence . Based on these equations, a PV panel model, which is able to predict the panel behavior in different temperature and irradiance conditions, is built and tested.

Page 1. New Positive-sequence Voltage Detector for Grid Synchronization of Power Converters under... more Page 1. New Positive-sequence Voltage Detector for Grid Synchronization of Power Converters under Faulty Grid Conditions P. Rodríguez , R. Teodorescu , I. Candela , AV Timbus , M. Liserre and F. Blaabjerg Technical University ...

IEEE Transactions on Power Electronics, 2007

Due to the growing changes in the electrical network related to the new distributed generation sc... more Due to the growing changes in the electrical network related to the new distributed generation scheme and the integration of renewable energy sources, new requirements for grid-connected power converters are being defined in the new grid codes. The injection of positive-and negativesequence current components is becoming necessary for achieving new capabilities like the reactive power injection during a grid fault. This paper deals with a fundamental issue in this topic, i.e., the performance of the current controller. Classical dq controllers, which are extensively used in industrial applications, degrade its performance when both sequences are involved, as unavoidable oscillations in the dq axes appear. In this paper, a new scheme for controlling positive-and negative-sequence currents using dq controllers is proposed, based on an enhanced Double Synchronous Reference Frame (DSRF) controller. In this paper the DSRF controller is improved by adding a decoupling network which counteracts the oscillations caused by the presence of both sequences. Experimental results will demonstrate the validity of the proposed Decoupled DSRF (DDSRF) controller.

This paper deals with one of the most important issues in the control of grid-connected converter... more This paper deals with one of the most important issues in the control of grid-connected converters, which is the detection of the positive sequence fundamental component of the utility voltage. The study carried out in this paper conducts to a fast, precise, and robust positive sequence voltage detector offering a good behavior, even if unbalanced and distorted conditions are present

This paper presents a positive sequence voltage detector based on a new "synchronous double refer... more This paper presents a positive sequence voltage detector based on a new "synchronous double reference frame PLL" (SDRF-PLL). This PLL exhibits a fast, precise and robust behavior under unbalanced utility conditions. When amplitude and phase of the positive sequence source voltage are known, various compensation strategies are feasible for the control of the unified power quality conditioner. Four suitable control strategies are shown. The performance of the proposed SDRF-PLL is verified by means of its application in the control of a unified power quality conditioner. In this paper, an analytical study and a verification by simulation are conducted.

IEEE Transactions on Industrial Electronics, 2007

The increasing penetration of distributed power generation into the power system leads to a conti... more The increasing penetration of distributed power generation into the power system leads to a continuous evolution of grid interconnection requirements. In particular, active power control will play an important role both during grid faults (lowvoltage ride-through capability and controlled current injection) and in normal conditions (reserve function and frequency regulation). The aim of this paper is to propose a flexible active power control based on a fast current controller and a reconfigurable reference current selector. Several strategies to select the current reference are studied and compared using experimental results that are obtained during an unsymmetrical voltage fault. The results of the analysis allow selection of the best reference current in every condition. The proposed methods facilitate multiple choices for fault ride through by simply changing the reference selection criteria.

IEEE Transactions on Power Electronics, 2009

Abstract—This paper discusses the evaluation of different cur-rent controllers employed for grid-... more Abstract—This paper discusses the evaluation of different cur-rent controllers employed for grid-connected distributed power generation systems having variable input power, such as wind tur-bines and photovoltaic systems. The focus is mainly set on linear controllers such as ...

This paper proposes a new technique for grid synchronization under unbalanced and distorted condi... more This paper proposes a new technique for grid synchronization under unbalanced and distorted conditions, i.e., the dual second order generalised integrator - frequency-locked loop (DSOGI-FLL). This grid synchronization system results from the application of the instantaneous symmetrical components method on the stationary and orthogonal alphabeta reference frame. The second order generalized integrator concept (SOGI) is exploited to generate in-quadrature signals used on the alphabeta reference frame. The frequency-adaptive characteristic is achieved by a simple control loop, without using either phase-angles or trigonometric functions. In this paper, the development of the DSOGI-FLL is plainly exposed and hypothesis and conclusions are verified by simulation and experimental results

The distributed power generation based on renewable energy sources such as wind and sun experienc... more The distributed power generation based on renewable energy sources such as wind and sun experiences a high penetration in the power systems around the world, having in some countries a large contribution to the total energy production. In order to protect the distribution and transmission systems, the grid operators are more and more talking about the ability of the distribution systems (mainly wind turbines WT systems) to behave as a conventional power plant. This paper discusses the possibilities of the distributed power generation systems (DPGS) to deliver power when grid disturbances are present in the utility network. The focus is set more on the control strategies for active power generation, and mainly on the creation of the reference currents which fulfill the demanded output power. Considerations about reactive power are also stated. Experimental results are presented in order to validate the theory behind the proposed control strategies on faulty grid

This work aims to present a generalized vector-based formulation for calculating the grid-side cu... more This work aims to present a generalized vector-based formulation for calculating the grid-side current reference of distributed power generation systems in order to independently control active and reactive power delivered to the grid. Strategies for current reference generation were implemented on the abc stationary reference frame and their effectiveness was demonstrated experimentally, perhaps validating the theoretical analysis even under grid fault conditions

This work presents the construction of a model for a PV panel using the single-diode five-paramet... more This work presents the construction of a model for a PV panel using the single-diode five-parameters model, based exclusively on data-sheet parameters. The model takes into account the series and parallel (shunt) resistance of the panel. The equivalent circuit and the basic equations of the PV cell/panel in Standard Test Conditions (STC) 1 are shown, as well as the parameters extraction from the data-sheet values. The temperature dependence of the cell dark saturation current is expressed with an alternative formula, which gives better correlation with the datasheet values of the power temperature dependence . Based on these equations, a PV panel model, which is able to predict the panel behavior in different temperature and irradiance conditions, is built and tested.

Page 1. New Positive-sequence Voltage Detector for Grid Synchronization of Power Converters under... more Page 1. New Positive-sequence Voltage Detector for Grid Synchronization of Power Converters under Faulty Grid Conditions P. Rodríguez , R. Teodorescu , I. Candela , AV Timbus , M. Liserre and F. Blaabjerg Technical University ...

IEEE Transactions on Power Electronics, 2007

Due to the growing changes in the electrical network related to the new distributed generation sc... more Due to the growing changes in the electrical network related to the new distributed generation scheme and the integration of renewable energy sources, new requirements for grid-connected power converters are being defined in the new grid codes. The injection of positive-and negativesequence current components is becoming necessary for achieving new capabilities like the reactive power injection during a grid fault. This paper deals with a fundamental issue in this topic, i.e., the performance of the current controller. Classical dq controllers, which are extensively used in industrial applications, degrade its performance when both sequences are involved, as unavoidable oscillations in the dq axes appear. In this paper, a new scheme for controlling positive-and negative-sequence currents using dq controllers is proposed, based on an enhanced Double Synchronous Reference Frame (DSRF) controller. In this paper the DSRF controller is improved by adding a decoupling network which counteracts the oscillations caused by the presence of both sequences. Experimental results will demonstrate the validity of the proposed Decoupled DSRF (DDSRF) controller.

This paper deals with one of the most important issues in the control of grid-connected converter... more This paper deals with one of the most important issues in the control of grid-connected converters, which is the detection of the positive sequence fundamental component of the utility voltage. The study carried out in this paper conducts to a fast, precise, and robust positive sequence voltage detector offering a good behavior, even if unbalanced and distorted conditions are present

This paper presents a positive sequence voltage detector based on a new "synchronous double refer... more This paper presents a positive sequence voltage detector based on a new "synchronous double reference frame PLL" (SDRF-PLL). This PLL exhibits a fast, precise and robust behavior under unbalanced utility conditions. When amplitude and phase of the positive sequence source voltage are known, various compensation strategies are feasible for the control of the unified power quality conditioner. Four suitable control strategies are shown. The performance of the proposed SDRF-PLL is verified by means of its application in the control of a unified power quality conditioner. In this paper, an analytical study and a verification by simulation are conducted.