Adaptive slope voltage control for distributed generation inverters with improved transient performance

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Reactive power injection in distributed generation inverters is an useful ancillary service for grid supporting purposes. For grid-feeding converters, the slope control method is the most common voltage regulation strategy used in local (communication-less) applications. Despite its simplicity, this method offers limited dynamic properties in scenarios with changing operation conditions. In this sense, this paper presents an adaptive slope voltage control which provides an improved transient performance against operating variations. To derive the control configuration, a control-oriented mathematical model is developed. The accuracy of the modeling and the performance of the proposed control are validated by selected experimental results.Peer ReviewedPostprint (author's final draft

Profiling wine tourists: a comparison between rural and city Wine Festivals in Campania, Italy.

Wine tourism (oenotourism) is becoming progressively important for wine producers and it is beginning to contribute billions of dollars annually to the global economy. Wine tourism is thus growing in relevance in the international scenario and it is considered to be at least one of the most important emerging segments of the global tourism sector. This opens a series of questions related to a better understanding of its tourism demand. The close connection between a knowledge of wine tourists’ profiles and the role of a wine festival are the strategic factors examined in this study. The research was based 220 interviews conducted with wine tourists attending the most representative rural and city wine festivals held in the Italian region of Campania (Avellino–Salerno). The aim of the paper was to perform a comparative analysis of the wine tourists’ profiles in relation to the different kind of events attended, in order to stimulate a fitted customer-driven strategy addressed to wine tourism stakeholders and to thus promote sustainability in this important sector

Voltage support experimental analysis of a low-voltage ride-through strategy applied to grid-connected distributed inverters

In recent decades, different control strategies have been designed for the increasing integration of distributed generation systems. These systems, most of them based on renewable energies, use electronic converters to exchange power with the grid. Capabilities such as low-voltage ride-through and reactive current injection have been experimentally explored and reported in many research papers with a single inverter; however, these capabilities have not been examined in depth in a scenario with multiple inverters connected to the grid. Only few simulation works that include certain methods of reactive power control to solve overvoltage issues in low voltage grids can be found in the literature. Therefore, the overall objective of the work presented in this paper is to provide an experimental analysis of a low-voltage ride-through strategy applied to distributed power generation systems to help support the grid during voltage sags. The amount of reactive power will depend on the capability of each inverter and the amount of generated active power. The obtained experimental results demonstrate that, depending on the configuration of distributed generation, diverse inverters could have different control strategies. In the same way, the discussion of these results shows that the present object of study is of great interest for future research.Peer ReviewedPostprint (published version

Model-based active damping control for three-phase voltage source inverters with LCL filter

(c) 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.This paper presents a robust model-based active damping control in natural frame for a three-phase voltage source inverter with LCL filter. The presence of the LCL filter complicates the design of the control scheme, particularly when system parameters deviations are considered. The proposed control method is addressed to overcome such difficulties and uses a modified converter model in an state observer. In this proposal, the converter model is modified by introducing a virtual damping resistor. Then, a Kalman filter makes use of this model to estimate the system state-space variables. Although the state estimates do not obviously match the real world system variables, they permit designing three current sliding-mode controllers that provide the following features to the closed loop system: a) robust ande active damping capability like in the case of using a physical damping resistor, b) robustness because the control specifications are met independently of variation in the system parameters, c) noise immunity due to the application of the Kalman filter, and d) power loss minimization because the system losses caused by the physical damping resistor are avoided. An interesting side effect of the proposed control scheme is that the sliding surfaces for each controller are independent. This decoupling property for the three controllers allows using a fixed switching frequency algorithm that ensures perfect current control. To complete the control scheme, a theoretical stability analysis is developed. Finally, selected experimental results validate the proposed control strategy and permit illustrating all its appealing features.Peer ReviewedPostprint (author's final draft

Optimal voltage-support control for distributed generation inverters in RL grid-faulty networks

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.During grid faults, the stability and reliability of the network are compromised, and the risk of a widespread disconnection of distributed generation power facilities is increased. Distributed generation inverters must support the power system to prevent this issue. Voltage support depends substantially on the currents injected into the grid and the equivalent grid impedance. This paper considers these two aspects and proposes an optimal voltage-support strategy in RL grids. The control algorithm guarantees a safe operation of the inverter during voltage sags by calculating the appropriate reference currents according to the equivalent impedance and the voltage sag characteristics, avoiding active power oscillations, and limiting the injected current to the maximum allowed by the inverter. Consequently, the grid can be better supported since the voltage at the point of common coupling is improved and the voltage support objectives are achieved. The proposed control strategy is validated through experimental tests in different grid scenarios. Throughout the work, it is assumed that the grid impedance is known, but the proposed solution requires calculating the grid impedance angle.Peer ReviewedPostprint (author's final draft

Control strategy for grid-connected three-phase inverters during voltage sags to meet grid codes and to maximize power delivery capability

Inverter-based distributed generation plays a vital role in the stability and reliability of new power systems. Under voltage sags, these systems must remain connected to the electrical network according to the stringent requirements of grid codes. Low-voltage ride-through control strategies are becoming a common trend in power electronics research. However, previous studies of these control strategies have not dealt with the different possible scenarios presented by new grid codes, and many of them focus on a very limited number of control objectives. In this study, an algorithm to maximize the converter capabilities was developed and subjected to experimental tests during different voltage sags. In this research, based on unbalanced voltage drops of several severity levels, six different cases of current injection are identified while taking into consideration the restrictions imposed by grid codes. The research results represent a further step towards the development of flexible controllers adaptable to the environments of intelligent electricity grids with high integration of distributed generation.Peer ReviewedPostprint (published version

Control scheme for a multiple-output DC/DC current source parallel resonant converter

© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The aim of this paper is to regulate the output voltages of a multiple-output DC/DC class-D current source parallel resonant converter. To this end, a sliding mode control scheme is presented consisting of an outer voltage loop, an inner current loop and a robust modulator. To devise this control scheme, the averaged large signal model of the converter is derived. In addition, this model is used to determine the stability range of the controller parameters. Some simulation results are provided to validate the expected features of the presented control configuration.Peer ReviewedPostprint (author's final draft

Control scheme for a multiple-output DC/DC current source parallel resonant converter

© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The aim of this paper is to regulate the output voltages of a multiple-output DC/DC class-D current source parallel resonant converter. To this end, a sliding mode control scheme is presented consisting of an outer voltage loop, an inner current loop and a robust modulator. To devise this control scheme, the averaged large signal model of the converter is derived. In addition, this model is used to determine the stability range of the controller parameters. Some simulation results are provided to validate the expected features of the presented control configuration.Peer Reviewe

Adaptive slope voltage control for distributed generation inverters with improved transient performance

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Reactive power injection in distributed generation inverters is an useful ancillary service for grid supporting purposes. For grid-feeding converters, the slope control method is the most common voltage regulation strategy used in local (communication-less) applications. Despite its simplicity, this method offers limited dynamic properties in scenarios with changing operation conditions. In this sense, this paper presents an adaptive slope voltage control which provides an improved transient performance against operating variations. To derive the control configuration, a control-oriented mathematical model is developed. The accuracy of the modeling and the performance of the proposed control are validated by selected experimental results.Peer Reviewe

Conscious sedation in termination of pregnancy Report of the Department of Health Expert Group

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