Nancy Visairo

Robust sigma–delta generalised proportional integral observer based control of a ‘buck’ converter with uncertain loads

This article describes the design of an observer based robust linear output feedback controller for the regulation and output reference trajectory tracking tasks in switched ‘buck’ converter circuits feeding a completely unknown time-varying load. The state-dependent perturbation effects of the unknown load resistance are on-line estimated by means of a generalised proportional integral (GPI) observer, which represents the dual counterpart of GPI controllers introduced in Fliess, Márquez, Delaleau and Sira-Ramírez (Fliess, M., Márquez, R., Delaleau, E., and Sira-Ramírez, H. (2002), ‘Correcteurs Proportionnels-intégraux Géneralisés’, ESAIM: Control, Optimisation and Calculus of Variations, 7, 23–41). The reconstructed perturbation complements the controller in a cancellation effort which allows the core of the feedback controller to become a traditional proportional derivative (PD) controller. The designed average feedback controller is then implemented via a sigma–delta-modulator, which effectively translates the designed continuous average feedback control input signal into a discrete valued switched input signal driving the converters input switch and preserving all relevant features of the average design. The Appendix collects some generalities about GPI observers.

A Robust Nonlinear Control Scheme for a Sag Compensator Active Multilevel Rectifier Without Sag Detection Algorithm

In this paper, a robust nonlinear control scheme is proposed for the single-phase active multilevel rectifier (SPAMR) subject to voltage input sags. The scheme is based on the input-output model of the rectifier system combined with exact linearization achieved via generalized proportional-integral (GPI) control. The GPI controller provides enhanced robustness for the SPAMR against unexpected voltage sags and load changes. The main contribution of this paper resides on avoiding the need for voltage sags detection algorithms while improving the dynamic response of the SPAMR. Simulation and experimental results obtained on a 1-kVA SPAMR laboratory prototype are presented.

Harmonic compensation in the AC mains by the use of current and voltage active filters controlled by a passivity-based law

Power active filters have proven to be a good alternative in providing the harmonic current-content demanded by a load aimed to preserve a good quality in the AC mains supply. Two topologies for the active current and voltage filters have been chosen in this paper. A development of nonlinear controllers based on the passivity technique applied to parallel and serial type power active filters is presented. The passivity-based technique allows a better filter performance as its physical characteristics are considered. This research work presents the corresponding nonlinear models in state-space form for the parallel (current) and series (voltage) active power filters and an analysis about the corresponding stability is presented. Some simulation and experimental results are also presented to validate the effect of the passivity-based control on the filter performance.

Avoiding a Voltage Sag Detection Stage for a Single-Phase Multilevel Rectifier by Using Control Theory Considering Physical Limitations of the System

The use of control theory in power electronics applications is aimed toward several objectives, which include, obtaining a good dynamic response, stabilizing in an operation point, regulation of state variable, reference tracking, rejecting of disturbances and robustness against parametric variations. It is also possible to eliminate stages that represent computational effort via control theory without loss of the main desirable characteristics. However, it should be considered the physical limitations of the topology given that even with sophisticated controllers they cannot achieve the established objectives if these limitations are exceeded. This paper aims at highlighting the importance of physical limitations of a single-phase multilevel rectifier (SPMR) using a nonlinear controller, an aspect not considered in previous works published by the authors. Thus, the design here presented is based on input–output linearization via feedback combined with a generalized PI controller. These controllers are used because they allow avoiding a voltage sag detection stage without changing the main characteristics of the topology. The procedure to reproduce these results is shown and the feasibility of the method is demonstrated by simulation and experimental results in a 1 kVA SPMR prototype.

Linear operating region of a single- phase BTB converter to bidirectional power transfer

Single phase back to back (SPBTB) converter is widely used for power transfer in order to increase the performance of electrical power systems; however to take advantage of a SPBTB response it is necessary to avoid over-modulation conditions. This paper deals with an analytical procedure to obtain a SPBTB operating region to guarantee power transfer of each one of the converters of a SPBTB without over-modulation. On the other hand, it is required to know the capacity of the energy store element; in this work, considering a dc link voltage ripple, a capacitor value is calculated in order to allow the adequate power management. Graphics simulations and experimental results are presented to demonstrate the analysis validity.

Feasibility assessment of the installation of a photovoltaic system as a battery charging center in a mexican mining company

This paper presents a study of feasibility assessment of the installation of a photovoltaic system to supply energy to the external lighting of a private mining company, located in Cerro de San Pedro, San Luis Potosí, Mexico. The photovoltaic system will charge batteries during the day, and then these batteries will be used to provide the electricity to the external lighting over the night. This scheme aims to replace the utilization of diesel generators used in conjunction with the lightning system. For completeness of this work, the economical study including the payback time is reported.

Single-phase analysis of BTB converter under unbalanced voltage conditions

This paper studies the performance of the Back to Back converter to control the power flow between two interconnected AC systems under unbalance grid voltage and voltage sag conditions. The first one system is considered the electrical grid, and the second one a Double Feed Induction Generator. To maintain the power transference under these disturbances a control-block diagram based on a decupled control strategy is proposed. The control strategy is performed using the single-phase dq transformation. In the study, the behavior of the BTB converter in the linear region, as well as the analysis of the DC link stage and the active/reactive power flow are presented. The operation of the controlled BTB converter is evaluated through simulations by using a 3KVA prototype. Results show the control-block diagram proposed is a suitable option to maintain the power transference under unbalance grid voltage and voltage sag conditions.

Wind resource assessment in the surroundings of San Luis Potosi, Mexico

The use of alternative sources of energy addresses a series of steps to be undertaken in order to maximize its commercial exploit. This requires a set of guidelines to determine the best way in which these sources can be evaluated. This contribution focuses on the principles of wind resource assessment and the application of them for the wind energy evaluation in the surroundings of the San Luis Potosi city.

Input - output linearization control for a three - phase AC/DC/AC voltage source converter for bidirectional power flow

In this paper the bidirectional power capability of a three-phase AC/DC/AC voltage-source converter is studied; based on the input-output linearization control theory, which is applied to the inner current loops that are connected in cascade with the outer loops. Both loops (inner and outer) allow a suitable control of the power flow. The controlled system is linearized and decoupled; based on the dq mathematical model the current control and the state feedback law is obtained. The control strategy allows the AC/DC/AC converter to increase its flexibility to process power by decoupling the active and reactive components in the full operating range. An integral control to robust the system and eliminate the tracking error is added. The proportional-integral controller of the inner loops offers global tracking of the system in real practices. By simulation and experimental results the proposed control approach is validated.

Analysis of the Boundaries to Compensate Voltage Sag Events Using a Single Phase Multi-Level Rectifier

Summary In this paper, it is established analytically the operation boundaries of the Single Phase Multi-Level Rectifier with voltage sag ride through capability (SPMLR with extended function). The analysis is based on its mathematical model and the switches power losses equations. These limits have been defined in terms of duty cycle, maximum current and power losses of the switches when voltage sag occurs. This information is very useful for converter design and for control purposes since safe operation and boundaries to compensate voltage sag are analytically known. To validate this analysis, simulation and experimental results are shown in a 1 kVA prototype.