Juan Ramón Rodriguez-Rodrıguez

A Novel Compensation Scheme Based on a Virtual Air Gap Variable Reactor for AC Voltage Control

Voltage control based on reactive power compensation is a fundamental aspect of the operation of ac electric power systems. This paper presents a novel shunt compensation scheme based on a virtual air gap variable reactor. The scheme is fully developed, from the adaptation of the virtual air gap principle to high-voltage applications and the determination of its expected performance, to the proposal of a digital cascade control using internal model and proportional-integral controllers. The suitability and flexibility of the device, and the voltage control and reactive power compensation scheme are verified by means of laboratory tests performed in a small-scale prototype. Measured results show that the proposed device and its control provide a robust load compensation scheme for ac systems.

A New Methodology for Tracking and Instantaneous Characterization of Voltage Variations

Accurate and fast characterization of voltage variations helps to evaluate their severity on equipment and activate protections. In this paper, a methodology for tracking and characterization of voltage variations, sample to sample, is presented. It consists of a Hilbert transform to estimate the voltage of the signals envelope, a fuzzy logic system to track down the type of voltage variation, and a rule-based method for the final identification and decision making according to IEEE Std 1159-2009. Unlike some techniques presented in the literature for tracking voltage variations such as the Kalman filter and adaptive linear network techniques, the proposed methodology requires neither a harmonic model nor an algorithm to adjust the model parameters, which in many cases increases the computational burden and time tracking. It is worth mentioning that the proposed classification stage does not need a training stage; therefore, its development is easier and its efficiency does not depend on a data training set. The performance of the proposed methodology is validated and tested using synthetic signals as well as real measurements of voltage variations. In addition, an implementation of our methodology into an field-programmable gate array based system is performed in an effort to offer a low-cost and portable system-on-a-chip solution for online and real-time monitoring of voltage variations.

A transformerless, single DC-input, DC-AC 7-levels boost converter for PV applications

This paper introduces a new transformerless multilevel topology for PV arrays systems. The 7-levels structure ensembles the best characteristics of three basic topologies to obtain a step-up DC-AC converter with only a single DC input and nine power switches. The advantages of the proposed structure are a higher power density, lower harmonic distortion and higher efficiency as no transformer is needed for the grid interconnection. The topology does not require a control scheme for balancing the capacitors voltage. The cases of study clearly show the capabilities of the combination, in cascade, of a DC-DC multilevel boost converter, a DCDC multilevel buck converter and an H-bridge.

Reactive power compensation in distributed networks with wind turbine integration using resonant corrector

In this paper, the control of a Distribution Static Synchronous Compensator (DSTATCOM) based on Resonant Corrector (RC) is proposed, for the reactive power compensation of a distribution network with wind turbine (WT) integration. The sinusoidal system transformation to the dq0 reference frame is usually made, in order to model Proportional + Integral (PI) controllers. However, these controllers are unable to completely remove voltage unbalance transients during the power interchange between the distribution network and the WT. The use of a Resonant Corrector (RC) for compensating voltage disturbances allows developing the control in the abc reference frame; thus, it is not necessary the use of a Phase Lock Loop (PLL) and the system with the minimum of components is managed, generating a sensorless control, working reliably in steady state and under unbalanced transient operation conditions. The distribution network through MATLAB & Simulink® is simulated.