A Single Nonlinear Current Control for PWM Rectifier Robust to Input Disturbances and Dynamic Loads

The requirements of PWM rectifiers for delivering power to motor drives include power factor correction and output voltage regulation even when strong variations such as voltage sags and dynamic load transients occur simultaneously. To achieve these objectives, the classic approach is to use a two-loop controller with its d-q model. In this paper, the authors propose a simplified approach to address that problem by using a feedback linearization-based nonlinear controller using only a single-loop current control and avoiding d-q modeling to reduce processing stages. To demonstrate the feasibility of this approach, several simulations are presented considering a 1.5 kW PWM rectifier

Detección y localización de fugas en un ducto

Tesis de Doctorad

Bifurcation Stability Analysis of the Synchronverter in a Microgrid

Synchronized converters are being studied as a viable alternative to address the transition from synchronous generation to power-electronics-based generation systems. One of the important features that make the synchronous generator an unrivaled alternative for power generation is its stability properties and inherent inertial response. This work presents a stability analysis of a synchronverter-based system conducted through the bifurcation theory to expose its stability regions in a grid-connected configuration with an aggregate load model conformed by a ZIP model and an induction motor model. One and two-parameter bifurcation diagrams on the gain, load, and Thévenin equivalent plane are computed and analyzed. All the results confirm the strong stability properties of the syncronverter. Some relevant findings are that the reduction in a droop gain or time constant results in Hopf bifurcations and inertia reduction, but the increase in the time constant leads to decoupling between the reactive and active power loops. It is also found that the increment of a specific time constant (τf>0.02 s) increases the stability region on the droop gains plane to all positive values. It is also found that a low lagging power factor reduces the feasible operating and stable operating regions. For a lagging power factor above 0.755, subcritical Hopf bifurcation disappears, and also, the feasible operating solution overlaps the stability region. Finally, it is also found how the Thévenin equivalent affects the stability and that the stability boundary is delimited by Hopf bifurcations. The bifurcation diagrams are numerically computed using XPP Auto software

A Comprehensive Modeling of a Three-Phase Voltage Source PWM Converter

This contribution reports the development of a time domain model of a three-phase voltage source converter (VSC) that can be used in the transient and steady state analysis of nonlinear power systems including their associated closed-loop control schemes. With this proposed model, the original discontinuous nonlinear power system can be transformed into a continuous system, while keeping the underlying harmonic nature of the VSC and avoiding typical and undesirable numerical problems associated with the large derivatives during the switching transitions. The development of this model was based on the dynamic Fourier series of the switching functions under a sinusoidal PWM modulation scheme, which require the calculation of the switching instants at each integration step; the switching instants and the dynamic Fourier series coefficients are calculated by explicit mathematical formulas. The proposed model of the VSC is suitable for the fast computation of the periodic steady state solution through the application of Newton method. Simulations were carried out in order to illustrate the benefits of the proposed VSC model