Julio Cesar Rosas-Caro

Output feedback control of a mechanical system using magnetic levitation.

This paper presents an application of a nonlinear magnetic levitation system to the problem of efficient active control of mass-spring-damper mechanical systems. An output feedback control scheme is proposed for reference position trajectory tracking tasks on the flexible mechanical system. The electromagnetically actuated system is shown to be a differentially flat nonlinear system. An extended state estimation approach is also proposed to obtain estimates of velocity, acceleration and disturbance signals. The differential flatness structural property of the system is then employed for the synthesis of the controller and the signal estimation approach presented in this work. Some experimental and simulation results are included to show the efficient performance of the control approach and the effective estimation of the unknown signals.

Modeling and control of an interleaved DC-DC multilevel boost converter

In this paper we study the modeling and control of an interleaved DC-DC multilevel topology that exhibits a high-voltage gain and a minimum ripple point design. In this configuration, the current ripple cancelation point can be arbitrarily defined according to a desired specification, which represents an advantage with respect to classical topologies whose minimum ripple point is constrained (e.g. by a duty cycle equal to 0.5). We present a generalized model for the converter that is valid for any number of levels and useful for control purposes. Experimental results of the ripple cancelation as well as a closed-loop implementation is presented.

Storage and Dissipation Limits in Resonant Switched-Capacitor Converters

The purpose of this manuscript is twofold, first we introduce an energy-based modeling framework for the analysis of resonant switched-capacitor (SC) converters and second we demonstrate that energy storage and dissipation in resonant SC with ideal switches are bounded by a fundamental physical limit that, up until now, has been only associated with the special case of pure SC topologies. For instance, we show that the maximum energy stored in the small size inductors in resonant SC converters is equal to the energy that would be dissipated by their purely SC counterpart. The presented analysis permits the computation of resonant inductances in terms of maximum current peak values, which is experimentally validated. Furthermore, we introduce a relative loss factor that permits determining the efficiency of a design for a general case in the presence of parasitic resistances. These results corroborate that migrating to resonant SC technologies is one of the most compelling alternatives to overcome well-known disadvantages in pure SC topologies.

Paralleling a synchronverter and a PWM-based converter for supplying a microgrid

The papers aim is to present the parallel operation of a synchronverter and a PWM-based inverter in order to feed the load of a microgrid. The main motivation lies on the fact that the power electronics advancements made feasible the creation of microgrids fed by renewable energies, which ordinarily have as common factor the use of voltage source converters. Results are promising for operating a microgrid in an isolated way.

Quadratic gain converter with output voltage ripple mitigation

This paper introduces a DC-DC converter topology with the following features: (i) quadratic voltage gain, which allows the converter to work with wide voltage line variations in a wide operation voltage range with a minimal variation of duty cycle and without the use of extreme duty cycles; (ii) output voltage ripple mitigation, this feature can be accomplished in a specific duty cycle by proper selection of components and PWM signals. The proposed converter can be designed to have zero output voltage ripple for the nominal gain (duty cycle), this allows the use of small values of capacitance. The operating principles and steady-state equations, for the discussed topology in CCM are presented in detail. Experimental tests are presented to validate the propositions.

Analysis and Implementation of an 84-Pulse STATCOM

This chapter describes the use of STATCOM for the reactive power compensation and the power quality improvement. The assembling of a Voltage Source Converter (VSC) that meets the IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems (IEEE Std. 519-1992) is emphasized. The low Total Harmonic Distortion (THD) that this VSC generates, qualifies this power conditioner to be considered for its use on stringent applications. The reinjection principle is used, that makes this proposal be considered as an affordable solution to the sinusoidal synthesis due to the reduced number of switches. The reinjection transformer is one of the most important elements in this configuration, and it can have a wide turn ratio variation without leading out the special application standards. Conventional Proportional-Integral (PI) controllers are applied to hold the output voltage of the STATCOM around nominal conditions. The followed strategy employs the error and its variation to break down the control action into smaller sections that can be selected according to simple rules.

Study of STATCOM in abc Framework

In this chapter, the STATCOM characteristics are analyzed when it is utilized for improving the voltage stability. This chapter aims to analyze the STATCOM in the abc coordinates, and its impact over the power system under steady state and transient conditions is studied. Mathematical description of the main components is included to represent the dynamic behavior. These elements are formulated by differential equations in order to demonstrate how the STATCOM influences overall power system performance and voltage stability margins. The proposed methodology is validated on a Synchronous Machine Infinite Bus (SMIB) and on the New England test power system, which comprises 39-buses, 46-transmission lines, and 10-generators.

Signal differentiation in position tracking control of dc motors

An asymptotic differentiation approach with respect to time is used for on-line estimation of velocity and acceleration signals in controlled dc motors. The attractive feature of this differentiator of signals is that it does not require any system mathematical model, which allows its use in engineering systems that require the signal differentiation for its control, identification, fault detection, among other applications. Moreover, it is shown that the differentiation approach can be applied for output signals showing a chaotic behavior. In addition a differential flatness control scheme with additional integral compensation of the output error is proposed for tracking tasks of position reference trajectories for direct current electric motors using angular position measurements only.

Bootstrap Cascaded Multilevel Converter

This paper presents a cascaded-type multilevel inverter whit only one DC voltage source, which uses a floating capacitor to feed the other cascaded H-bridge, the capacitor is charge in a bootstrap technique and then the converter can provide a peak voltage equal to twice the DC-source regard-less on the power factor in the load, the converter is ideal for renewable systems applications as inverter stage in energy generation or grid integration, experimental results with a 5-level prototype verify the converter behavior.