Maurício dos Santos Kaster

Nonlinear State Estimation and Control for Chaos Suppression in MEMS Resonator

During the last decade the chaotic behavior in MEMS resonators have been reported in a number of works. Here, the chaotic behavior of a micro-mechanical resonator is suppressed. The aim is to control the system forcing it to an orbit of the analytical solution obtained by the multiple scales method. The State Dependent Riccati Equation (SDRE) and the Optimal Linear Feedback Control (OLFC) strategies are used for controlling the trajectory of the system. Additionally, the SDRE technique is used in the state estimator design. The state estimation and the control techniques proved to be effective in controlling the trajectory of the system. Additionally, the robustness of the control strategies are tested considering parametric errors and measurement noise in the control loop.

A line-interactive UPS system operating with sinusoidal voltage and current references obtained from a self-tuning filter

This paper presents a single-phase line interactive uninterruptible power supply (UPS) system, allowing output voltage conditioning, such as voltage harmonic suppression and sag or swell compensation. Additionally, the UPS input current is also conditioned, allowing current harmonic suppression and reactive power compensation. In other words, the UPS system acts as a true unified power quality conditioner (UPQC), when it is working in standby operation mode. Both voltage and current sinusoidal UPS references are generated by using a phase-locked loop (PLL) combined with a self-tuning filter (STF), allowing the implementation of a simplified control strategy, in which by controlling the UPS dc-bus voltage, is possible to control the amplitude of the sinusoidal reference current of the series converter and, consequently, the power flow through the UPS. The power rate handled by both series and parallel PWM converters depends on the operation conditions of the UPS system, such as, among others, the amplitude difference between the input and output voltages. In standby mode, the amplitude of the UPS output voltage can vary in order to follow the amplitude of the input voltage within a limited range defined by design requirements. This strategy will allow an effective optimization of the UPS system efficiency. Mathematical analyses and validation results are presented in order to evaluate the performance of the line interactive UPS system.

Single-phase Power Quality Conditioners with series-parallel filtering capabilities

This paper deals with compensation algorithm schemes used in single-phase Power Quality Conditioners (PQCs), allowing harmonic suppression and sag/swell compensation of the input voltage. In addition, reactive power compensation and harmonic suppression of the input current are also carried out, resulting in an effective power factor correction. Two single-phase PQCs are discussed, namely, the single-phase Unified Power Quality Conditioner (UPQC) and the single-phase line-interactive Uninterruptible Power Supply (UPS) system. To compensate the input current and the output voltage, Synchronous Reference Frame (SRF) based controllers are used. Although the SRF method is itself based on balanced three-phase loads, it can be adapted for use in single-phase loads. Both the UPS and UPQC are composed of two single-phase PWM converters to perform the active power line filter functions. The single-phase PQCs can be implemented by adopting two different operation modes. In the first mode the series converter acts as a sinusoidal current source, while the parallel converter acts as a sinusoidal voltage source. In the second mode, the series converter acts as a non-sinusoidal voltage source, while the parallel converter acts as a non-sinusoidal current source. A comparative analysis of the two operation modes is made, in which the advantages and disadvantages of each are discussed. Validation results are presented to confirm the theoretical development and performance of the single-phase PQCs.

ANÁLISE DO USO DE CONTROLE PID NÃO LINEAR APLICADO A CONVERSOR BUCK

Resumo: Este trabalho propoe o uso de funcoes de ganho nao lineares em controladores tipo PID com objetivo de incremento no desempenho do controle. Sao apresentadas as proposicoes para os ganhos proporcional (funcao quadratica), integral (distribuicao gaussiana) e derivativo (funcao quadratica). No caso, todas sao funcoes continuas com derivadas continuas, com o intuito de evitar possiveis problemas relacionados com transicao abrupta dos ganhos. O trabalho apresenta o estudo e a simulacao de um controlador PID nao-linear utilizando como aplicacao o controle da tensao de saida de um conversor CC-CC de topologia Buck.

Single-stage high power factor converter without electrolytic capacitors to drive power LEDs

This paper proposes the use of a single-stage high-power-factor converter for power LEDs, without electrolytic DC bus capacitor. The power factor correction is obtained through direct connection of the Boost inductor between inverter stage and two input capacitor. A rectifier with output capacitor filter connected between the inverter stage and DC bus capacitors is used to obtain DC current in power LEDs. Experimental results are presented to prove proposed design methodology.

Chaos suppression in NEMs resonators by using nonlinear control design

In this work the chaotic behavior of a micro-mechanical resonator with electrostatic forces on both sides is suppressed. The aim is to control the system in an orbit of the analytical solution obtained by the Method of Multiple Scales. Two control strategies are used for controlling the trajectory of the system, namely: State Dependent Riccati Equation (SDRE) Control and Optimal Linear Feedback Control (OLFC). The controls proved effectiveness in controlling the trajectory of the system. Additionally, the robustness of each strategy is tested considering the presence of parametric errors and measurement noise in control.

Single-phase ups system with series-parallel filtering capabilities

This paper deals with compensation algorithm schemes used in single-phase Uninterruptiple Power Supply (UPS) system, allowing harmonic suppression and sag/swell compensation of the input voltage. In addition, reactive power compensation and harmonic suppression of the input current are also carried out, resulting in an effective power factor correction. To compensate the input current and the output voltage, Synchronous Reference Frame (SRF) based controllers are used. Although the SRF method is itself based on balanced three-phase loads, it can be adapted for use in single-phase loads. The UPS is composed of two single-phase PWM converters to perform the active power line filter functions. The single-phase UPS can be implemented by adopting two different operation modes. In the first mode the series converter acts as a sinusoidal current source, while the parallel converter acts as a sinusoidal voltage source. In the second mode, the series converter acts as a non-sinusoidal voltage source, while the parallel converter acts as a non-sinusoidal current source. A comparative analysis of the two operation modes is made, in which the advantages and disadvantages of each are discussed. Validation results are presented to confirm the theoretical development and performance of the single-phase UPS system.

Performance analysis of an adaptive Gaussian nonlinear PID control applied to a step-down CC-CC converter

In several industrial systems, designers have mainly explored topology variations, which are the case of space-vector control systems of electrical machines or active filters and power electronic converters, where the control loops still have traditional PID controllers. As the possibilities of topologies have been very explored, designers are turning attention towards nonlinear control schemes. However, in complex systems, the change of PID controllers to others nonlinear may be a very difficult task, and may require structural changes in the control system, like changing to fuzzy, sliding mode or others, and an exhaustive search for the optimal parameters. This work proposes an adaptive PID control based on gaussian functions, which are functions that presents predefined higher and lower limits, adjustable concavity, are smooth and without discontinuities. This means that little or no structural adjustments need to be made to the system. The optimal parameters are obtained by making a parametric sweep of the gaussian functions, where resulting setling-time and overshoot are considered. A comparison of simulation and experimental resutls are presented using a Buck converter with the controller implemented in an FPGA.

Performance comparison between nonlinear and linear controllers applied to a buck converter using poles placement design

A performance comparison of four control techniques (PID, LQR, SDRE and ANLPID-GGF) applied to a Buck converter is presented. The controllers are set so the operating point of the closed loop system presents the same natural frequency. The poles placement technique was used. Analyses of the results are performed.

An electronic AC power system with buck PFC and linear regulator to drive and control the current of power LEDs

This paper presents an electronic AC power system, with power factor correction, to drive and control the current of LEDs (Light Emitting Diodes). The power factor correction and the controlled DC bus voltage are performed by a Buck stage. A transistorized linear regulator coupled to the Buck will drive and control the LEDs. A study is presented considering the variation of the current ripple of LEDs as a function of the DC bus voltage ripple. A design methodology is presented for reducing losses in the linear regulator. Experimental results are presented to demonstrate the proposed design methodology.