Rodrigo V. Tambara

Robust Adaptive Controller Combined With a Linear Quadratic Regulator Based on Kalman Filtering

This work presents a control algorithm which incorporates a Reference Model Robust Adaptive Controller (RMRAC) and a Linear Quadratic Regulator based on Kalman Filtering (LQRKF) to obtain a high performance and robust control system. The adaptive portion of the controller deals with system uncertainties, while the optimum scheme, aided by a Kalman Filter, is designed to deal with harmonically related system disturbances. A proof of stability is presented in addition to a numerical example of the combined RMRAC - LQRKF controller to show the effectiveness of this new control approach.

Sliding mode control in a multi-loop framework for current control of a grid-tied inverter via LCL-filter

This paper proposes a current controller for grid tied Voltage Source Inverter (VSI) via a LCL filter using discrete-time Sliding Mode Control (SMC) in a multi-loop framework. The inner loop is implemented by the SMC with reference generated by an outer controller for the VSI side current. The tracking of the current entering the distribution network is ensured by a outer controller with a derivative + ressonant structure (for compensation and disturbance rejection with reference tracking). Simulation and experimental results are presented to validate the good performance of the proposed control strategy.

Analysis of performance of an RMRAC controller in discrete-time via Z transform and Delta transform

This paper presents a comparative study of performance between the Z Transform and the Delta Transform applied to a Robust Model Reference Adaptive Controller (RMRAC). To show the differences between the two discretization techniques, the design of a controller applied to an AC Power Source (ACPS) is performed. The simulation results are obtained in a scenario where the controller is implemented in a 16-bit fixed-point arithmetic with a sampling frequency of 25kHz. In this work the ACPS is used to generate waveforms up to 1kHz. It is observed that the RMRAC controller in discrete-time via Delta Transform presents better performance with fixedpoint arithmetic implementation when compared to the Z Transform.

Discrete-time adaptive control applied to voltage regulation of induction generator based systems

This paper deals with the development of an adaptive control system applied to voltage regulation of a standalone distributed power generation system, fed by self-excited induction generator. The generation system considers a four wire three-phase grid, composed by three phases plus neutral conductor, fed by three-phase three wires induction generator. The neutral conductor is created from the neutral point of star connection of excitation capacitors. The four-wire configuration allows the connection of three-phase loads in star or delta configuration, as well as single-phase loads. The voltage regulation is performed through a four-legs distribution static compensator (DSTATCOM) shunt connected to the AC bus. The adaptive controller proposed offers suitable voltage regulation in conditions of systems parameters variations such as, load connection and disconnection, and changes in induction generators unmodeled parameters. The proposed generating system was simulated in MATLAB, where simulation results were obtained to show the good performance of the voltage regulation control system during the connection and disconnection of three-phase loads. Additionally, some preliminary experimental results are presented as well.

Performance evaluation of dimmable electronic ballast based on frequency and bus voltage variation

This paper presents a performance comparison between two dimming methods for an electronic ballast that feeds a T5 HE 28 W fluorescent lamps. An IR21592 dedicated integrated circuit is employed in the half-bridge inverter stage with a LCC resonant filter. A PFC stage is implemented with a Single-Ended Primary Inductance Converter with constant output voltage or variable output voltage according to the dimming method. A standard circuit IR21592 is employed to dim the lamp based on a standard method of inverter frequency variation with a constant PFC output voltage. A modified operation mode of IR21592 is employed also to dim the fluorescent lamp through a PFC stage output voltage and inverter frequency variation dimming method. For both methods experimental results are presented in order to make a comparison and to evaluate the general performance.

Two-stage digitally controlled led driver based on buck-boost and DC/DC LLC resonant converter

In this study a digitally controlled Light Emitting Diode (LED) driver operating with high power factor, dimming capability and reduced DC-link capacitance is proposed. The proposed LED driver circuit topology, designed to supply a 100 W LED module, is composed by two independent stages. The Power Factor Correction stage is implemented with the buck-boost DC/DC converter, operating in Discontinuous Conduction Mode. This stage provide a high power factor and maintain the average bus voltage controlled in 400 V. Besides, a reduce DC-link capacitance with 25 μF is used, thus allowing the use of log lifetime film capacitors. The second stage comprises the DC/DC Half-Bridge LLC resonant converter, which is in charge to keep controlled the averaged LED current as function of the required dimming level. To avoid output luminous intensity modulation, the control loop of the second stage is designed in order to reduce the LED current ripple, arising from the low frequency bus voltage ripple. Experimental results are presented with the topology operating under output dimming and reduced DC-link capacitance.

Universal input voltage LED driver with dimming capability and reduced DC-link capacitance

This paper presents a digitally controlled Light Emitting Diode (LED) driver with high power factor, universal input voltage, dimming capability and reduced DC-link storage energy capacitance. A two-stage structure composed by the Power Factor Correction and Power Control stages is proposed. The buck-boost DC/DC converter, operating in Discontinuous Conduction Mode is employed for power factor correction, and is responsible for maintain the average bus voltage controlled in 400 V, as function of the input universal voltage (85 - 265 VRMS). The DC/DC Half-Bridge LLC converter composes the power control stage, which is in charged to keep controlled the averaged LED current as function of the required dimming level. Furthermore, the low frequency bus voltage ripple is compensated in this stage through a properly closed loop design. Simulations results are presented with the topology operating under universal input voltage, output dimming, and reduced DC-link capacitance.

Digital implementation of a RMRAC controller using Z Transform and Delta Transform

This paper presents a comparative study of performance between the Z Transform and the Delta Transform applied to a Robust Model Reference Adaptive Controller (RMRAC). To show the differences between the two discretization techniques, the design of a controller applied to an Uninterruptible Power Supply (UPS) is performed. The simulation results are obtained in a scenario where the controller is implemented in a 16-bit fixed-point arithmetic with a sampling frequency of 6kHz. It is observed that the RMRAC controller in discrete-time via Delta Transform presents better performance with fixed-point arithmetic implementation when compared to the Z Transform.