Panfilo R. Martinez

A Repetitive-Based Controller for the Compensation of

In this paper, a repetitive-based controller for the compensation of 6 lscr plusmn 1 harmonic components is proposed. This control scheme is more appropriate for processes that involve the use of six-pulse converters or other converters that mainly produce harmonic components at those frequencies. The control scheme is based on the feedback array of two delay lines plus a feedforward path that compensates only the 6 lscr plusmn 1 multiples of the fundamental frequency, thereby reducing the possibility of reinjecting unnecessary distortion into the system. The proposed scheme is, then, plugged into a generic feedback control system where a stability analysis is carried out. In addition, the passivity properties of the proposed scheme are presented, which open the possibility of control design following the passivity-based approach. Experiments that are based on a simple digital implementation are provided to illustrate the merits of our solution. These results include the open-loop responses of the proposed scheme and the responses in a practical example to validate its effectiveness in an application. For this latter result, the proposed scheme has been used in the controller of a 2-kVA shunt active filter to compensate the current harmonic distortion.

6\ell\pm 1

This paper presents a grid synchronization scheme aimed to provide an estimation of the angular frequency and both the positive and negative sequences of the fundamental component of an unbalanced three-phase signal. These sequences are provided in fixed-reference-frame coordinates, and thus, the proposed algorithm is referred to as fixed-reference-frame phase-locked loop (PLL) (FRF-PLL). In fact, the FRF-PLL does not require transformation of variables into the synchronous frame coordinates as in most PLL schemes. Therefore, the proposed scheme is not based on the phase angle detection. Instead, the angular frequency is detected and used for synchronization purposes. The design of the FRF-PLL is based on a complete description of the source voltage involving both positive and negative sequences in stationary coordinates and considering the angular frequency as an uncertain parameter. Therefore, the FRF-PLL is intended to perform properly under severe unbalanced conditions and to be robust against angular frequency variations, sags, and swells in the three-phase utility voltage signal. Due to the selective nature of the scheme, it shows certain capability to alleviate the effect of harmonic distortion that is present in the utility voltage signal.

Harmonic Components

A feedforward modification for both positive- and negative-feedback schemes of repetitive control is described. It was shown that repetitive controllers can be a useful tool for tracking of periodic reference signals and compensation of periodic disturbances, in other words, for harmonic compensation. It was shown that the feedforward modification considerably improves the frequency response and performance, providing higher gains with enhanced selectivity. Simple analog circuits are presented to implement both positive- and negative-feedback repetitive schemes. A description of the circuits and their corresponding experimental frequency responses are also given

Fixed-Reference-Frame Phase-Locked Loop for Grid Synchronization Under Unbalanced Operation

In this paper, a repetitive-based controller for a boost-based power factor precompensator is presented. The controller guarantees voltage regulation with a power factor close to unity, despite of the presence of harmonic distortion in the source voltage and uncertainties in the system parameters. It is shown that the repetitive scheme considered here is, in fact, equivalent to a bank of resonant filters, which has shown to be a useful technique in harmonic compensation. Out of this equivalence, a negative feedback structure is obtained for the repetitive scheme which is aimed for the compensation of odd harmonics only. This is in contrast to usual positive feedback repetitive schemes aimed to compensate for all harmonic components. The repetitive scheme consists on a simple feedback array involving a time delay plus a feedforward path, which is simple to implement. The closed-loop stability analysis of such and infinite-dimensional system is performed appealing to the well-known small gain theorem. Experimental results in a 400-W boost-based power factor compensator (PFC), with a fixed-point digital signal processor (DSP)-based implementation of the proposed controller, are provided to assess the performance of the controlled system.

Analog Circuits to Implement Repetitive Controllers With Feedforward for Harmonic Compensation

An adaptive controller for the compensation of output voltage ripple due to harmonic distortion in the input voltage is proposed for a pulse width modulated (PWM) boost converter. Following the Lyapunov approach, we designed an adaptive law to cope with uncertainties in the disturbance signals and parameters. Complexity of the proposed controller is reduced by rotations which transform the adaptive terms into a sum of resonant filters tuned at the frequencies of the harmonics under compensation, and operating on the output voltage error. To facilitate the implementation, we have tried to preserve the structure of the proposed controller as close as possible to the conventional one, which includes a voltage outer loop (basically a proportional plus integral (PI) control on the output voltage error) and an inner control loop (basically a proportional control plus a feedforward term). In the proposed controller, the bank of resonant filters appears as a refinement term added to the inner control loop. Indeed, they insert notches in the audio-susceptibility curve, which are tuned at the harmonics under compensation. Thus, in addition to the benefits of a conventional feedforward PWM control, the bank of resonant filters are able to cancel selected harmonics. Experimental results on a boost converter board, using a poorly regulated voltage source, are presented to assess the performance of our approach.

A Repetitive-Based Controller for a Power Factor Precompensator

In this paper, simple analog circuits to implement a repetitive control scheme are discussed. The repetitive control has shown to be a useful tool for tracking of periodic reference signals and for compensation of periodic disturbances. The main advantages of the proposed circuitry are: 1) no digital conversion required; 2) easy tuning to the corresponding frequency; and 3) cost effectiveness. A description of the circuits and corresponding experimental frequency responses are given.

A controller for a boost converter with harmonic reduction

This paper presents an electronic ballast based high power LEDs for headlights automobile. The ballast is based on a buck converter to feed a load of high power LED. The load is divided into five high power LED (10W), in automobile lighting systems rapid changes of lighting is required (power changes), therefore the buck converter must deliver constant voltage levels to changes in power and further the current necessary to maintain a flow of light required. To solve this problem this paper proposes a control law for buck converter control, which maintains a fixed voltage level for the different power (10.9W, 21.8W, 32.7W, 43.6W, 54.5W) dynamic response to these changes is fast and constant levels of current and luminous flux at each change of load is maintained.

Analog circuits to implement repetitive controllers for tracking and disturbance rejection of periodic signals

This paper presents a self-oscillating electronic ballast for a 36 W LED string. The design consists of a simple control that reduces the component number and cost of the ballast. Self-oscillating converters are popular in compact fluorescent lamps; therefore, it is proposed the use of this self-oscillating control technique for the LED lamp. The self-oscillating LED driver represents a very suitable solution in compact LED products. This paper describes the design of a self-oscillating electronic ballast at high frequency. The output of the sine wave of the resonant inverter is rectified and, then its high frequency yields a reduction in the value of output capacitor.

Analysis of buck converter control for automobile LED headlights application

In this paper presents the study and implementation of a model for an ultraviolet light-emitting diode (UV LED). This model is used to characterize series and parallel UV LED arrangements. The proposed model can be used for different power LED. An exponential expression of a term that describes the electrical characteristics of the V-I curve of a UV LED is used. The principle of implementation of UV LED is described, and in this way they can be used in simulation software. The proposed model this designed for any number of LED in series or parallel. To perform the proposed model radiation is analyzed in terms of temperature and power.

Design of self-oscillating electronic ballast for power LEDs

This paper presented a comparative study in function reliability between dc-dc converters used in power LED. Between dc-dc converters more used to power LED are the Buck and Flyback converter, because the Buck provides a lower output voltage than the input, and in the case of flyback has galvanic isolation. The study has objetive to determine the reliability obtaining the failure rate of the system and the average time when failures occurs, because the LED driver must have an average life similar to the LED lamp. The reliability analysis is based in the standard MIL-HDBK-217, for this study performed was used a LED load of 54.6 W in both converters. The results have shown that the buck converter has a lower failure rate and a higher mean time between failures, therefore has a longer useful life.