HYBRID DUAL-LOOP CONTROL FOR CURRENT REGULATION AND LOW-FREQUENCY RIPPLE REJECTION IN LED DRIVERS

The regulation of linearized multivariable system models, following input set point and load disturbance changes, is considered. An inner and outer closed-loop control strategy is outlined, enabling targeted recovery rates, offset attenuation and low steady state interaction to be achieved. Proportional control and passive network compensation alone are employed. Gain ratio selection and outer loop tuning are exercised, ensuring thereby the confinement of output perturbations to low-frequency load disturbances and reference input changes. Application studies are presented for purposes of comparison.

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Feedforward Control Based on Error and Disturbance Observation for the CCD and Fiber-Optic Gyroscope-Based Mobile Optoelectronic Tracking System

Electronics ◽

10.3390/electronics7100223 ◽

2018 ◽

Vol 7 (10) ◽

pp. 223 ◽

Cited By ~ 3

Author(s):

Yong Luo ◽

Wei Ren ◽

Yongmei Huang ◽

Qiunong He ◽

Qiongyan Wu ◽

...

Keyword(s):

Fiber Optic ◽

Control Method ◽

Feedforward Control ◽

Tracking System ◽

Sampling Rate ◽

Low Frequency ◽

Integration Time ◽

Fiber Optic Gyroscope ◽

Loop Control ◽

Boresight Error

In the mobile optoelectronic tracking system (MOTS) based on charge-coupled device (CCD) and fiber-optic gyroscope (FOG), the tracking performance (TP) and anti-disturbance ability (ADA) characterized by boresight error are of equal importance. Generally, the position tracking loop, limited by the image integration time of CCD, would be subject to a non-negligible delay and low-sampling rate, which could not minimize the boresight error. Although the FOG-based velocity loop could enhance the ADA of the system, it is still insufficient in the case of some uncertain disturbances. In this paper, a feedforward control method based on the results of error and disturbance observation was proposed. The error observer (EOB) based on the CCD data and model output essentially combined the low-frequency tracking feedforward and closed-loop disturbance observer (DOB), which could simultaneously enhance the low-frequency TP and ADA. In addition, in view of the poor low-frequency performance of the FOG due to drift and noise that may result in the inaccuracy of the observed low-frequency disturbance, the FOG-based DOB was used to improve the relatively high-frequency ADA. The proposed method could make EOB and DOB complementary and help to obtain a high-precision MOTS, for in practical engineering, we give more attention to the low-frequency TP and full-band ADA. Simulations and experiments demonstrated that the proposed method was valid and had a much better performance than the traditional velocity and position double-loop control (VPDC).

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EXPERIMENTAL RESULTS FOR THE SMALL-SIGNAL STUDY OF THE PWM BOOST DC–DC CONVERTER WITH AN INTEGRAL-LEAD CONTROLLER

Journal of Circuits System and Computers ◽

10.1142/s0218126695000436 ◽

1995 ◽

Vol 05 (04) ◽

pp. 747-755 ◽

Cited By ~ 8

Author(s):

MARIAN K. KAZIMIERCZUK ◽

ROBERT C. CRAVENS, II

Keyword(s):

Closed Loop ◽

Transfer Functions ◽

Low Frequency ◽

Input Voltage ◽

Open Loop ◽

Small Signal ◽

Loop Control ◽

Pulse Width Modulated ◽

Bode Plots ◽

Step Responses

An experimental verification of previously derived small-signal low-frequency open- and closed-loop characteristics and step responses of a voltage-mode-controlled pulse-width-modulated (PWM) boost DC–DC converter is presented. The Bode plots of the voltage transfer function of the control circuit, the converter and the PWM modulator, the open-loop control-to-output and input-to-output transfer functions, the loop gain, and the closed-loop control-to-output and input-to-output transfer functions are measured. The step responses to the changes in the input voltage, the duty cycle, and the reference voltage are measured. The theoretical results were in good agreement with the measured results. The small-signal model of the converter is experimentally verified.

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Practical Design Considerations for Performance and Robustness in the Face of Uncertain Flexible Dynamics in Space Manipulators

Frontiers in Robotics and AI ◽

10.3389/frobt.2021.708388 ◽

2021 ◽

Vol 8 ◽

Author(s):

Connor Holmes

Keyword(s):

Control Strategies ◽

Low Frequency ◽

Open Loop ◽

Unmodeled Dynamics ◽

Loop Control ◽

Stability Margins ◽

Flexible Mode ◽

Space Manipulators ◽

The Face ◽

And Performance

Low frequency dynamics introduced by structural flexibility can result in considerable performance degradation and even instability in on-orbit, robotic manipulators. Although there is a wealth of literature that addresses this problem, the author has found that many advanced solutions are often precluded by practical considerations. On the other hand, classical, robust control methods are tractable for these systems if the design problem is properly constrained. This paper investigates a pragmatic engineering approach that evaluates the system’s stability margins in the face of uncertain, flexible perturbation dynamics with frequencies that lie close to or within the bandwidth of the nominal closed-loop system. The robustness of classical control strategies is studied in the context of both collocated (joint rate) and non-collocated (force/torque and vision-based) feedback. It is shown that robust stability and performance depend on the open-loop control bandwidth of the nominal control law (as designed for a simplified, rigid plant). Namely, the designed bandwidth must be constrained to be lower than the minimum flexible mode frequency of the unmodeled dynamics by a given factor. This strategy gives credence to popular heuristic methods commonly used to reduce the effect of unmodeled dynamics in complex manipulator systems.

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ANALYSIS OF LOW-FREQUENCY RIPPLE TRANSMISSION TO DCM OPERATING CONVERTERS FOR LED DRIVERS

Eletrônica de Potência ◽

10.18618/rep.2020.1.0059 ◽

2020 ◽

Vol 25 (1) ◽

pp. 9-18

Author(s):

Jean Santis Brand ◽

Maicol Flores de Melo ◽

José Marcos Alonso Álvarez ◽

Marco Antônio Dalla Costa

Keyword(s):

Low Frequency ◽

Led Drivers

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A New Dynamic Voltage Restorer with Multi-level Open-end Winding Topology

E3S Web of Conferences ◽

10.1051/e3sconf/202016506013 ◽

2020 ◽

Vol 165 ◽

pp. 06013

Author(s):

Jingyuan Yin ◽

Jinke Li ◽

Qunhai Huo ◽

Lixin Wu ◽

Libo Han ◽

...

Keyword(s):

Control Strategy ◽

Level Structure ◽

Low Frequency ◽

Common Mode ◽

Loop Control ◽

Common Mode Voltage ◽

The Common ◽

Multi Level ◽

Voltage Feedback ◽

Open End Winding

In this paper, a variety of main circuit structures of DVR based on open-end winding are presented. Two inverters are connected in series to realize the multi-level structure and simplify the hardware cost. According to the mathematical model of open-end DVR, a three loop control strategy based on load voltage feedback is implemented to suppress the resonance of LCL filter. Aiming at the common mode voltage problem of open-end winding DVR, a common mode voltage suppression strategy based SVPWM is proposed to completely suppress the common mode voltage of high frequency and low frequency of the system. Finally, an open-end DVR experimental platform is built to verify the effectiveness of the control strategy and modulation strategy.

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Analysis and Control of Electrolytic Capacitor-Less LED Driver Based on Harmonic Injection Technique

Energies ◽

10.3390/en11113030 ◽

2018 ◽

Vol 11 (11) ◽

pp. 3030 ◽

Cited By ~ 7

Author(s):

Mahmoud Nassary ◽

Mohamed Orabi ◽

Manuel Arias ◽

Emad Ahmed ◽

El-Sayed Hasaneen

Keyword(s):

Power Factor ◽

Low Frequency ◽

Buck Converter ◽

Electrolytic Capacitor ◽

Injection Technique ◽

Led Driver ◽

Harmonic Injection ◽

Output Capacitor ◽

And Control ◽

Led Drivers

AC-DC LED drivers may have a lifespan shorter than the lifespan of LED chips if electrolytic capacitors are used in their construction. Using film capacitors solves this problem but, as their capacitance is considerably lower, the low-frequency ripple will increase. Solving this problem by limiting the output ripple to safe values is possible by distorting the input current using harmonic injection technique, as long as these harmonics still complies with Power Factor Regulations (Energy Star). This harmonic injection alleviates the requirements imposed to the output capacitor in order to limit the low-frequency ripple in the output. This idea is based on the fact that LEDs can be driven by pulsating current with a limited Peak-To-Average Ratio (PTAR) without affecting their performance. By considering the accurate model of LEDs, instead of the typical equivalent resistance, this paper presents an improved and more reliable calculation of the intended harmonic injection. Wherein, its orders and values can be determined for each input/output voltage to obtain the specified PTAR and Power Factor (PF). Also, this harmonic injection can be simply implemented using a single feedback loop, its control circuit has features of wide bandwidth, simple, single-loop and lower cost. A 21W AC-DC buck converter is built to validate the proposed circuit and the derived mathematical model and it complies with IEC61000 3-2 class D standard.

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Pre-Scheduled PID Control of a Solar Thermal Power Plant

Transactions of the Institute of Measurement and Control ◽

10.1177/014233129501700305 ◽

1995 ◽

Vol 17 (3) ◽

pp. 132-142 ◽

Cited By ~ 4

Author(s):

A. Meaburn ◽

F. M. Hughes

Keyword(s):

Closed Loop ◽

Feedforward Control ◽

Thermal Power ◽

Low Frequency ◽

Outlet Temperature ◽

Experimental Frequency ◽

Efficient Operation ◽

Loop Control ◽

Tuning Method ◽

Control Scheme

Efficient operation of a distributed solar collector field requires effective regulation of the outlet temperature. Control schemes utilising PI-based controllers, whether adaptive or fixed parameter, have been shown to be unsuitable for this application with a stable well-damped response only obtained at the expense of an unacceptably low speed of response. The reason for this is that collector fields possess low-frequency resonance dynamics which tend to restrict the bandwidth of such controllers. This paper examines the suitability and capability of PID controllers in this application area. Using experimental frequency response data, the Ziegler-Nichols tuning method for PID design is demonstrated to yield an unstable closed-loop system. However, by adopting a strategy which specifically aims to counter the adverse phase characteristics of the plant at resonance, good effective closed-loop control can be achieved. This is implemented as a pre-scheduled control scheme on the Acurex collector field at the Plataforma Solar de Almeria and tested in conjunction with a feedforward control scheme.

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