Seok-Kyoon Kim

Offset-Free Model Predictive Control for the Power Control of Three-Phase AC/DC Converters

This paper describes an offset-free model predictive control (MPC) algorithm using a disturbance observer (DOB) to control the active/reactive powers of a three-phase AC/DC converter. The strategy of this paper is twofold. One is the use of DOB to remove the offset error, and the other is the proper choice of the weighting matrices of a cost index to provide fast error decay with small overshoot. The DOB is designed to estimate the unknown disturbances of the ac/dc converter following the standard Luenberger observer design procedure. The proposed MPC minimizes a one-step-ahead cost index penalizing the predicted tracking error by performing a simple membership test without any use of numerical methods. A systematic way for choosing the weights of the cost index, which guarantees the global stability of the closed-loop system, is proposed. Use of the DOB eliminates the offset tracking errors in the real implementation. Using a 25-kW ac/dc converter, it is experimentally shown that the proposed MPC enhances the power tracking performance while considerably reducing the mutual interference of the active/reactive powers as well as the output voltage.

Singularity-Free Adaptive Speed Tracking Control for Uncertain Permanent Magnet Synchronous Motor

This paper presents an adaptive speed tracking control scheme for an uncertain surface-mounted permanent magnet synchronous motor (SPMSM) without any knowledge of the SPMSM parameters and the singularity problem; further, even the upper and lower bounds of the parameters are not necessary. The contribution of this study is twofold. The first one is to introduce a coordinate transformation so that the resulting controller does not suffer from a singularity problem caused by the denominator including the parameter estimates. Besides, although the number of the unknown parameters is increased by two times, the number of estimators is the same as the previous result. The second one is to prove that the slightly modified parameter adaptation law contributes in enhancing the closed-loop robustness against the disturbance caused by the time-varying component of the load torque. The effectiveness of the closed-loop performance is shown by performing the experiment using the 3-kW SPMSM without any SPMSM parameter knowledge.

Efficacy and possible mechanisms of topical tranexamic acid in melasma

Tranexamic acid (TA) has been suggested as an effective treatment for melasma.

Robust Feedback-Linearizing Output Voltage Regulator for DC/DC Boost Converter

This paper suggests a cascade output voltage regulation strategy for dc/dc boost converters that embeds a robust inner-loop current controller against parameter variations. The contributions of this paper are divided into two parts. The first contribution is to present a simple and robust inner-loop current controller despite parameter uncertainties, guaranteeing the stability of the whole closed-loop system including the first-order internal dynamics. The second contribution is to show that an outer-loop proportional-integral regulator can stabilize the output voltage error without relying on any parameter information. Simulations and experiments using a 3-kW dc/dc boost converter showed that the proposed method offers satisfactory closed-loop performance in the presence of parameter uncertainties.

Adaptive output voltage tracking controller for uncertain DC/DC boost converter

ABSTRACT This paper presents a cascade output voltage control strategy for an uncertain DC/DC boost converter adopting an adaptive current controller in its inner loop. Considering the non-linearity, load uncertainties and parameter uncertainties of the converter, the proposed controller is designed following the conventional cascade voltage controller design method. The proposed method makes the following three contributions. First, a coordinate transformation is introduced for the inner loop, enabling avoidance of the singularity problem caused by the estimates of uncertain parameters. Second, a slight modification to the adaptation law is performed to guarantee closed-loop stability in the presence of the time-varying component of the load current. Third, the outer-loop controller is devised such that its performance can be adjusted without any parameter information. The closed-loop performance is demonstrated through simulations and experiments using the DSP28335 with a 3 kW DC/DC boost converter.

In vivo time-sequential histological study focused on melanocytes: suggestion of golden time for intervention to prevent post-laser pigmentary changes

Post‐inflammatory pigmentary changes after laser treatments are challenging adverse effect.

Model predictive control for the power control of three-phase AC/DC converters using a disturbance observer

This paper describes an offset-free model predictive control (MPC) algorithm using a disturbance observer (DOB) to control the active/reactive powers of a three-phase AC/DC converter. The DOB is designed to estimate the unknown disturbances of the AC/DC converter following the standard Luenberger observer design procedure. The proposed MPC minimizes a one-step-ahead cost index penalizing the predicted tracking error by performing a simple membership test without any use of numerical methods. A systematic way for choosing the weights of the cost index, which guarantees the global stability of the closed-loop system, is proposed. Use of the DOB eliminates the offset tracking errors in the real implementation.

Model Predictive Control of Three-Phase Inverter for Uninterruptible Power Supply Applications under a Hexagonal Input Constraint Region

Using the classical cascade voltage control strategy, this paper proposes an analytical solution to an MPC (Model Predictive Control) problem with a hexagonal input constraint set for the inner-loop to regulate the output voltage of the UPS (Uninterruptible Power Supply). Focus is placed on how to deal with the hexagonal input constraint set without any approximation. Following the conventional cascade voltage control strategy, the PI (Proportional-Integral) controller is used in the outer-loop in order to regulate the output voltage. The simulation results illustrate that the capacitor voltage rapidly goes to its reference in a satisfactory manner while keeping other state variables bounded under an unexpected load changes.

Offset-Free Model Predictive Control for Output Voltage Regulation of Three-Phase Inverter for Uninterruptible Power Supply Applications

Abstract This paper proposes an offset-free model predictive control (MPC) method for output voltage regulation of the three phase inverter for an uninterruptible power supply (UPS) application. A use of a disturbance observer (DOB) is made to estimate the unknown disturbance caused by the load current and a plant-model mismatch. The proposed MPC optimizes the one step ahead cost function. The online computation considering the input constraint of the inverter system is very simple. It is shown that the closed-loop system is globally asymptotically stable in the presence of input constraints and that the integral action in the DOB eliminates the steady state errors caused by a plant-model mismatch. The effectiveness of the closed-loop system is experimentally shown under a use of resistive load.

Proportional-Type Output Voltage-Tracking Controller for Interleaved DC/DC Boost Converter with Performance Recovery Property

This paper proposes an offset-free proportional-type output voltage-tracking algorithm embedding the disturbance observers (DOBs) for the -phase interleaved DC/DC boost converter through a systematical multivariable approach. The contributions of this article fall into two parts. The first one is to design the first-order nonlinear DOBs for exponentially estimating the disturbances caused by the model-plant mismatches. The second one is to prove that the proposed proportional-type controller equipped with the DOBs guarantees the performance recovery property as well as the offset-free property. The performance of the proposed method is evaluated through simulations and experiments using a -kW four-phase interleaved DC/DC boost converter, comparing the proposed and feedback linearizing (FL) methods.