Chang-Seok Park

New active clamp technique for switching losses reduction of MIC systems

Recently, the MIC system have been actively studied to reduce switching losses and improve its reliability and efficiency. The Active clamp Flyback converter is based on the Flyback converter topology. But, the Flyback converter generates the voltage spike between Drain and Source of the MOSFET device. This spike causes losses and noises of the converter. So, the Active clamp Flyback converter is studied the focus of the voltage spike reduction. In this paper, The New Active Clamp Fly-back Converter is proposed to improve the efficiency by the Power-Sim simulator and the experiment.

Improved DC Offset Error Compensation Algorithm in Phase Locked Loop System

This paper proposes a dc error compensation algorithm using dq-synchronous coordinate transform digital phase-locked-loop in single-phase grid-connected converters. The dc errors are caused by analog to digital conversion and grid voltage during measurement. If the dc offset error is included in the phase-locked-loop system, it can cause distortion in the grid angle estimation with phase-locked-loop. Accordingly, recent study has dealt with the integral technique using the synchronous reference frame phase-locked-loop method. However, dynamic response is slow because it requires to monitor one period of grid voltage. In this paper, the dc offset error compensation algorithm of the improved response characteristic is proposed by using the synchronous reference frame phase-locked-loop. The simulation and the experimental results are presented to demonstrate the effectiveness of the proposed dc offset error compensation algorithm.

A Study on the Controllable Snubber for Switching Loss Reduction in Interleaved Fly-Back Converter

This paper proposes a new switching algorithm for an controllable clamp snubber to improve the efficiency of a fly-back converter system. This system uses an controllable clamp method for the snubber circuit for the efficiency and reliability of the system. However, the active clamp snubber circuit has the disadvantage that system efficiency is decreased by switch operating time because of heat loss in resonance between the snubber capacitor and leakage inductance. To address this, this paper proposes a new switching algorithm. The proposed algorithm is a technique to reduce power consumption by reducing the resonance of the snubber switch operation time. Also, the snubber switch is operated at zero voltage switching by turning on the snubber switch before main switch turn-off. Experimental results are presented to show the validity of the proposed controllable clamp control algorithm.

Permanent magnet structure optimization for cogging torque reduction of outer rotor type radial flux permanent magnet generator

To improve the efficiency of wind turbines, permanent magnet synchronous generator has been used instead of doubly-fed induction generator. Permanent magnet synchronous generator has higher efficiency than doubly-fed induction generator because it has no winding loss in the rotor, but it has cogging torque which increases the cut-in speed of wind turbines. Cut-in speed is a kind of major design factor of generators for the wind turbines. In previous studies, the cogging torque reduction methods are proposed but these methods have negative effects on performance or efficiency. In this paper, the rounded edge shape of permanent magnet is proposed to reduce cogging torque. The proposed method aims to design the edge of permanent magnet for minimizing the air-gap reluctance variation.

Online Dead Time Effect Compensation Algorithm of PWM Inverter for Motor Drive Using PR Controller

This paper proposes the dead time effect compensation algorithm using proportional resonant controller in pulse width modulation inverter of motor drive. To avoid a short circuit in the dc link, the dead time of the switch device is surely required. However, the dead time effect causes the phase current distortions, torque pulsations, and degradations of control performance. To solve these problems, the output current including ripple components on the synchronous reference frame and stationary reference frame are analyzed in detail. As a results, the distorted synchronous d-and q-axis currents contain the 6th, 12th, and the higher harmonic components due to the influence of dead time effect. In this paper, a new dead time effect compensation algorithm using proportional resonant controller is also proposed to reduce the output current harmonics due to the dead time and nonlinear characteristics of the switching devices. The proposed compensation algorithm does not require any additional hardware and the offline experimental measurements. The experimental results are presented to demonstrate the effectiveness of the proposed dead time effect compensation algorithm.

Demagnetization diagnosis of permanent magnet synchronous motor by using continuous wavelet transform

The permanent magnet synchronous motor which has permanent magnet instead of field winding in the rotor has especially higher efficiency and torque per weight than other types of motor. When the irreversible demagnetization is occurred, users can be exposed to high risk of accident by the fault operation of motor. Because of this, the irreversible demagnetization of permanent magnet should be detected by using any kinds of method to reduce the risk of accident. In this study, the demagnetization diagnosis method based on the result at the rated operating condition simulation is proposed for the permanent magnet synchronous motor. The input current waveforms are analyzed by using the continuous wavelet transform to detect demagnetized poles in the model.

A Study on Optimal Current Control Method for Small BLDC Motor Drive

This paper proposed a optimal current control method to improve efficiency of BLDC motors. The aim of the proposed method is to use the maximum torque operating method by increasing the effective voltage at the maximum torque point unlike existing SPM operating method. The proposed method is based on existing IPM maximum torque operating method grafting onto a square wave operating of SPM motors. As the method of increasing the effective output voltage from inverter using the maximum torque point, the proposed method is to improve efficiency of BLDC motors using the same amount of the existing current effectively. For this method, the maximum torque point is carried out by FEA and analysis of magnetic flux vector. In this paper, the prototype of general-purpose BLDC drive is manufactured and the performance characteristic and validity are verified.