• The Transactions of the Korean Institute of Power Electronics
• /
• v.25 no.2
• /
• pp.73-78
• /
• 2020

In this study, a novel reactive power control scheme is proposed to supply stable reactive power to the distribution line by compensating a ripple voltage of DC link. In a single-phase system, a magnitude of second harmonic is inevitably generated in the DC link voltage, and this phenomenon is further increased when the capacity of DC link capacitor decreases. Reactive power control was performed by controlling the d-axis current in the virtual synchronous reference frame, and the voltage control for maintaining the DC link voltage was implemented through the q-axis current control. The proposed method for compensating the ripple voltage was classified into three parts, which consist of the extraction unit of DC link voltage, high pass filter (HPF), and time delay unit. HPF removes an offset component of DC link voltage extracted from integral, and a time delay unit compensates the phase leading effect due to the HPF. The compensated DC voltage is used as feedback component of voltage control loop to supply stable reactive power. The performance of the proposed algorithm was verified through simulation and experiments. At DC link capacitance of 375 uF, the magnitude of ripple voltage decreased to 8 Vpp from 74 Vpp in the voltage control loop, and the total harmonic distortion of the current was improved.

• Proceedings of the KIPE Conference
• /
• 2001.07a
• /
• pp.223-226
• /
• 2001

In this paper, dc link ripple currents for three-phase ac/dc/ac PWM converters are analyzed in a frequency domain. The expression of the harmonic currents is developed by using switching functions and exponential Fourier series expansion. The dc link ripple currents with regard to power factor and modulation index are investigated. In addition, the effect of the displacement angle between the switching periods of line-side converters and load-side inverters on the do link ripple current is studied. The result of the do link current analysis is helpful in specifying the dc link capacitor size and its life time estimation.

• Proceedings of the KIPE Conference
• /
• 2019.07a
• /
• pp.207-209
• /
• 2019

This paper proposes a grid-tied photovoltaic (PV) system, consisting of Voltage-fed dual-active-bridge (DAB) dc-dc converter with single phase inverter. The proposed converter allows a small dc-link capacitor, so that system reliability can be improved by replacing electrolytic capacitors with film capacitors. The double line frequency free maximum power point tracking (MPPT) is also realized in the proposed converter by using Ripple Correlation method. First of all, to eliminate the double line frequency ripple which influence the reduction of DC source capacitance, control is developed. Then, a designing of Current control in DQ frame is analyzed and to fulfill the international harmonics standards such as IEEE 519 and P1547, $3^{rd}$ harmonic in the grid is directly compensated by the feedforward terms generated by the PR controller with the grid current in stationary frame to achieve desire Total Harmonic Distortion (THD). 5-kW PV converter and inverter module with a small dc-link film capacitor was built in the laboratory with the proposed control and MPPT algorithm. Experimental results are given to validate the converter performance.

• Proceedings of the KSR Conference
• /
• 2005.05a
• /
• pp.800-805
• /
• 2005

In this study, control schemes are proposed for a propulsion system of TTX(Tilting Train eXpress). In developed traction converter, unity power factor control, compensation method of dc link voltage have been applied. Output current of converter contains harmonic ripple at twice input ac line frequency, which causes a ripple in the dc link voltage so that beatless control is developed in inverter system to reduce the pulsating torque current. This system is verified by the system modelling and prototype test.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.37 no.6
• /
• pp.376-382
• /
• 1988

A small-signal low-frequency disturbance of the input line affects the regulated-output voltage of the series resonant converter. To mitigate the detrimental effect, the output feedback PI-controller is employed. Small-signal linear models are represented to characterize the closed loop series resonant converter system. Design equations for the PI-controller which satisfy stability and percent ripple conditions are derived from the closed-loop linear model. Experimental results are presented which show excellent correlation with theory.

• Proceedings of the KIPE Conference
• /
• 2000.07a
• /
• pp.689-692
• /
• 2000

This paper presents a designing for the Off-line UPS usig SMB Flywheel Energy Storage System. This described flywheel energy storage system is designed to replace of the conventional EMB(Electro Mechanical Battery) system. To realize the high efficiency and to minimize the torque ripple the waveform of the inverter output current is controlled to be sinusoidal. The actual performance of the Off-line UPS using flywheel energy storage system is described. The prototype device was manufactured, The experimental result has good characteristics at a time of power transition region and regeneration modes,

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.2 s.93
• /
• pp.161-166
• /
• 2005

The synthesis procedure of Marchand balun using planar coupled-line is presented. The design limitations of this type of balun have been described before its synthesis procedure. The balun has equi-ripple passband responses and balanced output without fourth balanced transmission line which is difficult to implement with conventional planar topology. As an example, 2:1 Marchand balun is designed and its momentum simulation result show good verification fur this methodology.

• Proceedings of the KIEE Conference
• /
• 2007.10c
• /
• pp.77-79
• /
• 2007

In previous structure of single phase LSPM, there is large torque ripple that makes a noise and a vibration by a distortion of flux distribution in air gap. By this reason, the single phase LSPM is not accepted home applications. So, in this paper, we propose new structure of single phase LSPM(Line Start Permanent magnet Motor). The proposed model is reduced a torque ripple about a half than previous model.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.8 no.5
• /
• pp.1068-1073
• /
• 2004

5 V/500 mA transless type power module was designed by using a semiconductor switching technique for a small-sized electric power source. It used voltage drop type chopper method, and is composed of switching circuit, control circuit, voltage detect circuit, and constant voltage circuit. The switching power module which is designed in this study, showed load regulation of 0.2 V, line regulation of 0.1 V, output ripple of 85 mVp-p, switching frequency of 64.7 kHz, maximum power efficiency of 58 %, and satisfied its reliability and EMC test.

• Proceedings of the KIEE Conference
• /
• 2001.07b
• /
• pp.974-976
• /
• 2001

This paper presents a method to reduce commutation torque ripples occurred during commutation in brushless do motor drives using a single DC-link current sensor. In brushless dc motor drives with a single dc current sensor instead of 3-phase line current sensors, it is noted that dc-link current sensor cannot give any information corresponding to the motor currents during line current commutation intervals. A new technique to resolve such a problem is dealt with based on a deadbeat current control in which motor armature voltage command is computed from a dc-link current reference, an actual current and counter emf voltage. The simulation results show that the proposed method reduces the torque ripple significantly.