• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.36S no.2
• /
• pp.108-119
• /
• 1999

In this paper, a three phase PWM AC to DC boost converter that operates with unity power factor and sinusodial input currents si presented. The current control of the converter is based on the space vector PWM strategy with fixed switching frequency and the imput current tracks the reference current within one sampling time interval. Space vector PWM strategy for current control was materialized as a digital control method by using DSP. By using this control strategy low ripples in the output voltage, low harmonics in the input current and fast dynamic responses are achieved with a small capacitance in the dc link.

• Progress in Superconductivity and Cryogenics
• /
• v.9 no.3
• /
• pp.21-25
• /
• 2007

Superconducting fault current limiter (SFCL) is attractive apparatus to reduce fault current in power grid. Since it is applied to the alternating current (AC) power line, the SFCL has losses in the normal operation. Recently, coated conductor (CC) is noticeable material employed for resistive bifilar winding type SFCL in many research groups. Bifilar structure is expected to have low AC loss by magnetic field offset as compared with the single tape structure in the same length. This paper reports about characteristic of bifilar pancake type coil for SFCL application in AC loss aspect. The bifilar coil is wound using CC with facing on HTS sides each other. Transport AC loss measurement and characteristic analysis of the bifilar coil using CC have been performed at 77K. The test results are compared with the Norris equations and the test results of non-inductively wound paralleled solenoid type coil which is suggested and tested in this group at present.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2007.05a
• /
• pp.187-192
• /
• 2007

The terminal voltage of a synchronous generator is maintained by the field current control of excitation system Generally AC/DC converter which is component of AVR(Automatic Voltage Regulator) system for excitation current control is connected to diode rectifier and DC/DC converter system In the case of diode rectifier system of phase controlled converter, AC/DC converter has low power factor and some low order harmonics in the line current. In this paper, two-stage three-phase PWM AC/DC converter is studied to solve these problems, The proposed method is verified by the computer simulations and experimental results in prototype generation system.

• Progress in Superconductivity and Cryogenics
• /
• v.15 no.2
• /
• pp.44-47
• /
• 2013

Large AC loss from the second generation (2G) high temperature superconducting (HTS) wires has been one of the major bottlenecks in power applications with HTS materials. Moreover, the large power applications also require the large current capacity from the HTS wires, which makes them produce larger AC losses. In order to reduce the AC loss from the HTS conductors with large current capacity, an HTS compact cable with some striations on the superconducting layers has been proposed. In this paper, we prepared some sample HTS compact conductors with striations, and measured their magnetization loss from the external magnetic field. We also made some slits on the superconducting layer of the HTS wire by laser cutting to reduce the aspect ratio of the superconducting layers. It would make the low eddy current loss and magnetic decoupling. Finally, the magnetization losses of the sample HTS compact conductors were measured and analyzed.

• Journal of Power Electronics
• /
• v.12 no.2
• /
• pp.276-284
• /
• 2012

AC/AC power conversion is widely used to feed AC loads with a variable voltage and/or a variable frequency from a constant voltage constant frequency power grid or to connect critical loads to an unreliable power supply while delivering a very balanced and accurate sinusoidal voltage system of constant amplitude and frequency. The load specifications will clearly impose the requirements for the inverter stage of the power converter, while wider ranges of choices are available for the rectifier. This paper investigates the utilization of a buck-type current source rectifier as the active front-end stage of an AC/AC converter for applications that require an adjustable DC-link voltage as well as elimination of the low-frequency common mode voltage. The proposed solution is to utilize a combination of two or more zero current vectors in the Space Vector Modulation (SVM) technique for Current Sources Rectifiers (CSR).

• Proceedings of the KIEE Conference
• /
• 2006.07b
• /
• pp.809-810
• /
• 2006

Reduction of AC losses is very important for realizing HTS cable and it had been reported that the same layer current controlled by twisting pitch and direction could reduce the AC losses effectively. During the long-term development of HTS cables, the superconductor AC losses will need to be reduced to a level determined by the economics of each installation and the efficiency of the refrigeration. Theoretical models have been developed to predict the magnitude of the losses in cables composed of several layers of flat HTS tapes. This paper is manufactured mini-model HTS cable and voltage signal line to spiral shape. Mini-model HTS cable is composed of 13 HTS tape. We measured to critical current and AC loss and compared used lock-in-amp to cancel coil. This data is useful to HTS cable of DAPAS program.

• Proceedings of the KIEE Conference
• /
• 1996.11a
• /
• pp.373-377
• /
• 1996

Recently, active power factor control for AC/DC converter has been required to replace for a conventional diode rectifier. A voltage type AC/DC converter is widely used to obtain higher regulated DC voltage than input voltage with a unity power factor and a sinusoidal line current. This paper describes several active power factor control method for AC/DC converter. The analysis of several active power factor control is given. The simulations for hysteresis control, peak current control. constant frequency control and average current mode control are represented and compared.

• Proceedings of the KIPE Conference
• /
• 2020.08a
• /
• pp.328-329
• /
• 2020

The AC/DC converter, which connects the AC grid to the DC grid in the microgrid, is a critical component in power sharing and stable operation. Sometimes the AC/DC converters are connected in parallel to increase the transmission and reception capacity. When connected in parallel, circulating current is generated due to line impedance difference or sensor error. As a result of circulating current, there is deterioration and loss in particular PCS(Power Conversion System). In this paper, we propose droop control with novel adaptive virtual impedance for reducing circulating current. Feasibility of proposed algorithm is verified by PowerSIM simulation.

• Proceedings of the KIPE Conference
• /
• 2000.07a
• /
• pp.282-285
• /
• 2000

A new current controller implemented in a-b-c frame for AC-DC converter is proposed. The proposed MTPWM(Modified Trapezoidal PWM) Which is quite suitable for three phase AC-DC converter. It is known that MTPWM has good harmonics characteristics for high modulation index. It is very simple and requires no transformation in it. The results of computer simulation are shown for the validity of proosal.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2001.02a
• /
• pp.102-103
• /
• 2001

In this paper we calculate the AC Loss in the superconducting slab carrying ac transport current. Magnetic diffusion equation for computation of the electric field and current distribution are based on Maxwell's equations and non-linear constitutive equation. The E-J characteristics of superconductor are applied to computation. We will present the result of the high-temperature superconductor case comparison with the slab of low temperature superconductor.