• Progress in Superconductivity and Cryogenics
• /
• v.14 no.4
• /
• pp.36-40
• /
• 2012

This paper presents an experimental and numerical study on current limiting characteristics of a fault current controller (FCC). The FCC consists of an AC/DC power converter, a superconducting coil, and a control unit. Even though some previous researches proved that the FCC could adjust the fault current level, the current limiting characteristics by the superconducting coil should be investigated for design of the coil. In this paper, four kinds of model coils were tested; 1) air core, 2) iron core without any bias, 3) reversely magnetized core (RMC) using permanent magnets, and 4) RMC using an electromagnet. Based on a comparative study, it is confirmed that a RMC by an electromagnet (EM) could increase the effective inductance of the coil. In this paper, a numerical code to simulate the HTS coil with RMC was developed. This code can be applied to design the HTS coil with active reversely magnetized bias coil.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.39 no.3
• /
• pp.254-262
• /
• 1990

In the active power filter, the PWM method for controlling the power converter plays an important role for the performance and the efficiency of the filter. In this paper, a new PWM method for the single phase current source type active power filter is presented, which is intended particularly for obtaining the maximum efficiency of the compensation. This method is basically based upon the optimized injection method, but in contrast to the existing method, this method adapts the optimized injection method by putting not only the pulse width, but also the pulse position into control variables. By doing this, when the number of pulses per one cycle is N, lower order harmonics up to the Nth order can be completely eliminated by the filter. So, this method is much more efficient than any other existing method. These characteristics are well verified by the computer simulations and the experiments.

• Proceedings of the KIEE Conference
• /
• 2001.10a
• /
• pp.233-235
• /
• 2001

On the active filter converter for power factor correction is used inverter for a air-conditioner's power supply to meet IEC standard In the active filter topology for power factor correction, extra switch only control the input current indirectly to satisfied with the IEC standard for reducing the cost and size. In this paper, by dividing the input current into two different modes, the current conduction period can be widened and harmonics can largely be canceled between the two modes. Hence, the harmonics characteristics can be significantly improved, whereby the lower order harmonics, such as the fifth and seventh orders, are much reduced. The results are confirmed by theoretical and experimental implementations.

• Proceedings of the KIEE Conference
• /
• 2001.10a
• /
• pp.239-241
• /
• 2001

Recently the power supply equipments have tendency to take multiple feedback loop paths. In this paper, the state space averaging technique is applied for the analysis of flyback type current mode control circuit. We made real converter for the gurantee of stable output characteristic and proper design of feedback circuit. The validity of proposed method is verified from test results. The improvement of stability is confirmed by sinusoidal signal injection method with isolated transformer. It is known that phase margin is sufficient and gain crossover frequency $f_c$, is nearly 1/5 of switching frequency $f_s$, from the experimental result with frequency response analyzer.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.5 no.2
• /
• pp.103-115
• /
• 2002

This paper describes the results on the design and implementation of large capacity cable checking system using I/O buffer method. The I/O buffer module which has feedback loops with input and output buffers is designed with logic gate in the VME board and controlled by MPC860 microprocessor. So this system can check a lot of cable at the same time with less size and less processing time than that of relay matrix method with the A/D converter. The size of the I/O buffer module can be variable according to the number of cable. And any type of cable can be checked even if the pin assignment of cable is changed.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.55 no.1
• /
• pp.39-46
• /
• 2006

PLL is a key item of power converter for power quality compensation and power flow control. This paper proposes a novel 3-phase PLL that is composed of ALC and PI controller. The operational principle was investigated through theoretical approach, and the performance was verified through computer simulations with MATLAB and experimental works with TMS320VC33 DSP board. The proposed 3-phase PLL shows accurate performance under the voltage disturbances such as sag, harmonics. phase-angle jump, and frequency change.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.41 no.6
• /
• pp.600-606
• /
• 1992

The series connection of power switching semiconductor elements is essential when a high voltage converter is made, so researches are being conducted to further develop this technology. In the series connection of power switching semiconductor elements, the main problem is that simultaneous conduction at turn-on and simultaneous blocking at turn-off together with voltage balancing are unattainable because of the difference of their switching characteristics. In this paper a novel series connection algorithm is proposed, which can implement not only the synchronization of the points of turn-on and turn-off time but the dynamic voltage balancing in spite of the difference of each switching characteristics. The proposed method is that the compensated control signal is attained from the voltage feedback signal and applied to the series-connected power transistors independently. Computer simulation and experimental results verify its validity.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.50 no.3
• /
• pp.140-145
• /
• 2001

The instantaneous voltage drop is occurred when the fault is happened on the nearby feeders. The instantaneous voltage drop is continued during relatively short period. But, the effect of it can be very severe to some sensitive devices. That is, it can be the reason of restart or malfunction of some devices. And these phenomenons can cause the enormous economical damage and shorten the lifetime of the devices. In this paper, the device which can compensate the instantaneous voltage drop, is studied. Through the computer simulation using PSCAD/EMTDC, the validity of the control algorithm using peak detection method is verified. And the Dynamic Voltage Restorer(DVR) prototype is designed and constructed. Through the experiment, the function and performance of the DVR prototype is verified.

• Journal of Power Electronics
• /
• v.9 no.1
• /
• pp.43-50
• /
• 2009

This paper deals with a novel solid state controller (NSSC) for an isolated asynchronous generator (IAG) feeding 3-phase 4-wire loads driven by constant power prime movers, such as uncontrolled pico hydro turbines. AC capacitor banks are used to meet the reactive power requirement of the asynchronous generator. The proposed NSSC is realized using a set of IGBTs (Insulated gate bipolar junction transistors) based current controlled 2-leg voltage source converters (CC- VSC) and a DC chopper at its DC bus, which keeps the generated voltage and frequency constant in spite of changes in consumer loads. The neutral point of the load is created using aT-configuration of the transformers. The IAG system is modeled in MATLAB along with Simulink and PSB (power system block set) toolboxes. The simulated results are presented to demonstrate the capability of the isolated generating system consisting of NSSC and IAG driven by uncontrolled pico hydro turbine and feeding 3-phase 4-wire loads.

• Journal of Power Electronics
• /
• v.11 no.5
• /
• pp.655-661
• /
• 2011

This paper presents two topologies for single-stage single-phase double-buck type PFC converters, designed to operate at high power factor, near sinusoidal input currents and adjustable output voltage. Unlike the known buck type PFC topologies, in which the output voltage is always lower than the maximum input voltage, the proposed converters can operate at output voltages higher than the ac input peak voltage. A reduced number of switches on the main path of the current are another characteristic of the two proposed topologies. To shape the input line currents, a fast and robust controller based on a sliding mode approach is proposed. This active non-linear control strategy, applied to these converters allows high quality input currents. A Proportional Integral (PI) controller is adopted to regulate the output voltage of the converters. This external voltage controller modulates the amplitude of the sinusoidal input current references. The performances of the presented rectifiers are verified with experimental results.