• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.9
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• pp.1288-1296
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• 2015

The ac side current of a line commutated converter(LCC) high voltage direct current (HVDC) is characterized by highly non-sinusoidal waveform. If the harmonic current is allowed to flow in the connected ac network, it may cause unacceptable levels of distortion. Therefore, ac side filters are required as part of the total HVDC converter station, in order to reduce the harmonic distortion of the ac side current and voltage to acceptably low levels. The ac filters are also employed to compensate the requested reactive power because LCC HVDC also consume substantial reactive power. Among different types of filters, triple-tuned filters have been widely utilized for HVDC system. This paper presents two design methods of triple-tuned filter; equivalent method and parametric method. Using a parametric method, in particular this paper proposes a design algorithm for a triple tuned filter. Finally, the performance of the design algorithm is evaluated for a 250kV HVDC system in Jeju island. The results cleary demonstrate the effectiveness of proposed design method in harmonics reduction.

• Journal of Power Electronics
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• v.12 no.3
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• pp.377-386
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• 2012

An interleaved bridgeless buck-boost AC/DC converter is presented in this paper to achieve the characteristics of low conduction loss, a high power factor and low harmonic and ripple currents. There are only two power semiconductors in the line current path instead of the three power semiconductors in a conventional boost AC/DC converter. A buck-boost converter operated in the boundary conduction mode (BCM) is adopted to control the active switches to achieve the following characteristics: no diode reverse recovery problem, zero current switching (ZCS) turn-off of the rectifier diodes, ZCS turn-on of the power switches, and a low DC bus voltage to reduce the voltage stress of the MOSFETs in the second DC/DC converter. Interleaved pulse-width modulation (PWM) is used to control the switches such that the input and output ripple currents are reduced such that the output capacitance can be reduced. The voltage doubler topology is adopted to double the output voltage in order to extend the useable energy of the capacitor when the line voltage is off. The circuit configuration, principle operation, system analysis, and a design example are discussed and presented in detail. Finally, experiments on a 500W prototype are provided to demonstrate the performance of the proposed converter.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.3
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• pp.165-172
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• 2003

This paper presents an operation scheme to enhance the power system security by applying FACTS on Power systems. Three main generic types of FACTS devices are suggested an illustrated. Flow congestions over lines have been solved by controlling active power of series-compensated FACTS devices and low voltages at buses have been solved by controlling reactive power of shunt-compensated FACTS devices. Especially, Especially, UPFC has been applied in both line congestion and low voltages. Two kinds of indices which indicate the power system security level related to line flow and bus voltage are utilized in this paper. They have been minimized to enhance the power system security level through the iterative method and the sensitivity vector of security index is derived to determine the direction to minimum. The proposed algorithm has been tested on the IEEE 57-bus system with FACTS devices in a normal condition and a line-faulted contingency.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.2
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• pp.148-155
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• 1998

A novel single-switch, single-stage, AC/DC forward converter with transformer magnetic energy feedback technique for power factor correction is proposed. The operational principle and analysis of the proposed converter is presented. The proposed converter gives the good power factor correction, low line current harmonic distortions, and tight output voltage regulation. The prototype shows the IEC 555-2 requirements are met satisfactorily with nearly unity power factor.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.81-87
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• 2007

This paper proposes a new capacitance estimation scheme for a DC-link capacitor in a three-phase AC/DC/AC PWM converter. A controlled AC voltage with a lower frequency than the line frequency is injected into the DC-link voltage, which then causes AC power ripples at the DC side. By extracting the AC voltage and power components on the DC output side using digital filters, the capacitance can then be calculated using the Support Vector Regression (SVR). By training of SVR, a function which relates a given input (capacitor's power) and its corresponding output (capacitance value) can be derived. This function is used to predict outputs for given inputs that are not included in the training set. The proposed method does not require the information of DC-link current and can be simply implemented with only software and no additional hardware. Experimental results confirm that the estimation error is less than 0.16%.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2138-2139
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• 2005

We demonstrate a simple CO2 laser by controlling firing angle of a TRIAC switch in ac power line. The power supply for our laser system switches the voltage of the AC power line (60Hz) directly. The power supply does not need elements such as a rectifier bridge, energy-storage capacitors, or a current-limiting resistor in the discharge circuit. In order to control the laser output power, the pulse repetition rate is adjusted up to 60Hz and the firing angle of TRIAC gate is varied from 45 to 135. A ZCS(Zero Crossing Switch) circuit and a PIC one-chip microprocessor are used to control the gate signal of the TRIAC precisely. The maximum laser output of 40W is obtained at a total pressure of 18Torr, a pulse repetition rate of 60Hz, and a TRAIC gate firing angle of 90.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.90-94
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• 2003

Recently, many nations have released standard such as IEC 1000-3-2 and IEEE 519 which impose a limit on the harmonic current drawn by equipment connected to AC line in order to prevent the distortion of an AC line. Among the wide variety of active methods for improving power factor and harmonic distortion, the boost converter is very effective because it has a continuous line current , small choke filter and high power factor. In high power application, however, the bridge diode loss in the boost converter has made the efficiency lower and the temperature of the board higher. A new approach without bridge diode to make the same characteristics of the conventional boost converter has also been developed. This paper present the comparisons between the continuous current mode(CCM) operated conventional boost converter and the boundary current mode(BCM) operated the bridgeless boost converter for high efficiency and high power factor.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.11
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• pp.2419-2422
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• 2010

The current marine internal communication systems are usually composed of NMEA0183, NMEA2000, and MiTS protocols which are located on the physical layer based on RS-422, RS-485, CAN, and EtherNet. However, general vessel communication method have a weak point that must establish the extra private line. But, the power line communication has advantage over general vessel communication method as it uses AC220V/DC24V without changing line. Therefore, we will propose a new bridge based on the DC-PLC(power Line communication) technique which support the NMEA0183 protocol inside vessel network systems.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04c
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• pp.111-114
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• 2008

The paper considers the relation between on-line monitoring and diagnostics on the one hand and high-voltage (HV) withstand and partial discharge (PD) on-site testing on the other. HV testing supplies the basic data (fingerprints) for diagnostics. In case of warnings by on-line diagnostic systems, off-line withstand and PD testing delivers the best possible information about defects and enables the classification of the risk. Because alternating voltage (AC) is the most important test voltage, the AC generation on site is considered. Frequency tuned resonant (ACRF) test systems are best adapted to on-site conditions. They can be simply combined with PD measuring equipment. The available ACRF test systems and their application to electric power equipment -from cable systems to power transformers - is described.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1577-1579
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• 1994

200-MW pulse modulators(total 11units) for the PLS linac employ the SCR phase control circuit. It controls 3-phase AC line voltage for the high-voltage DC power supply (DCPS, maximum of 25kVDC, 4.2A) which charges the pulse forming network(PFN). The PFN delivers 400kV, 500A, ESW $7.5{\mu}s$ pulse power to the 80-MW klystron amplifier tube. The SCR regulates 3-phase AC power and feeds to the high voltage transformer. Two different types of the transformer configurations namely ${\Delta}-{\Delta}$ and ${\Delta}-Y$, are alternatively installed to 11 modulator units for the suppression of harmonic noises. RC filters and reactors are also installed. Currently, approximately 110-kW of average AC power per unit is consumed at the normal operation level of the modulator with 30pps. This paper presents the operational characteristics of the high power pulse modulator, especially the experimental results of the AC line harmonic components generated by the operation of the high power pulse modulator to suppress the switching noises from the SCR and rectifying diode arrays.