• Journal of international Conference on Electrical Machines and Systems
• /
• 제3권2호
• /
• pp.176-183
• /
• 2014

Three-phase four-wire distribution systems are used for both three-phase three-wire loads and single-phase two-wire consumer appliances in South Korea, Myanmar and other countries. Unbalanced load conditions frequently occur in these distribution systems. These unbalanced load conditions cause unbalanced voltages for three-phase and single-phase loads, and increase the loss in the distribution transformer. In this paper, we propose constant DC capacitor voltage control based strategy for the active load balancer (ALB) in the three-phase four-wire distribution systems. Constant DC capacitor voltage control is always used in active power line conditioners. The proposed control strategy does not require any computation blocks of the active and reactive currents on the distribution systems. Balanced source-side currents with a unity power factor are obtained without any calculation block of the unbalanced active and reactive components on the load side. The basic principle of the constant DC capacitor voltage control based strategy for the ALB is discussed in detail and then confirmed by both digital computer simulations using PSIM software and prototype experimental model. Simulation and experimental results demonstrate that the proposed control strategy for the ALB can balance the source currents with a unity power factor in the three-phase four-wire distribution systems.

• Journal of Electrical Engineering and Technology
• /
• 제11권1호
• /
• pp.125-134
• /
• 2016

We propose an efficient high voltage level shifter for a high side Buck converter driving a light-emitting diode (LED) lamp. The proposed circuit is comprised of a low voltage pulse width modulation (PWM) signal driver, a coupling capacitor, a resistor, and a diode. The proposed method uses a property of a PWM signal. The property is that the signal repeatedly transits between a low and high level at a certain frequency. A low voltage PWM signal is boosted to a high voltage PWM signal through a coupling capacitor using the property of the PWM signal, and the boosted high voltage PWM signal drives a p-channel metal oxide semiconductor (PMOS) transistor on the high side Buck converter. Experimental results show that the proposed level shifter boosts a low voltage (0 to 20 V) PWM signal at 125 kHz to a high voltage (370 to 380 V) PWM signal with a duty ratio of up to 0.9941.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
• /
• pp.117-120
• /
• 1988

A new current source inverter (CSl) with dc-side commutation and load-side energy recovery circuit is proposed with analysis and explanation of the circuit operation. Proposed inverter overcomes the most drawbacks of the conventional CSI's - high device voltage stress, low operating frequency range, large commutation capacitance, etc. - by employing simultaneous recovery and commutation concept. The new CSI employs only one commutation capacitor and it can be built with considerably low cost. The commutation energies are temporarily stored into a large dc capacitor and recovered to the load side, thus the device voltage stress is low and the efficiency is high in the proposed inverter. Computer simulation results are given at the steady state, and a guideline determining the commutation circuit is given.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.57-61
• /
• 2006

In the single-phase switched reluctance motor (SRM) drive, the required DC source is generally supplied by the circuit consisting of bridge rectifier and large filter capacitor connected with DC line terminal. Due to the large capacity of the capacitor, the charged time of capacitor is very short from the AC source. Lead to the bridge rectifiers draws pulsating current from the AC source side, which results in reduction of power factor and low system efficiency. Therefore a novel single-phase SRM drive system is presented in this paper, which includes drive circuit realizing reduction of torque ripple and improvement of power factor with a novel switching topology. The proposed drive circuit consists of one switching part and diode, which can separate the output of AC/DC rectifier from the large capacitor and supply power to SRM alternately, in order to realize the torque ripple reduction and power factor improvement through the switching scheme. In addition, the validity of the proposed method is tested by some simulations and experiments.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2014년도 전력전자학술대회 논문집
• /
• pp.359-360
• /
• 2014

본 논문은 Y-capacitor와 미분기를 이용한 절연형 AC/DC컨버터의 제어신호 전송기법을 제안한다. 기존 SSR(Secondary Side Regulation)의 제어단(Photo-coupler, TL431 및 부가회로)은 바이어스 전류에 의한 대기전력 손실이 크다. 하지만 제안된 방식은 기존 SSR의 제어단을 제거하고, 2차 측 제어신호를 EMI노이즈 경로로 사용되는 Y-capacitor와 저항, 커패시터만을 이용하여 1차 측으로 전송한다. 제안 신호전송기법의 이론적 해석과 PSIM Tool을 이용한 Simulation 결과를 통하여 타당성을 검증하였다.

• 전력전자학회논문지
• /
• 제17권1호
• /
• pp.8-13
• /
• 2012

DSTATCOM is active filter that reduces nonlinear and unbalanced currents. Researches about DSTATCOM are mainly divided two parts, one is the reference value calculation of compensation current depending on the calculation of the load-side average active power and dc-link capacitor average voltage, the other part is actual current control depending on the reference value of compensation current. This paper proposes a calculation of dc-link capacitor average voltage ripple voltage extraction instead of conventional method using LPF. The utility of the proposed algorithm is verified through the theoretical analysis and the experiment under unbalance loads and non-linear load.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
• /
• pp.227-231
• /
• 2001

A new primary-side-assisted zero-voltage and zero-current switching (ZVZCS) three-level DC-DC converter with flying capacitor is proposed. The three-level converters are promising in high voltage applications, and ZVZCS is a very effective means for reducing switching losses. The proposed DC-DC converter uses only one auxiliary transformer and two diodes to obtain ZCS for the inner leg. It has a simple and robust structure, and offers soft-switching capability even in short-switching conditions. The proposed converter was verified by experiments in a 6KW prototype designed for communication applications and operating at 100kHz.

• Journal of Power Electronics
• /
• 제13권1호
• /
• pp.20-30
• /
• 2013

This paper presents a soft switching DC/DC converter for high voltage application. The interleaved pulse-width modulation (PWM) scheme is used to reduce the ripple current at the output capacitor and the size of output inductors. Two converter cells are connected in series at the high voltage side to reduce the voltage stresses of the active switches. Thus, the voltage stress of each switch is clamped at one half of the input voltage. On the other hand, the output sides of two converter cells are connected in parallel to achieve the load current sharing and reduce the current stress of output inductors. In each converter cell, a half-bridge converter with the asymmetrical PWM scheme is adopted to control power switches and to regulate the output voltage at a desired voltage level. Based on the resonant behavior by the output capacitance of power switches and the transformer leakage inductance, active switches can be turned on at zero voltage switching (ZVS) during the transition interval. Thus, the switching losses of power MOSFETs are reduced. The current doubler rectifier is used at the secondary side to partially cancel ripple current. Therefore, the root-mean-square (rms) current at output capacitor is reduced. The proposed converter can be applied for high input voltage applications such as a three-phase 380V utility system. Finally, experiments based on a laboratory prototype with 960W (24V/40A) rated power are provided to demonstrate the performance of proposed converter.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.320-323
• /
• 2001

A ZVZCS(Zero-Voltage and Zero-Current-Switching) Three Level DC/DC Converter is presented to secondary auxiliary circuit. The converter presented in this paper used a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switch. A secondary auxiliary circuit, which consists of one small capacitor and two small diode, is added in the secondary to provides ZVZCS conditions to primary switches, and aids to clamp secondary rectifier voltage. The auxiliary circuit Includes neither lossy component nor addition active switch, which makes the proposed converter efficient and effective. The principle of operation, feature, and design considerations are illustrated and verified through the experiment with a 500W 50kHz prototype converter.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.200-204
• /
• 2001

A ZVZCS(Zero Voltage and Zero Current Switching) Three Level DC/DC Converter is presented to secondary auxiliary circuit. The new converter presented in this paper used a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switch. A secondary auxiliary circuit, which consists of one small capacitor two small diode and one coupled inductor is added in the secondary to provides ZVZCS conditions to primary switches, ZVS for outer switches and ZCS for inner switches. Many advantages including simple circuit topology high efficiency, and low cost make the new converter attractive for high power applications. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 1kW 50kHz IGBT based experimental circuit.