• Journal of Power Electronics
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• 제18권2호
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• pp.604-614
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• 2018

This paper proposes a synchronous switching technique for a Vienna rectifier that uses carrier-based pulse width modulation (CB-PWM). A three-phase Vienna rectifier, similar to a three-level T-type converter with three back-to-back switches, is used as a PWM rectifier. Conventional CB-PWM requires six independent gate signals to operate back-to-back switches. When internal switches are operated synchronously, only three independent gate signals are required, which simplifies the construction of gate driver circuits. However, with this method, total harmonic distortion of the input current is higher than that with conventional CB-PWM switching. A reactive current injection technique is proposed to improve current distortion. The performance of the proposed synchronous switching method and the effectiveness of the reactive current injection technique are verified using simulations and experiments performed with a set of Vienna rectifiers rated at 5 kW.

• 전기학회논문지P
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• 제57권3호
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• pp.231-235
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• 2008

Thyristor rectifiers are still the preferred choice for large magnet power supplies. However, large harmonic voltages, resulting in large current ripple, and slow dynamic response are major drawbacks of these converters. Joos presented a topology and a control technique for a hybrid large-power high-precision magnet power supply in 1996. The system consists of a phase controlled rectifier (PCR) connected in series with a high-frequency PWM converter. This paper improves the power circuit of the PWM converter using interphase transformer. Simulation result proves effect of the proposed system.

• 전력전자학회논문지
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• 제7권6호
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• pp.563-569
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• 2002

본 연구는 60Hz 절연변압기가 없는 형태의 고주파링크방식의 계통연계형 PCS(Power Conditioning System)를 개발하였다. 본 시스템은 고주파 DC-DC 컨버터, 고주파 절연변압기, 풀브리지 다이오드 정류기, DC filter, 저주파 인버터, LC 필터로 구성되어 있다. 고주파 DC-DC 컨버터는 20kHz의 bipolar PWM 펄스를 발생시키며, 이 펄스는 고주파 절연변압기를 통해 승압되고, 풀브리지 다이오드를 통해 정류된다. 마지막으로 저주파 인버터를 통해 정현파 전류가 계통에 유입되게 된다. 제안한 고주파링크방식의 시스템은 기존의 60Hz 절연변압기를 사용하는 시스템 보다 많은 스위칭 소자가 사용되지만, 60Hz 절연변압기를 생략함으로서 시스템의 소형경량화 및 저가화를 이룰 수 있었다.

• 조명전기설비학회논문지
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• 제19권6호
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• pp.16-21
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• 2005

본 논문에서는 고주파 트랜스의 여자 전류를 이용하지 않고, 인덕턴스를 이용한 새로운 부분공진 영전압 스위칭 PWM제어 고주파 절연형 풀-브리지 DC/DC 컨버터의 회로를 제안하여 그 동작 원리를 기존 방식과 특성을 비교하였다. 또한 고주파 절연 트랜스 2차측에 동기 정류용 전력용 MOSFET에 새로운 기능을 부가한 온-오프 제어방식을 이용하여 넓은 부하 범위에 걸쳐 안정된 영전압 스위칭(ZVS)동작을 실현하였다. 또한 제안한 DC-DC 컨버터의 실험장치에 의해서 실측 효율을 97[%]이상 달성하였고 직류 무정전전원의 PWM 정류기의 출력단에 이용되는 새로운 방식이 스위칭 전원으로서 유효성을 증명하였다.

• Journal of Power Electronics
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• 제15권1호
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• pp.202-215
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• 2015

This paper investigates the stability and performance of model predictive controlled active-front-end (AFE) rectifiers for energy storage systems, which has been increasingly applied in power distribution sectors and in renewable energy sources to ensure an uninterruptable power supply. The model predictive control (MPC) algorithm utilizes the discrete behavior of power converters to determine appropriate switching states by defining a cost function. The stability of the MPC algorithm is analyzed with the discrete z-domain response and the nonlinear simulation model. The results confirms that the control method of the active-front-end (AFE) rectifier is stable, and that is operates with an infinite gain margin and a very fast dynamic response. Moreover, the performance of the MPC controlled AFE rectifier is verified with a 3.0 kW experimental system. This shows that the MPC controlled AFE rectifier operates with a unity power factor, an acceptable THD (4.0 %) level for the input current and a very low DC voltage ripple. Finally, an efficiency comparison is performed between the MPC and the VOC-based PWM controllers for AFE rectifiers. This comparison demonstrates the effectiveness of the MPC controller.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.525-528
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• 2002

A Novel Zero Current Switching(ZCS) Pulse Width Modulation(PWM) boost converter for reducing two rectifiers reverse recovery related losses Is proposed. The switches of the proposed converter are operating to work alternatively turn-on and turn-off with soft switching(ZVS, ZCS) condition. The reverse recovery related switching losses and EMI problems of the proposed converter eliminates the reverse recovery current of the freewheeling diode(D, Dl) by adding the resonant inductor Lr, in series with the switch S2. The voltage and current stresses of the components are similar to those in its conventional hard switching counterpats. As mentioned above, the characteristics are verified through experimental results.

• 대한전기학회논문지
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• 제34권9호
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• pp.361-367
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• 1985

A new injection method is proposed for active power filters to eliminate AC harmonics in ac input current of nonlinear loads such as rectifiers. By injecting the PWM current determined by the proposed injection method, all the harmonics up to order nn can be eliminated to exactly zero. This PWM injection current can be generated by sampling total harmonic wave at the rate of M and the sampled values are converted into the proposed PWM wave with N pulse-width variables and adjustable current magnitude Im. These variables are deetermined by solving a set of N nonlinear harmonic equations and the harmonic-elimination characteristics of the new injection are investigated through digital computer sinmulation. Also by comparing between the simulated results and the ones synthesized by data stored in EPROM, the possibility of the suggested injection method can be shown.

• Journal of Power Electronics
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• 제19권2호
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• pp.560-568
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• 2019

This paper studies the inherent relationship between currents and zero-sequence components. Then a precise algorithm is proposed to calculate the injected zero-sequence component to control the DC-Link neutral-point voltage balance, which can result in a more efficient and flexible neutral point voltage balance with a desirable performance. In addition, it is shown that carried-based PWM with the calculated zero-sequence component scheme can be equivalent to space-vector pulse-width modulation (SVPWM). Based on the proposed method, the optimal zero-sequence component of the feasible modulation indices is analyzed. In addition, the unbalanced load limitation of the DC-Link neutral-point voltage balance control is also revealed. Simulation and experimental results are shown to verify the validity and practicality of the proposed algorithm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.1313-1315
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• 2002

This paper proposes an inverter for the grid-connected photovoltaic system based on the transformer-less inverter. This system consists of a high frequency inverter bridge, high frequency transformer, diode bridge rectifiers, a DC filter, a low frequency inverter bridge, and an AD filter. The high frequency inverter bridge switching at 20kHz is used to generate bipolar PWM pulse, which is subsequently rectified by diode bridge rectifiers to result in a full-wave rectified sine wave. Finally, it is unfolded by a low frequency inverter bridge to result in a 60Hz sine wave power output. In this paper, the control algorithm for synchronous current feedback control method and a maximum power point tracking (MPPT) method using DSP are described. And, the simulation and experimental results are shown to verify the validity of the proposed system.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.117-122
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• 2005

This paper proposes an inverter for the grid-connected photovoltaic system based on the transformer-less inverter. This system consists of a high frequency converter bridge, high frequency transformer, diode bridge rectifiers, a DC filter, a low frequency inverter bridge, and an AC filter. The high frequency converter bridge switching at 20kHz is used to generate bipolar PWM pulse, and the high frequency transformer raise its voltage twice, which is subsequently rectified by diode bridge rectifiers to result in a full-wave rectified sine wave. Finally, it is unfolded by a low frequency inverter bridge to result in a 60Hz sine wave power output. Even though the high frequency link system needs more power semiconductors, a reduced size, light weight, and saved parts cost make this system more comparative than the other systems due to elimination of 60Hz transformer.