• Journal of Power Electronics
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• 제8권3호
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• pp.248-258
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• 2008

The Voltage Source Converter (VSC) is replacing the conventional line commutated current source converters in High Voltage DC (HVDC) transmission systems. The control of a two-level voltage source converter and its design dealt with HVDC systems and various factors such as reactive power, power factor, and harmonics distortion are discussed in detail. Simulation results are given for the two-level converter and designed control is used for bidirectional power flow. The harmonics minimization is taken by extending the 6-pulse VSC to multipulse voltage source converters. The control is also tested and simulated for a 12-pulse voltage source converter to minimize the harmonic distortion in AC currents.

• Journal of Power Electronics
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• 제18권6호
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• pp.1879-1888
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• 2018

With power level of grid-connected converters rising, the switching frequency of the switching devices is commonly greatly reduced to improve its power capacity. However, this results in serious couplings of the dq current components, which leads to degradation of the static and dynamic performances of grid-connected converters and fluctuations of the reactive power in dynamic processes. In this paper, complex vector models under low switching frequency are established for an L/LCL grid-connected converter, and the relationship between the switching frequency and the coupling degree is analyzed. In addition, a series decoupling current control strategy is put forward. It is shown that the proposed control strategy can eliminate the couplings, improve the performances and have good robustness to parameter variations through static and dynamic characteristics analyses and a sensitivity analysis. Experimental and simulation results also verify the correctness of the theoretical analyses and the superiority of the proposed control strategy.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 추계학술대회
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• pp.124-125
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• 2019

This paper proposes a novel control method to minimize conduction losses of dual active bridge (DAB) converters for on-board chargers of electric vehicles (EVs). In the control method, two variables are regulated, which are the phase-shift angle between the primary and secondary full bridges and the switching frequency. From time-domain analysis, an optimal phase-shift angle is derived to achieve the minimum RMS value of the transformer current. The proposed method was implemented for a 3.6-kW SiC-based prototype to validate its effectiveness. A high efficiency over 97.3% has been achieved for a wide output voltage range.

• Journal of Power Electronics
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• 제18권4호
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• pp.985-996
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• 2018

The implementation and performance evaluation of an interleaved boundary conduction mode (BCM) boost power factor correction (PFC) converter is presented in this paper by employing three wide band-gap switching devices: a super junction silicon (Si) MOSFET, a silicon carbide (SiC) MOSFET and a gallium nitride (GaN) high electron mobility transistor (HEMT). The practical considerations for adopting wide band-gap switching devices to BCM boost PFC converters are also addressed. These considerations include the gate drive circuit design and the PCB layout technique for the reliable and efficient operation of a GaN HEMT. In this paper it will be shown that the GaN HEMT exhibits the superior switching characteristics and pronounces its merits at high-frequency operations. The efficiency improvement with the GaN HEMT and its application potentials for high power density/low profile BCM boost PFC converters are demonstrated.

• JSTS:Journal of Semiconductor Technology and Science
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• 제7권1호
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• pp.43-50
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• 2007

In a high-speed flash style or a pipelining style analog-to-digital converter (A/D converter), the DC reference fluctuation caused by external noises becomes serious, as the sampling frequency is increased. To reduce the fluctuations in conventional A/D converters, capacitors have been simply used, but the layout area was large. Instead of capacitors, a low-noise and small-size DC reference circuit based on transmission gate (TG) is proposed in this paper. In order to verify the proposed technique, we designed and manufactured a 6-bit 2GSPS CMOS A/D converter. The A/D converter is designed with a 0.18um 1-poly 6-metal n-well CMOS technology, and it consumes 145mW at 1.8V power supply. It occupies the chip area of 977um by 1040um. The measured result shows that SNDR is 36.25 dB and INL/DNL is within 0.5LSB, even though the DC reference fluctuation is serious.

• Journal of Power Electronics
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• 제13권5호
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• pp.746-756
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• 2013

The modularized subunit of an electronic power transformer (EPT) is a series connection of two H-bridge voltage-source converters and a DC-DC converter with a high-frequency isolation transformer (HFIT). On the basis of cascading and paralleling the modularized subunits, EPT can be used in high-voltage and large-current applications in the power system. This paper discusses the steady state analysis of the modularized subunit of EPT. Theoretical analysis considers the influences of the two H-bridge voltage-source converters on the two sides of the DC-DC converter. We deduce the formulas of the theoretical calculation on the internal electrical characteristics of EPT (e.g., the voltages of the DC-bus capacitor and the primary side peak current of the HFIT). This paper provides guidance on the design and selection of EPT key elements (e.g., the DC-bus capacitors and HFIT). Experimental results are obtained from a single subunit of a laboratory model rated at 962 V, 15 kVA. All calculations, simulations, and experiments confirm the theoretical analysis of the subunit of EPT.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권11호
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• pp.635-644
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• 2002

Many generating units can be in parallel connection to one battery and inverter. However, one of the biggest problems we encountered is that wind speed is fluctuated sharply in accordance with the unstable weather conditions. To solve this problem, we need energy storage equipment such as storage lead-acid battery. We design a system and analyze its modeling so that it supplies a stable power to the load through DC-AC inverter part. In this paper, we applied dual step-up/down buck-boost converter and dual high-frequency half-bridge converter to the proposed system. These converters are used to store energy in the battery regardless of the change of the wind speed. The operation process of two proposed types of converters for high-power battery charging is discussed along with simulation and experimental result. We design a charging circuit which is applicable in the actual wind power generation system for 30kw and confirm the circuit's validity.

• 조명전기설비학회논문지
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• 제23권9호
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• pp.98-107
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• 2009

기존의 하드 스위칭 고주파 PWM DC-DC 컨버터는 펄스 변조 캐리어 주파수의 고주파화를 수반하고, 전력용 반도체 스위칭 소자의 스위칭 손실의 증대나 스위칭 과도현상이 수반된 전압 서지나 전류 서지에 의한 EMI 등의 문제점들이 있다. 이러한 문제를 효과적으로 해결하기 위해 본 논문에서는 새로운 소용량 승압형 PWM 쵸퍼 회로의 동작원리를 서술하고, 시뮬레이션과 실험을 통하여 특성을 도출하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 D
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• pp.2201-2202
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• 2006

In this paper, we designed high performance, high quality and high density switch mode power supply for precision electronics, and communication equipments. For this, we used two parallel DC-DC converters, which have opposite phases, to support proper high performance and high quality power. To reduce switching losses and make high switching frequency, active-clamp and ZVS technique were employed in each converter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.569-570
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• 2006

In this paper, we designed high performance, high quality and high density switch mode power supply for precision electronics, and communication equipments. For this, we used two parallel DC-DC converters, which have opposite phases, to support proper high performance and high quality power. To reduce switching losses and make high switching frequency, active-clamp and ZVS technique were employed in each converter.