• Journal of Power Electronics
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• 제17권3호
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• pp.653-663
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• 2017

Multilevel active neutral-point-clamped (ANPC) converter combines the advantages of three-level ANPC converter and multilevel flying capacitor (FC) converter. However, multilevel ANPC converter often suffers from capacitor voltage balancing problems. In order to solve the capacitor voltage balancing problems for five-level ANPC converter, phase-shifted pulse width modulation (PS-PWM) is used, which generally provides natural voltage balancing ability. However, the natural voltage balancing ability depends on the load conditions and converter parameters. In order to eliminate voltage deviations under steady-state and dynamic conditions, the active voltage-balancing control (AVBC) methods of floating capacitors and dc-link capacitors based on PS-PWM are proposed. First, the neutral-point current is regulated to balance the neutral-point voltage by injecting zero-sequence voltage. After that, the duty cycles of the redundant switch combinations are adjusted to balance the floating-capacitor voltages by introducing moderating variables for each of the phases. Finally, the effectiveness of the proposed AVBC methods is verified by experimental results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.295-296
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• 2014

본 논문에서는 저 전압 스트레스 및 다채널 전류평형을 위한 Floating 전압 스택형 단일스위치 LED(Light Emitting Diode) 구동회로를 제안한다. 기존의 다채널 LED 구동회로는 LED 채널 수 만큼 boost converter가 필요하지만, 제안된 LED 구동회로는 단 하나의 buck converter와 n-1개의 balancing capacitor만을 필요로 한다. 기존 boost converter의 경우 모든 구성 요소는 LED 전압만큼의 높은 전압 스트레스를 갖지만 제안 회로의 경우 모든 구성 요소들은 기존 대비 절반 정도의 전압 스트레스를 갖는다. 또한 제안 LED 구동회로는 다채널의 LED 전류의 평형을 위하여 balancing capacitor만을 사용하기 때문에 높은 신뢰성과 비용의 효율성을 제공한다. 최종적으로 제안된 구동회로의 우수성과 이론적 분석의 타당성 검증을 위하여 46" 2채널 LED 구동회로를 위한 시작품을 제작하여 고찰된 실험결과를 제시한다.

• Journal of Power Electronics
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• 제12권5호
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• pp.739-747
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• 2012

This paper applies carrier phase shifted pulse-width modulation (CPS-PWM) to transformerless modular multilevel converters (MMC) to improve the output spectrum. Because the MMC topology is characterized by the double-star connection of six legs consisting of cascaded modular chopper cells with floating capacitors, the balance control of the DC-link capacitor voltage is essential for safe operation. This paper presents a leg-balancing control strategy to achieve DC-link voltage balance under all operating conditions. This strategy based on circulating current decoupling control focused on DC-link balancing between the upper and lower legs in each phase pair by considering the six legs as three independent phase-pairs. Experiments are implemented on a 100-V 3-kVA downscaled prototype. The experimental results show that the proposed leg-balancing control is both effective and practical.

• Journal of Power Electronics
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• 제14권6호
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• pp.1109-1118
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• 2014

A Fundamental Frequency Sorting Algorithm (FFSA) is proposed in this paper to balance the voltages of floating dc capacitors for Modular Multilevel Converters (MMCs). The main idea is to change the sequences of the CPS-PWM carriers according to the capacitor voltage increments during the previous fundamental period. Excessive frequent sorting is avoided and many calculating resources are saved for the controller. As a result, more sub-modules can be dealt with. Furthermore, it does not need to measure the arm currents. Therefore, the communication between the controllers can be simplified and the number of current sensors can be reduced. Moreover, the proposed balancing method guarantees that all of the switching frequencies of the sub-modules are equal to each other. This is quite beneficial for the thermal design of the sub-modules and the lifetime of the power switches. Simulation and experimental results acquired from a 9-level prototype verify the viability of the proposed balancing method.