• 전력전자학회논문지
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• 제25권1호
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• pp.68-71
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• 2020

As a T-type three-level PWM converter has several intrinsic advantages, it has been widely studied for many applications. However, it requires an additional voltage control loop for balancing each DC link voltage. Generally, satisfying this requirement involves the use of an offset voltage to provide a neutral point current without affecting other variables, such as the total DC link voltage and three-phase input current. In this study, the theoretical relationship between the offset voltage and the neutral point current is analyzed. The results can be beneficial for effective voltage balancing controller design. The effectiveness of the analytical modeling is verified by simulation and experimental results.

• 전력전자학회논문지
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• 제27권5호
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• pp.417-424
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• 2022

This study proposes a current-balancing technique for an interleaved buck converter using a variable inductor and a snubber capacitor. The proposed scheme balances the inductor current by using the variable inductor and enables zero voltage switching under all load ranges. With the variable inductor, the ripple of inductor current changes according to load variation. In addition, a 1.6 kW prototype is built to verify the validity of the proposed scheme, and the experimental results are successfully obtained.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.550-558
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• 2018

This paper presents the current limit strategy of voltage controller of delta-connected H-bridge static synchronous compensator (STATCOM) under an unbalanced voltage fault event. When phase to ground fault happens, the feasibility to heighten the magnitude of sagging phase voltage is considered by using symmetric transformation method in delta-structure STATCOM. And the efficiency to cover the maximum physical current limit of switching device is considered by using vector analysis method that calculate the zero sequence current for balancing the cluster energy in delta connected H-bridge STATCOM. The result is simple and obvious. Only positive sequence current has to be used to support the unbalanced voltage sag. Although the relationship between combination of the negative sequence voltage with current and zero sequence current is nonlinear, the more negative sequence current is supplying, the larger zero sequence current is required. From the full-model STATCOM system simulation, zero sequence current demand is identified according to a ratio of positive and negative sequence compensating current. When only positive sequence current support voltage sag, the least zero sequence current is needed.

• 정보처리학회논문지D
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• 제15D권1호
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• pp.73-86
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• 2008

최근 RFID(Radio Frequency Identification) 기술은 사물에 대한 자동적인 인식을 가능케 함으로써 물류, 의료, 식품관리 등과 같은 분야에 적용되고 있다. 부하 분산은 과부하 상태인 노드로부터 부하가 적은 노드로 작업 부하를 이동시켜 시스템의 확장성을 향상시키는 기본 기술이다. 시스템의 부하를 예측하기 어렵고 부하량의 편차가 큰 경우에는 적응적 부하 분산이 효과적인 것으로 알려져 있다. RFID 미들웨어는 많은 수의 리더로부터 수신된 태그 정보를 효율적으로 처리하기 위하여 기존의 부하 분산기술이 도입될 필요가 있다. RFID 시스템이 부하량을 예측하기 힘들고 편차가 큰 환경에 적용될 경우 실행시간에 시스템의 전체 부하량에 따라 적합한 정책으로 변경할 수 있는 적응적 부하 분산 기법을 사용하는 것이 바람직하다. 본 논문에서는 RFID 미들웨어에 적응적 부하 분산 기법을 도입하기 위한 접근 방법과 결과를 제시한다. 먼저 RFID 미들웨어의 작업 부하 모델을 결정한다. 그리고 부하 모델을 바탕으로 다양한 부하 분산 정책을 시스템의 부하 상태 별로 적용하여 시스템의 부하 상태에 적합한 부하 분산 정책을 선택한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 추계학술대회
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• pp.26-27
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• 2011

This paper focuses on the zero-voltage/zero current transition voltage equalization circuit for the series connected battery cell. By adding auxiliary resonant cells at the main switching devices such as MOSFET or IGBT, zero current switching is achieved and turned off loss of switching elements is eliminated and by the voltage/second balancing of the inductor, zero voltage switching can be applied to switching element. Transformer coupling between battery cells and ZVZCT (Zero Voltage Zero Current Transition) switching method allow the fast balancing speed and high frequency operation, which reduces the size and weight of the circuit. The validity of the battery equalization is further verified using simulation involving four lithium-ion battery cell models.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.195-196
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• 2012

In recent years, in an effort to improve the efficiency and the power density of the front-end power factor correction(PFC), the interleaving of multiple converter is employed. The conventional interleaved continuous conduction mode(CCM) boost PFC converter requires input and output voltage sensing and three current sensing to obtain current balancing between modules. In this paper, the interleaved CCM PFC converter based on modulated carrier control is proposed. With the proposed method, two phase interleaved PFC can be realized simply without line voltage sensing resistor and can achieve current balancing without additional current sensing resistor on common return path. The simulation studies are carried out to verify the effectiveness of the proposed control scheme.

• Journal of Power Electronics
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• 제3권4호
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• pp.205-214
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• 2003

This paper proposes a simple control strategy based on the discontinuous PWM (DPWM) to balance the DC-link voltage of three-level neutral-point-clamped (NPC) inverter at low modulation index. It introduces new DPWM methods in multi-level inverter and one of them is used for balancing the DC-link voltage. The current flowing in the neutral point of the DC-link causes the fluctuation of the DC-link voltage of the NPC inverter. The proposed DPWM method changes the path and duration time of the neutral point current, which makes the overall fluctuation of the DC-link voltage zero during a sampling time of the reference voltage vector. Therefore, by using the proposed strategy, the voltage of the DC-link can be balanced fairly well and the voltage ripple of the DC-link is also reduced significantly. Moreover, comparing with conventional methods which have to perform the complicated calculation, the proposed strategy is very simple. The validity of the proposed DPWM method is verified by the experiment.

• Journal of Power Electronics
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• 제12권4호
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• pp.567-577
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• 2012

This paper introduces a new scheme to balance the DC bus voltages of a cascaded H-bridge converter which is used as a Distribution Static Synchronous Series Compensator (D-SSSC) in electrical distribution network. The aim of D-SSSC is to control the power flow between two feeders from different substations. As a result of different cell losses and capacitors tolerance the cells DC bus voltage can deviate from their reference values. In the proposed scheme, by individually modifying the reference PWM signal for each cell, an effective balancing procedure is derived. The new balancing procedure needs only the line current sign and is independent of the main control strategy, which controls the total DC bus voltages of cascaded H-bridge. The effect of modulation index variation on the capacitor voltage is analytically derived for the proposed strategy. The proposed method takes advantages of phase shift carrier based modulation and can be applied for a cascaded H-bridge with any number of cells. Also the system is immune to loss of one cell and the presented procedure can keep balancing between the remaining cells. Simulation studies and experimental results validate the effectiveness of the proposed method in the balancing of DC bus voltages.

• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.629-638
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• 2016

This paper proposes a State-of-Charge (SOC) balancing control of Battery Power Modules (BPMs) for a modularized battery for Electric Vehicles (EVs) without additional balancing circuits. The BPMs are substituted with the single converter in EVs located between the battery and the inverter. The BPM is composed of a two-phase interleaved boost converter with battery modules. The discharge current of each battery module can be controlled individually by using the BPM to achieve a balanced state as well as increased utilization of the battery capacity. Also, an SOC balancing method is proposed to reduce the equalization time, which satisfies the regulation of a constant DC-link voltage and a demand of the output power. The proposed system and the SOC balancing method are verified through simulation and experiment.

• 한국산학기술학회논문지
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• 제21권3호
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• pp.585-593
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• 2020

현재까지 총 29건의 전기저장장치의 화재가 발생되었는데, 이 중 22건이 신재생에너지 연계용이며, 완전충전 이후, 운전대기 상태인 휴지기간 동안에 계절과 무관하게 화재사고가 발생되었다. 이것은 병렬로 연결된 셀들의 SOC 상태가 서로 다른 경우, 의도하지 않게 SOC가 높은 셀에서 낮은 셀로 전류가 이동하는 셀프에너지 밸런싱 현상으로, 일부 셀이 과충전되어 열폭주로 인한 화재의 원인으로 평가되고 있다. 따라서, 본 논문에서는 전기저장장치의 셀프에너지 밸런싱을 방지하는 새로운 BMS의 회로구성과 운용 알고리즘 그리고 SOC 평가알고리즘을 제안한다. 제안한 알고리즘과 구현한 BMS를 바탕으로 리튬이온전지의 열화 특성과 열화 및 정상 셀 간의 셀프에너지 밸런싱 특성을 분석한 결과, 정상 셀 대비 열화 셀의 방전 용량 비율은 91.75[%]이며, 열화율이 8.25[%]임을 알 수 있었고, SOC가 높은 정상 셀에서 SOC 낮은 열화 셀로 전류가 이동하는 셀프에너지 밸런싱 현상이 발생함을 확인하였다. 또한, 셀프에너지 밸런싱 전류가 과도하게 높아지는 경우, BMS가 확실하게 셀들의 병렬연결을 분리하여, 리튬이온전지의 안전성을 향상시킬 수 있어, 본 논문에서 제안한 BMS의 유용성을 확인하였다.