• 전기전자학회논문지
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• 제27권4호
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• pp.430-438
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• 2023

The Modular Multilevel Converter (MMC) has emerged as a key component in HVDC systems due to its ability to efficiently transmit large amounts of power over long distances. In such systems, accurate estimation of the MMC capacitor voltage is of utmost importance for ensuring optimal system performance, stability, and reliability. Traditional methods for voltage estimation may face limitations in accuracy and robustness, prompting the need for innovative approaches. In this paper, we propose a novel distributed neural network observer specifically designed for MMC capacitor voltage estimation. Our observer harnesses the power of a multi-layer neural network architecture, which enables the observer to learn and adapt to the complex dynamics of the MMC system. By utilizing a distributed approach, we deploy multiple observers, each with its own set of neural network layers, to collectively estimate the capacitor voltage. This distributed configuration enhances the accuracy and robustness of the voltage estimation process. A crucial aspect of our observer's performance lies in the meticulous initialization of random weights within the neural network. This initialization process ensures that the observer starts with a solid foundation for efficient learning and accurate voltage estimation. The observer iteratively updates its weights based on the observed voltage and current values, continuously improving its estimation accuracy over time. The validity of proposed algorithm is verified by the result of estimated voltage at each observer in capacitor of MMC.

• 전기학회논문지P
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• 제59권4호
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• pp.378-383
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• 2010

Due to the large capacity and low cost, DC link electrolytic capacitors with of energy storage and voltage regulation are used for almost all types of power converter as the DC/AC inverter or DC/DC converter. Electrolytic capacitor, which is the most of the time affected by the aging effect, plays very important role for the power converter system quality and reliability. Therefore, this paper proposes a simple method to estimate the capacitance variation of an electrolytic capacitor in order to analyze the internal characteristic decrease and worn-out state of an electrolytic capacitor. Simulation results by using capacitor storage energy computation show the validity of the proposed capacitance estimation method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.57-60
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• 2000

An aluminum electrolytic capacitor is used in DC Link of ac motor drive system. In this case it usually has the shortest lifetime in the system and then determines the system lifetime. Therefore life estimation of the electrolytic capacitor is needed for maintenance of th circuit. In this paper a method for life estimation is presented with a ESR(equivalent series resistance) model and a heat transfer model of capacitor that can be used to estimate operating temperature it is investigated through a simple example using ESR and heat transfer.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.819-822
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• 1998

A new active power filter (APF) circuit with a current compesation estimation method is proposed. The current compensation estimation method replaces a current sensor with an estimating circuit and therefore reduces the implementation cost In addition, a simple control scheme, based on the energy balance concept, is adopted to control the voltage of a DC capacitor. Therefore energy change in the DC capacitor can be compensanted in the next cycle. Since a sampling technique is used, a larger DC capacitor voltage ripple can be permissible and a relatively smaller DC capacitor can be used. The proposed method has advantages of the reduction of one current sensor, low implementation cost, and fast transient responses. The theoretical analysis and simulation results are given. The proposed control method is successfully verified by computer simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 A
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• pp.243-245
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• 2000

In general, aluminum electrolytic capacitors are used in the DC link of PWM inverters fur ac motor drives. The capacitor usually has the shortest lifetime in the system and then determines the lifetime of the inverter system. In this paper, a method of capacitor lifetime estimation is proposed by using an ESR(equivalent series resistance) model and a heat transfer model of capacitor, from which internal operating temperature is estimated. Then, the lifetime is predicted by Arrhenius's equation. A practical example is presented.

• 전기학회논문지
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• 제56권1호
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• pp.81-87
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• 2007

This paper proposes a new capacitance estimation scheme for a DC-link capacitor in a three-phase AC/DC/AC PWM converter. A controlled AC voltage with a lower frequency than the line frequency is injected into the DC-link voltage, which then causes AC power ripples at the DC side. By extracting the AC voltage and power components on the DC output side using digital filters, the capacitance can then be calculated using the Support Vector Regression (SVR). By training of SVR, a function which relates a given input (capacitor's power) and its corresponding output (capacitance value) can be derived. This function is used to predict outputs for given inputs that are not included in the training set. The proposed method does not require the information of DC-link current and can be simply implemented with only software and no additional hardware. Experimental results confirm that the estimation error is less than 0.16%.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권7호
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• pp.338-346
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• 2001

In this paper, dc link currents for the three-phase diode rectifiers and PWM inverters are analyzed and an algorithm of estimating the life of dc link electrolytic capacitors using the analyzed ripple current is presented. Since the capacitor life is dependent on the operating temperature, the power dissipation in capacitors should be calculated. For this, the ESR(equivalent series resistance) model of the capacitor is derived and ripple currents through the capacitor are analyzed. Relating the power dissipation and the heat transfer equation, the internal operating temperature is calculated. Then, the capacitor life can be predicted by using Arrhenius's equation. An example for applications is given for the practical system.

• 전기학회논문지P
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• 제59권1호
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• pp.40-46
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• 2010

DC link electrolytic capacitors are widely used in various PWM power converter system, such as adjustable speed driver(ASD) or DC/DC converter. Electrolytic capacitors, which is the most of the time affected by aging effect, plays a very important role for the power electronics system quality and reliability. This objective of this paper is to propose a improvement method to detect the rise of equivalent series resistor(ESR) in order to realize the online failure prediction of electrolytic capacitor for DC link of PWM power converter. The ESR detection scheme is based on the determination of the electrolytic capacitor AC losses calculated from voltage/current measurement using AC coupling. Therefore, the preposed online failure prediction method has the merits of easy ESR computation and circuit simplicity compare with BPF method. Simulation results show the veridity of the proposed on-line ESR estimation method.

• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.653-661
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• 2016

This paper proposes a capacitance estimation method of the dc-link capacitor for brushless DC motor (BLDCM) drive systems. In order to estimate the dc-link capacitance, the BLDCM is operated in quadrant-II or -IV among four-quadrant operation. Quadrant-II and -IV are called reverse braking and forward braking, respectively. During the braking operation of the BLDCM, the capacitor is charged by the phase current and then the voltage is increased during the braking operation time. The capacitor current and voltage can be obtained by using the phase current sensor of BLDCM and the dc-link voltage sensor. The capacitance and be easily obtained by the voltage equation of the capacitor. The proposed method guarantees the reliable and simple calculation of the dc-link capacitance without additional hardware system except several the sensors already installed for the motor control system. The effectiveness of the proposed method is verified through both the simulation and experimental results.

• 한국ITS학회 논문지
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• 제8권6호
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• pp.180-186
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• 2009

DC/DC 컨버터 등의 전력변환장치와 같은 비선형부하에 대해 알루미늄 전해 커패시터는 에너지의 일시적 저장이나 전압 평활용으로 많이 사용되고 있다. 그러나 전해 커패시터는 사용 시간이 늘어나면서 온도 상승 및 전해액(electrolyte)의 증발 등으로 인하여 고장이 매우 빈번하게 나타난다. 따라서 본 논문에서는 이러한 사고에 대한 고장모드를 분류하고 이를 진단하기 위한 사전 단계로 전해 커패시터의 주파수 변화에 따른 특성 해석과 이를 바탕으로 한 커패시턴스 용량 추정 알고리즘을 제안하였다. 기본파에 해당하는 저주파의 주파수 분석 결과에 따른 모의 실험의 결과는 제안한 알고리즘의 타당성을 입증하였다.