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Pu X.-S.,Advanced Drive Technology Company | Nguyen T.H.,Yeungnam University | Lee D.-C.,Yeungnam University | Lee K.-B.,Ajou University | Kim J.-M.,Pusan National University
IEEE Transactions on Industrial Electronics | Year: 2013

In this paper, a novel scheme for the estimation of the equivalent series resistance (ESR) of the dc-link electrolytic capacitor in three-phase ac/dc pulsewidth-modulation converters is proposed for condition monitoring. First, a controlled ac current component is injected into the input. Then, it induces ac voltage ripples on the dc output. By manipulating these ac voltage and current components with digital filters, the value of the ESR can be calculated, where the recursive least squares algorithm is used for reliable estimation results. In addition, the value of the ESR is corrected by considering the temperature effect, for which a simple temperature-sensing circuit has been designed. The simulation and experimental results show that the estimation error of the ESR is within a reasonable range, thereby enabling the determination of the appropriate time for the replacement of the capacitor. © 1982-2012 IEEE. Source


Kim H.,POSCON Co. | Yoon C.,Advanced Drive Technology Company | Choi S.,Korea University
IEEE Transactions on Power Electronics | Year: 2010

In spite of having many advantages, such as low switch voltage and easy implementation, the voltage-fed dc-dc converter has been suffering from problems associated with large transformer leakage inductance due to high transformer turn ratio when it is applied to low-voltage, high-current step-up application such as fuel cells. This paper proposes a new three-phase voltage-fed dc-dc converter, which is suitable for low-voltage, high-current applications. The transformer turn ratio is reduced to half owing to Δ-Y connection. The zero-voltage and zero-current switching (ZVZCS) for all switches are achieved over wide load range without affecting effective duty cycle. A clamp circuit not only clamps the surge voltage but also reduces the circulation current flowing in the high-current side, resulting in significantly reduced conduction losses. The duty cycle loss can also be compensated by operation of the clamp switch. Experimental waveforms from a 1.5 kW prototype are provided. © 2010 IEEE. Source


Yoon C.,Advanced Drive Technology Company | Kim J.,Korea University | Choi S.,Korea University
IEEE Transactions on Power Electronics | Year: 2011

In this paper, multiphase dc-dc converters are proposed for high-voltage and high-power applications. A generalized converter is configured such that the boost-half-bridge (BHB) cells and voltage doublers are connected in parallel or in series to increase the output voltage and/or the output power. In addition to reduced device voltage and current ratings by the connection, the proposed converter has the following features: high-step-up voltage gain with significantly reduced transformer turn ratio, low-input current ripple due to interleaving effect, zero-voltage switching turn-ON of switches and zero-current switching turn-OFF of diodes, no additional clamping and start-up circuits required, high-component availability and easy thermal distribution due to the use of multiple small components, and flexibility in device selection resulting in optimized design. A design guideline of determining the optimum circuit configuration for given output voltage and power level is presented. Experimental results are also provided to validate the proposed concept. © 2006 IEEE. Source


Kim J.-S.,Sungkyunkwan University | Choe G.-Y.,Sungkyunkwan University | Kang H.-S.,Advanced Drive Technology Company | Lee B.-K.,Sungkyunkwan University
Journal of Electrical Engineering and Technology | Year: 2010

In this work, an accurate analysis of low frequency current ripple in residential fuel cell power generation systems is performed based on the proposed residential load model and its unique operation algorithm. Rather than using a constant dc voltage source, a proton exchange membrane fuel cell (PEMFC) model is implemented in this research so that a system-level analysis considering the fuel cell stack, power conditioning system (PCS), and the actual load is possible. Using the attained results, a comparative study regarding the discrepancies of low frequency current ripple between a simple resistor load and a realistic residential load is performed. The data indicate that the low frequency current ripple of the proposed residential load model is increased by more than a factor of two when compared to the low frequency current ripple of a simple resistor load under identical conditions. Theoretical analysis, simulation data, and experimental results are provided, along with a model of the load usage pattern of low frequency current ripples. Source

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