• Journal of the Semiconductor & Display Technology
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• v.19 no.1
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• pp.42-48
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• 2020

As global warming accelerates, eco-friendly electric cars are being developed to reduce carbon dioxide emissions, and power conversion inverters are used to drive motors. Among inverter components, DC-link capacitor is heated by high current usage, which causes problems such as performance and life-saving of inverter. Although metal cases with good thermal performance have been used to solve this problem, it is difficult to apply them in practice due to insulation problems with other parts. In this paper, the Heat-Generation influence factor of DC-link capacitor is analyzed. Variables on heat-generation are set at 3 levels for film width, inductance, and film thickness. Box-Behnken to 13 tests using the design and minimal deviations, e.g. through the experiment three times by each level. The surface of the film k type by attaching the sensor current is measured temperature. Capacitance was set to a minimum level of 200 ㎌ and had a frequency of 16 kHz with Worst case, ambient temperature of 85℃ and a ripple current of 50 Ams was applied. The temperature at the measurement point was collected in the data logger after sampling at 1 minute intervals for 2 hours after saturation with the ambient temperature. This experiment confirmed that setup factors are correlated with heat-generation.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.1
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• pp.59-64
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• 2003

This paper presents a new rotor position estimation method for brushless DC motors. The estimation error of the rotor position clearly provokes the phase shift angle misaligned between the phase current and the back-EMF waveforms, which causes torque ripple in brushless DC motor drives. Such an estimation error can be reduced with the help of the proposed neutral-voltage-based estimation method, which is structured as a closed loop observer. A neutral voltage appearing during the normal mode of the inverter operation is found to be an observable and control table measure, which can be used for estimating an exact rotor position. This neutral voltage is obtained from the DC-link current, the switching logic, and the motor speed values. The proposed algorithm, which can be easily implemented by using a single DC-link current and the motor terminal voltage sensors, is verified by simulation and experiment results.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.6
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• pp.572-581
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• 2014

A design and control method of DC/DC converter, which can control variable DC-link voltage to drive a fuel cell electric vehicle (FCEV), is proposed in this study. Given that a fuel cell has low-voltage and high-current characteristics, the required voltage for operating motor must be output through the DC/DC boost converter in the system to drive an FCEV. The proposed converter can choose the output voltage of battery or fuel cell in consideration of the driving mode, as well as control DC-link voltage in accordance with the back electromotive force. The switching lag-time to prevent shortage of pulse-width modulation inverter arms makes distorted current waveform caused by voltage distortion. Through this control method, the proposed converter can reduce the output voltage distortion and current ripple of the inverter, thereby reducing the distorted torque. Simulations and experimental results are presented to verify the reliability of the proposed DC/DC converter.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1343-1345
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• 2005

In this paper, control schemes are proposed for a propulsion system(Converter/Inverter) of the TTX(Tilting Train express). In developed traction converter, unity power factor control, compensation method of dc link voltage have been applied. Output current of converter contains harmonics ripple at twice input ac line frequency, which causes a ripple in the dc link voltage so that control scheme is developed in inverter system to reduce the pulsating torque current. At low speed region, vector control scheme is applied and slip frequency control is adopted at high speed region. The performance of propulsion system will be verified by simulation and prototype experimental results.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.365-366
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• 2016

This paper presents a single-phase transformerless photovoltaic (PV) power converter systems based on the AC/DC boost inverter, which is capable of solving the leakage current and second-order ripple power issues. By eliminating the inherent ripple power in single-phase inverter, the bulky electrolytic capacitor can be replaced by a small film capacitor. The validity of the proposed scheme has been verified by the simulation results.

• Journal of Power Electronics
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• v.16 no.6
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• pp.1991-2004
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• 2016

An LC filter is required to reduce the output current ripple in the auxiliary resonant snubber inverter (ARSI) for high-performance applications. However, if the traditional control method is used in the ARSI with LC filter, then unnecessary current flows in the auxiliary circuit. In addressing this problem, a novel load-adaptive control that fully uses the filter inductor current ripple to realize the soft-switching of the main switches is proposed. Compared with the traditional control implemented in the ARSI with LC filter, the proposed control can reduce the required auxiliary current, contributing to higher efficiency and DC-link voltage utilization. In this study, the detailed circuit operation in the light load mode (LLM) and the heavy load mode (HLM) considering the inductor current ripple is described. The characteristics of the improved ARSI are expressed mathematically. A prototype with 200 kHz switching frequency, 80 V DC voltage, and 8 A maximum output current was developed to verify the effectiveness of the improved ARSI. The proposed ARSI was found to successfully operate in the LLM and HLM, achieving zero-voltage switching (ZVS) of the main switches and zero-current switching (ZCS) of the auxiliary switches from zero load to full load. The DC-link voltage utilization of the proposed control is 0.758, which is 0.022 higher than that of the traditional control. The peak efficiency is 91.75% at 8 A output current for the proposed control, higher than 89.73% for the traditional control. Meanwhile, the carrier harmonics is reduced from -44 dB to -66 dB through the addition of the LC filter.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.808-812
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• 2013

Multilayer capacitors with high ripple current and high capacitance were manufactured. The electrical properties of these capacitors were characterized for potential application for DC-link capacitors in hybrid electric vehicle inverters. Internal electrode structures were designed to achieve high capacitance and reliability. A single multilayer capacitor showed $0.46{\mu}F/cm^3$ of capacitance, 0.65% of dielectric loss, and 1450 V to 1650 V of dielectric breakdown voltage depending on the design of the internal electrode. The capacitor module designed with several multilayer capacitors gave a total capacitance of $450{\mu}F$, which is enough for hybrid electric vehicles. In particular, an equivalent series resistance of $4.5m{\Omega}$ or less will result in 60 $A_{rms}$, thereby reaching the allowed ripple current for hybrid electric vehicles.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.495-497
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• 1994

Given the constraint of the AC input power factor and the DC-link voltage and current ripple in voltage source inverter, minimizing the size and cost of the DC-link fitter components is very important. This paper presents a procedure for the selection of DC-link filler element values in a three-phase PWM voltage source inverter-fed induction motor drive system, which can not only satisfy the requirements for the system performance but also minimize the filter size.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.3
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• pp.276-282
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• 2014

In a single-phase grid-connected power system consisting of a dc-dc converter and a dc-ac converter, the current drawn from renewable energy sources has a tendency to be pulsated and contains double-fundamental frequency ripple components, which results in several drawback such as a power harvesting loss and a shortening of the energy source's life. This paper presents a new double-fundamental current reduction-scheme with a fast dc-link voltage loop for two-stage dc-dc-ac grid connected systems. In the frequency domain, an adequate control design is performed based on the small-signal transfer function of a two-stage dc-dc-ac converter. To verify the effectiveness of proposed control algorithm, a 1 kW hardware prototype has been built and experimental results are presented.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.560-564
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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(WPC) inverters at low modulation index. New DPWM methods in multi-level inverter are also introduced. The proposed DPWM method changes the path and duration to flow the neutral point current out of or into neutral point of the DC-link and it makes the overall fluctuation of the DC-link voltage zero during a sampling time of reference voltage vector. Therefore, the voltage of the DC-link can be balanced fairly well and also the voltage ripple of the DC-link is reduced significantly. Moreover, comparing with conventional methods, the proposed strategy is very simple. The validity of the proposed DPWM method is verified by experiment