• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.1
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• pp.58-64
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• 2004

This paper proposes a novel control scheme for the harmonic reduction of DC power regenerating systems, which can regenerate the excessive DC power from DC bus line to AC supply in subway systems. In the developed regenerating systems controlled by MAC(Modified a-Conduction) method, the order of remaining harmonics are 12k$\pm$1. In SHE(Selected Harmonic Elimination) method proposed in this paper, however, the l1th and 13th harmonics are additionally eliminated. And moreover 23rd harmonics, lowest order harmonics among the remaining harmonics, is eliminated by 23rd AC filter furnished at the output terminals of regenerating systems. To verify the validity of the proposed SHE-based harmonic reduction technique, computer simulations are carried out. Simulation results show that the THDs of output voltages are lower than that of the MAC method and the THDs in the control range are in the range of 0.53-0.68 percents.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.5
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• pp.410-415
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• 2001

This paper proposes a new control scheme for the power factor improvement of DC power regenerating systems, which can regenerate the excessive DC power from DC bus line to AC supply in substations for traction systems. From the viewpoint of both power capacity and switching losses, the system is designed on the basis of three-phase square-wave inverters and composed of two inverters, zig-zag connected output transformers, and an AC filter. The output voltages of the regenerating system are not sinusoidal. However, regenerated complex power is analyzed on the basis of fundamental components and thus the reactive power produced by harmonics is not considered. Therefore, it is needed a new control scheme capable of controlling the reactive power nearly to zero even for nonsinusoidal cases. To verify the validity of the proposed control scheme, computer simulations are carried out. And the results show that the power factor is theoretically higher than 0.99.

• Journal of the Korea Convergence Society
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• v.7 no.3
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• pp.77-85
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• 2016

We propose a digital signal processing technic that can compensate the non-linearity inherent in audio amplifiers, and present the result of the simulation. The inherent non-linearity of the audio power amplifier arising from analog devices is compensated via a digital signal processing technic consisting of indirect learning architecture and an adaptive filter. The simulation results show that the compensator can be realized using a third-order polynomial and compensates odd-order non-linearity efficiently. The even-oder non-linearity is mainly due to the dc offset at the output, which is difficult to eliminate with the proposed method. Care must be taken in designing the bias circuit to avoid the DC offset at the output. The proposed technic has significance in that digital signal processing technic can compensate for the impairment that is an inherent characteristic of an analog system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.2
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• pp.145-151
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• 2004

This paper presents a fully integrated 5 GHz band low phase noise LC tank VCO. The implemented VCO is tuned by integrated PN diodes and tuning rage is 5.01∼5.30 GHz with 0∼3 V control voltage. For improved phase noise performance, a LC filtering technique is adapted. The measured phase noise is -87.8 dBc/Hz at 100 kHz offset frequency and -111.4 dBc/Hz at 1 MHz offset frequency which is excellent performance. Moreover phase noise is improved by 5 dB after employing the LC filter. It is the first experimental result in field of InGaP/GaAs HBT VCOs. The figure of merit of the fabricated VCO with LC filter is -172.1 dBc/Hz. It is the best result among 5 GHz InGaP HBT VCOs. Moreover this work shows lower DC power consumption, higher output power and more fixed output power compared with previous 4, 5 GHz band InGaP HBT VCOs.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.155-159
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• 2003

This paper presents fully integrated 5 GHz band low phase noise LC tank VCO. The implemented VCO is tuned by integrated PN diode and tuning rage is $5.01{\sim}5.30$ GHz under $0{\sim}3 V$ control voltage. For good phase noise performance, LC filtering technique, common in Si CMOS process, is used, and to prevent degradation of phase noise performance by collector shot-noise and to reduce power dissipation the HBT is biased at low collector current density bias point. The measured phase noise is -87.8 dBc/Hz at 100 kHz offset frequency and -111.4 dBc/Hz at 1 MHz offset frequency which is good performance. Moreover phase noise is improved by roughly 5 dEc by LC filter. It is the first experimental result in InGaP/GaAs HBT process. The figure of merit of the fabricated VCO with LC filter is -172.1 dBc/Hz. It is the best result among 5 GHz InGaP HBT VCOs. Moreover this work shows lower DC power consumption, higher output power and more fixed output power compared with previous 4, 5 GHz band InGaP HBT VCOs.

• Journal of electromagnetic engineering and science
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• v.2 no.2
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• pp.117-123
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• 2002

This paper describes the design for the resistive FET mixer with low If for the 4-Ch DBF(Digital Beam Forming) receiver This DBF receiver based on the direct conversion method is generally suitable for high-speed wireless mobile communications. A radio frequency(RF), a local oscillator(LO) and an intermediate frequency(If) considered in this research are 2.09 GHz, 2.08 CHz and 10 MHz, respectively. This mixer is composed of band pass filter, a low pass filter and a DC bias circuit. Super low noise HJ FET of NE3210S01 is considered in design. The RE input power, LO input power and Vcs are used -10 dBm, 6 dBm and -0.4 V, respectively. In the 4-Ch resistive FET mixer, the measured If and harmonic components of 10 MHe, 20 MHz and 2.087 CHz are about -19.2 dBm, -66 dBm and -48 dBm, respectively The If output power observed at each channel of 10 MHz is about -19.2 dBm and it is higher 28.8 dBm than the maximum harmonic component of 2.087 CHz. Each If output spectrum of the 4-Ch is observed almost same value and it shows a good agreement with the prediction.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.1
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• pp.61-69
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• 1998

In this paper, discrete current control of voltage source inverters is proposed. As a current control scheme, the constant switching frequency predictive current control is adopted and implemented with DSP microprocessor system. In particular, the proposed method is for the compensation of the control lagging due to calculation delays in the microprocessor controller. In controlling the current, the inverter output voltage saturation problem is inevitable and usually affects the current control performance. So, the saturation boundary condition of the inverter output voltage and its effects on the current controal performance of the proposed current control scheme are investigated with experiment. Finally, the proposed scheme is applied to the active power filter system and some results are described for validation.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.267-269
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• 2006

In this paper, a new single phase voltage sag/swell compensator using direct power conversion is introduced. A new compensator consists of input/output filter, series transformer and direct ac-ac converter, which is a single-phase back-to-back PWM converter without dc-link capacitors. Advantages of the proposed compensator include: simple power circuit by eliminating dc-link electrolytic capacitors and thereby, improved reliability and increased life time of the entire compensator; simple PWM strategy to compensate voltage sag/swell at the same time and reduced switching losses in the ac-ac converter. Further, the proposed scheme is able to adopt simple switch commutation method without requiring complex four-step commutation method commonly required in the direct power conversion. Simulation results are shown to demonstrate the advantages of the new compensator and PWM strategy.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.447-449
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• 1996

The main objective of this paper is to increase the efficiency, to eliminate the harmonics wave and to acomplish the zero voltage regulation of the output voltage. To accomplish the goal, DC-to-DC converter model with ERS(Energy Recovery Snubber) is developed. And, to realize the detail purpose, we are used ZVS soft switching snubber, ripple steering filter and, function control law etc.. So, we presented to show superior operation of this convertor with the zero voltage regulation function.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.1093-1096
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• 2002

In this paper, a novel multi voltage inverter system is proposed for reductions of harmonics, which can compensate reactive power. At first, we remove capacitor at input side for reactive power compensation. Secondly, by adding DC voltage to the filter capacitor, it can control power factors as lead-phase according to alterations of loads at power reception. Thirdly, if winding and single phase-bridge inverter(auxiliary circuit) is installed to DC power for reduction of harmonic, waveform of output voltages become to 36-steps. Thus, SVC(static var compensator) systems which can reduce harmonics are designed.